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DUBLIN CITY UNIVERSITY
School of Electronic Engineering
Master of Engineering
Thesis
THE DEVELOPMENT OF AN INTELLIGENT MOBILE
MAINTENANCE WORKSTATION FOR APPLICATION
IN AUTOMATED CNC MACHINE REPAIR
Author: Mustafa Houreh
B.Eng
Supervisor: Dr. Charles MCCorkell
September 1991
THIS THESIS IS BASED ON THE AUTHORS OWN RESEARCH RESULTS
ABSTRACT
The project
focuses
is justified given
on electronic repair in CNC machine. This
that
electronic
causes
determine
a
high
percentage of automated CNC machine failures.
An intelligent maintenance workstation is proposed as a vehicle for
redressing the problem of uncertainty in the skill
staff and as
a
level of repair
means of enhancing the pace of repair under normal
circumstances.
The suitability of expert systems
in electronic fault diagnosis is
established through a review of the literature and a realistic role
for an expert
system
in
the
definition
determined. Circuit interrogation
combination of instruments, probes
'C'. Procedural guidance
detailed circuit knowledge
available
carried
workstation
out
using
is
a
and driving software written in
from
the
expert
system
and
is reproducible in the workstation from
pre stored CAD data base files. In
carry out the
is
of the
implementation,
the absence of a CNC machine to
a partial implementation
only
was
possible. However all of the elements were included and credibility
given to the proposal.
ACKNOWLEDGEMENTS
I am
indebted to my project supervisor, Dr. Charles McCorkell,
for his continued help and encouragement.
Thanks
to all the staff
of the School of Electronic Engineering at Dublin City
especially Mr. John
Whelan
University,
and Mr. Noel Murphy for their help. To
my fellow Postgrads and friends at
Dublin
City University, I wish
you good luck with your respective careers.
I must acknowledge
the
advising me during
builting my project.
Finally my sincerest
great
gratitude
help given by Mr. John
to
my
wife
constant support and understanding throughout.
for
Whelan,
her
in
patience,
!Declaration
I hereby declare
that
this
thesis is entirely of my own work and
has not been submitted as an exercise to any other university.
— -------
Mustafa Jioureti
v m 'D ic v n c x X ,
my parents, as they enter theirgoCden years.
CONTENTS
1.
2.
INTRODUCTION
1
1.1 Motivation for the Project
1
1.2 Summary of the Proj ect
3
1.3 Aim of the Project
6
WORKSTATION SPECIFICATION
7
2.1 Introduction
7
2.2 General Workstation Specification
7
2.2.1 Service Engineer Specification
2.2.2 Test Equipment Specification
2.3 Breakdown Time
10
2.4 The Alternative Solution
11
3. HARDWARE CONFIGURATION
15
3.1. Introduction
15
3.2. The Controller
15
3.3. IEEE Interface Card
16
3.3.1 Introduction to Digital Communication
3.3.1.1 Serial Data Transfer
3.3.1.2. Parallel Data Transfer
3.3.1.3
Asynchronous Serial Data
3 .3 .1.4. Baud Rate
3.3.1.5 Synchronous Serial Data
3.3.2. The Solution
3.3.3. The IEEE-488 Bus Lines
3.3.3.1. Data Connections
3 .3 .3 .2 . Handshaking Connect ions
3.3.3.3 Interface Management Connections
3.3.4. Addressing
3.3.5. Setting the DIL Switch on HP-IB Interface Card
3.3.6. Connecting Peripherals
3.4. The Digital Oscilloscope
3.4.1. Addressing HP 54501A Oscilloscope
3.5. The Logic Analyzer
3.5.1. Addressing 1241 Logic Analyzer
APPLICATION OF EXPERT SYSTEM IN DIAGNOSTICS
4.1. Introduction
4.2. Introduction to Artificial Intelligence
4.2.1. Application of Artificial Intelligence
4.3. Expert Systems
4.3.1. Widely Used Expert Systems
4.3.2. Advantages of Expert Systems
4.3.3. Disadvantages of Expert Systems
4.3.4. Expert System's Type
4.3.5. Expert System Architecture
4.3.5.1. The Knowledge base
4.3.5.2. The Data Base
4.3.5.3. The Inference Engine
4.3.5.4. User Interface
4.3.6. Expert System Features
4.3.6.1. Explanation Facility
4.3.6.2. Ease Of Modification
4.3.6.3
Transportability
4.3.6.4 Adaptive Learning Ability
4.3.7. Uncertainty
4.3.8.
Fuzzy Logic
4.3.9. Expert System Applications
4.3.9.1
Control
4.3 .9 .2 Debugging
4.3.9.3 Design
4.3.9.4 Diagnosis
4.3.9.5 Instruction
4.3.9.6.
Interpretation
4.3 .9 .7 . Planning
4.3.9.8.
Prediction
4 .3 .9 .9. Repair
4.4.
Electronic Fault Diagnosis
58
4.5.
Shallow Knowledge
60
4.6.
Shallow Knowledge Based Systems
60
4.7.
Deep Knowledge
61
4.8.
Deep Knowledge (model) basedsystems
63
4.9. Advantages and Disadvantages of Shallow and Deep Knowledge
Based Systems
4.9.1. Advantages
65
and
Disadvantages
of
Shallow
Knowledge
Based Systems
4.9.2. Advantages and Disadvantages
of
Deep Knowledge Based
Systems
4.10. Systems Incorporating both Deep and Shallow
66
Knowledge
4.10.1. Exp-Test System
INTEGRATING EXPERT SYSTEM AND ON-LINE TEST
5.1.
Introduction
73
73
5.2. Using Expert System in Building Intelligent
74
Workstation
5.3. Improving the Productivity
76
5.4. Developing an Intelligent Mobile Workstation
76
for On-Line Test.
6. INTEGRATING GRAPHIC CAD KNOWLEDGE WITH EXPERT
89
SYSTEM AND ON-LINE TEST
6.1 INTRODUCTION
89
6.2 CAD System
89
6.2.1 Overview
6.2.2. OrCAD/SDT III System
6.2.3. OrCAD Plot File
6.3.
Programs
6.4. Integrating OrCAD/SDT III System with EXP-Test
99
109
System
7. IMPLEMENTATION
111
7.1.
Introduction
111
7.2.
U.U.T. description
112
7.3.
Approach Adopted
117
7.4.
Design and Development
117
7.4.1. Introduction
7.4.2. Structure
7.4.2.1. Supporting Software
7.4.2.2. Designing the Rule Set
7.4.2.3. Domain expertise
7 .4.2.4 . Knowledge Engineering
7.5. Certainty Factors
127
7.6. EXP-Test System in Operation
127
8. CONCLUSION
137
REFERENCES
139
APPENDIX
CHAPTER 1
INTRODUCTION
1.1 Motivation for the Project
During the
last
20
years,
the
complexity of the mechanical
aspect of machine tools has significantly
increased; this has been
accompanied by a corresponding complexity of electronics.
In the early 197 0's, Alfred Herbert limited introduced a variety of
computer numerical control
continuously modified in
CNC turning machine tools.
the
field; subsequently, updated
light
models
of
experience
were
These
were
gained in the
developed
and,
recently, microprocessor control, together with manual
data
more
input
CNC systems were introduced.
Because of its
considerable inherent flexibility, a CNC machine is
capable of producing an output (machining
rate)
of up to three to
four times the
output of manually operated conventional
Because of the
high
output
machines.
of these machines, breakdowns have an
increased significance, since the breakdown of a single CNC machine
can result in the production of
an
entire
workshop
being halted
[34] .
In short, CNC equipment availability seldom reached much beyond the
60 percent level,
because
nine times out of ten
the
maintenance
people could not make the necessary repairs. So it was necessary to
call in the
machine
course, were not
manufacturer's
immediately
maintenance
available,
measured in days.
1
so
the
people,
down
who, of
time
was
To solve the
maintenance
problem,
a
technician
was
hired,
to
specifically cope with control unit emergencies and maintenance. So
he instituted a preventive maintenance
restore equipment to
(when parts were
operating condition within
available)
an
hour
or
two
instead of the two or three days. But
when this technician left the plant
original status.
program, and he was able to
the
situation reverted to its
The search for a more practical solution led some
plants to a nation wide CNC maintenance service,
signed a contract
with
the
manufacturer's
preventive maintenance, which is
the
key
that
for
to
means
minor
they
and major
improve operational
efficiency [3].
JACK MOORHEAD [4]
recommended
maintenance and operation
to
the
be
provisions
for
programming
made before the CNC machine tool
arrive on the shopfloor, and the CNC
users should be in a position
to support and sustain CNC operation internally, even
though there
is considerable assistance available from the outside.
He said, that
"to develop this internal capability it is important
to select the right people and train them thoroughly.
Three groups are involved :
(1) part programmer.
(2) machine operators.
(3) maintenance technicians."
He added "a minimum number of adequately
trained
people
can keep
the CNC running".
Also when these
trained
people
left
the
plant
the
situation
reverted to its
original status, and the breakdown time will cause
a halt of the production to the entire workshop.
To solve the problem of depending
on expert people, some companies
developed expert systems, however, until the early eighties, expert
2
systems required tremendous
development
work
and
often
special
purpose hardware.
"The appearance of micro-computerization
and
more
user
friendly
computer program languages led us to investigate the application of
these new techniques to corrective maintenance of NC machine-tools"
[33] .
1 .2 sinnmrv of the Project
Usually, any
workshop, which contains a large
machines, has its
special
workstation.
controlled by a service engineer,
any problems that
might
happen
who
to
This
is
any
number
of
CNC
workstation
is
responsible for solving
of the machines
in
the
workshop.
In the case
of
a
breakdown
to any machine, the service engineer
will collect all the information
about
the
machine,
with service catalogues and some testing devices,
will
and equiped
go
to the
machine location to fix it.
That work may
take
one or two weeks with a non-expert person, and
may only take
hours
engineers are forced
with
to
an expert.
As
a
result,
keep up with advances in
any
maintenance
technology
that will reduce downtime.
But as mentioned,
in the case of the absence of the expert person,
the maintenance will depend on the non-expert, who will take a long
time to fix the broken machine.
This project concentrated on CNC machine corrective maintenance. So
an intelligent mobile workstation
Fig. 1-1, shows
inside the CNC
was
developed for this purpose.
the intelligent mobile workstation
machine
workshop.
workstation is controlled by EXP-Test
3
This
System
(mobile
unit)
intelligent
mobile
(the
system
expert
1
CMC
a
MACHINE
SERUICE
i
!
CMC
ENGINEERS
1
! MACHINE I
!_______ — i
MOBILE
I.
I -------------
I CnC
1 MACHINE
i
UNIT
* »
!
fig. 1-1. The Intelligent Mobile Workstation
which was developed
EXP-Test System is
inside
a
highly
VP-Expert
flexible,
pattern_directed inference system,
fault diagnosis, and
is
system; a functional
dimension,
system
user
friendly,
that is adequate
accompanied
by
and
a
circuit
for
and
hardware
a two dimensions graphic
physical
physical dimension sketches the circuit layout and
dimension sketches the
shell).
schematic.
this
dimension.
the
The
functional
is important for
accessing any component on the circuit.
As a result this will reduce the breakdown
time of the CNC machine
and will allow any maintenance engineer or technician
experience to repair
the
machine
returning to the service manual for
machine, having an
integrated
with
little
quickly. This he can do without
information
system
which
about
contains
the broken
complete
information, procedural and graphic.
The intelligent mobile
workstation
4
(mobile
unit)
has
five
IESI SIGNALS
fig. 1-2. The Components of the Mobile Unit
components as shown in fig. 1-2 :
(1) User interface (P.C. screen).
(2) Expert system (VP-EXPERT).
(3) TURBO.C system (TC2).
(4) Graphic system (OrCAD).
(5) Hardware
system
(controller,
IEEE
interface
card
Digital Oscilloscope, and Logic Analyzer) .
In the case of a problem the service
engineer will move the mobile
unit to the location of the broken machine, switch
on the unit and
follow the instruction of the expert system.
The main input
to
the
system
is
the
test signal from the test
equipment. This signal is compared with the reference signal inside
TURBO.C system, then the result
is
5
chained
through
the function
test rules and a list of components in which the fault might lie is
produced, this is the fault candidate list.
The expert system will inform the user and guide him on were to put
the probe to
get
the
test
signal-
In
addition
it will call a
program in TURBO.C, which converts an OrCAD program for drawing the
schematic and layout
diagrams by
mentioned diagrams on
the
(HP
plotter),
screen of the P.C.
and
using
sketch
the
the
graphic
library in (TC2).
The system backward-chains
through
these
discovering which of the fault candidates
rules
is
with the goal of
indeed faulty. If it
is difficult to get some information using the test
Expert System will
query
the
user
system gets the extra information
for
equipment, the
that information. So the
that it needs to isolate a fault
by asking the user about the faulty device, and the
existence
and
nature of signals at various points in the circuit.
1.3 Aim of the Project
The aim
of
the
project
was
to develop a mobile intelligent
workstation that will:
(1) Include an expert system
for
electronic fault diagnosis
which incorporates both deep and shallow knowledge.
(2) Be
independent
of
the
need
for
an
expert
service
engineer.
(3) Achieve
a
quick
and easy corrective maintenance to any
CNC machine.
(4) Decrease the number of service
engineers and technicians
that are needed for maintenance.
(5) Decrease the downtime of any CNC equipment.
(6) Transfer
the
knowledge
6
between
service
engineers.
CHAPTER 2
WORKSTATION SPECIFICATION
2.1 Introduction
As mentioned
in
the
previous chapter, a CNC machine has high
output, which increases the significance
of
breakdown
the breakdown of a single CNC machine can result in
of an entire
workshop
associated with a
CNC
being
halted.
workshop
has
time since
the production
The maintenance workstation
more
significance
than
workstation inside other workshops where linked production
going on. This
chapter
will
is
a
not
describe the CNC machine maintenance
workstation specification and the software tools which are designed
to reduce breakdown time.
2.2 General Workstation Specification
In general
every
workstation
will
have
a
number
of
specifications, to achieve its aims.
In this case they can be broken down into:
1.
Service engineer specifications.
2.
Test equipment specifications.
2.2.1 Service Engineer Specifications
For the propose of maintaining the CNC machine,
very complex machine,
worked in the
an
expert
service
maintenance field
for
a
engineer
long
time,
which
is
a
who will have
following
a
training course at a CNC machine manufacturer is necessary.
So the service
engineer
would
typically
7
have
as
minimum
specification :
1.
A good knowledge in maintenance from experience.
2.
A specific background in fixing CNC machines.
3.
Because
circuit
complexity
is
increasing (doubling
about every two years) he must be able to keep up with
advances in any technology that will reduce downtime.
2.2.2 Test Equipment Specification
Usually in any workshop which
deals with manually controlled
machines, the basic test tools which are adequate for testing power
supply, some electrical
components,
and
simple
logic
circuits
should be available. These tools include :
The test or
1.
Analog multimeter.
2.
Digital multimeter.
3.
Oscilloscope.
4.
Function generator.
5.
Power supply.
service
equipment used in CNC machine troubleshooting
is basically the same as that used
That is, most
procedures
(including high voltage
in other fields of electronics.
are performed using conventional
meters
for
meters
measurement of video terminal
CRT voltages), multitrace oscilloscopes
(for measurement of pulses
on data and address buses, clock and other control
lines,
etc. ),
and assorted clips, patchcords, power supplies, and hand tools.
Theoretically, all CNC
machine
troubleshooting
problems
can
be
solved using such instruments.
However, there are some specialized
test
instruments that greatly
simplify microcomputer service (just as they do for
digital device composed
any programed,
mostly of ICs). such specialized equipment
8
includes :
(1) LOGIC PROBE
Such probes
will detect and indicate high and low (1 or 0)
logic levels,
as
well
as
intermediate
or
"bad"
levels, including an open circuit, on a single
logic
line of CNC
machine circuit.
(2) LOGIC PULSER
Such pulsers
are
hand-held
logic
generators
used
for
injecting controlled pulses into digital logic circuits.
(3) CURRENT TRACER
Such current tracers are
hand-held
probes that enable the
precise localization of low-impedance faults
systems (including
typical
CNC
machine
in electrical
printed-circuit
wiring).
(4) LOGIC CLIP
Such clips are designed for
logic-level determination only
on ICs using TTL and DTL circuits.
Generally, clips
can
test
buffers, adders,
shift
flip-flops,
registers,
not test ICs with nonstandard
input
gates,
counters,
and the like, but will
levels
or expandable
gates.
(5) LOGIC COMPARATOR
Such comparators
comparison scheme,
clip
onto
16-pin
instantly
ICs
display
and,
any
through
logic
a
state
differences between the test IC and a reference IC.
Logic differences are identified
to
the
specific
pins of the IC with the comparator's display
lighted LED corresponds to a logic difference.
(6) LOGIC ANALYZER
9
pin or
of 16 LEDs. A
Although single
stepping
and a check of system timing can
pinpoint many CNC machine
problems. First,
problems,
present-day
there are two obvious
multitrace oscilloscopes
do
not have enough traces to accommodate all the lines in data
and address
buses
simultaneously.
important, a typicaldata byte is
8
8 clock pulses, or 8one-at-a-time
Second,
more
bits, and thus requires
pushes
of
step button. Since all program steps require
byte (and
and
the singleat
least one
often two or three bytes, possibly 24 bits), you
must push that button many
times if the malfunction occurs
at step 3333 of the program! This means that you must spend
endless hours
comparing
program
lists
against
binary
readouts at addresses.
(If you
are
already
familiar with troubleshooting of any
programmed device, you know
that
the
most time-consuming
part of the task is in making such comparison.)
The logic
analyzer
permitting you
to
overcomes
this
basic problem
by
select the data at a particular address
for display. The logic analyzer
will
then run through the
program at near the normal system speed (a
fraction
second) and
at the
display
the
selected
data
of
a
desired
breakpoint or between two breakpoints in the program [69].
2 .3 B r e a k d o w n T i m a
In the case of a breakdown to
workshop, the service
about the broken
engineer
any CNC machine in the mentioned
will collect all
the
information
machine and equipped with the service catalogues,
and all the test equipment which have
to the machine location to fix it.
10
just been mentioned, will go
That work may
take
one
or
two
weeks
(service engineer or technician,
who
an
expert
a non-expert person
doesn't
specification for the service engineer
take hours with
with
meet
the
previous
sec. 2.2.1),
and
may only
(person who has the service engineer's
specification).
2.4 The Alternative Solution
To solve the problems which
installing workstations inside
machines, and to
allow
out the necessary
will
face
his
plant,
service
was
manufacturer when
which
contain
CNC
engineers or technicians to carry
maintenance
intelligent mobile unit
any
to
any
of
the
developed, controlled
machines,
by
an
an
expert
system.
Two situations have been mentioned viz:
1. Maintenance
where
the
skill
level
of
the
maintenance
of
the
maintenance
engineer or technician is uncertain.
2. Maintenance
where
the
skill
level
engineer is high.
In specifying the
workstation,
realistic situation of
the
intention is
to
the
an uncertain skill level in the maintenance
staff (arising through inadequate
training,
turnover etc.) whilst
attempting through maximum support in the workstation,
the level of
assume
performance
possible
with
the
to
achieve
highly
skilled
maintenance person.
Translating this intention into appropriate technology-hardware and
software- is the essence of this project.
The make-up of the hardware has already
been
components are:
(1) A controller
(Personal Computer).
11
hinted at. The major
(2) Digital Oscilloscope.
(3) Logic Analyzer.
(4) A suitable hardware interface.
(5) Probes and other ancillary equipment.
In chapter three
the
hardware make-up of the workstation is dealt
with in more detail.
In defining the software many more issues arise such as:
1. What routine software is necessary to drive the instruments?
2. How should the man_machine interface be defined?
3. What level of support is possible with an expert system?
4. If an expert system is to
expert system
be
be
integrated
used,
with
can
a
an
off-the-shelf
standard
programing
language such as 'C'?
5. How
do
we
define
the
knowledge
context- electronic circuit
graphically yet
base
given
the
knowledge is usually documented
maintenance
procedures
may
be
stated
linguistically?
6. Maintenance
procedures
and
distinct levels- shallow
solutions
and
deep-
can
how
be at two very
do we accommodate
that?
These are examples of the many unfolding issues that
attempt to define
the
software.
Most
of
the
arise
in any
agonizing centres
around the question of knowledge encapsulation and representation.
Following considerable reading in
this
area we concluded that any
attempt to encapsulate known diagnostic procedures
in a linguistic
based expert system
would be impossible given the near infinity of
loops and breakdown
possibilities
electronic and electromechanical
knowledge into "shallow"
in
systems.
even
The
modestly
complex
partitioning
of
and "deep" is useful and has been used as
12
follows.
Routine isolated faults
faults (power supply
that
constitute
problems for
the largest group of all
example)
are
classifiable
as
shallow from a knowledge point of view.
Any problem which
requires
information which is
information
normally
with
detailed
circuit
preserved graphically is classified
as 'deep' from a knowledge point of view.
The following assumptions
underpin
the
proposed
intelligent
maintenance workstation.
1. Shallow
knowledge with
encapsulated in
diagnostic
a standard
expert
procedures
can
system
and will
shell
be
enhance the pace of early fault diagnosis.
2. The normal context applying
in
the diagnosis
of
complex
faults must be acknowledged in the sense that:
(a) Graphical information is available and used.
(b) convergence
to fault
identification
uncertain, interactive,
involves
is
open-ended,
learning
whilst
persueing the fault, and the outcome is unpredictable.
The conclusion reached
in
defining
the
software
specification
therefore is that all of the following elements must be available.
1. Routine
software
for
signal
detection
and
instrument
driving.
2. An
expert
system shell for shallow knowledge encapsulation
and user guidance.
3. A
graphical facility to allow
the
introduction
of
"deep
knowledge” in the context of complex fault diagnosis.
Specifically the following
hardware
constitute the workstation.
13
and
software
elements
This unit consists of four hardware parts which are:
(1) Controller (personal computer).
(2) IEEE interface card.
(3) Digital oscilloscope.
(4) Logic analyzer.
And from four software packages which are:
(1) VP-EXPERT system.
(2) TURBO.C system.
(3) Oread system.
(4) IEEE software system.
By including all
the information which is important for fixing CNC
machines, plus the schematic diagram
and
layout
inside the data base of the expert system, and by
base follow the
maintenance
circuit diagram,
making
the data
tree, the CNC machine maintenance can
be made very easy.
As a result this will reduce the breakdown
time of the CNC machine
and will allow any maintenance engineer, or technician with limited
experience of repair
of
CNC
machines
to
complete
without having to refer to paper based information.
14
the
service
CHAPTER 3
HARDWARE CONFIGURATION
3 »1♦ Introduction
As mentioned in chapter 1, the intelligent mobile unit has five
components, which are :
(1) User Interface.
(2) Expert System.
(3) TURBO C. System.
(4) Graphic System.
(5) Hardware Sys tem.
This chapter will
give
a
more
specific
hardware system, which is illustrated
in
discussion
about
the
fig. 3-1 and consists of
five
parts:
(1) C o n t r o l l e r ( P . C . ) .
(2)
IEEE Interface Card.
(3) Digital Oscilloscope.
(4) Logic Analyzer,
(5) Cables.
3.2. The Controller
The controller
sends the command signals to the test equipment
(Digital Oscilloscope and Logic Analyzer),
through
the IEEE card,
those command signals cause :
1. Initialize the IEEE bus and the instruments.
2. Sending the setup information to the test equipments.
3. Command
the
instruments
to get the information
15
from
the
D I ( il T A L
oscilloscopi:
I
f
1
i
i
p
p
* .v
I
it------------- I
I E tE
IN T E R F A C E
CARD
r
IJ N IT
4 ---------------------I
I
I
UNDER
VEST
1
L O G IC
A N A L ÏS E R
4-----------------------------
!
fig. 3-1. The Hardware Configuration
U.U.T..
4. Command the instruments to send data to the controller.
5. Check that the correct information was received.
After the controller receives the information from the instruments,
it compares that information with the reference.
3.3. IEEE Interface Card
The intention is to look into automating a test procedure for a
volume product, so
as to reduce costs. This calls for some kind of
computer, a program and some interface to particular pieces of test
equipment needed for this job.
Unfortunately, each piece of test
equipment has a different number
and type of control input, this will require a number
16
of different
in te r fa c e card s in
th e
co m p u ter,
each
w ith a d if f e r e n t so ftw a r e
d r iv e r .
A ll t h i s in t e r f a c i n g i s an o v e r h e a d
o f s p e c if y in g and
w r itin g
t o a c t u a lly d o in g th e r e a l jo b
th e program th a t m a n ip u la te s
th e
test
in str u m e n ts to a u tom ate th e t e s t p r o c e d u r e .
W hat i s r e q u i r e d ,
is
in te r fa c e ca rd s. I t
th at
every
test
in str u m e n t
w o u ld b e p r e f e r a b l e
if
h a v e t h e sam e
c o m m u n ic a tio n
v ia
a
com m on b u s i n t o o n e c a r d i n t h e c o m p u t e r w e r e a v a i l a b l e .
B efo re th e s o lu tio n
is
d e sc r ib e d ,
a
b r ie f
r e v ie w
of
D ig ita l
C o m m u n ica tio n p r i n c i p l e i s g i v e n .
3.3.1 Introduction to Digital Communication
S e r ia l and
p a r a l l e l d a t a t r a n s f e r a r e t h e tw o b a s i c m e th o d s o f
co m m u n ica tin g d i g i t a l in f o r m a tio n
p e r ip h e r a l e q u ip m en t. B o th
th rou gh ou t th e in d u str y
b etw een
tec h n iq u es
and
each
m ic r o p r o c e sso r s
and
in
w id e sp r e a d
use
its
a d v an tages
and
are
has
d isa d v a n ta g e s.
3.3.1.1 Serial Data Transfer
S e r ia l d ata
tra n sfer
is
c o m m o n ly
used
w henever
d ig ita l
in fo r m a tio n m ust be r e la y e d o v e r a r e l a t i v e l y lo n g d i s t a n c e .
The d a ta i s o f t e n t r a n s f e r r e d th r o u g h t h e t e le p h o n e
w ir e s
or over
t h e a ir w a v e s v i a som e fo rm o f r a d i o c a r r i e r .
The m a in r e a s o n
in th e num ber
fo r lo n g -d is ta n c e s e r ia l tr a n s f e r i s th e r e d u c tio n
of
w ir e s
U n fo r tu n a te ly th e sp eed
s e r i a l l y i s n o r m a lly
r e q u ir e d
at
lim ite d
w h ich
to ,
to
carry
th is
at
b i t s p e r s e c o n d o v e r c o m m e r c ia l v o i c e
d a ta can
th e
be
in fo r m a tio n .
tran sferred
p r e s e n t , no m ore th a n 4 ,8 0 0
grade
te le p h o n e
eq u ip m en t.
L ea sed s e r v i c e i s a v a i l a b l e f o r r a t e s o f 9 ,6 0 0 b i t s p e r se c o n d .
17
In th e o r y a
v o ic e
g rad e ch a n n el can c a r r y up to a b o u t 2 0 ,0 0 0 b i t s
p e r s e c o n d . H ig h e r
speed s
are
a tta in a b le
if
sp e c ia l
d ig ita l
c o m m u n ic a tio n s l i n k s a r e l e a s e d from t h e t e l e p h o n e co m p an y.
3.3.1.2. Parallel Data Transfer
P a r a lle l tr a n sm issio n
sp eed o f in fo r m a tio n
is
used fo r sh o rt d ista n c e s
tra n sfer
co m m u n ica tio n i s fo u n d
in
is
new er
c r itic a l.
T h is
ty p es
co m p u ter
of
form
e q u ip m en t w it h t r a n s f e r s p e e d s o f up t o o n e m i l l i o n
s e c o n d . T h is e q u ip m en t
w here
th e
of
d a ta
p e r ip h e r a l
ch a ra cters p er
in c lu d e s p r in te r s , d is k d r iv e r s and v a r io u s
o t h e r form s o f p e r ip h e r a l co m p o n en ts.
3.3.1.3
Asynchronous Serial Data
S e r ia l d a ta
is
tra n sferred
in
e ith e r
th e
asynchronous
or
s y n c h r o n o u s fo rm . In a s y n c h r o n o u s t r a n s m i s s i o n , som e t i m e s r e f e r r e d
to as sta r t-sto p
tr a n sm issio n ,
tr a n s m itte d w ith ea ch
b yte
s t a r t and s to p b i t
of
in fo r m a tio n
for
in te r v a ls
th e
are
purpose
of
s y n c h r o n i z a t i o n . No c l o c k w a v e fo r m i s t r a n s m i t t e d w i t h a s y n c h r o n o u s
d a ta , s in c e th e s t a r t and s to p b i t s a r e u sed fo r s y n c h r o n iz a tio n .
In syn ch ron ou s d a ta tr a n s m is sio n ,
tr a n s m ittin g a sy n c h r o n iz a tio n
la r g e b lo c k o f
d a ta .
In
sy n c h r o n iz a tio n
ch a ra cter
o r tw o,
is
e f f e c t e d by
fo llo w e d
by
a
a d d itio n to th e sync c h a r a c te r s, a c lo c k
w aveform m ust a l s o b e t r a n s m it t e d .
T h erefo re, sy n c h r o n iz a tio n o c cu rs
syn ch ron ou s sy ste m and
fo r
a
b lo c k
fo r each p ie c e o f d a ta in
of
an
d ata
in
a
asynchronous
sy stem .
F ig . 3-2 i l l u s t r a t e s
th e t y p i c a l fo rm a t u s e d f o r t r a n s m it t in g d a ta
a s y n c h r o n o u s ly . E ach p i e c e o f in f o r m a tio n
b it th a t is
is
preceded
a t a lo g ic zero or, by d e fin itio n , a
18
space.
by a s t a r t
T h is
is
STOP
™ 7 ■
1
1
1
I
1
t
1
STOP
h
1
1
H
1
1
L
!
1
1
1
START
1
!
d„
,
1
d
, ;
[
T"
D’ !
D-. !
D,
Dh |
X
!
1
P
1
1
1
f i g . 3 - 2 . A sy n ch ro n o u s S e r i a l D a ta
fo llo w e d by d a ta
b i t s t h a t c o m p r ise t h e in f o r m a tio n t h a t i s a lw a y s
tr a n s m itte d w ith th e le a s t s ig n if ic a n t
b i t f i r s t . The s to p b i t , or
b i t s i n som e o l d e r s y s t e m s , f o l l o w s t h e d a t a a n d
is
a lw a y s a t th e
l o g i c one l e v e l o r , by d e f i n i t i o n , a m ark.
3.3. 1 .4. Baud Rate
The s p e e d a t w h ic h s e r i a l d a t a i s t r a n s f e r r e d i s r e f e r r e d t o a s
i t s baud r a t e . The baud r a t e i s a r r iv e d a t by t a k in g t h e r e c i p r o c a l
o f th e b i t tim e i n t e r v a l f o r m o st a p p l i c a t i o n . R e fe r t o t h e s e c t i o n
o n PSK ( p h a s e s h i f t k e y i n g ) f o r a d i f f e r e n t d e f i n i t i o n o f b a u d r a t e
a s i t a p p l i e s t o t h a t form o f d a t a . F o r e x a m p le , a b i t t i m e o f 9 .0 9
ms w o u l d h a v e
a
ra te
of
1 1 0 b a u d , e x c e p t f o r P SK . I f t h e s e r i a l
m essage c o n s is t s o f a s ta r t b it ,
s y s te m w o rk in g a t
th is
8
d a ta b i t s , and 2 s to p b i t s , a
r a t e w o u ld b e c a p a b le o f
tr a n sfe r r in g
10
b y tes o f d ata per secon d .
T a b l e 3 - 1 i l l u s t r a t e s s o m e c o m m o n ly u s e d b a u d r a t e s , a l o n g w i t h t h e
num ber o f s t o p
b its
and
d a ta b i t s , ty p e o f t r a n s m is s io n , and th e
norm al a p p lic a tio n o f each .
N o te th a t a l l o f th e baud r a t e s l i s t e d
b au d , w h ich
is
used
are
m u ltip le s,
e x c e p t 110
fo r c o m m u n ic a tio n s b e tw e e n e le c t r o m e c h a n ic a l
t e l e t y p e w r i t e r s (w h ic h a r e
q u ic k ly d i s a p p e a r i n g ) . The o n ly sy s te m s
e m p lo y in g 2 s t o p b i t s o r 1 .5 s to p b i t s w ere d e s ig n e d f o r m e c h a n ic a l
d e v i c e s . The e x t r a tim e a llo w e d by
19
a d d itio n a l
sto p s
was r e q u ir e d
i
'
1
Baud
O
o
110
110
600
1200
241)0
4800
9600
Data
Bits
Stop
Bits
5
7 + P*
7 + P
7 + P
7 + P
Variable
Variable
Variable
1.5
2
1
1
1
-
T>pe
Application
Asynchronous
Asynchronous
Asynchronous
Asynchronous
Asynchronous
Synchronous
Synchronous
Synchronous
Baudot TTY
ASCII TTY
FSK MODEM
FSK MODEM
FSK MODEM
PSK MODEM
PSK MODEM
PSK MODEM
NO TE: ’ P = Parity
T T Y = Telet\ new rile r
M O D EM = MOdulLilor DEM odnlatur
t a b l e . 3 - 1 . C o m m o n ly U s e d B a u d R a t e s
fo r m e c h a n ic a l s y n c h r o n iz a tio n
in t h e s e d e v ic e s . A ll o th e r sy ste m s
u se 1 sto p b it .
3.3 .1.5 Synchronous Serial Data
In syn ch ron ou s tr a n s m is sio n ,
d ata
is
tr a n sm itte d
p u ls e s , so i t i s n ot n ec essa ry to send sy n c h r o n iz a tio n
w ith c lo c k
b its
a lo n g
tr a n sm ittin g
sync
w ith th e d a ta , a s w ith th e asyn ch ron o u s sy ste m .
S y n c h r o n iz a tio n can be
a c c o m p lish e d
by
in fo r m a tio n p e r io d ic a lly .
F or ex a m p le, t r a n s f e r r i n g 100 b y t e s
o f in fo r m a tio n by a sy n ch ro n o u s
m eth o d s w o u ld t a k e 1000 b i t t im e s . T h is a ssu m e s t h a t
sto p b it per
b yte
of
d a ta i s b e in g t r a n s m it te d . In a sy n ch ro n o u s
sy stem th a t sen d s 1 syn c b y te b e fo r e
end o f m essage
1 s t a r t and 1
th e s t a r t o f tr a n s m is sio n and
c h a r a c te r a t th e end o f tr a n s m is s io n ,
it
r e q u ir e s
o n ly 816 b i t tim e s .
I f in fo r m a tio n i s
tr a n sm itte d
fo r
any
ex ten d ed
p e r io d o f tim e ,
s y n c h r o n o u s c o m m u n ic a tio n i s o b v i o u s l y m uch m ore e f f i c i e n t .
S in c e t h i s s y n c h r o n o u s co m m u n ica tio n
co m p u ter m a n u fa c tu r e r s h a v e
can
d e v e lo p e d
20
tak e
m any
sta n d a rd
form s;
m any
co m m u n ica tio n s
p r o to c o ls , such as
BISYNC ( b i n a r y s y n c h r o n o u s c o m m u n i c a t i o n s ) , a n d
HDLC ( h i g h - l e v e l d a t a
lin k
Svncronization
Svnc
char
1
c o n tr o l) .
Data
S\ nc
char
Data
b\ le
Data (I
bs te ) )
Data
b\ le
if
3
T
1
Data
bvte
N
Data
b\ te
N
Data
b\ te
N
End
of
transmission
Bisync data format
Opening
address
control
o m in o
8 bits
8 bits
Information N-bits
Error check
closing
16-bit CRC
om ino
H D L C / S D L C data format
f i g . 3 - 3 . Two F o r m s o f S y n c h r o n o u s S e r i a l C o m m u n i c a t i o n s P r o t o c o l s
T h ese ty p e o f p r o t o c o ls a r e i l l u s t r a t e d in f i g . 3 - 3 .
BISYNC
b y te o r ie n te d p r o to c o l;
b it
SDLC
and
HDLC
are
b oth
is
a
o r ie n te d
p r o to c o ls [7 5 ].
3.3.2. The Solution
T he IE E E -4 8 8 p a r a l l e l d a t a t r a n s f e r
th e H e w le tt-P a c k a r d C o r p o r a tio n
sta n d a rd
was d e v e lo p e d by
fo r u se in t h e ir
in stru m en ts.
It
w a s a d o p t e d a s a g e n e r a l p u r p o s e i n s t r u m e n t a t i o n b u s (G P IB ) b y IEEE
in 197 5 . T h is
sta n d a rd
is
lik e
th e
d e fin e s th e p in c o n n e c tio n s, p r o to c o l,
R S -23 2C s t a n d a r d b e c a u s e i t
and
sta n d a rd
m essages fo r
co m m u n ic a tio n s.
T he IE E E -4 88 i n t e r f a c e
bus i s a m eans o f c o n n e c t in g
a
num ber
of
i n s t r u m e n t s t o a com m on i n p u t / o u t p u t p o r t o f a c o m p u t e r .
An 8 l i n e
bus
c a r r ie s
addresses,
in s tr u m e n ts and t h e c o m p u te r . E ach
a d d r esse s a ssig n e d to i t
d a ta
and
in stru m en t
co m m a n d s
has
( u s u a l l y b y m e a n s o f a D IL
21
an
b etw een
address or
sw itc h
on th e
in s tr u m e n t) and can be c a l l e d up by th e co m p u te r.
A fter a c tiv a tio n th e
ad d ressed
in str u m e n t
m ay
e ith e r
send d ata
(ta lk ) o r r e c e iv e d a ta ( l i s t e n ) , b e fo r e b e in g d e - a c t iv a t e d (u n ta lk ,
u n lis t e n ) and th e n e x t in str u m e n t a c t iv a t e d .
An i n s t r u m e n t t h a t c a n s e n d d a t a i s
th a t can r e c e iv e
d a ta
is
r e c e iv e is c a lle d
a
ta lk e r ,
c a lle d a ta lk e r .
L ik e w ise , one
a l i s t e n e r and on e th a t
can
l i s t e n e r . The co m p u ter
send or
is c a lle d th e
c o n tr o lle r .
T h e r e m ay b e
o n ly
one
tim e , a lth o u g h c o n tr o l
a n o th e r . A lso , th e r e
c o n tr o lle r
a c tiv e
on
th e
m ay b e t r a n s f e r r e d f r o m o n e
m ay
be
bus
at
any
c o n tr o lle r
to
o n ly one t a lk e r a c t iv e on th e bus a t
a n y o n e t i m e , a l t h o u g h t h e r e m ay b e m an y l i s t e n e r s i f d e s i r e d .
P h y sic a l ( e le c t r ic a l) lim it a t io n s
are,
u p t o 15 d e v i c e s c o n n e c t e d
t o t h e b u s , w it h no m ore th a n 2 m e te r s b e tw e e n th em
bus le n g th o v e r a ll.
A lso ,
m ore
th an
50%
of
or
20
th e
m eters
in stru m en ts
c o n n e c te d m ust be p ow ered up ev en i f n o t u s e d .
now adays, bus e x te n d e r s e x i s t to b o th
ex te n d th e bus in le n g th and
t o in c r e a s e t h e num ber o f in s t r u m e n t s on t h e b u s .
3.3.3. The IEEE-488 Bus Lines
R e fe r r in g to
fig .
3 -4
th e bus co m p rises a
num ber
of
lin e s
co n n ected to ea ch in stru m en t in tu r n .
The e l e c t r i c a l n a tu r e
of
t h e i n t e r f a c e a t e a c h in s tr u m e n t i s show
i n t h i s f i g u r e . A s a " w i r e OR" f u n c t i o n
is
im p lem e n ted ,
th e
bus
l i n e i s a c t i v e o r t r u e w hen lo w , i . e . a t 0 . 4 v o r l e s s .
When n o t h i n g i s d r i v i n g t h a t p a r t i c u l a r b u s l i n e ,
it
w ill
sit at
ab ou t + 3 .3 v and be rea d a s in a c t iv e or f a l s e .
T h e m axim um b u s
tra n sfer
speed
is
tr a n s fe r s p er seco n d . In a c tu a l f a c t ,
22
supposed
to
be
one m illio n
v e r y few m easurem ent s e t_ u p s
THE IEEE
m
BUS LINES
+5V
DATA
DATA
CONTROLLER
BUS LINE "INACTIVE"
BUS LINE "ACTIVE"
V
B
= + 3 . 3V
BV =
+ 0 .4 V
+5V
+5V
INSTRUMENT 1
INSTRUMENT 2
com e a n y w h e r e n e a r t h i s s p e e d .
R e fe r rin g to f ig .
3 - 5 t h e b u s i s m ad e u p o f 1 6 l i n e s a n d 8 g r o u n d s
m a k in g 24 l i n e s i n a l l .
f i g . 3 - 5 . T h e GPIB B u s L i n e s
I g n o r in g t h e g r o u n d s f o r t h e m ea n tim e ,
th e
16
lin e s
i n t o t h r e e g r o u p s , nam ed t r a n s f e r c o n t r o l l i n e s o r
are d iv id e d
H an d sh ak e,
Bus
M anagem ent l i n e s an d t h e D a ta B us.
The D a ta Bus
c o n sists
of
e i g h t l i n e s c a r r y i n g a l l com m ands, d a t a
and a d d r e s se s b i - d i r e c t i o n a l l y b etw een in s tr u m e n ts and c o n t r o l l e r .
The H an dshake l i n e s a r e m a n ip u la te d
to en su re th a t each 8 b it b yte
i s s u c c e s s f u lly read by th e lis t e n e r .
T he Bus M anagem ent
lin e s
b e t w e e n d a t a , co m m a n d s
and
are
p r im a r ily
ad d resses
on
num ber o f m is c e ll a n e o u s c o n t r o l f u n c t i o n s
used
th e
bus,
d iffe r e n tia te
as w e ll as a
r e g a r d in g th e p a s s in g o f
d a t a , s t a t u s a n d com m an d s t r e a m s b e t w e e n d e v i c e s .
24
to
3.3.3.1. Data Connections
The d a ta
c o n n e c tio n s
l o g i c . In m ost
m ay
be
a p p lic a tio n s
th ese
b id ir e c t io n a l d a ta tr a n s c e iv e r s ,
freq u en cy range o f
th e
because a th r e e -sta te
n etw ork t h a t c h a r g e s
r e d u c tio n in zero
bus.
to
one
sin c e
The
d r iv e r
th e
open
are
or th r e e -sta te
use
a
range
lo w
tim e
is
la b e le d
u sa b le
in c r e a se d
p u llu p
q u ic k ly .
T h is
h ig h e r
d ata
a llo w s
D I01 th r o u g h D I0 8 ,
[76] .
p in num bers a r e i l l u s t r a t e d in f i g . 3 - 6 .
SIQJAL GROUND
ATN GND
SRQ GND
SFC GND
NDAC GND
NRFD GND .
DAV GND
* TWISTED PAIR WITH
SIGNAL CABLE OF SAME NAME.
f i g . 3 - 6 . G PIB I n t e r f a c e C o n n e c t o r P l u g
25
th e
im p ed a n ce
m ore
w h ere D I01 i s t h e l e a s t s i g n i f i c a n t b i t p o s i t i o n
*
*
*
*
*
*
*
th ree-sta te
th ey in c r e a se
c a p a c ita n c e
tr a n sitio n
t r a n s m i s s i o n r a t e s . The d a t a p i n s
lin e s
freq u en cy
co n ta in s
lin e
c o lle c to r
The a c t u a l
3.3.3.2. Handshaking Connections
To e n s u r e
th at
b y t e s p a s s from t a l k e r t o l i s t e n e r ( s ) , a t h r e e
l i n e h a n d s h a k e i s i m p l e m e n t e d w i t h DAV, NDAC a n d N R FD .
DAV
T h e DAV,
or d a ta a v a ila b le ,
is
issu e d
by
th e
ta lk e r
in d ic a te s th e a v a i l a b i l i t y or v a lid it y o f d a ta on
to
th e
d ata
bus c o n n e c tio n s.
NRFD
T h e NRFD
c o n n e c tio n , or n ot ready fo r d a ta p in , i s is s u e d
th e lis t e n e r to in d ic a te s
th e
r e a d in e ss
of
th e
by
d e v ic e or
d e v ic e s co n n ected to th e bus to r e c e iv e d a ta .
NDAC
T h e NDAC, o r n o t d a t a a c c e p t e d ,
in d ic a te s th e
c o n d itio n
is issu e d by
o f a ccep tan ce
by
th e lis te n e r to
th e
d e v ic e s
co n n ected to th e b u s .
T h is
hand shake a llo w s b y te s to
be p a ssed
at
th e
ra te
s lo w e s t l i s t e n e r ca n ta k e th em . The h a n d sh a k e o c c u r s f o r
t r a n s f e r , ir r e s p e c t iv e o f w h eth er th a t tr a n s f e r i s
th a t th e
ev ery b yte
d a ta ,
co m m a n d s
or addresses.
B efore a b y te
is
s e n t from t h e t a l k e r t o t h e l i s t e n e r s , t h e t h r e e
hand sh ake lin e s sh o u ld be in th e s t a t e s g iv e n by t a b le 3 - 2 .
LINE
STATE
DAV
High
Data not available
NRFD
Eigh
Ready for data
NDAC
Low
Data not accepted
MEANING
t a b le 3 - 2 . Q u ie s c e n t S t a t e o f th e H an dshake L in e s
R e f e r r i n g t o f i g . 3 -7 when t h e t a l k e r
i n p u t s NRFD a n d
is
ready to ou tp u t d a ta , i t
NDAC (A, B) a n d , p r o v i d i n g t h e y a r e
26
in
th e
sta te
g iv e n in ta b le
3 -2 ,
it
ou tp u ts
a
b y te o n to th e d ata b u s. A fte r
a llo w in g a few n a n o se co n d s s e t t l i n g
tim e
it
d r iv e s
DAV
l o w (C)
s i g n a l l i n g th a t d a ta i s v a lid on th e b u s.
M e a n w h i l e , t h e l i s t e n e r s a r e l o o k i n g a t DAV, w a i t i n g
lo w a n d , w hen
i t d o e s , t h e y t a k e l o w t h e NRFD l i n e
fo r
i t to go
(D ), s ig n a llin g
t o th e t a lk e r t h a t i t m ust n o t ch an ge i t ' s d a ta .
A t t h e sam e t im e , t h e l i s t e n e r s l a t c h
done so , r e le a s e
th e
a c c e p t e d d a t a . Due
to
NDAC
lin e
in th e d a ta b y te and, h a v in g
(E) s i g n a l l i n g
th a t
th ey
have
t h e p a r t y l i n e n a t u r e o f t h e b u s , NDAC w i l l
n o t go h ig h u n t i l th e s lo w e s t l i s t e n e r h as a c c e p te d th e d a ta .
MEANING
DATA NOT VALID
DATA UALID
DA¥
NRFD
READY FOR DATA
KOI READV FOR DATA
NDAC
DATA ACCEPTED
f i g . 3 - 7 . The H an dshake
O n c e t h e NDAC g o e s h i g h , t h e t a l k e r
p rep are fo r th e
next
t a k i n g DAV h i g h
a g a in
in itia te s
a r e s e t sequence to
b y te t r a n s f e r , i f a n y . T h is
(F )
and
re m o v in g
l i s t e n e r s i n r e s p o n s e t o DAV g o i n g
h ig h ,
d ata
le t
happens
by
it
from th e b u s . The
NDAC
go
lo w
(G ),
s ig n a llin g th a t th ey have not y e t a ccep ted th e su b seq u en t d ata b yte
( b e c a u s e i t h a s n ' t y e t b e e n s e n t ! ! ) a n d t h e y l e t NRFD
go h ig h (H ),
t o s i g n a l t o t h e t a l k e r t h a t t h e y a r e r e a d y f o r (n e w ) d a t a .
27
3.3.3.3 Interface Management Connections
T h e s e c o n n e c t i o n s , IF C , ATN, SRQ, REN, a n d E O I, m a n a g e t h e f l o w
o f i n f o r m a t i o n t h r o u g h t h e G P IB .
IFC
T h e IF C ,
or in te r fa c e c le a r , is issu e d by th e c o n tr o lle r to
i n i t i a l i z e a l l in s t r u m e n t s on t h e b u s t o t h e i r known s t a t e s .
ATN
T h e ATN,
or a tte n tio n , is
issu e d
o n ly by th e c o n tr o lle r to
i n d i c a t e t h a t t h e b y t e o n t h e b u s i s a co m m a n d ,
or
address
and n ot d a ta .
SRQ
T h e SRQ,
o r s e r v ic e r e q u e s t, i s is s u e d b y an y d e v ic e n e e d in g
s e r v i c e from t h e c o n t r o l l e r .
REN
The rem o te
e n a b le
c o n n e c tio n s, i s is s u e d by th e c o n tr o lle r
w hen i t w a n ts r e m o te c o n t r o l o v e r a l l t h e in s t r u m e n t s on t h e
bus.
EOI
T he E O I,
o r end or id e n t if y ,
send
by
th e
ta lk e r w ith th e
l a s t b y te o f a d a ta strea m t o in d ic a t e end o f d a ta .
3.3.4. Addressing
A s a l l i n s t r u m e n t s s h a r e a com m on b u s , t h e r e
o f s e l e c t i n g an
in str u m e n t
from
oth ers
to
m ust
b e a m eth od
m ake i t do s o m e th in g
sp e c ific .
T he IE E E -4 8 8 b u s p r o t o c o l d o e s t h i s
by
a llo w in g th e c o n tr o lle r to
s e n d a n a d d r e s s d ow n t h e b u s b e f o r e s o m e co m m a n d
or
d ata is s e n t.
The a d d r e s se d in str u m e n t r e c o g n iz e s i t s a d d r e s s and p r e p a r e s i t s e l f
f o r som e k in d o f a c t i v i t y .
An a d d r e s s m ay
b e s e n t d o w n t h e b u s b y m a k i n g ATN l o w , a t t h e s a m e
tim e a s t r a n s m it t in g
a
H ex
address
in
th e
range
20
to
3E
(c o r r e sp o n d in g t o a d d r e ss 0 t o 3 0 in d e c im a l) , i f th e in str u m e n t i s
t o b e c o m e a l i s t e n e r . A l t e r n a t i v e l y , m a k i n g ATN l o w
5E w i l l m a k e t h e a d d r e s s e d i n s t r u m e n t a t a l k e r .
28
w i t h H e x 40 t o
In stru m en ts g e n e r a lly have
th e
sam e a d d r e s s f o r t a l k o r l i s t e n a s
s e t b y t h e a d d r e s s s e l e c t i n g D IL
sw itc h ,
or
by
th e
o th e r w ays,
d e p e n d in g on th e in str u m e n t i t s e l f .
F or ex a m p le, s e l e c t i n g
in stru m en t to resp o n d
04
to
on
th e
D IL
address
sw itc h
w ill
cau se
th e
H ex 24 f o r l i s t e n o r H ex 44 f o r
ta lk .
I t s h o u ld b e rem em bered t h a t m ore
th an
one l i s t e n e r can be a c t iv e
on t h e b u s a t any o n e tim e , b u t n o t m ore th a n o n e t a l k e r .
3.3.5. Setting the DIL switch on HP-IB Interface Card
The c o n f i g u r a t i o n s w i t c h e s on t h e H P -IB i n t e r f a c e
card s e t th e
in t e r f a c e 's o p e r a tin g p aram eters.
T h ey a r e s e t a t t h e f a c t o r y a s show n b e lo w f i g . 3 - 8 .
f i g . 3 - 8 . The C o n fig u r a t io n S w itc h e s
T h is s e t t i n g s p e c i f i e s
s e le c t
code
7
(m em o ry a d d r e s s D C 0 0 0 ) a n d
in terr u p t le v e l 3.
A s a p r o c e d u r e t o c h e c k t h e H P -IB
in te r fa c e
card c o n fig u r a tio n , a
c o m p a r is o n h a s b e e n m ade b e tw e e n t h e s w i t c h s e t t i n g
and w ith th o s e
show n
of
th is
card
a b o v e . As t h i s c o n f i g u r a t i o n i s s a t i s f a c t o r y
29
fo r m ost s y s te m s , i t was k ep t a s i t i s .
The a d d r e s s s w itc h e s
s e le c t code o f
(1 t h r o u g h 4) d e t e r m i n e
th ein te r fa c e .
recom m ended s e t t i n g ,
If it
an a d d r e s s
sam e a s t h e a d d r e s s
t h e m em ory a d d r e s s a n d
is
w ish e d
(o r s e l e c t
code)
to
change th e
th a t i s n ' t th e
(or s e l e c t co d e) o f any o t h e r c a r d i n s t a l l e d in
th e sy ste m sh o u ld be ch o se n .
T a b le 3 -3 h e lp
fo r
set
th e
a d d r e ss and s e l e c t
code,
it
show s
a d d r e s s e s u s e d b y s o m e comm on s y s t e m c o m p o n e n t s .
oo
U
Memory Select 1 Switdies
Potential Conflicts
Address Code ! 1 2 3 4
16 I0 0 0 0 Used by VGA and EGA.
1 0 0 0 1 Used by VGA.
C-iOOO
2 0 0 1 0 Used by hard-disk controller on pre-19'5'5 Vectra PC
C8000
■:cooo
3 0 0 1 1
4 0 I 0 0
D0000
5 0 1 0 1
D4000
DSOQO
6 0 1 1 0
DC000
7 0 1 1 1 Recommended setting.*
E0000
3 1 0 0 0 Used by VGA performance setting on Vectra ES
E4000
9 1 0 0 1 Used by VGA performance setting on Vectra ES.
E3000
10 1 0 1 Û Used by VGA performance setting on Vectra ES
ECOOO 11 1 0 1 1 Used by VGA performance setting on Vectra ES.
F0000
12 1 1 0 0 Reserved for system ROM.
13 1 1 0 1 Reserved for system ROM.
F4000
14 1 1 1 0 Reserved for system ROM.
FS000
15 1 1 1 1 Reserved for system ROM.
FC000
* if
-u have more th an one HP-IB interface, only one can use this setting
t a b l e 3 - 3 . The A d d r e ss and S e l e c t Code
The in t e r r u p t s w it c h e s
(5
H P -IB I n t e r f a c e i n t e r r u p t s
a n d 6) d e t e r m i n e t h e l e v e l a t w h i c h t h e
th e
CPU.
fa ctory se ttin g .
30
In terru p t
le v e l
3
is
th e
3.3.6. Connecting Peripherals
An H P - I B
sy stem
can
accom m od a te
up
to
14
p e r ip h e r a ls
in
a d d it io n t o t h e co m p u ter, w h ic h i s th e " c o n t r o lle r " o f t h e s y s te m .
The p e r ip h e r a ls h a v e b een c o n n e c te d
u sin g
(RS
4 8 9 -3 6 8 )
c a b le s 1
m eter lo n g . T hat was done by fo llo w th e fo llo w in g in s t r u c t io n s :
1 . As r e f e r r e d in t h e p e r i p h e r a l m anual t o f i n d o u t
th e p e r ip h e r a l,
its
pow er
c a b le
was
how
co n n ected
t o s e t up
, and i t was
sw itc h e d on (b e fo r e c o n n e c tin g i t to th e c o m p u te r ).
2 . Then i t w as t u r n e d o f f .
3 . A bus a d d ress fo r th e p e r ip h e r a l th a t d oes n o t c o n f lic t w ith th e
a d d r e sse s o f o th e r p e r ip h e r a ls was d e te r m in e d .
E ach p e r ip h e r a l m u st h a v e a u n iq u e
address
(th e
H P - I B Command
L ib r a r y u s e s a d d r e s s 30 f o r t h e c o n t r o l l e r a d d r e s s , s o i t s h o u ld
not be u s e d ).
4. A fte r th a t th e p e r ip h e r a ls w ere c o n n ected .
H ere a r e som e
p o in ts
w h ic h a r e im p o r ta n t w hen c o n n e c t in g
several
p e r ip h e r a ls to th e in te r fa c e :
( 1 ) Up t o 1 4 p e r i p h e r a l s c a n b e c o n n e c t e d t o a s i n g l e i n t e r f a c e .
(2) D e v ic e s ca n b e in t e r c o n n e c t e d in a n y sch em e a s lo n g a s t h e r e i s
an u n b rok en
p ath
b etw een
ea ch p e r ip h e r a l and th e c o n t r o lle r .
S e v e r a l d e v ic e s can be co n n ected
at
one
co n n ector,
or
each
d e v ic e can be co n n ected to th e n e x t .
(3) The t o t a l c a b l e l e n g t h on o n e i n t e r f a c e s h o u ld n o t e x c e e d
2 m eters
(6 f e e t ) t i m e s t h e n u m b e r o f c o n n e c t e d
co m p u ter i s
d e v ic e s
(th e
c o n sid e r e d as one d e v ic e ) and i t sh o u ld n o t e x c e e d
20 m e t e r s ( 6 6 f e e t ) .
For h ig h -sp e e d d a ta t r a n s f e r , th e
le n g th sh o u ld n o t e x c e e d 1 m eter
(3 f e e t ) t i m e s t h e n u m b e r o f d e v i c e s , a n d n o t m o r e
(50 f e e t ) .
31
th an
15 m e t e r s
3.4.
The Digital Oscilloscope
In t h i s
p ro ject
th e
HP
54501A
D ig ita l O sc illo sc o p e , b ecau se i t
o sc illo sc o p e th at is fu lly
is
O sc illo sc o p e
was
used as a
a g en era l purpose, d ig itiz in g
p ro g ra m m a b le a n d t r a n s p o r t a b l e .
e x c e lle n t g en era l purpose d ig it iz in g o s c illo s c o p e
Itis
because
an
of th e
f r i e n d l y u s e r i n t e r f a c e , y e t i t h a s m any s o p h i s t i c a t e d c a p a b i l i t i e s
and m u lt ip le t r ig g e r in g f u n c t io n s .
3.4.1.
Addressing HP 54501A Oscilloscope
The f r o n t
panel
of
th e
(HP
54501A)
is
sep a ra ted in to s ix
f u n c t i o n a l a r e a s , a s show n i n f i g . 3 - 9 .
T h e M en u s S e c t i o n c o n s i s t s
o f n in e k ey s to s e l e c t
from :
* T im eb a se
* C hannel
* T r ig g e r
* D isp la y
* W a v e f o r m M a th
* W aveform S a v e
* D e fin e M easure
* U tilitie s
* D e lta -t/D e lta -v
The D is p la y S e c t i o n c o n t a i n s t h e
v e r t i c a l c o lu m n o n
screen
and
s e l e c t i o n k e y s. In a
th e r ig h t sid e o f th e screen
is
th e
fu n c tio n
d isp la y .
The f u n c t i o n s t h a t a r e d i s p l a y e d a t a n y o n e tim e w i l l c o r r e s p o n d t o
a key in
t h e s e l e c t i o n c o lu m n . T h e s e k e y s ca n s e l e c t a n y a v a i l a b l e
fu n c tio n or f i e l d th a t is d is p la y e d in h a lf r ig h t.
T h e U t i l i t i e s M enu K e y s h o u l d b e p r e s s e d
T h is w i l l g iv e
access
to
t o a d d r e s s t h e HP 5 4 5 0 1 A .
th e c a lib r a t io n and s e r v ic e
32
fu n c tio n s,
f i g . 3 - 9 . T h e F r o n t P a n e l o f t h e (HP 5 4 5 0 1 A )
as w e ll as
setu p
th e
H P -IB
The sub m en u s w h ich a p p e a r a t t h i s tim e i n c l u d e s :
In terface.
(as i l l u s t r a t e d in
f i g . 3-10)
f i g . 3 - 1 0 . T h e S u b m e n u s o f t h e U t i l i t i e s M enu
33
* H P -IB m enu
* S e l f t e s t m enu
* P r o b e c a l m en u
* S e l f c a l m enu
* S e r v i c e m enu
S o i f t h e s e l e c t i o n k e y w h ic h m a tc h e s t h e H P -IB su b m en u i s p r e s s e d ,
i t w il l a llo w
th e
u s e r t o m a k e s e t t i n g s s o t h e HP 5 4 5 0 1 A c a n t a l k
to p e r ip h e r a l d e v ic e s .
As i l l u s t r a t e d in f i g . 3 -1 1 , t h i s i n t e r f a c e i n c l u d e s :
* T a lk o n l y m ode
* A d d r e s s e d m od e
* EOI
* Form f e e d
* P aper le n g th
f i g . 3 - 1 1 . T he H P -IB su b m en u
1 . T a lk o n ly
S et th e
m ode
o sc illo sc o p e
to
ta lk
o n ly
when a h a r d c o p y ,
w ith o u t
i n t e r v e n t i o n from
an
ex te rn a l
c o n tr o lle r ,
is
w ish e d .
The
a tta c h e d p r in t e r m ust b e s e t in th e l i s t e n o n ly o r l i s t e n a lw a y s
m ode.
2 . A d d r e s s e d m ode
T h is m ode a l l o w s a c o n t r o l l i n g d e v i c e t o s e l e c t i v e l y a d d r e s s t h e
HP 5 4 5 0 1 A f o r t a l k i n g o r l i s t e n i n g . T h e a d d r e s s o f t h e HP 5 4 5 0 1 A
can b e s e l e c t e d w h ile th e in str u m e n t i s in th e a d d r e s s e d m ode.
3 . EOI k e y
T h e EOI (E n d o r I d e n t i f y ) k e y
to g g le s
t h i s fu n c tio n on o r o f f .
EOI i s a l i n e o n t h e H P - I B a s s e r t e d w i t h t h e l a s t d a t a b y t e o f a
m essage.
I f t h is fu n c tio n
i s o n , EOI w i l l b e a s s e r t e d b y t h e HP 5 4 5 0 1 A o n
th e la s t b y te o f
each m essage se n t. I f i t i s o f f ,
EOI
w ill not
be a s s e r te d .
T h is f u n c tio n
T he H P -IB
o n ly
w ill
a ffects
accept
any
m essages
s e n t f r o m t h e HP 5 4 5 0 1 A .
of
le g a l
th e
IE E E -4 88
m essage
te r m in a to r s r e g a r d le ss o f th e s e t t in g o f t h i s fu n c tio n .
I E E E - 4 8 8 r e q u i r e s t h a t EOI i s a s s e r t e d . T h e r e f o r e , w i t h EOI o f f ,
t h e HP
54501A
r u le s c o n c e r n in g
w i l l sen d m essages th a t do n o t
E O I.
EOI
sh o u ld
o n ly
be
fo llo w
IE E E -4 88
tu rn ed o f f i f th e
c o n t r o l l e r d o e s n o t d e a l w i t h EOI a p p r o p r i a t e l y .
4 . F orm F e e d k e y a n d P a p e r L e n g t h k e y
A re u s e f u l when t h e o s c i l l o s c o p e i s c o n n e c t e d t o a p r i n t e r .
I n t h i s p r o j e c t t h e a d d r e s s e d m ode
was g iv e n to
th e
o sc illo sc o p e
was
and
s e l e c t e d (as i l l u s t r a t e d in f i g . 3 -1 2 )
35
s e l e c t e d , t h e n a d d r e s s (7)
case
"on" f o r
th e
EOI
was
f i g . 3 - 1 2 . A d d r e s s i n g HP 5 4 5 0 1 A O s c i l l o s c o p e
3.5. The Logic Analyzer
The T e k t r o n ix
1241
was
used
in
th is
p ro ject
as
a
lo g ic
A n a ly z e r , b e c a u se i t i s a p o r ta b le , g e n e r a l p u r p o se, d i g i t a l d e s ig n
and t r o u b le s h o o tin g t o o ls
th a t
1241 L o g ic A n a ly z e r
a l i q u i d c r y s t a l c o l o r s h u t t e r (LCCS) t o
produce a th r e e
uses
c o lo r
o ffe r s sim ila r fea tu re
d isp la y screen ,
ex p a n sio n f e a t u r e th a t
d o u b les
it
a lso
has
th e h e ig h t o f th e
sets.
a
tim in g
The
v e r tic a l
d ia g r a m
tra ces.
Two t y p e s o f
d ata
c o n fig u r e d to m eet
a c q u isitio n
th e
sp e c ific
su p p o r ts h ig h -s p e e d hardw are
a t 1 0 0 MHZ
(1 0
ns)
and
cards
a llo w
th e in str u m e n t t o b e
re q u ir e m e n ts.
The
1240D 1
a n a ly s is w ith 9 a c q u is it io n
card
c h a n n e ls
6 n s g l i t c h d e t e c t i o n . T h e 1 2 4 0 D 2 h a s 18
a c q u i s i t i o n c h a n n e l s a t 50 MHZ a n d
fea tu re.
36
in c lu d e s
a
bus d e m u ltip le x in g
In stru m en t c o n fig u r a tio n s in c lu d e
any
1240D2 a c q u i s i t i o n c a r d s up t o a
c o m b in a tio n
m axim u m
of
fou r
of
1240D1 and
cards.
A 1241
c o n fig u r e d w ith b o th ca rd ty p e s i s an e f f e c t i v e t o o l fo r e v a lu a tin g
h a rd w a re-so ftw a re in te g r a tio n .
The 1241 L o g ic A n a ly z e r p r o v id e t h e f o llo w in g f e a t u r e s :
(1) A c q u i s i t i o n w i t h
one
or
tw o
tim e b a s e s .
A synchronous
or
synchronous s e le c tio n s are a v a ila b le .
(2) P o w e r f u l t r i g g e r i n g w i t h tw o e v e n t r e c o g n i z e r s t h a t c a n b e u s e d
in d e p e n d e n tly o r t o g e t h e r . The g l o b a l e v e n t r e c o g n iz e r t r i g g e r s
on a s i n g l e e v e n t in o n e o r tw o t im e b a s e s . The s e q u e n t i a l e v e n t
r e c o g n iz e r c o n s is t
of
up
to
14
s p e c i f i e s i t s ow n e v e n t a n d a
s e p a r a t e l e v e l s . E ach l e v e l
tr ig g e r ,
w a it,
ju m p , d e l a y , o r
r e se t a c tio n .
(3) D a ta d i s p l a y in s t a t e t a b l e o r t im i n g d ia g r a m f o r m a t s .
(4) S im p le , m e n u - o r ie n t e d
k eyb oard and
a
u ser in te r fa c e fe a tu r in g
a
fro n t-p a n el
d is p la y sc r e e n w ith t o u c h _ s e n s it iv e , o n -sc r e e n
so ftk ey s.
(5) A u t o - a c q u i s i t i o n m ode,
fo r
rep eated
a c q u isitio n s
w ith o u t
m a n u a lly r e s t a r t i n g th e in s tr u m e n t.
(6) E x p a n d a b le a c q u i s i t i o n
m em o r y
d ep th
w ith
a m em ory
c h a in in g
fea tu re.
(7) D a ta s e a r c h an d co m p are f u n c t i o n s .
(8) Non v o l a t i l e
m em o r y
ensures
th a t
c u r r e n t se tu p and a n o th e r s e tu p
of
tw o in s t r u m e n t s e t u p s ( th e
th e
user
c h o ic e ) a re n o t
l o s t w hen p o w er i s t u r n e d o f f .
( 9 ) F u l l p r o g r a m m a b l e ( b y a d d i n g t h e G PIB COMM p a c k
A n a ly z e r .
37
to
th e
L o g ic
3.5.1. Addressing 1241 Logic Analyzer
The o p e r a t io n s
of
th e
1241
L o g ic
th r o u g h m enus d i s p l a y e d on t h e s c r e e n .
A n a ly z e r
U se
th e
are
c o n tr o lle d
MENU
k eys on th e
f r o n t p a n e l t o s e l e c t g e n e r a l m en u g r o u p s , s e l e c t i n d i v i d u a l
th rou gh o n -s c r e e n s o f t
keys.
E ach
so ft
key
is
o u tlin e d
m enus
on th e
sc r e e n and h a s a la b e l d e s c r ib in g i t s fu n c tio n .
T h e m en u g r o u p s a s i l l u s t r a t e d i n
fig .
3 -1 3 , c o n s is t o f fiv e keys
t o s e l e c t from :
* CONFIG
* TRIGGER
* DATA
* EDIT
* U T IL IT Y
G>
P
Ï F
ST A RT
n
i T
ST O P
C
B
n
M
SCROLL
AUTO
0 MENU ^
C O N F IG
cm cm cm
T R IG G E R
d>
Gxnj m
~
■
DATA
E D IT
U T IL IT Y
^
----
«
CURSOR
I
Gu
cm cm cm
cm Gu cm
G L IT C H
D O N ’T C A R I
cm cm cm
f i g . 3 - 1 3 . The F ron t P a n el o f th e 1241 L o g ic A n a ly z e r
38
T h e U T IL IT Y m en u
key
sh o u ld
be p r e s s e d t o a d d r e s s th e 1241 L o g ic
A n a l y z e r . T h i s w i l l g i v e a c c e s s t o t h e STORAGE MEMORY MANAGER m e n u ,
a COMM PORT CONTROL m en u ( i f COMM P a c k
i s i n s t a l l e d ) a n d ROM P a c k
m en u ( i f ROM P a c k i s i n s t a l l e d ) .
S o o n c e t h e COMM P a c k h a s b e e n i n s t a l l e d ,
e n t e r t h e m en u
(a s show n
in f i g . 3 -1 4 ),
b y p r e s s i n g t h e U T IL IT Y k e y , a n d t h e n t h e COMM PORT
CONTROL s o f t k e y .
R E T A IN IN G S P U R S . Snap the han dle on the
pack over these ^nurs to se cu re the p a ck tirm ly
S ecure the p a ck firmly to the 1240 by sn a p p in g
the handle over the retaining spurs
4 3 *1 0.8
f i g . 3 - 1 4 . T h e COMM P a c k i n s t a l l a t i o n
F ig . 3 -1 5 show s
a
ty p ic a l
COMM p o r t
co n tro l
m enu
The p o r t s t a t u s ,
GPIB a d d r e s s , a n d m e s s a g e t e r m i n a t i o n
d isp la y .
ty p e can be
s e l e c t e d b y u s i n g t h e COMM p o r t c o n t r o l m e n u .
* G P IB
port
sta tu s:
V a l i d s e l e c t i o n s a r e ONLINE a n d O FFLIN E ,
i n O FFLIN E , n o c o m m u n i c a t i o n o c c u r s
and 1241,
(b efore
b etw een
th e c o n tr o lle r
c h a n g in g any o th e r p a r a m e te r s,
39
th e
1241
must be
OFFLINE).
When
the
1241
goes
ONLINE,
it sends a
s e r v ic e r e q u e st to th e
•
LOCAL
STORAGE
■
MEMORY
I
MANAGER
1
-
SERUICt; REQUEST
KNOB=SELECT
PORT 1
CQHTPGL 1
G P IB PORT STATUS =
S R M !«
1 2 4 0 ’S GPIB ADDRESS = 611
MESSAGE TERMINATION = I H )
REQUEST
SETUP
UPLOAD
REQUEST
SETUP
DOWNLOAD
REQUEST
REFMEM
DOWNLOAD
REQUEST
REFNEM
UPLOAD
REQUEST
ACQMEM
UPLOAD
f i g . 3 - 1 5 . A T y p i c a l COMM P o r t C o n t r o l M enu D i s p l a y
of
its
ONLINE
sta tu s.
* 1 2 4 1 ' s G PIB A d d r e s s :
V a lid a d d r e sse s a r e 0 -3 0 .
* M essag e T e r m in a tio n :
V a l i d t y p e s a r e E O I, a n d LF OR E O I .
I f EOI i s
se le c te d ,
co n cu rr en t w ith th e
m essages
la st
r e c e p t io n , r e c e iv in g an
t e r m i n a t o r , i f LF
OR
b yte
of
EOI
EOI
are
is
is
c o n c u r r e n t w i t h EOI i s s e n t a s
In t h i s p r o j e c t t h e a d d r e s s (1)
te r m in a te d
th e
th e
m essage.
o n ly
se le c te d ,
a
by
a
se n d in g
D u r in g
r e c o g n iz e d
CR
fo llo w e d
EOI
m essage
m essage
by
LF
m essage te r m in a to r .
was
se le c te d
A n a l y z e r a n d t h e EOI a s a m e s s a g e t e r m i n a t o r .
40
fo r
th e 1241 L o g ic
CHAPTER 4
APPLICATION OF EXPERT SYSTEM
IN DIAGNOSTICS
4.1.
Introduction
D ia g n o sis has
been
co n sid e r e d
sy stem s s o lu tio n s s in c e
s y s te m s . T h is i s
d e fin e d and n o t
because
in
th e
d ia g n o stic
ta sk
w e ll su ite d to expert
sh ort
h isto r y
p r o b lem s
are
of
not
expert
c le a r ly
w e l l s u i t e d t o a lg o r it h m ic s o l u t i o n s . The e m p h a sis
w ith e x p e r t sy stem s
p r o c e d u r e s b u t on
e a r ly
a
has
not
been
on
sp e c ific
p ro b lem
k n o w le d g e a b o u t t h e p r o b le m d o m a in
p roced u res th a t reason
w ith
th is
and
so lv in g
general
k n o w led g e. D ia g n o s t ic t a s k s can
e a s i l y b e r e p r e s e n te d in t h i s form at [ 3 5 ] .
T he m a in c o m p o n e n ts o f d i a g n o s i s ca n b e su m m a riz e d a s f o l l o w s :
Givens
(1) A c a s e o f m a l f u n c t i o n i n g , u n u s u a l 's y m p to m s ';
(2) A s t a n d a r d s e t o f d i a g n o s t i c t e s t s .
Goals
(1) To f i t c a s e i n t o know n ' d i s e a s e , f a u l t ' c l a s s e s ;
(2) To f i n d p r o b a b le c a u s e s o f sym p tom s;
(3) To recom m end t r e a t m e n t m e th o d s .
Constraints
( 1 ) T h e t e s t s m ay b e n u m e r o u s a n d d i f f i c u l t t o s e l e c t ;
( 2 ) T h e t e s t s m ay b e c o s t l y
( in tim e o r m o n e y );
( 3 ) T h e t e s t s m ay b e u n r e l i a b l e .
Operations
(1) D ed u ce p o s s i b l e c a u s e s o f sym p tom s.
41
(2 ) g a t h e r d a t a a b o u t sym p tom s a n d c h a r a c t e r i s t i c s o f t h e c a s e .
(3) C l a s s i f y
p o s s ib le cau ses in to d is e a s e or fa u lt h y p o th eses.
(4) D i s t i n g u i s h c o m p e t in g h y p o t h e s e s .
(5) T ak e a c c o u n t o f t h e i n t e r a c t i o n s o f s e v e r a l c a u s e s .
[52]
4.2. Introduction to Artificial Intelligence
A r tific ia l in te llig e n c e
c a p a b i l i t y , a l l o w i n g th em
g iv e s
to
co m p u ters
e x h ib it
ex tra
c o m p u tin g
m ore i n t e l l i g e n t
b e h a v io r .
I n t e l l i g e n c e , t h e a b i l i t y o f a hum an b e i n g t o a c q u i r e k n o w l e d g e a n d
a p p ly i t , m eans
th e
c a p a b ility
of
th in k in g
c e r ta in d egree, a r t i f i c i a l in te llig e n c e
k n o w l e d g e f r o m h u m an
in p u t,
th en
and r e a s o n in g . To a
a llo w s co m p u ters t o a c c e p t
use
th a t
k n o w led g e
th rou gh
r e a s o n in g p r o c e s s e s t o s o lv e p r o b le m s.
The m a in e le m e n t
of
any
a r tific ia l
k n o w le d g e , an u n d e r s t a n d i n g o f som e
in te llig e n c e
su b ject
a p p lic a tio n is
a r ea o b ta in e d th rou gh
e d u c a t io n o r e x p e r i e n c e . The p r o b le m t h a t t h e co m p u te r
e x p e r ie n c e s or le a r n
as
th e
hu m an
m in d
k n o w l e d g e g i v e n t o i t b y hum an e x p e r t s .
can.
cannot have
So i t can a c q u ir e
T h is k n o w led g e c o n s i s t s o f
f a c t s , p r o ced u res and in fo r m a tio n t h a t h a s b een o r g a n iz e d
i t u n d e r sta n d a b le and
a p p lic a b le
to
p r o b lem
to
m ake
so lv in g or d e c isio n
m a k in g . M ost k n o w le d g e b a s e s t y p i c a l l y c o n c e n t r a t e on som e s p e c i f i c
d o m a in .
A fter b u ild in g th e
k n o w le d g e
base,
a r tific ia l
t e c h n iq u e s w i l l b e u s e d t o g iv e t h e co m p u ter r e a s o n in g
So t h e co m p u ter
w ill
be
a b le
to
th in k ,
reason,
in te llig e n c e
c a p a b ility .
and
reach
c o n c lu s io n s b a s e d on t h e f a c t s c o n t a in e d in t h e k n o w le d g e b a s e .
42
4.2.1. Application of Artificial Intelligence
The a r t i f i c i a l
in te llig e n c e
p r o b le m r e q u ir in g i t s
s p e c ia l
a lg o r ith m ic s o lu tio n ) b ecau se
so ftw a re
can
q u a litie s
(a
be
a d o p ted t o any
p r o b le m
o f th e u n b e lie v a b le
w ith
no
fle x ib ility
of
th e a r t i f i c i a l in t e llig e n c e p r o c e ss.
N o n -n u m e r ic a l p ro b lem s and
p ro b le m s
w ith
o fte n n ot s u ita b le fo r th e a lg o r ith m ic
u n c e r ta in ty
process,
are
w h ich
b oth
are
e a sily
s o lv e d w ith a r t i f i c i a l in t e llig e n c e te c h n iq u e s .
" W ith a l g o r i t h m i c s o f t w a r e , t h e p r o b l e m i s g u a r a n t e e d t o b e s o l v e d ;
w it h A I, t h e r e ca n b e p a r t i a l s o l u t i o n s o r e v e n no s o l u t i o n .
As a r e s u l t ,
AI
often
w o r ld b e t t e r th a n
sh a d e s o f g r a y ."
fits
th e
co n v e n tio n a l
d iso r g a n iz e d ,
so ftw a re
im p e r fe c t
real
b eca u se i t can d e a l w ith
[68]
The m ost im p o r ta n t a p p l i c a t i o n s t o a r t i f i c i a l i n t e l l i g e n c e a r e :
( 1 ) G am es
(2) G e n e r a l P r o b le m S o l v i n g
(3) E x p e r t S y ste m s
(4) N a t u r a l L a n g u a g e P r o c e s s i n g
(5) C o m p u ter V i s i o n
(6) R o b o t ic s
(7) E d u c a tio n
4.3. Expert Systems
The m a jo r u s e o f a r t i f i c i a l i n t e l l i g e n c e
sy ste m s. E xpert sy stem s
th a t act as
in te llig e n t
are
now adays i s in ex p ert
th e a r t if ic ia l in te llig e n c e
a d v iso r s
or
s t o r e d k n o w le d g e i n a s p e c i f i c d o m a in ,
c o n su lta n ts.
43
u sin g th e
a n o n -e x p e r t u s e r can s o lv e
p r o b le m s and m ake d e c i s i o n s i n a s u b j e c t a r e a n e a r l y
ex p ert.
By
program s
a s w e l l a s an
An e x p e r t s y s t e m
m ore e x p e r t s t o
p er m its
be
th e
ca p tu red
k n o w led g e
and
and e x p e r ie n c e o f one or
sto red
in
a
co m p u ter.
k n o w le d g e ca n th e n b e u s e d b y a n y o n e r e q u i r i n g i t .
an e x p e r t sy s te m
is
The
T h is
purpose o f
n o t t o r e p l a c e t h e e x p e r t s , b u t t o m ake t h e i r
k n o w led g e and e x p e r ie n c e
m ore
w id e ly
a v a ila b le .
So
th e
expert
sy stem p e r m its n o n -e x p e r t u s e r s to in c r e a s e t h e i r p r o d u c t iv it y
and
s o l v e p r o b le m s when an e x p e r t i s n o t a v a i l a b l e .
An e x p e r t s y s t e m
c o n sists
of
t h r e e m a jo r c o m p o n e n ts: a k n o w le d g e
b a s e , an in f e r e n c e e n g in e , and a u s e r i n t e r f a c e .
The k n o w led g e b a s e c o n t a in s a l l th e
fa cts
and id e a s o f a s p e c i f i c
d o m a in . T he i n f e r e n c e e n g i n e a n a l y z e s t h e k n o w le d g e a n d e x t r a c t s
c o n c l u s i o n s from i t .
w ith th e u se r
and
The
p e r m its
u s e r i n t e r f a c e im p le m e n ts
new
k n o w le d g e
c o m m u n ic a tio n
to be e n te r e d in to th e
k n o w le d g e b a s e .
To u s e an
e x p e r t sy stem , th e u s e r
sta rts
up
th e
expert
sy stem
s o ftw a r e . The e x p e r t sy ste m th e n a sk s th e u s e r v a r io u s q u e s t io n s to
c o l l e c t som e i n i t i a l in f o r m a t io n a b o u t t h e p r o b le m
The u s e r ca n
key
in
th e
to
be
so lv e d .
in f o r m a t i o n r e q u e s t e d o r s e l e c t i t from
a l t e r n a t i v e s p r e s e n t e d i n m en u f o r m . O n c e t h e e x p e r t s y s t e m h a s t h e
in p u t i t n e e d s, i t s t a r t s s e a r c h in g
for
a s o lu t io n and r e a c h in g a
c o n c lu sio n .
U su a lly u s e r s do n o t t r u s t e x p e r t sy stem s so th e y
d ir e c t
th em
to
e x p la in t h e p r o c e s s by w h ic h t h e c o n c lu s io n w as r e a c h e d .
An e x p e r t s y s t e m
can
be
created
to
r e p a ir a c o m p le x d e v i c e s . The v a r io u s
g iv e n to an
h e lp u s e r s tr o u b le s h o o t and
t r o u b l e s a n d sym p tom s c a n b e
e x p e r t sy ste m w h ich th e n i d e n t i f i e s
th e
p r o b lem
and
su g g ests th e so lu tio n .
E xpert sy ste m s a ls o can be u sed t o a id in d ia g n o s in g m e d ic a l c a s e s .
S y m p to m s a n d t e s t
r e su lts
ca n b e g iv e n t o t h e e x p e r t s y s te m w h ich
44
th e n s e a r c h e s i t s k n o w led g e b a s e in an a tte m p t t o m a tch t h e s e in p u t
c o n d itio n s w ith a
p a r t ic u la r d is e a s e . T h is r e s u l t s in a c o n c lu s io n
a b o u t t h e i l l n e s s an d som e p o s s i b l e s u g g e s t i o n s o n how t o t r e a t i t .
S uch an e x p e r t
sy stem
d o e sn 't r e p la c e
d o cto rs,
but
h e lp s
th em
c o n f i r m t h e i r ow n d e c i s i o n s .
E xpert sy stem s have
been
used
to
h e lp
lo c a te o il
and
m in e r a l
d e p o sits.
4.3.1. Widely Used Expert Systems
T here a re
few
num ber
of
expert
o p e r a tio n th e y r e p r e s e n t j u s t a sm a ll
sy stem s
a v a ila b le
p ercen ta g e
of
in te llig e n c e
d e v e lo p m e n t.
So
in
a l l co m p u ter
s o f t w a r e i n u s e . S om e o f t h e s e e x p e r t s y s t e m s p l a y e d
p a r t in a r t i f i c i a l
now
an
im p o r ta n t
th ey
m ake g o o d
m o d e ls f o r s tu d y in g th e s t r u c t u r e o f an e x p e r t s y s te m .
MYCIN
MYCIN i s p r o b a b l y t h e b e s t k n ow n
was d e sig n e d by
Edward
m id -1 9 7 0 s . I t i s
a
o f a l l th e ex p ert sy stem s. I t
S h o r t liff e o f S ta n fo rd U n iv e r sity
in
th e
m e d ic a l e x p e r t sy stem th a t d ia g n o s e s b a c t e r ia l
in fe c tio n s [47 ].
DENDRAL
DENDRAL i s a n o t h e r e a r l y e x p e r t
re se a rch ers a t S tan ford
U n iv e r sity .
sy stem
DENDRAL
it
is
was
a
product
d e v e lo p e d
of
to
i d e n t i f y t h e m o le c u la r s t r u c t u r e o f unknown com pounds [ 5 4 ] .
XCON and XSEL
XCON i s
an
expert
s y s te m t h a t h e lp s c o n f ig u r e l a r g e co m p u ter
s y s te m s . D e v e lo p e d j o i n t l y by D i g i t a l
and r e se a r c h e r s a t
C a r n e g ie
t r a n s la t e a c u sto m e r 's
order
E q u ip m en t
C o r p o r a t i o n (DEC)
M e l l o n U n i v e r s i t y (CM U),
XCON
h e lp s
f o r a DEC VAX 1 1 / 7 8 0 s e r i e s c o m p u t e r
sy ste m in t o co m p le te f i n a l sy ste m s p e c i f i c a t i o n s .
45
XSEL i s a n o t h e r DEC-CMU e x p e r t s y s t e m w i t h k n o w l e d g e o f VAX l l \ / 7 8 0
c o m p u t e r s y s t e m s . XSEL
was
d esig n e d
to
h e lp
DEC
s a le s person s
s e l e c t c o m p o n e n t s f o r a VAX s y s t e m .
Prospector
P ro sp ec to r i s an e x p ert sy stem th a t h e lp s g e o lo g is t s lo c a te o re
d e p o sits.
T h is e x p e r t
sy stem a n a ly z e s
t r a n s is t o r s , d io d e s , and
e le c tr o n ic
r e sisto r s.
c ir c u its
A sc h e m a tic
c o n sist
d ia g ra m
of
of
th e
c i r c u i t i s e n t e r e d i n t o t h e c o m p u t e r a n d EL a n a l y z e s i t .
SOPHIE
SOPHIE w a s
d e sig n e d
to
h e lp
e l e c t r o n i c c i r c u i t s . The s y s te m
stu d en ts
p resen ts
a
le a r n to tr o u b le sh o o t
sim u la te d
c i r c u i t an d a p ro b lem , th e n p e r m its t h e s t u d e n t t o
e le c tr o n ic
tr o u b le sh o o t i t
[36] .
DELTA
DELTA w a s
D e v elo p ed
m a in te n a n c e p e r s o n n e l in
b y t h e G e n e r a l E l e c t r i c Com pany t o a s s i s t
lo c a tin g
p ro b le m s
in
d ie se l
e le c tr ic
lo c o m o tiv e e n g in e s .
POLIO
T h is i s an e x p e r t sy ste m t h a t h e lp s s t o c k b r o k e r s
in
h a n d lin g
in v e stm en ts fo r t h e ir c l i e n t s .
VP-Expert
V P -E x p ert r e p r e s e n ts
th e f i r s t lo w -c o s t e x p e r t sy ste m program .
For t h e f i r s t tim e , p e r s o n a l co m p u ter
e x p e r t sy s te m s on
th e ir
ow n
w ith
ow ners
can d e v e lo p p o w erfu l
l i t t l e or no
k n o w le d g e
of
a
s p e c i a l p ro g ra m m in g la n g u a g e .
V P -E x p ert ca n c r e a t e
e x p e r t sy stem s fo r p r o v id in g a d v ic e fo r le g a l
c o n s u lt a t io n , f in a n c ia l p la n n in g ,
m e d ic a l d ia g n o s e s , o r e l e c t r o n ic
46
fa u lt d ia g n o sis [6 5 ],
[6 6 ].
4.3.2. Advantages o f Expert Systems
The p r e v i o u s
p ro g ra m s p o i n t o u t som e o f t h e m a in a d v a n t a g e s o f
e x p e r t s y s te m s . L ik e o th e r c o n v e n t io n a l
so ftw a re,
expert
sy stem s
o f f e r som e a d v a n t a g e s a s f o l l o w i n g :
(1) P e r m it n o n _ e x p e r t s t o d o t h e w o rk o f e x p e r t s .
(2) Im p rove p r o d u c t i v i t y b y im p r o v in g e f f i c i e n c y .
(3) S a v e tim e i n a c c o m p lis h in g a s p e c i f i c o b j e c t i v e .
(4) S i m p l i f y som e o p e r a t i o n s .
(5) A u to m a te r e p e t i t i v e , o r c o m p le x p r o c e s s e s .
E xpert sy stem s o f f e r
som e a d d i t i o n a l a d v a n t a g e s o v e r
c o n v e n tio n a l
so ftw a re, such a s:
(1) P e r m it new k in d s o f p r o b le m s t o b e s o l v e d .
(2) C a p tu r e an d s t o r e v a l u a b l e k n o w le d g e t h a t m ig h t b e l o s t d u e
to th e r e s ig n a tio n , r e tir e m e n t, or d ea th o f an e x p e r t.
( 3 ) M ake e x p e r t k n o w l e d g e a v a i l a b l e t o a w i d e r u s e r s .
4.3.3. Disadvantages of Expert Systems
The d i s a d v a n t a g e s o f e x p e r t s y s t e m s a r e su m m a riz ed a s f o l l o w :
(1) E x p e r t s y s t e m s a r e e x p e n s i v e .
(2) I t
is
v e r y d i f f i c u l t to d e v e lo p an e x p e r t sy ste m and hard
to fin d good ex p erts.
(3) M o st e x p e r t s y s t e m s s t i l l
m ust
be
im p le m e n te d
on
a b ig
th e
user
m a in fra m e o r m in ic o m p u te r .
(4) E x p e r t
sy stem s
a r e n o t 100% r e l i a b l e . S o
th at
s h o u ld a lw a y s p r o v id e th e f i n a l ju d g m en t.
T hese d isa d v a n ta g e s a re s i g n i f i c a n t b u t c e r t a in ly n o t im p o s s ib le to
overcom e.
47
4.3.4.
Expert System's Type
T here a re
tw o
b a sic
ty p e s o f e x p e r t sy ste m s: th e sta n d _ a lo n e
s y s te m and th e em bedded t y p e .
(1) S t a n d - A lo n e s y s te m
In t h i s c a s e th e co m p u ter
program , w h ile
is
it
to ta lly
d e d ic a te d
is
to
th a t
ru n n in g
it.
(2) Em bedded s y s t e m
T h is program
F ir s t, th e
is
ju s t a p o r tio n o f a n o th e r la r g e r program .
e x p e r t sy stem
is
b u ilt
in to
an
a lg o r ith m ic
program . T h is i s i l l u s t r a t e d in f i g . 4 -1 A .
S econd, an
a lg o r ith m ic
program i s b u i l t
in to
an
expert
s y ste m . T h is i s i l l u s t r a t e d in f i g . 4 -1 B .
fft) COMPUTER MEMORY
<B> MEMORY
ALGORITHMIC
PROGRAM
EXPERT SYSTEM
EMBEDDED
EXPERT
i
EMBEDDED
i Ai/iOS* fUMifJ
I SUBROUTINE
I
SYSTEM
---------
I___________
f i g . 4 - 1 . T y p es o f Em bedded S y s te m s
V P -E x p ert i s a
r e a l ex a m p le o f t h e em bedded s y s t e m . I t l i n k s t o an
e x te r n a l so ftw a re package such as
a
TURBO
C.
s y s te m . D u r in g t h e
i n f e r e n c i n g p r o c e s s , t h e V P - E x p e r t s y s t e m m ay r e a c h
d a t a i n TURBO
C.
to
get
enough
W h ile t h e s e p ro gram s a r e n o t r e a l l y
sam e. T hey u s u a lly
k n o w led g e
to reach a s o lu tio n .
em bedded,
s h a r e m em o r y w i t h t h e e x p e r t
program lin k s to i t .
48
o u t and a c c e s s
th e
effect
sy stem
and
is th e
have
4.3.5.
Expert System Architecture
An e x p e r t
sy stem
is
sim p ly
co m p on en ts t h a t p e r m its an e x p e r t ' s
an
arrangem ent
of
so ftw a re
k n o w le d g e t o b e u s e d by o t h e r s
f o r p r o b le m s o l v i n g a n d d e c i s i o n m a k in g i n a s p e c i f i c d o m a in .
T he m a in c o m p o n e n ts o f a n e x p e r t s y s t e m a r e t h e k n o w le d g e b a s e , t h e
in fe r e n c e e n g in e , th e d a ta b a se , and th e u s e r i n t e r f a c e .
b lo c k d ia g ra m i s
A general
show n in f i g . 4 - 2 . E ach o f t h e s e e le m e n t s w i l l b e
e x p la in e d in th e fo llo w in g s e c t io n s .
DATA BASE
(WORKING MEMORV)
KNOWLEDGE BASE
V“
5
INFERENCE ENGINE
7T-----I
USER
INTERFACE
/
f
I
\
USER
W
I
f i g . 4 - 2 . A G e n e r a l B lo c k D ia g ra m o f a n E x p e r t S y s te m
4 .3.5.1.
The K n o w l e d g e b a s e
The k n o w le d g e b a s e i s t h e h e a r t o f a n y e x p e r t s y s t e m . T h ere a r e
d i f f e r e n t w ays f o r r e p r e s e n t in g k n o w le d g e in e x p e r t s y s te m , s u c h a s
fra m es, se m a n tic n etw o rk s, and p r o d u c tio n r u l e s . I t
is proved th a t
p r o d u c tio n r u le s i s th e b e s t way f o r r e p r e s e n t in g k n o w le d g e .
" It h as b een d ete r m in e d th ro u g h c o n s id e r a b le e x p e r ie n c e th a t on e o f
t h e b e s t m eth od s
o f k n o w led g e r e p r e s e n t a t i o n f o r e x p e r t s y s te m s i s
49
p r o d u c t io n r u l e s . M ost
c o m m e r c ia l
and e x p e r im e n ta l e x p e r t sy ste m s
u s e t h e p o p u l a r IF_TH E N r u l e s f o r m a t . "
[68]
Production Rules
P r o d u c tio n r u le s a r e g e n e r a lly
easy
to w r ite , and i t i s q u ic k
t o b u i l t t h e d e s i r e d k n o w led g e b a s e .
R u le s i s f o r m a tte d i n t o tw o p a r t s . The f i r s t , t h e l e f t - h a n d s i d e o f
th e r u le ,
(IF ) p a r t , s t a t e s som e p r e m is e o r c o n d i t i o n .
th e r ig h t-h a n d s id e
of
a
p r o d u c tio n
c o n c lu sio n or a c tio n th a t w ill ta k e
r u le ,
(THEN) p a r t , s t a t e s a
p la c e i f th e c o n d itio n s on th e
l e f t - h a n d s i d e o f t h e r u l e h a v e b e e n m e t . W hen t h e
o f th e r u le
is
im p lem e n ted ,
The s e c o n d ,
th e
r ig h t-h a n d s id e
r u le i s s a id t o b e f i r e d . As an
e x a m p le o f r e p r e s e n t i n g k n o w le d g e b y u s i n g p r o d u c t i o n r u l e :
IF
th e p a tie n t has headache
THEN
t h e p a t i e n t n e e d s a s p i r i n , CF .7
E ach r u l e i s m ade up o f c l a u s e s .
T here
is
one
IF c l a u s e an d o n e
THEN c l a u s e t o e v e r y r u l e . T h e I F p a r t o f t h e r u l e m ay c o n t a i n m o r e
th a n o n e c l a u s e . T h e se a r e c a l l e d com pound c l a u s e s ,
and
th ey
are
l i n k e d b y AND o r OR.
The c e r t a i n t y f a c t o r
(CF)
is
a
num ber
b etw een
0
and
1
th at
in d ic a te s th e c o n fid e n c e in th e v a lid it y o f th e c o n c lu s io n .
W h ile e a c h p r o d u c t io n
r u le
rep resen ts
an
in d iv id u a l
r e l a t e d t o m any o t h e r r u l e s .
p ie c e
The
of
k n o w led g e, i t i s
u su a lly
r u le s
lin k to g eth er to
e s t a b l i s h a l i n e o f r e a s o n in g . T h is c o l l e c t i o n o f
r u l e s w i l l form t h e k n o w le d g e b a s e .
F in a lly , w ith p r o d u c tio n r u le s i t
is
v e r y e a s y t o m o d ify o r add a
new k n o w le d g e t o t h e k n o w le d g e b a s e .
4.3.5.2. The Data Base
The d a ta b a s e c o n t a in s a b ro a d r a n g e o f in fo r m a tio n
50
about
th e
current sta tu s o f
th e
w o r k i n g m em o r y w h e r e
p rocess is sto red .
p r o b le m
b e in g
th e cu rren t
A lso
th e
so lv e d .
sta tu s
of
I t is a p o r tio n o f
th e
d ata b ase reco rd s
p r o b le m -so lv in g
fa cts
about
th e
p ro b lem . I n i t i a l l y , th e
K nown f a c t s a r e s t o r e d t h e r e . T h e n t h e n e w
f a c t s , w h ich p ic k e d
from t h e
up
in fe r e n c e
process,
The i n i t i a l c o n d i t i o n s o f t h e p r o b le m t o b e s o l v e d
are
added.
are a ls o sto red
in th e d a ta b a s e .
U su a lly , th e e x p e r t
s y s te m a s k s t h e u s e r f o r som e b e g in n in g i n p u t .
T h is in fo r m a tio n g i v e s th e e x p e r t
sy stem a s t a r t in g p o in t to b e g in
th e search p r o c e ss.
The i n f e r e n c e e n g in e b e g in s i t s s e a r c h , m a tc h in g
th e
k n o w led g e b a s e a g a i n s t
th e
th e
in fo r m a tio n
in
r u le s in th e
d ata
base.
4.3.5.3. The Inference Engine
The i n f e r e n c e e n g in e i s s o f t w a r e
th a t
im p le m e n ts a s e a r c h and
p a tte r n _ m a tc h in g o p e r a t io n . I t e x a m in es th e r u l e s
seq u en ce lo o k in g fo r
g iv e n in th e
in
a p a r tic u la r
m atch es t o th e i n i t i a l and c u r r e n t c o n d it io n s
d a ta b a s e . As r u l e s
m a tc h in g
th ese
c o n d itio n s
are
fou n d , th e r u le s a r e f ir e d .
As t h e r u l e s c o n t i n u e t o f i r e , t h e y w i l l r e f e r e n c e
form a n i n f e r e n c e
c h a in .
E ach
on e a n o th e r and
t im e a new r u l e i s e x a m in e d , i t i s
checked a g a in st th e cu rren t s ta tu s
of
t h e p ro b lem s o l u t i o n s t o r e d
i n t h e d a t a b a s e . T h e f i r i n g o f a p a r t i c u l a r r u l e m ay a d d n e w f a c t s
to th e d ata
base.
in fo r m a tio n t o go
T h is
g iv e s
th e
in fe r e n c e
e n g in e
a d d itio n a l
o n . T h is p r o c e s s c o n t in u e s u n t i l t h e s o l u t i o n i s
fou n d .
The i n f e r e n c e e n g in e ca n t a k e tw o b a s i c a p p r o a c h e s t o s e a r c h f o r an
a n sw er. T h ese a r e forw ard and backw ard c h a in in g .
51
Forward Chaining
In t h i s
c a s e , th e in f e r e n c e e n g in e a tte m p ts t o m atch a f a c t in
th e d a ta b a se to th e s itu a tio n s ta te d
in
th e IP p a r t o f th e r u le .
O nce a f a c t h a s b e e n m a tc h e d , t h e r u l e i s f i r e d . The
a c tio n sta te d
c o u ld p r o d u c e a new f a c t t h a t i s s t o r e d i n t h e k n o w le d g e b a s e . T h is
n e w f a c t m ay
th en be u sed to se a r c h o u t th e n e x t a p p r o p r ia te r u le .
T h is s e a r c h in g and
m a tch in g
process
c o n tin u e s
u n til
a
fin a l
c o n c lu sio n r u le is fir e d .
Backward Chaining
In t h i s c a s e , th e in fe r e n c e e n g in e s t a r t s w ith
in th e d a ta
th e
b a s e . T h e n i t b e g i n s e x a m i n i n g t h e THEN p a r t s o f r u l e s
lo o k in g f o r a m a tc h . The i n f e r e n c e
e n g in e s e a r c h e s fo r e v id e n c e to
su p p o r t th e h y p o t h e s is o r i g i n a l l y s t a t e d . I f a m atch
d ata b a se is
i s fo u n d , th e
u p d a ted r e c o r d in g th e c o n d it io n s t h a t th e r u le s t a t e d
a s n e c e s s a r y fo r su p p o r tin g th e m atch ed
p r o c e ss c o n tin u e s w ith
s id e o f th e
h y p o th e sis
r u le
c o n c lu sio n .
th e sy stem a tte m p tin g to
a g a in st
th e
current
c o r r e s p o n d in g IP s i d e s o f th e r u l e s
m atch ed
The
m atch
sy ste m 's
are
new in t e r m e d ia t e h y p o t h e s is w h ic h a r e r e c o r d e d in
c h a in in g
th e
r ig h t
sta tu s.
The
u sed to g en era te
th e
d a ta
base.
The backw ard c h a in in g c o n t in u e s u n t i l th e h y p o t h e s is i s p r o v e d .
4.3.5.4. User Interface
The u s e r
in te r fa c e
is
a p ie c e o f so ftw a re th a t le t s th e u ser
co m m u n ica te w i t h t h e s y s t e m . I t
asks
ch o ic e s fo r e n te r in g
in itia l
p r o v id e s a m enus
of
c o m m u n ica tin g
has b een fou n d .
Any
in te r m e d ia te
q u e stio n s
in fo r m a tio n
or
in th e
p r e s e n t s m enu
d ata
base.
It
th e answ er o r s o lu t io n on ce i t
c o m m u n ic a tio n s
d u r in g
th e
p r o b le m _ so lv in g p r o c e s s a re ta k en c a r e o f by th e u s e r in t e r f a c e .
The c l a u s e s u s e d in th e r u l e s a r e u s e d a s o u t p u t s w it h
52
a p p r o p r ia te
p r e f a c e s i n s i m p l e s y s t e m s . Som e e x p e r t s y s t e m s a l s o , a s V P - E x p e r t ,
can in c lu d e b lo c k s
of
t e x t w ith ea ch r u le and a t th e b e g in n in g or
th e end o f th e e x p e r t sy stem . T hese
a r e u sed to p r o v id e a d d itio n a l
in fo r m a tio n o r e x p la n a tio n s .
4.3.6. Expart System Features
E xp ert sy stem s
are
fe a tu r e s . T h ese in c lu d e
m ore u s e f u l i f t h e y h a v e
an
e x p la n a tio n
som e
a d d itio n a l
fa c ility ,
ease
of
m o d ific a tio n , t r a n s p o r t a b ilit y , and a d a p tiv e le a r n in g a b i l i t y .
4.3.6.1. Explanation Facility
U s u a lly th e f i r s t tim e u s e r s o f th e e x p e r t s y ste m a r e s u r p r is e d
a t how q u i c k l y i t com es up w it h a
b e lie v e i t . U sers
fr e q u e n tly
sy stem a r r iv e d a t
th a t
c o n c lu sio n .
want
answ er.
T hey
t o know j u s t
c le a r ly d o n 't
how
th e
expert
M ost o f th e e x p e r t s y s te m s h a v e a
m eans f o r e x p l a i n i n g t h e i r c o n c l u s i o n .
T y p ic a lly ,
th is
ta k es th e
form o f sh o w in g t h e r u l e s in v o lv e d in t h e d e c i s i o n a n d t h e s e q u e n c e
in w h ic h t h e y w e re f i r e d .
W hen u s e r s w a n t t o k n o w t h e e x p e r t s y s t e m ' s l i n e o f r e a s o n i n g , t h e y
can rea d th e r u le s and f o llo w th e l o g ic th e m s e lv e s .
The e x p la n a t io n f a c i l i t y
i s im p o r ta n t b e c a u s e i t
h e lp s
th e
user
f e e l m ore c o m fo r ta b le w ith t h e o u tc o m e .
V P_E xpert h as v e r y
p ow erfu l
e x p la n a tio n
f a c i l i t y . T hese in c lu d e :
BECAUSE, HOW?, WHY?.
BECAUSE
The b e c a u s e keyw ord a p p e a r s in
th e
r u le
b a s e . I t p r o v id e s an
e x p la n a tio n o f th e e x p e r t s y s te m 's r u le s d u r in g e x e c u t io n .
u s add r e a so n s
It le ts
to th e r u le s in a r u le b a s e . T hese r e a so n s d e s c r ib e
how t h e r u l e w o r k s a n d w hy t h e r u l e
53
r e q u i r e s s p e c i f i c a n s w e r s from
the user.
HOW?
T h e HOW?
com m and l e t s u s a s k h o w V P - E x p e r t a s s i g n e d a s p e c i f i c
v a lu e t o a v a r ia b le . I f V P -E x p ert a s s ig n e d th e v a lu e t o a v a r ia b le ,
t h e HOW? co m m a n d d i s p l a y s t h e BECAUSE
tex t.
If
th e r u le d oes n ot
c o n t a i n a BECAUSE k e y w o r d a n d t e x t , V P - E x p e r t d i s p l a y s t h e r u l e .
WHY?
T h e WHY?
com m and
l e t s u s a sk V P -E x p ert why
s p e c if ic q u e stio n . I f
th e
r u le
c o n ta in s
t e x t , V P - E x p e r t d i s p l a y s t h e BECAUSE
it
is
a sk in g
a
t h e BECAUSE k e y w o r d a n d
tex t.
If
th e
r u le does not
c o n t a i n t h e BECAUSE k e y w o r d , V P - E x p e r t d i s p l a y s t h e r u l e .
[65]
4.3.6.2. Ease Of Modification
In d o m a in s w h ere r a p id c h a n g e s t a k e p l a c e , i t i s im p o r ta n t t h a t
som e m ea n s b e
p r o v id e d
k n o w le d g e. I f th e
fo r q u ic k ly and e a s i l y in c o r p o r a tin g
expert
sy stem
d e v elo p m e n t t o o l s , i t i s a s im p le
was d e v e lo p e d
m atter
to
u sin g
th is
m odern
m o d ify t h e k n o w led g e
b a s e b y w r i t i n g new r u l e s o r r e m o v in g r u l e s .
4.3.6.3
Transportabi1ity
The w id e r t h e a v a i l a b i l i t y o f an e x p e r t s y s te m
it w ill be.
The
m ore
d iffe r e n t
th e m ore u s e f u l
ty p e s o f co m p u ters f o r w h ic h th e
e x p e r t s y ste m i s a v a i l a b l e , th e m ore
w id e ly
th e
e x p e r t is e can be
used.
4.3.6.4 Adaptive Learning Ability
T h is i s a n a d v a n c e d f e a t u r e o f som e e x p e r t s y s t e m s
them t o l e a r n
from
th e ir
o p era ted , th e in fe r e n c e
ow n
e n g in e
th a t a llo w s
u s e . As t h e e x p e r t s y s te m i s b e in g
w ill
54
draw
c o n c lu sio n s
th a t
can
p r o d u c e new k n o w le d g e .
T h is new k n o w le d g e i s s t o r e d t e m p o r a r ily in
t h e d a t a b a s e , b u t i n som e s y s t e m s t h e y c a n l e a d t o t h e c r e a t i o n o f
a new r u l e w h ic h ca n b e s t o r e d in t h e k n o w le d g e b a s e an d u s e d a g a in
in a f u t u r e p r o b lem .
4.3.7. Uncertainty
E xpert sy stem s
has
th e
a b ility
to
deal
w ith
u n c e r ta in
in f o r m a t io n . I f an e x p e r t s y s te m , in c o l l e c t i n g i t s i n i t i a l in p u t s ,
a s k a q u e s t io n f o r w h ic h t h e u s e r d o e s n o t h a s a n sw e r , t h e u s e r ca n
s im p ly sa y t h a t h e d o e s n o t know. E x p ert sy s te m s
are
d e sig n e d
to
d e a l w ith in p u ts su ch a s t h i s .
T h ere a r e s e v e r a l m eth od s o f d e a lin g w it h u n c e r t a in in f o r m a tio n . In
r u le based ex p ert
sy ste m s,
n u m e r ic a l
p r o b a b ility o f c o n c lu sio n are u sed
T h ese n u m e r ic a l f a c t o r s
are
as
known
fa cto rs
a
as
in d ic a tin g
th e
m easure fo r u n c e r ta in ty .
c e r ta in ty
fa cto rs
(C F ).
4.3.8. Fuzzy Logic
Fuzzy lo g ic
is
a n o th er
m eth od
k n o w le d g e . I t i s a s y s te m c o n c e iv e d
Z adeh f o r d e a lin g
of
by
d e a lin g
co m p u ter
in u n r e lia b le in fo r m a tio n . In
w ith
u n c e r ta in
s c ie n tist
th is
L o tfi
m eth od ,
an
a t t e m p t i s m ade t o a s s i g n n u m e r ic a l r a n g e s w i t h a p o s s i b i l i t y v a l u e
b etw een ze ro and one to c o n c e p ts su ch a s t a l l , good , h o t, and o th e r
e le m en ts w ith v a lu e s th a t a r e h ard to d e te r m in e .
[82]
4.3.9. Expert System Applications
The a p p l i c a t i o n s
k n o w led g e w i l l b e
th a t
f i t th e way an e x p e r t sy ste m r e p r e s e n ts
e x p la in e d ,
d e te r m in e w h eth er a
ex p ert sy stem . E xpert
p a r tic u la r
sy stem s
in
d e ta ils
a p p lic a tio n
in
is
th is
se c tio n ,
su ita b le
fo r
to
an
are d e fin ite ly not su ita b le for a ll
55
situ a tio n s.
4.3.9.1 Control
The co m p u ter,
in
th is
a p p lic a tio n ,
s y s te m . T h ere a r e tw o b a s i c t y p e s
lo o p . The c o m p u te r ,
p rocedu re to cau se
sy stem . A c lo s e d
in
is
in te r fa c e d
o f c o n tr o l, open lo o p and c lo s e d
an open lo o p sy s te m , f o llo w s
a
p a r tic u la r
feed b a ck ,
th at
sy ste m s t a t u s . T h is fe e d b a c k i s th e k ey t o u s e th e
m o n ito r s
expert
th e
sy stem s
b eca u se i t g iv e s th e e x p e r t sy stem in p u ts
t o u s e i n m a k in g d e c i s i o n s . W ith t h i s
k in d o f in p u t in fo r m a tio n in
a d d i t i o n t o i t s ow n k n o w l e d g e b a s e , a n e x p e r t s y s t e m
c h a n g in g c o n d it io n s . I t
step _ b y _ step
ty p e o f b e h a v io r t o o ccu r in th e
lo o p c o n tr o l u s e s
in c o n tr o l a p p lic a t io n s ,
to oth er
can
a lso
d ia g n o se
can
adapt to
p r o b le m s, and c o r r e c t
th em b y d e v e lo p p l a n s f o r o v e r c o m in g th em .
4.3.9.2 Debugging
D e b u g g in g i s
p r o b le m s in a
th e
process
sy stem
of
andcom es
tr o u b le sh o o tin g ,
th a t
up w ith a c o r r e c t iv e
fin d s
so lu tio n .
4.3.9.3 Design
fo r c e r ta in ty p e s o f p ro d u cts can be sto r e d
D e sig n in fo r m a tio n
in an e x p e r t sy ste m . A u se r can
th en
c a ll
th e
expert
th e
d e sig n
sy stem to
p ro d u ct.
4.3.9.4 Diagnosis
E xpert sy stem s
can
be
used
to
d e v i c e o r s y s t e m . F ro m t h i s a s p e c t
d ia g n o se
th ey
e x p e r t sy stem s e x c e p t
th a t th ey
p ro b lem . A d ia g n o s is
sy stem o b se r v e s
are
a m a lfu n c tio n in a
s i m i l a r t o d e b u g g in g
do n ot g iv e a
56
so lu tio n
to
th e
th e b e h a v io r o f th e d e v ic e or
s y s te m an d m akes n o t e o f im p ro p er p e r f o r m a n c e .
4.3.9.5 Instruction
An e x p e r t s y s t e m d o m a in c a n b e u s e d i n t e a c h i n g s t u d e n t s h o w t o
s o l v e p ro b le m s in
th e
fie ld
of
th ro u g h d i f f e r e n t p ro b le m s w it h
e x p e r tise .
th e
expert
The s tu d e n t can w ork
sy stem .
By u s i n g t h e
e x p la n a tio n su b system , th e stu d e n t can n o t ic e th e seq u en ce o f r u le s
b e in g u sed to re a ch a c o n c lu s io n . So th e s tu d e n t
a b o u t w h at k n o w led g e
an
expert
can
get
an id e a
n e e d s and how i t i s u s e d t o s o l v e
p r o b le m s.
4.3.9.6. Interpretation
In te r p r e ta tio n is one o f th e
sy stem . I n te r p r e ta t io n sy stem s
o b s e r v a tio n s and o th e r
d a ta .
best
a p p lic a tio n s
a re g iv e n in p u ts
T hen,
u sin g
in fe r e n c in g sy stem , th e in t e r p r e t a t io n
p a r t i c u l a r s i t u a t i o n from
f o r an e x p e r t
th at
c o n sist
of
i t s k n o w led g e b a s e and
sy stem a tte m p ts t o d ed u ce a
th e in p u t d a ta . I t a tte m p ts
to
e x p la in
t h e s i t u a t i o n w h ic h i t r e p r e s e n t s .
4.3.9.7. Planning
A p la n n e r
a ttem p ts
to
com e up w i t h a m e th o d o r a p p r o a c h t h a t
w i l l a c h ie v e a g o a l . G iv e n t h e o b j e c t i v e
w e l l a s som e
p o ssib le
p r o d u c e a n o p t im u m
p la n
in te r m e d ia te
and
sta r tin g
s te p s , an e x p e r t
p o in t,
sy stem
as
can
f o r a c h ie v in g t h a t g o a l . F o r v e r y c o m p le x
p r o j e c t s , p la n n in g i s a d i f f i c u l t
h u m an
ta sk .
sy s te m w it h t h e a p p r o p r ia te k n o w led g e an d in p u t s ,
easy ta sk .
57
But
fo r an ex p ert
p la n n in g
is
an
4.3.9.8. Pradiction
P r e d ic t in g m eans
to
fo r e te ll
th e fu tu r e . A p r e d ic t io n sy stem
r e c e iv e s in p u t d a ta ab ou t a g iv e n
situ a tio n .
T hen
o u tc o m e s . W ea th er f o r e c a s t i n g i s g o o d ex a m p le o f
it
an
deduce th e
e x p e r t sy stem
of th is ty p e.
4.3.9 .9. Repair
R e p a ir i s
th e
process
of
r e tu r n in g
o r ig in a l s t a t e . A r e p a ir e x p e r t sy stem
o f th e sy stem .
That
a c c o m p lish
d ia g n o s is , d e b u g g in g , and
by
broken d e v ic e to i t s
im p lem e n ts a u to m a tic r e p a ir
b u ild in g
th e
c a p a b ility
of
p la n n in g in t o i t . The s y s te m l o c a t e s th e
tr o u b le , s u g g e s ts th e f a u lt c a n d id a te
th e n im p le m e n ts i t .
a
list,
w orks o u t a p la n , and
[68]
4.4. Electronic Fault Diagnosis
D ia g n o s is i s c o n c e r n e d w ith p r o d u c in g a h y p o t h e s is
why th e o b s e r v e d
b e h a v io r
of
a
sy stem
e x p e c te d b e h a v io u r . T h is d e f i n i t i o n
of
is
to
d iffe r e n t
d ia g n o sis
e x p la in
from
its
is p a r tic u la r ly
s u ita b le in th e a rea o f e le c t r o n ic f a u lt d ia g n o s is .
In
g e n e r a l, d ia g n o s is h a s tw o t a s k s . The f i r s t t a s k
h y p o t h e s i s (a f a u l t )
d e v ic e o r to
th a t
e x p la in s
produce a h y p o th e sis
(a
th e
is
to
m a lfu n c tio n in g
d ise a se )
th a t
fin d a
of
th e
e x p la in s
a
p a r t i c u l a r s e t o f sym p tom s.
The s e c o n d t a s k
in
b oth
cases
is
th e
e x tr a c tio n
of
ex tra
in fo r m a tio n th a t i s r e q u ir e d t o fo r m u la te th e h y p o th e s is .
T here a re th r e e s ta g e s in th e d ia g n o s tic p r o c e ss:
Abduction:
a r r i v e a t a h y p o t h e s i s t o e x p l a i n t h e sym p tom s.
Deduction:
d e r iv e e x p e r im e n ta l
ou tcom es o f th e
carry out te s ts .
56
h y p o th e s is and
Induction:
co n c lu d e th e h y p o th e s is to be tr u e o r f a l s e .
[77]
MYCIN
s y s te m i s o n e o f t h e e a r l y , fam ou s e x p e r t s y s te m s f o r m e d ic a l
d ia g n o sis [4 7 ]. I t
is
a
backw ard
c h a in in g r u le b a sed sy stem fo r
d ia g n o sin g and t r e a t in g in f e c t io u s
b lo o d
d ise a se s.
a b o u t t h e p r o b le m d o m a in i s r e p r e s e n t e d a s
IP - THEN
The k n o w le d g e
r u le s , th u s i t
i s s h a llo w k n o w led g e.
T h is s h a llo w k n o w led g e
r e p r e se n ta tio n
is
c h a r a c te r istic
of
d i a g n o s t i c e x p e r t s y s t e m s i n m e d i c i n e [ 4 6 ] . On t h e o t h e r h a n d , s o m e
o f th e e x p e r t sy ste m s d e v e lo p e d fo r e l e c t r o n i c f a u lt d ia g n o s is h ave
been m odel b ased
([4 4 ]
d if f e r e n c e in th e
n atu re
or
[3 6 ]).
o f th e
T h is
g iv e s
r e a so n in g
th e
in v o lv e d
d ia g n o s is and in e l e c t r o n i c f a u lt d ia g n o s is . M e d ic a l
b a s e d on m o d e ls
of
th e s e are sh a llo w
th e
p a th o lo g y
of
m o d e ls w h erea s
fu n d a m en ta l
in
m e d ic a l
d ia g n o sis
is
th e sy stem under d ia g n o s is
e le c tr o n ic
fa u lt
d ia g n o sis
is
b a s e d on m o d e ls o f a c o r r e c t l y f u n c t io n in g c i r c u i t .
T h is d i s t i n c t i o n d o e s
not
o n ly
e x ist
in th e way
h u m an
ex p erts
p erfo rm t h e s e ta s k s b u t i s a ls o r e f l e c t e d in th e way e x p e r t sy ste m s
a r e d e s ig n e d t o o p e r a t e in t h e s e d o m a in s.
T h a t m ean t h a t
expert
sy stem s
fo r
m e d ic a l d ia g n o s is
b a s e d on s h a llo w k n o w led g e r e p r e s e n t a t i o n s
w h ile
th o se
need to be
d e v e lo p e d
fo r tr o u b le sh o o tin g e l e c t r i c a l c ir c u it s can be b ased on e it h e r deep
o r s h a l l o w k n o w l e d g e . An e l e c t r o n i c f a u l t d i a g n o s i s
sy stem
can be
m o d e l b a s e d o r i t c a n b e b u i l t u s i n g s h a l l o w r u l e s l i n k i n g sym p tom s
to cau ses [6 4 ].
T h ere a r e tw o
ty p es
o f hum an e x p e r t s , t h e d e s i g n e n g i n e e r a n d t h e
t e s t t e c h n ic ia n . T h eir r e a so n in g
str a te g ie s
co m p le te ly d if f e r e n t . In
a d d itio n
d iffe r e n t str a te g ie s at
d iffe r e n t
59
th a t
one
for
d i a g n o s i s m ay b e
expert
m ig h t
use
s ta g e s . A te c h n ic ia n w ill s ta r t
o f f r e a so n in g th e
fir st
p r in c ip le s
e le c t r o n ic s and w i l l
proceed
l i n k i n g sym p tom s t o
p o ssib le
w ith th e c i r c u i t .
So
he
to
of
le a rn
what
he
sh a llo w
r u le s
ca u ses as he becom es
m ig h t
o p era te
b a s e d s y s te m . A d e s ig n e n g in e e r m ig h t
knows
of
m ore
about
th u m b
fa m ilia r
lik e a q u a lit a t iv e m odel
be
c o n sid e r e d
m od el b a s e d e x p e r t s y s te m . So h e m ig h t o p e r a t e l i k e
sim ila r to a
a q u a n tita tiv e
m odel b a sed sy stem .
The a r c h i t e c t u r e f o r
a k n o w led g e b a s e d s y s te m f o r e l e c t r o n i c f a u l t
d ia g n o s is sh o u ld r e f l e c t on e o f th e s e a p p ro a ch es [3 5 ].
4.5. Shallow Knowledge
C o n c lu s io n s a r e draw n d i r e c t l y
from
fa cts
th a t
p ro b lem in s h a llo w r e a s o n in g . S h a llo w k n o w le d g e i s
as 'r u le s o f
th u m b '
T h e se w o u ld b e
th a t
sim p le
d e sc r ib e
r u le s
a
d e sc r ib e th e
b e s t c o n sid e r e d
p a r t i c u l a r p r o b le m d o m a in .
lin k in g
sym p tom s
to
d i a g n o s i s . Human e x p e r t s m ay a c q u i r e t h e i r k n o w l e d g e
o r t h e y m ay
a c q u ir e
cau ses
in
at th is le v e l
th em a t a d e e p e r l e v e l w h ere t h e k n o w le d g e i s
b a sed on a m odel o f th e sy ste m and
th e
r e a s o n in g i s d on e from th e
f i r s t p r i n c i p l e s in t h i s m o d e l.
I f a p a r tic u la r
a v a ila b le in a
p ro b lem
sy stem
i s u n so lv a b le w ith th e sh a llo w
th en
c o v e r t h a t p r o b le m .
T h is
p ro b lem o n l y . T h is
e x p la in
r e p r e s e n ta tio n s . A sh a llo w
k n o w led g e
t h e k n o w le d g e b a s e ca n b e e x te n d e d t o
e x te n sio n
th e
w ill
m a in
cover
p ro b lem
th a t
p a r tic u la r
w ith
sh a llo w
k n o w led g e b a s e d s y s te m w i l l n o t p e r fo r m
w e l l on c a s e s n o t c o n s id e r e d in i t s c o n s t r u c t i o n .
4.6. Shallow Knowledge Based Systems
S h a llo w k n o w led g e b a s e d s y s te m s a r e u s u a l l y r u l e b a s e d s y s t e m s .
The k n o w le d g e o f
a p a r t i c u l a r d o m a in
60
is
rep resen ted
as
IF -T H E N
r u l e s . The s h a llo w
k n o w le d g e i s c o n s i d e r e d t o h a v e som e a d v a n t a g e s
in c lu d in g :
(1) S h a llo w r u l e s a r e an e a s y
way
of
r e p r e s e n t i n g t h e d o m a in
k n o w led g e o f an e x p e r t .
(2) The
k n o w le d g e b a s e ca n b e e a s i l y e x t e n d e d
by
a d d in g
new
r u le s.
(3)
The
use
of
a
backw ard
c h a in in g
f a c i l i t a t e s t h e d e v e lo p m e n t
of
a
user
in fe r e n c e en g in e w i l l a u to m a tic a lly a sk
r u le
based
sy stem
in te r fa c e
as th e
th e u ser
fo r
any
in fo r m a tio n t h a t i s n o t a v a i l a b l e t o th e s y s te m [39] .
(4)
It
i s e a sy to have a r u le b a sed sy stem e x p la in i t s
lin e of
en q u ir y .
The a d v a n ta g e s and d is a d v a n ta g e s o f s h a llo w r u l e s b a s e d s y s te m s can
b e c o n s i d e r e d u s i n g t h e PROCESSEX
sy s te m w h ich i s an e x p e r t sy ste m
f o r f a u l t d i a g n o s i s i n d i g i t a l e l e c t r o n i c s . I t i s w r i t t e n i n EMYCIN
w h ic h i s a b ack w ard c h a in in g s y s te m .
PROCESSEX c o n t a i n s a b o u t
w r itte n in b o th
one
hundred
and f i f t y r u le s
w h ic h
are
E n g lish and th e L is p - lik e co d e u sed by th e sy ste m .
EMYCIN u s e t h e E n g l i s h r e p r e s e n t a t i o n
in i t s e x p la n a tio n f a c i l i t y .
The r u l e s e t h a s a r e a s o n a b ly c o m p le x
stru ctu re as
4 - 3 . T h is c o m p lex
stru ctu re
in h e r e n t
in
th e
show n i n
r u le
base
fig .
is
c h a r a c t e r is t ic o f m ost r u le b a sed sy ste m s and c o n t r a d ic t s t h a t r u le
b a se sy stem s a re e a s ily ex te n d ed .
If
t o th e sy ste m th e n c a r e m ust be ta k e n
an e x tr a r u le i s t o b e added
to ensure th a t i t
f i t s in to
t h e e x i s t i n g s t r u c t u r e . [64]
4.7. Deep Knowledge
A m odel
based
sy stem
is
m ore
s h a llo w k n o w led g e b a s e d s y s te m a s
general
th an
th e e q u iv a le n t
s p e c i f i c h e u r i s t i c s w h ic h h a n d le
61
f i g . 4 - 3 . T h e C o m p le x S t r u c t u r e o f PROCESSEX
in d iv id u a l c a se s need
n o t be en co d ed . I t sh o u ld be a b le t o p erfo rm
w e l l on p ro b le m s n o t c l e a r l y c o n s id e r e d in i t s c o n s t r u c t i o n . A t th e
sam e tim e a m o d e l b a s e d s y s te m s h o u ld
p erfo rm
r e a so n a b ly
w e l l on
p ro b lem s on th e p e r ip h e r y o f i t s k n o w le d g e.
The r e a s o n i n g m ech a n ism s h o u ld b e a b l e t o d ra w c o n c l u s i o n s
in
a ll
c a s e s from t h e f i r s t p r i n c i p l e s d e s c r ib e d i n t h e m o d e l. T he c o n t r o l
s tr u c tu r e s r e q u ir e d a re
m ore
c o m p lex
T hey a l s o ta k e lo n g e r t o e x e c u t e .
because o f th is g e n e r a lity .
That b eca u se o f t h i s c o m p le x ity ,
and b e c a u se th e in fe r e n c e c h a in s a r e lo n g e r due t o
o f t h e k n o w led g e [ 6 3 ] .
62
th e
sm a ll s iz e
4.8. Deep Knowledge
(model) based g y e t S M
K n o w led g e e l i c i t a t i o n d i f f i c u l t i e s w i t h s h a l l o w k n o w le d g e b a s e d
sy ste m s a r e p r o b a b ly
a f a c t o r c o n tr ib u t in g t o th e am ount o f e f f o r t
in v e s t e d in p r o d u c in g m odel b a se d
expert
sy stem s
fo r
e le c tr o n ic
f a u l t d ia g n o s is . T h is i s an im p o r ta n t d i f f e r e n c e b e tw een
b ased sy stem s fo r
k n o w le d g e
m ed ic a l d ia g n o s is and th o s e fo r e l e c t r o n i c f a u lt
d ia g n o sis.
M ost m e d ic a l d ia g n o s i s s y s te m s a r e
s h a llo w k n o w led g e b a s e d s y s te m s
b e c a u s e d e e p m o d e l s o f t h e p r o b l e m d o m a in w o u l d b e v e r y c o m p l e x a n d
a r e n o t u s e d b y hum an e x p e r t s . I n s t e a d e x p e r t s u s e
v a r io u s p a th o lo g ie s o f
th e
m o d e ls
of
th e
sy ste m . T h is i s r e f l e c t e d in an e x p e r t
s y s te m f o r d ia g n o s is o f g la u co m a
c a lle d
CASNET. CASNET s t a n d s f o r
c a u s a l - a s s o c i a t i o n a l n etw ork and i s se m a n tic n etw o rk
based
sy stem
[4 8 ] .
The e q u iv a le n t t o
th ese
d ia g n o sis are fa u lt
p a th o lo g ic a l
m o d e ls;
th ese
m o d e ls
are
in e le c tr o n ic fa u lt
m o d e ls
of
th e
v a r io u s
d if f e r e n t ty p es o f f a u lt th a t can occu r in a c i r c u i t .
C la s s e s o f f a i l u r e , a s u sed by D a v is, a r e g e n e r a l f a u l t
m o d e ls b u t
a r e p e r i p h e r a l t o t h e m o d e l b a s e d d i a g n o s i s s y s t e m [4 1 ] . D a v is m a in
m odel i s a m odel o f th e s tr u c t u r e and b e h a v io u r o f th e sy ste m .
The a d v a n ta g e s and
d isa d v a n ta g es
of
d ee p k n o w le d g e b a s e d s y s te m s
c a n b e c o n s i d e r e d u s i n g t h e DART s y s t e m .
C o n sid e r th e f u l l- a d d e r r e p r e s e n t e d
b y t h e c i r c u i t d ia g ra m in f i g .
4-4.
The s t r u c t u r a l in fo r m a tio n
about
th is c ir c u it is
rep resen ted
by
L i s p - l i k e e x p r e s s i o n s , o f w h ic h t h e f o l l o w i n g a r e e x a m p le s :
(XORG
X I)
(CONN
(OUT 1 X I )
(IN 1 X 2 ))
The f i r s t o f t h e s e e x p r e s s i o n s i n d i c a t e s t h a t XI i s an O R -g a te . The
63
F1
n ext one in d ic a te s
th a t th e o u tp u t o f XI i s c o n n e c te d t o th e f i r s t
in p u t o f X 2 . The b e h a v io u r a l in fo r m a tio n i s r e p r e s e n t e d a s f o llo w s :
( I F (AND (ORG d ) (VAL ( I N 2 d ) t O N ))
(VAL (OUT 1 d ) t O N ))
I f t h e d e v i c e i s an O R -g a te an d
th e
secon d
in p u t
o u tp u t i s o n . The p r o c e s s f o r t r a c in g th r o u g h t h i s
i s on th en th e
m odel to fin d a
f a u lt i s d e s c r ib e d in f i g . 4 -5 .
f i g . 4 - 5 . F l o w c h a r t o f t h e DART D i a g n o s t i c S y s t e m
64
The co m p u ta tio n o f
su sp ects
produces
a s u s p e c t s e t w h ic h h a s th e
f o l l o w i n g form :
(OR (NOT p i )
(NOT p n ) )
W h ere p i i s a s t a t e m e n t f r o m t h e
known t o b e
tru e.
s ta g e w here i t
c ir c u its
d e sig n
d e sc r ip tio n not
For in s ta n c e , i f th e d ia g n o s is
knows
th a t
e ith e r o f
had
reached
th e X O R -gates, XI
a
o r X2 i s
broken, th e s e t w ill be:
(OR (NOT (XORG X I ) )
(NOT (XORG X 2 ) ) )
C le a r ly t h e d ia g n o s is i s c o m p le te w hen t h e s e t o f s u s p e c t s c o n t a in s
o n ly one e n tr y .
The
set
of su sp ects
is
reduced
by
g e n e r a tin g
d i s t i n g u i s h i n g t e s t s b e tw e e n th em .
The d i f f e r e n c e b e tw e e n q u a l i t a t i v e and q u a n t i t a t i v e
im p o rta n t w ith d i g i t a l
e le c tr o n ic s
is not
w here th e b a s ic o n e -z e r o m odel
is th e o n ly r e a so n a b le r e p r e s e n ta tio n .
On
th e
o th er
d e v i c e s h a v e an i n f i n i t e num ber o f p o s s i b l e s t a t e s
c o n s id e r a b le d if f e r e n c e b etw een
m o d e ls
q u a n tita tiv e
hand a n a lo g
so
th ere
and
is a
q u a lita tiv e
m o d e ls.
T hese d i g i t a l f a u lt
d ia g n o s is sy stem s
are
p resen ted
w o rk in g
s im p le c i r c u i t s . R e a l d i g i t a l c i r c u i t s a r e m ore c o m p le x
So i t seem s
lik e ly
d ia g n o sis w ill be
on
th an t h i s .
th a t pure m odel b a sed e x p e r t sy stem s fo r f a u lt
e stim a te ly
very
d iffic u lt
fo r
th e
ex p ected
fu tu r e . T h is i s v e r y s im ila r t o th e c a s e w ith a n a lo g c i r c u i t s w here
q u a n t i t a t i v e m o d e ls a r e v e r y c o m p le x .
A . 9. Advantages and
Disadvantages
[2 4 ], [4 0 ],
of Shallow and
[42]
Deep
Knowledge
Based Svat-amH
The a d v a n ta g e s
and th e d is a d v a n ta g e s o f b o th , d eep and sh a llo w
k n o w le d g e b a s e d s y s t e m s ,
w ill be
p resen ted
se c tio n .
65
in
su m m a ry
in
th is
4.9.1. Advantages and
Disadvantages
of
Shallow
Knowledge
Based
Systems
The a d v a n ta g e s o f t h e s h a llo w k n o w le d g e b a s e d s y s te m s a r e :
(1) S p eed o f e x e c u t io n .
(2) E a se
o f r e p r e se n ta tio n
of
expert
k n o w le d g e
as
sh a llo w
r u le s.
The d is a d v a n t a g e s o f t h e s h a llo w k n o w le d g e b a s e d s y s te m s a r e :
(1) D i f f i c u l t t o e x te n d t h e k n o w le d g e b a s e .
(2) W i l l
n o t p e r fo r m w e l l on p ro b lem c a s e s n o t
c o n sid e r e d
in
sy stem c o n s tr u c tio n .
(3) K n o w led g e
m ay
be
d istr ib u te d
th rou gh ou t
th e sy stem and
th erefo re d if f ic u lt to a lte r .
4.9.2. Advantages and Disadvantages of Deep Knowledge Based Systems
The a d v a n ta g e s o f t h e d e e p k n o w le d g e b a s e d s y s te m s a r e :
(1) S h o u ld b e a b l e t o p e r fo r m
r e a so n a b ly
w e ll
on
cases
not
c o n sid e r e d e x p l i c i t l y in th e c o n s tr u c tio n o f th e sy stem .
(2) E a s i l y a l t e r e d t o o p e r a t e i n a n o t h e r p r o b le m
situ a tio n
by
c h a n g in g th e m o d e l.
The d is a d v a n ta g e s o f t h e d ee p k n o w led g e b a s e d s y s te m s a r e :
(1) S lo w o f e x e c u t i o n .
(2) R e a s o n in g
m ec h a n ism
w ill be d if f ic u lt to g en era te b ecau se
o f it s g e n e r a lity .
[35]
4.10. Systems Incorporating both Deep and Shallow Knowledge
A d e e p k n o w led g e b a s e d s y s te m
w o u ld b e t h e i d e a l s o l u t i o n w e r e
i t n o t f o r t h e p r o b le m o f p e r fo r m a n c e . I t seem s u n a v o id a b le
sy stem th a t r e a so n s
about
th a t a
a c i r c u i t from f i r s t p r i n c i p l e s w i l l b e
s lo w . The o b v io u s s o l u t i o n i s t o i n c o r p o r a t e som e s h a l l o w k n o w le d g e
66
i n t o t h e s y s te m in o r d e r t o ' s h o r t c u t ' som e o f t h i s r e a s o n in g from
f i r s t p r i n c i p l e s . T h is a p p r o a c h i s s u p p o r te d in [38] an d [ 4 5 ] ,
T h is p r o j e c t w i l l
be
d e s c r ib e d a s an ex a m p le o f a k n o w le d g e b a s e d
sy stem fo r e le c t r o n ic f a u lt d ia g n o s is
in c o r p o r a tin g
b o th deep and
s h a llo w k n o w le d g e.
4.10.1. EXP-Test System
E le c tr o n ic fa u lt
d ia g n o se s i s c o n sid e r e d a s u it a b le
e x p e r t sy stem s a p p lic a t io n s
d ocu m en ted [ 3 8 ] ,
approach to th e
[4 1 ],
and
[45].
p r o b le m
fo r
th e r e se a r c h in t h is a rea i s w e ll
It
of
area
is
c o n sid e r e d
g e n e r a tin g
tr o u b le sh o o tin g e le c t r o n ic c ir c u it r y
and s h a llo w k n o w led g e in t h e s y s te m
is
th a t
expert
to
th e
best
sy stem s
fo r
in c o rp o r a te b o th deep
[4 5 ]. T h is ap p roach r e c o g n iz e s
t h e u s e f u l n e s s o f b o t h t y p e s o f k n o w led g e a n d u t i l i z e s
b oth in th e
tr o u b le sh o o tin g p r o c e ss.
G iv e n sym p tom s o f
m isb e h a v io u r ,
th e e x p e r t sy ste m m ust b e a b le t o
d e te r m in e t h e s t r u c t u r a l d e f e c t s r e s p o n s i b l e f o r t h e f a u l t from t h e
d e e p k n o w le d g e b a s e
[55] .
The
stru ctu ra l
k n o w le d g e
co m p on en ts: a f u n c t io n a l p a r t and a p h y s ic a l p a r t .
p art is sim ila r
The
has
tw o
fu n c tio n a l
t o th e sc h e m a tic o f th e c i r c u i t w h ile th e p h y s ic a l
p a rt corresp on d s to th e c ir c u it la y o u t.
E X P -T est S y s te m w as d e v e lo p e d a s
d ia g n o sis. I t has
a
sy stem
fo r
e le c tr o n ic
th e ad v a n ta g es o f th e b o th ty p e s
s h a llo w and d eep k n o w led g e ,
of
fa u lt
k n o w le d g e ,
(T h e s h a l l o w k n o w l e d g e i s t h e k n o w l e d g e
a b o u t f a u l t p r o c e d u r e and th e d ee p k n o w le d g e i s t h e k n o w le d g e a b o u t
e le c tr o n ic c ir c u itr y ).
The f o l l o w i n g e x a m p le
w ill
d e sc r ib e
r e p r e s e n t t h e s h a llo w an d d eep k n o w led g e
o u tp u t o f th e tr a n s fo r m e r ):
67
th e
way
(th is
E X P -T est
S ystem
e x a m p le c h e c k s t h e
RUNTIME;
!
This
statement
eliminates the Rules and Values
1 w in d o w s w h en t h e u s e r r u n s t h e r u l e b a s e .
ACTIONS
! T h i s s t a t e m e n t a n d FIN D c l a u s e d e f i n e t h e s t e p s
1
f o r s o l v i n g a p ro b lem .
WELCOME TO
DISPLAY “
E X P -T E ST SYSTEM
SYSTEM FOR TESTING CNC MACHINE
<PRESS ANY KEY TO START>
CLS
i T h is c l a u s e c l e a r s t h e c o n s u l t a t i o n w in d o w .
FIN D THE_PROBLEM;
RULE
POWER_SUPPLY
IF
CHECK__TRANSFORMER = YES
THEN
CALL \T C 2\SK E T C H 1
CALL \ T C 2 \SKETCH2
CALL \T C 2 \E X P _ T l
LOADFACTS
F IL E 9
FIN D THE_TEST
THE_PROBLEM = FOUND;
RULE
P0WER_SUPPLY1
IF
d e l t a l >= ( s t a n d e r l )
THEN
WOPEN 1 , 1 5 , 1 , 8 , 6 0 , 4
1 T h is c la u s e d e f in e t h e p o s i t i o n ,
! s i z e , a n d b a c k g r o u n d c o l o r o f a w in d o w .
ACTIVE 1
! T h is c l a u s e d i s p l a y s a w in d o w o n t h e s c r e e n .
DISPLAY
"THERE I S A PROBLEM
IN
THE
TRANSFORMER, I SUGGEST
YOU TO REPLACE I T .
PRESS <ENTER>, THEN <Q> TO E X I T . - "
WCLOSE 1 I T h i s c l a u s e r e m o v e s a w i n d o w f r o m t h e s c r e e n .
RESET d e l t a l
! T h e RESET k e y w o r d s e t s t h e v a l u e o f a
68
RESET s t a n d e r l
! v a r ia b le t o unknown.
THE_TEST = FOUND
ELSE
CLS
DISPLAY
"THE
TRANSFORMER
IS
OK,
<PR E SS
ANY KEY> TO
CONTINUE TESTING T H IS D E V I C E .-"
ASK
RESET
d e lta l
RESET
sta n d e r l;
CHECK_TRANSFORMER
:
"TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM ( J 9 ) .
THEN
PUT THE O SC ILLO SCO PE'S PROBE AT POINT ( 1 ) .
TO LOCATE POINT ( 1 ) AND CONTINUE THE T EST,
CHOOSE Y E S, AND PRESS
<ENTER>. OTHERWISE CHOOSE NO,
AND PRESS <E N T E R >. " ;
CHOICES
CHECK_TRANSFORMER : Y E S, NO;
The p r e v io u s ex a m p le c o n t a i n , t h e tw o t y p e s o f k n o w le d g e
deep
and
s h a llo w k n o w led g e.
The s h a llo w k n o w led g e
in E X P -T est S y ste m w as r e p r e s e n t e d in n e a r l y
o n e h u n d r e d o f t h e IF -T H E N r u l e s .
T hese
IF -T H E N
r u le s
s y s t e m a n e a s y w ay t o r e p r e s e n t t h e d o m a in k n o w le d g e
in th e m a in te n a n c e ,
gave
th e
o f th e ex p ert
a ls o i t g a v e th e sy stem a h ig h sp e e d e x e c u tio n
an d t h e a b i l i t y t o e x te n d t h e s y s te m e a s i l y , by a d d in g som e r u l e s .
The s y s te m b a c k w a r d -c h a in s th r o u g h
th ese
r u le s
w ith
th e g o a l o f
d i s c o v e r i n g w h ich o f f a u l t c a n d id a t e s i s f a u l t y . The c l a u s e s on t h e
l e f t - h a n d s id e o f th e r u le s m ust b e fou n d t r u e in
th e c la u s e on
th e
r ig h t-h a n d
c la u s e s on th e le ft-h a n d s id e i s
sid e .
not
69
If
th e
know n
order
to
in fo r m a tio n
prove
in th e
t o th e sy stem th en i t
w i ll query th e
user
for
th a t
in fo r m a tio n . So th e sy ste m g e t th e
e x tr a in fo r m a tio n th a t i t n eed s to
iso la te
a
f a u lt by a sk in g th e
user.
The u l t i m a t e p r o b le m , o r " g o a l" o f c o n s u l t a t i o n
is
d e fin e d
in
a
FIN D c l a u s e i n t h e ACTIONS b l o c k o f t h e k n o w l e d g e b a s e . T h i s c l a u s e
in s tr u c ts th e in fe r e n c e
e n g in e
to
v a r i a b l e , w h ich we
c a ll th e "goal
nam ed in t h e
c la u se
FIN D
FIN D
a
v a lu e
fo r
a g iv e n
The
goal
v a r ia b le
v a r ia b le " .
o f E X P - T e s t S y s t e m ' s ACTIONS
THE_PROBLEM. O n c e THE_PROBLEM
has
been
b lo c k
id e n tifie d as
v a r ia b le , th e in fe r e n c e e n g in e s e a r c h e s
th e
THE_PROBLEM,
th e
goal
th e k n o w le d g e b a s e f o r t h e
f i r s t r u le th a t can a s s ig n a v a lu e t o th e g o a l v a r ia b le .
go a l v a r ia b le is
is
S in c e th e
in fe r e n c e e n g in e lo o k s fo r th e
f i r s t r u l e c o n t a i n i n g t h e v a r i a b l e THE_PROBLEM i n i t s c o n c l u s i o n .
T h is i s t h e
r u l e POWER_SUPPLY.
in fe r e n c e en g in e lo o k s a t th e
o f th e r u le .
lo o k s fo r th e
If
O nce
th e
r u le
is
fo u n d ,
f i r s t v a r i a b l e nam ed
in
th e p r e m ise
it
does
not
fir st
r u le
c o n ta in in g
th e
know t h e v a l u e o f t h e v a r i a b l e , i t
th a t
v a r ia b le
in
its
c o n c lu sio n .
The o n ly v a r i a b l e
CHECK_TRANSFORMER.
nam ed
in
th e
p r e m ise
of
S in c e th e in fe r e n c e e n g in e
v a l u e o f CHECK_TRANSFORMER, i t s c a n s
th e
POWER_SUPPLY
d o e sn 't
know
k n o w led g e b a s e
f i r s t r u le w h ich m ig h t p r o v id e th e v a lu e ,i n o t h e r w o r d s,
r u le w h ic h m ig h t
co n ta in s
c o n c lu s io n . B ecau se th e r e
no
th e
fo r th e
th e f i r s t
t h e v a r i a b l e , THE_TRANSFORMER,
is
is
in
its
s u c h r u l e in t h e k n o w le d g e b a s e ,
th e in fe r e n c e en g in e ( a f t e r sc a n n in g a l l th e r u le s fo r one th a t can
a s s i g n a v a l u e t o t h e v a r i a b l e THE_TRANSFORMER)
sta te m en t th a t can
p r o v id e a
v a lu e fo r
lo o k s
fo r
a n ASK
THE_TRANSFORMER.
ASK
s ta te m e n t w i l l prom pt th e u s e r f o r in fo r m a tio n n o t c o n ta in e d in t h e
k n o w l e d g e b a s e . T h e n t h e i n f e r e n c e e n g i n e w i l l s e a r c h f o r a CHOICES
70
s t a t e m e n t n a m in g t h e sam e v a r i a b l e , w h ic h c r e a t e s a m enu o f o p t i o n s
t o accom pany th e
q u e stio n
d u r in g
a
c o n s u lta tio n . In th e stu d ie d
c a s e t h e ASK s t a t e m e n t w i l l a s k t h e u s e r :
TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM ( J 9 ) .
THEN
PUT THE OSCILLO SCO PE'S PROBE AT POINT ( 1 ) .
TO LOCATE POINT ( 1 ) AND CONTINUE THE T E ST ,
CHOOSE Y E S, AND PRESS
<E N T E R >. OTHERWISE CHOOSE NO,
AND PRESS <E N T E R >.
The c h o ic e s w i l l b e:
YES
NO
H ere t h e u s e r m akes c h o i c e , s o i f h e c h o o s e s YES.
v a l u e o f CHECK_TRANSFORMER.
YES
becom es th e
S in c e th e in f e r e n c e e n g in e h a s fo u n d a
v a l u e f o r CHECK_TRANSFORMER, i t w i l l
g o b a c k t o r u l e POWER_SUPPLY,
t o g i v e CHECK_TRANSFORMER t h e d e f i n e d v a l u e .
S i n c e t h e v a l u e o f CHECK_TRANSFORMER i s Y E S, t h e
w i l l f i r e POWER_SUPPLY.
W hen
POWER_SUPPLY
e n g in e w i l l c a l l s f i r s t o f a l l th e
in fe r e n c e
is f ir e d th e in fe r e n c e
SKETCH1
file ,
w h ic h
s c h e m a t ic d ia g r a m o f t h e c i r c u i t , t h e n t h e i n f e r e n c e
t h e SKETCH2 f i l e ,
w h ic h
draw
th e
th en th e in fe r e n c e en g in e c a l l s
s i g n a l from t h e
p e r ip h e r a l
e n g in e
draw th e
e n g in e
c a lls
la y o u t d ia g r a m o f t h e c i r c u i t ,
th e
EXP_T1
file ,
w h ich
in str u m e n ts and com pare
it
g e t th e
w ith
th e
r e fe r e n c e s ig n a l, and g iv e th e r e s u l t v a lu e t o v a r ia b le d e l t a l , and
c a lc u la te th e a llo w a b le
t h e n EXP_T1 p r o g r a m
to le r a n c e
saves d e lta l
and g iv e i t s v a lu e to s ta n d e r l,
and
sta n d erl
in
( F I L E 9 ) . T h e i n f e r e n c e e n g i n e t h e n g a t e F IL E 9 f r o m
g iv e th e v a lu e
FOUND
to
THE_PROBLEM, w h i c h j u s t w a s a n
f o u n d . T h e FIN D
sta te m en t
in fe r e n c e e n g in e th ro u g h
th e
in d e x
in sid e
to
a
TURBO
goal
tel
POWER_SUPPLY
th a t
tex t
C .,
file
and
v a r ia b le
th e
r u le ,
m atch i s
le a d
th e
t h e k n o w le d g e b a s e , b y g i v i n g a new g o a l .
71
A fter th a t th e
in fere n ce
e n g in e
g o t o P0WER_SUPPLY1 r u l e , w h i c h
v a r ia b le
in i t s
c o n c lu sio n .
c o n ta in th e g o a l
co m p a r iso n b e tw e e n t h e
v a lu e
of
'd e lta l'
D ep en d in g
and
th e
on
th e
v a lu e
of
' s t a n d e r l ' t h e i n f e r e n c e e n g i n e w i l l f i r e t h e P0WER_SUPPLY1 r u l e o r
i t w ill n ot.
The d eep m odel
sh o u ld c o n ta in
a
stru ctu ra l
and
b e h a v io u r a l
d e sc r ip tio n o f th e c ir c u it .
The d e e p k n o w led g e w as r e p r e s e n t e d in t h e g r a p h ic accom p an y t o e a c h
t e s t a p p ly in g on th e c ir c u it , t h is
p h y s ic a l d im e n sio n (la y o u t
g r a p h ic
has
tw o d im e n sio n t h e
d ia g ra m ), and th e f u n c t io n a l
d im e n sio n
(sc h em a tic d ia g r a m ).
In a d d itio n to
r e p r e s e n t in g th e d e e p k n o w le d g e i n t h e g r a p h ic , t h e
d ee p k n o w led g e ca n
be
rep resen ted
in
th e
in te llig e n c e
t e c h n ic ia n and th e p r o d u c tio n r u l e s . As m e n tio n e d ,
r u le s, i t is
very
easy
t o m o d ify
k n o w le d g e
in c o m p le te , th e sy ste m
le a d t o w rong
w ill
so lu tio n s.
th e
w ith p r o d u c tio n
o r add a new k n o w le d g e t o t h e
k n o w le d g e b a s e . The k e y t o t h e s u c c e s s
in te g r ity of it s
of
of
an
base.
If
be
p o o r p r o b l e m s o l v e r a n d i t m ay
a
T h erefo re, i t
th e
e x p e r t sy stem i s th e
is
k n o w led g e
im p o r ta n t
base
th a t
is
th e
k n o w led g e b a s e b e k e p t up t o d a t e a t a l l t i m e s . In e l e c t r o n i c f a u l t
d i a g n o s i s a new
k n o w led g e
is
b e in g added
c o n tin u a lly .
E x p erts
c o n t in u e t o g a i n d i f f e r e n t e x p e r i e n c e s a n d im p ro v ed p r o b le m _ s o lv in g
m eth od s. A ll o f
th is
sh o u ld
be
in c o r p o r a te d
e x p e r t sy ste m t o k eep i t up t o d a t e .
The
r u le
r e g u la r ly in to th e
form at
e a s y b e c a u s e i t b r e a k s t h e k n o w le d g e down i n t o s m a l l
o ld r u le s can
be
k n o w le d g e i s a d d e d
r e w r itte n
to
p i e c e s . So an
a cco m m o d a te c h a n g e s .
by sim p ly w r it in g
th e k n o w led g e b a s e .
72
m akes t h i s
A ls o a new
new r u l e s an d s t o r i n g th em in
CHAPTER 5
INTEGRATING EXPERT SYSTEM
AND ON-LINE TEST
5.1. Introduction
The term
'e x p e r t
la r g e ly a c o lle c tio n
s y s te m ' r e f e r s t o a co m p u ter p ro gram t h a t i s
of
d e t a i l e d d o m a in f a c t s
s p e c i a l p r o b lem s o f
h e u r istic
th at
som e
have
r u le s
(r u le s
proven
te c h n ic a l
u sefu l
in
th u m b )
and
so lv in g
th e
f i e l d . E xpert sy stem s to d a te
a r e an o u tg ro w th o f a r t i f i c i a l i n t e l l i g e n c e
f o r m any y e a r s
of
(A I), a f ie ld th a t has
b een d ev o ted to th e stu d y o f p r o b le m -so lv in g
h e u r is tic s , to th e
c o n str u c tio n
k n o w le d g e a b o u t t h e
w o r ld ,
of
sy m b o lic
to th e
process
r e p r e se n ta tio n s
of
c o m m u n ic a tin g
in
of
n a t u r a l la n g u a g e , an d t o le a r n from e x p e r ie n c e . E x p e r t i s e
d e fin e d to be
th a t
body
of
c la ss
of
p ro b lem .
O ne o f t h e
e x p e r t sy stem i s th a t i t i s c o n str u c te d
i n t e r a c t i o n o f tw o
very
p r a c tic in g e x p e r t in
e n g in e e r , an AI
is o ften
k n o w le d g e t h a t i s a c q u i r e d o v e r m any
y e a r s o f e x p e r ie n c e w ith a c e r ta in
h a llm a r k s o f an
d iffe r e n t
som e
p e o p le :
te c h n ic a l
sp e c ia list
u sin g
sk ille d
a
d o m a in
d o m a in ;
in
and
a n a ly z in g
from
th e
ex p ert,
a
a
k n o w led g e
an
e x p e r t's
p r o b l e m - s o l v i n g p r o c e s s a n d e n c o d in g th em i n a c o m p u te r s y s t e m . The
b e s t hu m an e x p e r t i s e
is
th e
r e su lt o f y ea rs, perhaps decades, o f
p r a c t ic a l e x p e r ie n c e , and th e b e s t
p r o f i t e d from c o n t a c t
expert
sy stem
( v i a t h e k n o w led g e e n g in e e r )
is one th a t has
w ith
a
hum an
exp ert [52].
R e p a ir o f e l e c t r o n i c
d o m a in w e l l s u i t e d
sy stem s
an d e le c t r o m e c h a n ic a l eq u ip m en t i s a
to e x p e r t sy stem s
73
te c h n o lo g y .
E xpert
sy stem s
h a v e b e e n b u i l t i n a w i d e v a r i e t y o f d o m a i n s [7 8 ] i n c l u d i n g s y s t e m s
t h a t s p e c i f i c a l l y d e a l w ith r e p a ir . F or ex a m p le , e x p e r t sy s te m s f o r
tr o u b le sh o o tin g have been
d e v e lo p e d f o r co m p u ter i n s t a l l a t i o n s an d
m in ic o m p u te r s. D art [2 4 ],
[54]
is
a
sy stem
used
t e c h n i c i a n in f in d in g f a u l t s in a co m p u ter s y s te m .
D art have been
r e c e n tly
th e
a ssist
a
Two v e r s i o n s o f
r e p o r te d th a t u se d if f e r e n t e x p e r t sy stem
t o o l s a s b a s i c b u i l d i n g b l o c k s . E m y c in
w as e m p lo y e d i n
to
[7 9 ],
a r u le -b a s e d sy stem ,
f i r s t D art v e r s io n [2 4 ], w h ile
a
m e ta -le v e l
r e a s o n i n g s y s t e m [ 8 0 ] w a s u s e d i n t h e s e c o n d s y s t e m [ 5 4 ] . ID T [ 5 6 ] ,
an I n t e l l i g e n t D ia g n o s t ic
T o o l,
i s a sy stem d e sig n e d to a s s i s t in
i d e n t i f y i n g f a u l t s i n PDP 1 1 / 0 3 c o m p u t e r s .
T h is
sy stem
u s i n g O P S -5 [ 8 1 ] , a r u l e - b a s e d s y s t e m d e v e l o p e d a t
was b u ilt
C a r n e g ie -M e llo n
[53] .
In t h i s r e s e a r c h on r e p a ir s y s te m s . I t w as h y p o th e s iz e d t h a t e x p e r t
sy stem s can c a p tu re
th e
r e p a ir
k n o w le d g e
h um an e x p e r t s i n a p a r t i c u l a r d o m a i n .
A
of
th e b est q u a lifie d
su c c e ssfu lly
s e r v i c e a d v i s o r y s y s t e m w o u ld a l l o w a t e c h n i c i a n w i t h
tr a in in g p e r io d to
conduct
e x p e r tly
g u id e d
R e d u ctio n o f s e r v ic e tim e and o v e r a ll
and u n ifo r m ly a p p lie d
k e e p in g a r e am ong
th e
se r v ic e
ex p ected
b e n e fits
o n ly a b r ie f
se r v ic e
m a in te n a n c e
s tr a te g ie s,
im p le m e n te d
and
of
procedures.
c o s t s , im p ro v ed
au tom ated
th e
record
u s e o f su ch an
e x p e r t s e r v ic e a d v iso r y sy stem .
S.2. Using Expert System in Building Intelligent Workstation
An e x p e r t
sy stem i s th e i n t e l l i g e n t
e le m e n ts w h ic h a s s i s t
U sin g an e x p e r t
sy stem
in
b u ild in g
am ong
in te llig e n t
th e
m a in
w o r k sta tio n .
in c o n s tr u c tin g an i n t e l l i g e n t w o r k sta tio n
w i l l m ean im p le m e n tin g t h e a r t i f i c i a l
t h i s w o r k s ta tio n . T h is
an
e le m e n t
in te llig e n c e
w i l l g iv e th e w o r k sta tio n
74
te c h n iq u e s
an
on
in te llig e n c e
a t t r ib u t e and w i l l le a d to a p o w erfu l w o r k s ta tio n .
E l e c t r o m e c h a n i c a l s y s t e m s s u c h a s CNC m a c h i n e s h a v e s e r v i c e m a n u a l s
w h ic h d e s c r i b e r e p a ir
d e ta il, e g ., about
R e p a ir o f su ch
procedures
board
is
n o r m a lly
R e p la c e a b le
r e p la c e m e n t o f d e f e c t i v e
r e p a ir ta s k in
th ese
a c e r ta in p r a c tic a l le v e l o f
or e le c tr o m e c h a n ic a l
sy stem s
r e p la c e m e n t o f F ie ld
at
sy stem s.
re p la c e m e n t.
a c c o m p lish e d
U n its
FRUs a r e
u n it
th e
(F R U s).
b a sic
by
D e te c tio n
o b je c tiv e s
D e p e n d in g on t h e
d ir e c t
typ e
of
of
and
th e
sy stem
s e r v i c e d , s e r v i c e m a n u a ls v a r y c o n s i d e r a b l y i n c o m p l e x i t y . F o r som e
s y s te m s , c o m p le x d e c i s i o n
m anual w h ile in
o th er
trees
sy stem s
and
flo w c h a r ts
are
o n ly
r u d im en ta ry
p a rt o f th e
in fo r m a tio n
on
r e p a ir i s p ro v id ed [5 3 ].
An e x p e r t ' s ' i n t u i t i o n '
m a n u a ls an d s u c h
and
e f f i c i e n c y a r e n o t fo u n d
in fo r m a tio n
is
co m p le x
r e p a ir
en d _ u ser. In f a c t ,
n o r m a lly
not
procedures
in
p r o v id e d
are
p r o v id e in a m a n u a l. F or e x a m p le , b a s i c o p e r a t i o n s
se r v ic e
to
d iffic u lt
th e
to
such as s e ttin g
up h y p o t h e s i s b a s e d on sym p tom s, p r o v in g h y p o t h e s i s , an d s u g g e s t i n g
and v e r if y in g c o r r e c t iv e
p resen ce o f su b c la sse s
focu s o f a tte n tio n
a c tio n s
are
o ften
c o m p lic a te d
o r su b p r o b lem s
w h ich
r e q u ir e
a n d /o r
c h a n g in g
p ro b lem . E f f e c t i v e f o c u s in g
str a te g ie s
m ec h a n ism s
s tr a te g ie s cannot be r e a d ily su g g ested
and
in
a
w hen
by
th e
c h a n g in g
so lv in g
fle x ib le
a
so lu tio n
a s e r v ic e m anual due to
l a c k o f c o n t e x t u a l i n f o r m a t i o n . H o w e v e r , t h e s e m e t h o d s t h a t a hu m an
e x p e r t r e a d ily p erfo rm s
can
be
im p lem e n ted
u sin g
a r tific ia l
in t e llig e n c e te c h n iq u e s [5 3 ].
T h a t m ean t h a t t h e m a in t a s k o f t h e e x p e r t s y s t e m i s t o c a p t u r e t h e
r e p a ir k n o w le d g e o f
th e
best
th e
expert
q u a lifie d
hum an
ex p erts
in
its
k n o w led g e b a s e .
So th e e x i s t e n c e
of
sy stem
75
in sid e
th e
in te llig e n t
w o r k sta tio n g iv e s a
su c c e ssfu lly
im p le m e n te d
s y s te m w h ich i s th e b e s t s o l u t i o n
to
sto p
se r v ic e
c a llin g
p e r so n e v e r y tim e a breakdow n h app ened t o any o f
a d v iso r y
in th e ex p ert
th e
CNC m a c h i n e s
in th e
w orkshop.
5.3. Improving the Productivity
By b u i l d i n g t h e i n t e l l i g e n t w o r k s t a t io n
r e p a ir k n o w led g e in
depend on a
its
w h ic h in c lu d e s a l l th e
e x p e r t s y s t e m 's k n o w led g e
te c h n ic ia n
w ith
a
lim ite d
base,
e x p e r ie n c e
we
can
to s o lv e any
m a c h in e 's breakdow n p r o b le m s. T hat w i l l re d u c e th e s e r v i c e tim e and
o v e r a l l m a in te n a n c e c o s t s , a l s o t h a t
k n o w le d g e d ay b y
day
by
fix in g
te c h n ic ia n
m a ch in es u s in g
w i l l in c r e a se h is
th e
in te llig e n t
w o r k s t a t i o n . I f h e ad d s t h e a c q u ir e d new k n o w le d g e t o t h e k n o w led g e
b ase o f th e
expert
sy stem ,
he
w ill
o t h e r t e c h n i c i a n s a f t e r h im t o a c h i e v e
th e fu tu r e . That
of
course
w ill
be a b le to h e lp h im s e lf and
a
q u ic k f a u lt d ia g n o s is in
red u ce th e breakdow n
tim e
and
in c r e a s e th e p r o d u c t iv it y and th e b e n e f i t t o t h e w h o le p la n t .
5.4. Developing an Intelligent Mobile Workstation for On-Line Test.
As i l l u s t r a t e d
i s a m o b ile
u n it,
in
f i g . 1 -1 th e i n t e l l i g e n t m o b ile w o r k s ta tio n
w h ich ca n b e
e a sily
m oved
from
th e
se r v ic e
s t a t i o n t o a n y CNC m a c h i n e i n s i d e t h e w o r k s h o p .
The t o t a l s y s te m c o n f i g u r a t i o n , w h ic h i s show n in f i g . 5 - 1 , c o n s i s t
o f:
(1) E X P -T est S y s te m .
(2) G r a p h ic s .
(3) T e c h n i c i a n .
76
INTFLLIGENT WORKSTATION
Exp_Teat System
The h ig h ly s p e c i a l i z e d p ie c e
of
so ftw a re th a t a ttem p ts to
d u p l i c a t e th e f u n c t io n o f an e x p e r t in som e f i e l d o f e x p e r t i s e .
The program a c t s a s an i n t e l l i g e n t c o n s u lt a n t o r a d v is o r in th e
d o m a in o f
e x p e r ts in
i n t e r e s t , c a p tu r in g t h e k n o w led g e
its
k n o w led g e
base.
of
one
or
m ore
N o n _ ex p erts can th en tap th e
E X P -T est S y s te m t o s o l v e r e p a i r p r o b le m s , a n d m ake d e c i s i o n s i n
t h a t r e p a ir d o m a in .
77
Graphics
As m en tio n e d
th e
G r a p h ic
e le m e n t
w o r k s ta tio n c a p tu r e s th e im p o r ta n t
o f th e sy stem ,
we w i l l
in
part
th e
o f t h e d e e p k n o w le d g e
(b e c a u s e t h e G r a p h ic e le m e n t i s
d ev ote
a
in te llig e n t
v e r y im p o rta n t,
co m p le te c h a p te r t o e x p la in th e in t e g r a t in g
g r a p h i c CAD k n o w l e d g e w i t h e x p e r t s y s t e m a n d o n - l i n e t e s t ) .
Technician
The t e c h n i c i a n
b e in g c o n sid e r e d
is
a
p r a c titio n e r
l im it e d e x p e r ie n c e . T h is m eans a t e c h n i c i a n w it h
o n ly
w ith
a b r ie f
t r a in in g p e r io d on g u id e d s e r v ic e p r o c e d u r e s i s s u i t a b l e . So an
e x p e r t w ith a h ig h l e v e l o f p erfo rm a n ce i s n o t r e q u ir e d .
The u n io n o f
th e s e th r e e e le m en ts co m p r ise s th e i n t e l l i g e n t m o b ile
w o r k sta tio n .
As m e n tio n e d , th e
i n t e l l i g e n t m o b ile
k n o w le d g e a n d t h e
deep
in c o r p o r a te a l l th e
k n o w le d g e.
k n o w le d g e
k n o w le d g e
(IF -T H E N ) o f E X P - T e s t
is
S ystem
It
in sid e
sy ste m in a s h o r t - t im e o r d u r in g
j u s t th e sh a llo w
u n it
th e
is
s y s te m i t w o u ld b e e s s e n t i a l f o r
very
th e
th e
th e
of
to
base o f th e
th e sy ste m . So
sta g e.
to
sh a llo w
d iffic u lt
in th e p r o d u c tio n
e a r ly
user
th e
k n o w le d g e
c r e a tio n
in c lu d e d
at
c o n ta in s
r u le s
By u s i n g t h e
r e fin e th e sh a llo w
k n o w le d g e an d t o a d d new c a s e s w h ic h a r e e n c o u n t e r e d d u r in g t h e u s e
o f t h is sy stem .
The s h a llo w k n o w led g e i s u p d a te d
c o n tin u o u sly w h ile th e
sy stem
is
b e in g
c o n ta in s n e a r ly one hundred p r o d u c tio n
used.
r u le s,
been
it
E X P -T est
expands
S ystem
th e s e r u le s c o n ta in
t h e k n o w l e d g e o f t h e e x p e r t i n t h e CNC m a c h i n e . A
G r a p h ic f a c i l i t y h a s
and
tw o
d im e n sio n a l
in c o r p o r a te d in t h i s w ork, th e p h y s ic a l
d im e n sio n ( la y o u t d ia g r a m ), and t h e f u n c t io n a l d im e n sio n (s c h e m a tic
d ia g ra m ) o f t h e c i r c u i t b o a r d w h ic h i s g o in g t o b e c h e c k e d .
The d ee p k n o w le d g e r e s i d e s i n t h e
G r a p h ic s f a c i l i t y , w h ich c o n t a in
78
th e s tr u c t u r a l in fo r m a tio n
about
th e
U .U .T .
(u n it
under
test)
c i r c u i t r y , and th e i n t e l l i g e n c e o f th e t e c h n i c i a n . A v e r y im p o r ta n t
p a r t i s p la y e d
by
th is
te c h n ic ia n
in
a n a ly z in g
d ia g ra m o f t h e c i r c u i t an d in d e f i n i n g t h e s o l u t i o n
th e
sc h e m a tic
if
a new c a s e
is en cou n tered .
By i n t e g r a t i n g t h e
f a c i l i t y and w ith
E X P -T est
th e
in te llig e n c e
te c h n ic ia n , th e in t e llig e n t
b o th deep and
S y ste m w it h t h e a c co m p a n y in g G r a p h ic s
sh a llo w
and
m o b ile
th e
k n o w led g e
w o r k sta tio n
w ill
of
th e
in c o r p o r a te
k n o w le d g e . T h is in c o r p o r a t io n w i l l g i v e th e
i n t e l l i g e n t m o b ile w o r k s ta tio n th e
c a p a b ility
of
s o lv in g a l l th e
p r o b le m s w h ic h m ig h t o c c u r .
Now, l e t u s a s k t h i s q u e s t i o n :
How c a n t h a t a c c o m p l i s h ?
In th e c a se
of
a
m a ch in e w i l l c a l l
breakdow n
th e
t o a CNC m a c h i n e , t h e
se r v ic e
te c h n ic ia n ,
im m e d ia te ly w i l l m ove th e i n t e l l i g e n t
m o b ile
user
who
of
w o r k sta tio n
l o c a t i o n o f th e b rok en -d o w n m a c h in e . T h ere h e w i l l
sw itc h
of
th e
course,
to
th e
on
th e
w o r k s t a t io n an d c a l l E X P -T est S y s te m . E X P -T est S y s te m w i l l b e g in t o
g u id e th e t e c h n i c i a n t o d ia g n o s is t h e p r o b le m .
The u s e r i n t e r f a c e
w ill
h elp
th e
t e c h n i c i a n f o r som e in f o r m a t io n an d
E X P -T est
w ill
S ystem
to
ask
th e
a s k h im a l s o t o m ove t h e
( D ig it a l O s c illo s c o p e 's p ro b e o r th e L o g ic A n a ly z e r 's
p r o b e ) , from
o n e p o i n t t o a n o t h e r , t o g e t som e t e s t s i g n a l s .
The G r a p h ic f a c i l i t y
has
been
i n t e g r a t e d w it h E X P -T est S y ste m in
su c h a way t h a t E X P -T est S y ste m p l o t s
th e d e s ir e d c i r c u i t b oard on
t h e s c r e e n . T hen i t show s t h e p o i n t w h ic h n e e d s t o
E X P -T est S y s te m .
A t t h i s s t a g e t h e r e a r e tw o p o s s i b i l i t i e s :
79
be
checked
by
1. I f th e
ty p e
of
fa u lt,
w h ic h
is
on t h e m a ch in e, i s in c lu d e d
w it h i n t h e k n o w le d g e b a s e o f E X P -T est
S ystem ,
w i l l d e f in e th e p r o b lem and w i l l p r i n t o u t t h e
l i s t . T h is
w ill
E X P -T est
fa u lt
S ystem
c a n d id a te
d ep en d on th e in fo r m a tio n w h ich i s p r o v id e d by
th e te c h n ic ia n and on th e r e s u lt
of
co m p a r in g t h e t e s t s i g n a l s
w ith th e r e fe r e n c e s ig n a ls o f ea ch p o in t .
The f o llo w in g
u ser fo r
e x a m p le , e x p l a i n s how E X P -T est
in fo r m a tio n ,
p r o b e from
ask
p o in t to a n o th er,
S ystem
asks
th e
h im a l s o t o m o v e t h e o s c i l l o s c o p e ' s
and
how
it
d e fin e s
th e
fa u lt
c a n d id a te l i s t :
When t h e
user
sta rt
E X P -T est
S ystem ,
it
w ill
d isp la y :
WELCOME TO
EXP-TEST SYSTEM
SYSTEM FOR TESTING CNC MACHINE
<PRESS ANY KEY TO CONTINUE>
The u s e r
m ust
fo llo w
a l l th e in s t r u c t i o n s w h ich a p p ea r on th e
s c r e e n , s o i f h e i s r e a d y f o r t e s t i n g t h e m a ch in e, h e w i l l p r e s s
any k ey on th e k ey b oard . I f th a t
h a p p e n e d , E X P -T est S y ste m w i l l
d isp la y :
CHECK THE MAIN POWER PLUG (220) ACV,
IF THE MAIN POWER IS OFF,
<ENTER>,
(MOVE THE CURSOR
OFF AND PRESS
IF ON PRESS <ENTER>.
OFF
ON
In t h is
TO
case
th e
user
s h o u l d c h e c k t h e m a in p o w er a n d n o t i f y
eo
E X P -T est S y ste m ,
what
i s t h e r e s u l t . I f t h e m a i n p o w e r i s OFF,
E X P -T est S y ste m w i l l d i s p l a y :
SWITCH ON
THE MAIN POWER
AND
BE
SURE
OF
THE
CONNECTION
BETWEEN THE MAIN POWER AND THE DEVICE.
PRESS <ENTER> TO RETRY THE PREVIOUS TEST.
B u t i f t h e m a in p o w e r i s o n , E X P -T e st S y s te m d i s p l a y :
TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM (J9).
THEN PUT THE OSCILLOSCOPE'S PROBE AT POINT (1).
TO LOCATE POINT (1) AND CONTINUE THE TEST,
CHOOSE
YES,
AND
PRESS <ENTER>. OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
NO
YES
I f th e
user
p r e s s e s Y E S, E X P - T e s t S y s t e m w i l l d o t h e f o l l o w i n g
p roced u res. F ir st o f a ll, i t w ill
c a l l SKETCH1 p r o g r a m f r o m t h e
TURBO C . s y s t e m , TO d r a w t h e s c h e m a t i c d i a g r a m
The u s e r
sh o u ld
p ress
d ia g r a m
tran sform er area
of
th e c ir c u it .
a n y k e y , t h e n E X P -T est S y ste m w i l l c a l l
SKETCH2 p r o g r a m f r o m TURBO C . s y s t e m .
th e la y o u t
of
A lso ,
th e c ir c u it ,
and
t h i s program draw s
w ill
cause
th e
, and p o i n t (1) t o f l a s h , h e n c e l o c a t i n g p o in t
( 1 ) . A f t e r t h a t t h e SKETCH2 p r o g r a m
w i l l zoom o n t o t h e f l a s h i n g
(th e tra n sfo rm e r) a rea around p o in t (1 ), and w i l l d is p la y :
PRESS ANY KEY TO CONTINUE.
The u s e r s h o u ld p u t th e p ro b e a t p o in t ( 1 ) , th e n h e s h o u ld p r e s s
81
any key on the keyboard.
E X P -T est S y s te m
w ill
c a ll
E X P_T1 p r o g r a m , w h i c h a s m e n t i o n e d ,
w i l l r e t u r n tw o v a r i a b l e s : d e l t a l an d s t a n d e r l .
If d e lta l
>=
sta n d erl
(if
E X P -T est S y ste m w i l l t e l
th e
r e c e iv e d s ig n a l
is
w ron g),
th e u s e r t h a t t h e r e i s a p r o b le m in th e
tran sform er, so i t w ill d is p la y :
THERE IS
A
PROBLEM
IN THE TRANSFORMER, I
SUGGEST
YOU
TO
REPLACE IT.
PRESS <ENTER>, THEN <Q>, TO EXIT.
But i f
d e lta l
<
sta n d e r l ( i f th e r e c e iv e d s ig n a l is c o r r e c t),
E X P -T est S y ste m w i l l d i s p l a y :
THE TRANSFORMER IS OK, <PRESS
ANY
KEY> TO CONTINUE
TESTING
THIS DEVICE.
A t t h i s s t a g e i f t h e u s e r p r e s s e s an y k e y , E X P -T est
S ystem w i l l
d isp la y :
PUT THE OSCILLOSCOPE'S PROBE A T POINT (2),
IF YOU ARE READY, CHOOSE YES, AND PRESS <ENTER>.
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
The G r a p h ic
fa c ility
has
b e e n c o n n e c t e d j u s t t o p o i n t (1)
(to
p r o v e t h e c a p a b i l i t y o f i n t e g r a t i n g E X P -T est S y s te m w it h G r a p h ic
fa c ility ).
82
I f t h e u s e r c h o o s e s Y E S, a f t e r h e p u t s t h e o s c i l l o s c o p e p r o b e a t
p o in t (2 ),
E X P -T e st S y s te m w i l l c a l l EXP_T2, w h ic h w i l l g e t t h e
s i g n a l a t p o i n t (2) an d r e t u r n
d e lta l
an d s t a n d e r l t o E X P -T est
S ystem .
If d e lta l
>=
sta n d erl
(if
th e
r e c e iv e d
sig n a l
is
w ron g),
E X P -T est S y ste m w i l l d i s p l a y ( i n s i d e f l a s h i n g w in d o w ):
THERE IS
A
PROBLEM
IN
THE
COMPONENTS CAUSE THIS PROBLEM,
OTHER POINTS
(5V)
OUTPUT,
YOU
TO DEFINE WHICH
SHOULD MAKE TEST TO SOME
BETWEEN POINT (1), AND POINT
(2),
<PRESS
ANY
KEY> TO CONTINUE.
B ut i f d e l t a l < s t a n d e r l , t h e n E X P -T est S y s te m w i l l d i s p l a y :
THE (5V)
OUTPUT
IS OK, <PRESS ANY KEY>, TO CONTINUE TESTING
THIS DEVICE.
A ssum e t h a t ( d e l t a l >= s t a n d e r l )
in
th e
p r e v io u s c a se ,
(w ron g
s ig n a l is r e c e iv e d a t p o in t (2 )).
I f t h e u s e r p r e s s e s a n y k e y , E X P -T est S y ste m w i l l d i s p l a y :
PUT THE OSCILLOSCOPE'S PROBE AT POINT (3).
IF YOU ARE READY, CHOOSE YES, AND PRESS <ENTER>.
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
I f t h e u s e r c h o o s e s YES, t h e n E X P - T e s t S y s t e m w i l l
w h ic h w i l l
get
th e
sig n a l
at
r e fe r e n c e s ig n a l and re tu r n d e lt a l
83
c a l l EXP_T3,
p o in t ( 3 ) , com pare i t w ith th e
and
sta n d e r l.
(If th e u ser
c h o o s e s NO,
th e sy stem w i l l w a it u n t i l th e u s e r i s read y and i t
w i l l p ro m p t h im a g a i n ) .
I f d e l t a l >= s t a n d e r l , E X P -T e st S y s te m w i l l d i s p l a y :
THERE IS A PROBLEM BETWEEN POINT (3), AND POINT
TO BE MORE SPECIFIC,
(1),
<PRESS ANY KEY> TO CONTINUE TESTING (5V)
LINE.
B ut i f d e l t a l < s t a n d e r l , E X P -T est S y ste m w i l l d i s p l a y t h e f a u l t
c a n d id a te l i s t :
THE EXPECTED DAMAGED COMPONENTS ARE:
(1) U21.
(2) V R 1 .
(3) C30.
(4) C28 .
(5) C 5 _ 7 .
T hat w ork w i l l ta k e by e x p e r ie n c e , a b o u t 5 m in u te s .
2.
If a
new
d efect
te r m in a te d a f t e r
is
en cou n tered ,
several
E X P -T est S y ste m
t r i a l s and a m essa g e
w ill
w ill
be
be
g iv e n
sh o w in g t h a t a new p r o b le m i s b e in g p r o c e s s e d .
The f o l l o w i n g e x a m p le , e x p l a i n s how E X P -T est S y s te m a s k t h e u s e r
fo r m ore
in fo r m a tio n ,
and
te ll
h im
th a t a
new
case
is
U .U .T .,
to
en cou n tered :
T h is e x a m p le w i l l c h e c k t h e
d r iv e
m otors
o f th e
d e f i n e i f t h e m a lf u n c t io n i s from o n e o f t h e m o to r s
m o to r 's d r iv e r .
84
o r from t h e
SWITCH THE
A T LEAST,
PLOTTER
(U.U.T.) OPP, PUT A BLANK PAPER, ONE PEN
(NOl). THEN PRESS
(PI)
&
(P2),
AT THE SAME TIME
SWITCH ON THE PLOTTER. THE TEST PROGRAM W I L L RUN, TESTING THE
OPERATION OF
EVERY
MOTOR,
THAT CALLED
PROGRAM) . BY
LOOKING CAREFULLY TO THE MOTORS, PRESS <ENTER>,
IF ALL OF THEM WORK PERFECTLY,
(THE
INTERNAL
TEST
O R MOVE THE CURSOR TO PROBLEM
AND PRESS < E N T E R >.
PROBLEM
NO_PROBLEM
I f t h e u s e r f i n d s a p ro b lem in t h e p e r fo r m a n c e o f
an y m otor, he
w i l l s e l e c t PROBLEM.
In t h i s c a s e E X P -T est S y ste m w i l l p r i n t o u t on t h e s c r e e n :
ONE OF
THE
DRIVE
MOTORS
DOESN'T
WORK,
<PRESS ANY KEY> TO
DEFINE WHICH ONE.
Now t h e s y s t e m w i l l a s k t h e u s e r :
MOVE THE CURSOR TO THE SUITABLE DRIVE MOTOR WHICH YOU NOTICED
DOESN'T W O R K AND PRESS <ENTER>.
PAPER_DRIVE_MOTOR
PEN_DRIVE_MOTOR
PEN_SOLENOID
I f th e
user
se le c ts
CAROUSEL_STEPPER_MOTOR
PAPER_DRIVE_MOTOR, E X P - T e s t
S ystem
d isp la y :
<PRESS ANY KEY>, TO DEFINE THE DAMAGED COMPONENTS.
W hen t h e u s e r p r e s s e s a n y k e y , t h e s y s t e m d i s p l a y s :
85
w ill
PUT THE
OSCILLOSCOPE'S
PROBE
A T POINT
THEN ROTATE THE MOTOR MANUALLY,
ON THE
FRONT
(ENCAX), OR
(BY USING ONE OP THE BUTTONS
PANEL OF THE PLOTTER) . IF THERE
SIGNAL PRESS <ENTER>,
(ENCBX).
IS
A
SQUARE
IF THERE IS NO SIGNAL:
MOVE THE CURSOR TO NO, AND PRESS <E N T E R > .
NO
YES
I f th e
user
observes
th e
sq u are s ig n a l on th e o s c illo s c o p e 's
s c r e e n , h e w i l l s e l e c t YES. In
th is
case
E X P -T est S y ste m w i l l
d isp la y :
THE ENCODER IS OK, <PRESS A NY KEY>, TO CONTINUE
TESTING THIS
UNIT.
The u s e r
sh o u ld
p ress
any
key
to
c o n tin u e , th e n th e sy stem
d isp la y s:
SWITCH ON THE LOGIC ANALYZER,
THEN
CHOOSE
YES,
AND
PRESS
< E N T E R > . OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
NO
YES
Now t h e s y s t e m w i l l c a l l EXP_SE T1 p r o g r a m , w h i c h
L o g ic A n a ly z e r .
When
th e
L o g ic
A n a ly ze r
is
w ill setu p th e
r e a d y , E X P -T est
S y stem d is p la y s :
CONNECT POD (0), CHANNEL
(0), TO POINT
BUTTON, ON THE LOGIC ANALYZER
FRONT
(A), A ND PRESS
PANEL.
ANALYZER GET DATA ON IT'S SCREEN, THEN CHOOSE
WAIT
NO
86
TILL
THE
YES, AND PRESS
<ENTER>. OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
YES
(START)
A t t h i s p o i n t t h e e x p e r t s y s t e m w i l l c a l l E X P _T 11 p r o g r a m , w h i c h
w ill get
th e
sig n a l
from t h e A n a ly z e r an d co m p are i t w i t h t h e
r e f e r e n c e s i g n a l . T h e n E X P _T 11
c a lc u la te s th e t o t a l d iffe r e n c e ,
save i t
and
in
v a r ia b le
d e lta l,
retu rn d e lt a l
to
E X P -T est
S ystem .
If d e lta l
>
0 (w ron g s i g n a l i s r e c e i v e d ) , E X P -T e st S y s t e m w i l l
d isp la y :
THERE IS A PROBLEM IN THE INPUT
THIS IS
A
NEW
PROBLEM, YOU
OUTPUT OF
It is
OF
THE
PAPER MOTOR DRIVER.
CASE, TO DEFINE WHICH COMPONENTS
SHOULD
DO
SOME
(U6) GATE ARRAY.
OTHER
CAUSE
THE
TESTS TO THE INPUT AND
PRESS <ENTER», THEN <Q> TO EXIT.
a v e r y d i f f i c u l t jo b fo r an
expert
t o know o f a l l t h e t y p e s
o f p ro b lem s w h ich
m ig h t o c c u r t o a m a c h in e . T h a t
a lw a y s a la c k
t h e k n o w le d g e b a s e o f E X P -T est S y s te m . T h is l a c k
in
can be com p en sated fo r by in t e g r a t in g
E X P -T est
m eans
th ere
is
S y s t e m 's k n o w le d g e
b a s e w it h t h e k n o w le d g e w h ic h i s in c lu d e d in t h e G r a p h ic
su b system
an d t h e k n o w le d g e o f t h e t e c h n i c i a n .
So i f E X P -T est
S ystem
d i d n ' t com e t o an y s o l u t i o n , t h e t e c h n i c i a n
h a s t o a n a ly z e t h e s c h e m a tic d ia g r a m
of
th e
c ir c u it,
and tr y to
fin d ou t th e f a u lt .
H ow ever, t h e r e a r e
The f i r s t o n e ,
tw o r e a s o n s why t h i s w i l l n o t
because
ta k e
too
lo n g .
E X P -T est S y s te m h a s a lr e a d y c o m p le t e d p a r t
o f th e a n a ly s e s . The seco n d , i s
th e
great
h e lp
w h ic h
w ill
th e
g r a p h ic s f a c i l i t y g iv e .
When t h i s t e c h n i c i a n
E X P -T est S y s te m w h ic h
com es up w it h th e s o l u t i o n ,
he
w ill
u p d a te
m ay b e e a s i l y a c c o m p l i s h e d b y a d d i n g t h e n e w
c a s e t o i t ' s k n o w led g e b a s e .
87
As m e n tio n e d , i t
i s v e r y e a s y t o u p d a te E X P -T est S y s te m , by a d d in g
o r m o d ify in g i t ,
because
i t c o n sists
of
m any
p r o d u c tio n
r u le s
(IF -T H E N ), i e . i t i s m o d u la r .
U p -d a tin g E X P -T est S y ste m
w ill
p r o v id e
e x p e r i e n c e s , im p ro v e p r o b le m - s o l v in g
new
in sig h ts,
m eth od s,
and
d iffe r e n t
in c r e a se
th e
d e p th o f t h e k n o w le d g e i n s i d e i t ' s k n o w le d g e b a s e a t t h e sam e t im e .
That w ill ea se th e ta sk fo r th e
new
te c h n ic ia n
in
th e
case
of
a b sen c e, r e tir e m e n t o r d ea th o f th e p r e v io u s t e c h n ic ia n .
The new t e c h n i c i a n
ad v a n ta g es o f a l l
(te c h n ic ia n 2
in
fig .
5 -1 )
w ill
get
th e
t h e k n o w led g e o f t h e e x p e r t a n d t h e k n o w le d g e o f
t h e p r e v i o u s t e c h n i c i a n . He w i l l
fin d
b a s e o f E X P -T est S y s te m .
88
th em
in sid e
t h e k n o w le d g e
CHAPTER 6
INTEGRATING GRAPHIC CAD KNOWLEDGE WITH
EXPERT SYSTEM AND ON-LINE TEST
6.1 INTRODUCTION
C om p u ters h a v e b e e n u s e d t o f a c i l i t a t e t h e d e s i g n p r o c e s s s i n c e
th e e a r ly 1960s.
A p p lic a tio n s
have
s im u la tio n , and ev en th e c o m p le te
in c lu d e d a n a ly s is o f d e s ig n s ,
a u to m a tio n o f som e o f t h e d e s ig n
p r o c e s s e s . In th e e a r ly 1 9 7 0 s , i n t e r a c t i v e co m p u ter g r a p h ic s becam e
a p r a c tic a l to o l
fo r su p p o r tin g g r a p h ic s -b a s e d d e s ig n .
th e g r e a t m a jo r ity
of
co m p u ter-b a sed
P r e se n tly ,
w o r k -sta tio n s
su p p o r tin g
d e s ig n a r e o f t h e i n t e r a c t i v e co m p u ter g r a p h ic s t y p e .
D u r in g t h e p r e c e d in g t w e n ty -y e a r
p e r io d
th e
a c r o n y m CAD h a s b e e n
u se d t o a p p ly t o any or a l l o f th e v a r io u s a p p lic a t io n a r e a s [7 2 ].
C o m p u ter a i d e d d e s i g n
(C A D ),
co m p u ter, h a s e v o lv e d
to
or
d e sig n in g
w ith
th e
a id
of
a
th e p o in t w here ea ch one w i l l be ex p osed
t o i t s c a p a b i l i t i e s . T oday, d e s ig n in g w it h t h e a i d o f a co m p u ter i s
n o t r e s e r v e d fo r a ch o se n few . Anybody
who
h as a p o p u la r p e r so n a l
c o m p u t e r c o u l d p u r c h a s e a CAD p a c k a g e f o r a f e w h u n d r e d d o l l a r s a n d
b e g in d e s ig n in g to d a y [7 3 ].
6.2 CAD System
6.2.1 Overview
T h e o b j e c t i v e o f CAD i s t o i n c r e a s e p r o d u c t i v i t y
co m p u ters in th e
d e sig n
by
u tiliz in g
p r o c e s s . The m ea n in g o f p r o d u c t i v i t y h e r e
i s th e r a t i o o f la b o r h ou rs r e q u ir e d
fo r
a m anual d e s ig n fu n c tio n
t o th e la b o r h o u r s r e q u ir e d i f a co m p u ter i s u s e d
69
to
support
th e
fu n c tio n .
CAD i s a b r o a d s u b j e c t t h a t f i t s i n t o a b r o a d s p e c t r u m o f a u t o m a t e d
m e t h o d s . T h e f o l l o w i n g d i a g r a m ( f i g . 6 - 1 ) s h o w s t h e p l a c e o f CAD i n
th e sp ectru m o f au tom ated m e th o d s:
A u to m o te d m ethods
1
1
C o n s tru c tio n
G ro u p
m anagem ent
te c h n o lo g y
E„s, „ u
and d e sig n
CAM
1
.
S im u la tio n
1
1
.
O p t im iz a tio n
1
C o m p u te r a id e d
C o m p u te r a id e d
e n g r.
d e s ig n (C A D )
I
C o m p u te r -a id e d
C o m p u te r -a id e d
d e s ig n a n d d r a ftin g
(C A D D )
d r a ftin g
(C A D )
f i g . 6 - 1 . P l a c e o f CAD i n t h e S p e c t r u m o f A u t o m a t e d M e t h o d s
CAD s y s t e m s m ay b e e i t h e r t w o - d i m e n s i o n a l o r t h r e e d i m e n s i o n a l , a n d
t h e y m ay b e
d e sig n e d
to
p r o v id e
e ith e r
sp e c ia l-p u r p o se
g e n e r a l-p u r p o s e a p p l i c a t i o n s . A lth o u g h
th ere
th e acronym s,
t o "3D" ( t h r e e - d i m e n s i o n a l )
CADD
sy stem s th a t b u ild
g e n e r a lly
a
m odel
refers
of
d r a f t i n g . C o m p u te r -a id e d d e s ig n
a
d e sig n
(C A D ),
is
or
and
g e n e r a lly
no s t r ic t u se o f
ten d
t o au tom ate
refers
t o “2D"
(tw o -d im e n s io n a l) s y s te m s t h a t s u p p o r t d r a f t i n g m ore d i r e c t l y .
A " sp e c ia l-p u r p o se " a p p lic a tio n r e f e r s to a sy ste m
s p e c i f i c narrow a p p lic a tio n ,
such
as
d e d ic a te d
to a
PCB b o a r d s , p i p i n g , a n d t h e
l i k e . S p e c i a l - p u r p o s e CAD s y s t e m s a r e o f t e n r e f e r r e d t o a s v e r t i c a l
sy stem s.
90
A " g e n era l-p u r p o se" a p p lic a t io n
i s a m ore g e n e r a l a p p l i c a t i o n su c h
a s a h i g h e r - l e v e l la n g u a g e th a t
can
be
a p p lie d
in
a p p l i c a t i o n a r e a s . G e n e r a l - p u r p o s e CAD s y s t e m s a r e
a
num ber o f
often
referred
to as h o r iz o n ta l sy ste m s.
The g r e a t m a j o r it y
2D s y s t e m s t h a t
o f CAD s y s t e m s i n u s e t o d a y a r e g e n e r a l - p u r p o s e
are
b e in g
a p p lie d
to
d i s c i p l i n e s a r c h it e c t u r e , m e c h a n ic a l,
h e lp
d r a ftin g
c iv il,
in
any
e le c tr ic a l,
or
e le c tr o n ic .
A l l CAD s y s t e m s
th a t
in an y way a id o r a u to m a te d r a f t i n g h a v e th e
fo llo w in g co m p on en ts:
(1) C om p u ter
(2) G r a p h ic s s c r e e n
(3) G r a p h ic s in p u t s u c h a s a d i g i t i z e r , k e y b o a r d , m o u se
(4) G r a p h ic s o u t p u t s u c h a s a p l o t t e r
C om p u ter g r a p h i c s i s
used
in
a rt,
e n g in e e r in g ,
m a n u fa c tu r in g , b u s i n e s s m an agem en t,
a r e a s . An a r c h i t e c t
can
la y
out
co m p u ter an d s p e c i a l i z e d g r a p h ic
m o v ie s a l s o ta k e
p r o g r a m . O ne o f
ad v an tage
th e
m ost
e d u c a tio n ,
of
or
d e sig n
so ftw a re.
c o n str u c tio n ,
and
a
m any
oth er
b u ild in g u sin g a
A n im a te d
co m p u ters and g r a p h ic
c a r to o n s and
a p p lic a tio n
b a s i c form s o f co m p u ter g r a p h ic s i s th e
bar ch art or graph.
S im u la tio n and t r a in in g o f p i l o t s
g r a p h ic s has had
great
is
a n o th er
p a y o ffs.
a r e a w h ere co m p u ter
W ith
th ree
d im e n sio n s
r e p r e s e n ta tio n s o f an
a i r c r a f t ' s c o n tr o ls and an a i r p o r t ' s la n d in g
s tr ip , stu d en t p ilo t s
can
w a stin g e x p e n s iv e f u e l.
a ir s t r ip a llo w a
The
lea rn
th e
sim u la tio n
b a sic s
of
of
an
fly in g
a ir c r a ft
w ith o u t
and
an
stu d e n t to e x p e r ie n c e th e v is u a l a s p e c t o f f ly in g
w ith o u t h a v in g t o s te p in t o a p la n e .
91
CAD Applications
A v a r ie ty
o f CAD
a p p lic a tio n s
are
c u r r e n tly
c o m p u te r s , from m a in fr a m e s t o p e r s o n a l c o m p u te r s .
g r o w in g s o f a s t
in
use
on
The in d u s tr y i s
t h a t i t ' s now n e c e s s a r y t o s p e c i a l i z e i n a s p e c i f i c
a p p l i c a t i o n a r e a j u s t t o m a in ta in a g o o d k n o w led g e
of
th a t f ie ld .
O ne o f T h e m o s t i m p o r t a n t a p p l i c a t i o n s i s :
Printing Circuit Design
I f t h e r e i s a s i n g l e f i e l d i n CAD t h a t h a s b e n e f i t t e d m o s t ,
it is
th e
p r in te d
c ir c u it d e sig n
e le c t r o n ic s in d u str y
b ec o m in g
process.
m ore
W ith
th e
c o m p e titiv e
in
d e v e lo p in g new e l e c t r o n i c p r o d u c t s , t h e n e e d
d e sig n e r 's f i r s t
p r in te d c ir c u it
for
s k e tc h e s t o f i n a l a rtw o rk i s e s s e n t i a l . A
CAD
sy stem
can
reduce
e v e r y th in g
d e s ig n t o m a n u fa c tu r in g th e p r in t e d c i r c u i t
tim e and
co st.
to
b oard s in b o th
th e m anual m eth od , ca n be
u p t o f o u r t o o n e . A p r i n t e d c i r c u i t CAD
b ills of
from
The p r o d u c t i v i t y g a in e d by u s in g a p r in t e d
c i r c u i t CAD s y s t e m , c o m p a r e d
r e p e t i t i v e and
ta k in g a
tim e -c o n su m in g
m a te r ia ls,
and
task s
m anual
sy stem
such
as
d e sig n
au tom ates
g e n e r a tin g
c h e c k in g .
a p p lic a tio n program s
fo r p r in te d c ir c u it
d e sig n e r in
th e s c h e m a tic d ia g ra m d i r e c t l y on th e
d ra w in g
screen . A lib r a r y o f c ir c u it
sy m b o ls
d e sig n
The
(a v a ila b le
a id
th e
o n -lin e )
a r e u s e d t o p l a c e c o m p o n e n t s o n t h e s c h e m a t i c d i a g r a m . W hen
f i n i s h e d , t h e d ra w in g ca n b e r e p r o d u c e d b y
a
h ig h -q u a lity
pen p l o t t e r o r a sim p le p r in t e r .
A CAD
m eth od
a llo w s
a
d e sig n e n g in e e r to c r e a te o n - lin e
f i n i s h e d s c h e m a t ic d ia g r a m
p r e -s to r e d c h ip
lib r a r y . T hese
d ra w in g s.
CAD
d e s c r ip t io n s and com ponent
lib r a r y
sy stem s c o n ta in
sy m b o ls
in
a
sy m b o ls becom e t h e b u ild in g b lo c k s
92
f o r s c h e m a tic d ia g r a m d e s i g n .
A CAD s y s t e m
m ust c o n s i s t o f a cp u , a s t o r a g e d e v ic e l i k e a flo p p y
d is k d r iv e , a m o n ito r , an in p u t d e v ic e
su ch a s d i g i t i z e r o r m ouse,
and a k e y b o a r d . The s o f tw a r e r e q u ir e d i s an o p e r a t in g
ex a m p le , f o r a
p erson al
d ra w in g s
h a v e tw o b a s i c
p a rts:
(fo r
c o m p u t e r , M S -D O S ); g r a p h i c s s o f t w a r e ( f o r
e x a m p l e : O rCAD /SDT I I I S y s t e m ) ;
sto r a g e or th e
sy stem
and
produced.
hardw are
a
d atab a se
to
co n tro l
A ll th e g r a p h ic
th e
in sta lla tio n s
and s o f tw a r e . The hardw are i s th e
co m p u ter and i t s a s s o c i a t e d p e r i p h e r a l s .
6.2.2. OrCAD/SDT III System
OrCAD /SDT I I I
S ystem
is
a co m p le te
and
fle x ib le
c a p t u r e p a c k a g e . E a s y t o u s e m en u d r i v e n co m m a n d s h e l p
crea te, e d it, save,
p r in t,
d e v e lo p e d s p e c i f i c a l l y t o
run
c o m p a t i b l e s , O rCAD /SDT I I I
b o a rd s, p r in t e r s , and
and
sch em a tic
th e u ser to
p lo t e le c t r o n ic sc h e m a tic s. I t is
on
IBM
su p p o rts
p lo tte r s.
p erson al
co m p u ters
m ost o f th e p o p u la r
T h is
e lim in a te s
s p e c ia l, p r o p r ie ta r y hardw are by e n a b lin g
th e
and
g r a p h ic s
need
for
th e u s e r to u se sta n d a rd
o u tp u t e q u ip m e n t.
T h e OrCAD /SDT I I I
so ftw a re
d r a f t i n g p r o g r a m DRAFT,
a
package
g r a p h ic a l
c o n sists
of
th e
sc h e m a tic
lib r a r y o b je c t e d ito r c a lle d
L IB E D IT , n e t l i s t , d e s i g n c h e c k , p a r t l i s t i n g , a n d o t h e r u t i l i t y a n d
lib r a r y program s.
DRAFT
DRAFT i s t h e s c h e m a t i c d r a f t i n g
program
th a t e n a b le s th e u se r
t o c r e a t e , e d i t and s a v e s c h e m a tic w o r k s h e e t. The m ajor f e a t u r e s o f
DRAFT i n c l u d e :
(1) U se r d e f i n a b l e t e m p la t e d im e n s io n s a t 1 m il r e s o l u t i o n .
(2) U s e r d e f i n a b l e t e x t s i z e .
93
(3) E ig h t p a r t f i e l d s .
(4) O ver 3 5 0 0 U n iq u e l i b r a r y p a r t s .
(5) D eM organ E q u i v a l e n t p a r t s .
(6) P la c e m e n t o f w i r e s , b u s e s , c o n n e c t o r s , l a b e l s , a n d j u n c t i o n s .
(7) R e a l- t im e r u b b e r b a n d in g
of
w ir e s
and
b u s e s w hen o b j e c t s a r e
m oved.
(8) P a r t r o t a t i o n a n d m i r r o r i n g .
(9) M o v in g , r e p l i c a t i n g , an d d e l e t i n g o b j e c t s o r b l o c k s o f o b j e c t s .
( 1 0 ) P o w e r f u l s t e p - a n d - r e p e a t co m m a n d .
(11) V i s i b l e g r id d o t s and a n g le d b u s e n t r i e s .
(12) A u to m a tic p a n n in g o f t h e w o r k s h e e t .
(1 3 ) F i v e zoom l e v e l s .
(14) O ver 100 u s e r - a s s i g n a b l e m a cr o s.
(15) U n lim ite d l e v e l s o f h ie r a r c h y .
(1 6 ) O n -L in e p a r t b r o w s in g an d l i b r a r y d i r e c t o r y .
(17) P S p ic e a n a lo g s i m u l a t i o n s h e l l (P S p ic e n o t i n c l u d e d ) .
(18) S t r i n g s e a r c h in g .
(19) V e r t i c a l t e x t p la c e m e n t .
( 2 0 ) S u s p e n s i o n o f s e s s i o n f o r DOS com m and e x e c u t i o n .
( 2 1 ) S u p p o r t s "A" t h r o u g h “E " , a n d c u s t o m s i z e w o r k s h e e t s .
Part Libraries
I n c l u d e d w i t h O rCA D /SD T I I I a r e e x t e n s i v e p a r t l i b r a r i e s o f t h e
m o s t c o m m o n ly u s e d d e v i c e s i n t h e i n d u s t r y .
Creating Custom Libraries
O rCAD /SDT I I I
e n a b le s th e u s e r
to
create
h is
ow n
" cu stom "
l i b r a r i e s , o r m o d ify e x i s t i n g o n e s , in tw o e a s y w a y s.
F ir s t, th e u ser
can
L IB E D IT . W ith t h i s
in v o k e
e d ito r ,
th e
th e
g r a p h ic a l o b je c t
user
t h o s e o f O rCAD/SDT I I I t o c o n s t r u c t
94
e d ito r
c a lle d
c a n u s e co m m a n d s s i m i l a r t o
o r m o d ify a p a r t on t h e s c r e e n
and add i t to a
new o r e x i s t i n g l i b r a r y .
Second, th e u se r
can
f i l e . A lib r a r y
so u rce f i l e i s an
u se a te x t e d ito r to c r e a te a lib r a r y sou rce
A SC IIt e x t
file
th a t c o n ta in s
i n s t r u c t i o n s i n t h e OrCAD S y m b o l D e s c r i p t i o n L a n g u a g e .
Utility Programs
O rC A D /SD T I l l ' s
fle x ib ility
c o n tin u e s
after
th e
sc h e m a tic
d e sig n p r o c e ss w ith e a s y -to -u s e u t i l i t y program s, in c lu d in g :
* ANNOTATE:
T h isprogram
scans
a u to m a tic a lly
a h ie r a r c h y o r f l a t f i l e and
u p d a tes
a ll part
referen ce
part
referen ce
d e sig n a to r s.
* BACKANNO:
The
BACKANNO
u tility
d e sig n a to r s in
program , a
th e
list
u p d a tes
user
of
d e s ig n . The in p u t t o th e
o ld
and
new
d e s ig n a to r s , i s u se d t o u p d a te th e
referen ce
user
sc h e m a tic
w o rk sh eets.
* CLEANUP:
T h is u t i l i t y c h e c k s th e w o r k s h e e t f o r w ir e s , b u s e s ,
ju n c tio n s, la b e ls ,
m o d u le p o r t s , an d o t h e r o b j e c t s
th a t a r e p la c e d on to p o f ea ch o th e r .
* COMPOSER: I f t h e u s e r c h o o s e
to c r e a te lib r a r y p a r ts u sin g a
t e x t e d i t o r , COMPOSER i s t h e l i b r a r y
co n v erts th e
u tility
th at
u s e r cu stom lib r a r y s o u r c e f i l e s in t o
th e h ig h ly com pressed
lib r a r y o b je c t f i l e s u se d by
DRAFT.
* CROSSREF:
T h is
u tility
sca n s th rou gh th e sc h e m a tic
g a th e r s in fo r m a tio n
in th e
sch em a tic
fo r
file s,
a ll
and
referen ce lis t in g th a t t e l l s th e
file s,
p a rts
crea tes
user
used
a
w here
cross
each
p art is lo c a te d .
* DECOMP:
I f th e u se r ch o o se to c r e a te lib r a r y p a r ts u sin g a
95
te x t e d ito r ,
DECOMP
e n a b le s th e
user
i s a lib r a r y d e -c o m p ile r th a t
to
convert
th e
O r C A D -su p p lie d
lib r a r y o b je c t f i l e s to lib r a r y sou rce f i l e s .
* ERC:
T h is i s a u t i l i t y t h a t p e r fo r m s an e l e c t r i c a l r u le s
ch eck o f th e u s e r sch em a tic w o r k s h e e ts .
* LIBARCH:
T h is u t i l i t y ta k e s a l l t h e l ib r a r y
th e sch em a tic
file s
so u r c e , an a r c h iv e d
and
m akes
p a rts
a
used
in
s in g le lib r a r y
lib r a r y , c o n ta in in g o n ly p a r ts
w h ic h a r e u s a b le f o r t h o s e s c h e m a tic f i l e s .
* L IB E D IT :
T h is
u t i l i t y e n a b le s th e u s e r t o
create
lib r a r y
com p on en ts on t h e s c r e e n .
* N E T L IST :
T h is
program g e n e r a te s a n e t l i s t o f th e w o rk sh eet
s ig n a l and p a r t c o n n e c tio n s .
* PAR T L IST: T h i s u t i l i t y s u m m a r i z e s
a ll
th e
p a rts
u sed in a
sch e m a tic o r group o f sc h e m a tic s h e e t s .
* PLOTALL:
PLOTALL
p lo t s a sch em a tic o r group
of
sch e m a tic
s h e e t s , in b a tc h m ode.
* PRINTALL:
PRINTALL
p r in ts a sch em a tic o r group o f sch e m a tic
s h e e t s , in b a tc h m ode.
* T R E E L IST :
A
program
th a t
o r g a n iz a tio n o f
scans
a
sh e e ts to d isp la y
h ie r a r c h ic a l
th e
stru ctu re,
s h e e t n am es, and s h e e t p a th nam es o f t h e h ie r a r c h y .
6.2.3.
OrCAD Plot File
D u r in g t h e
been u sed a s
la st
a
tw en ty
p ow erfu l
s p e c ia lly in e le c tr o n ic
y e a r s CAD ( C o m p u t e r A i d e d D e s i g n ) h a s
tool
in
en g in e e r in g
a ll
e n g in e e r in g
fie ld ,
and
d isc ip lin e s,
p r in te d
c ir c u it
board d e sig n .
I t was v e r y
im p o r ta n t
to
in co rp o r a te
96
CAD s y s t e m i n t h i s w o r k t o
a c h ie v e th e i n t e r a c t i v i t y , in t e g r it y and g e n e r a lit y .
T h e OrCAD/SDT I I I ,
w h ic h
is
a
co m p u ter
a id e d d r a ftin g package,
c a p a b l e o f d r a w i n g 2D d i a g r a m s , h a s b e e n a d o p t e d .
OrCAD /SDT I I I p a c k a g e i s a c o m p l e t e
and f l e x i b l e sc h e m a tic ca p tu re
pack age b e in g u sed in th e d ep artm en t. I t h as an e a sy
d r i v e n com m ands, w h ic h
h e lp
to
d ra ft
and
to
p lo t
use
m en u
e le c tr o n ic
sc h e m a tic s.
In o r d er t o
in te g r a te
n ecessa ry to adopt
a
OrCAD w i t h
n eu tra l
th e
file ,
E X P -T est
w h ic h
can
S ystem ,
be
it
produced
was
by
O rCAD /SDT I I I a n d r e a d b y a n e x t e r n a l p r o g r a m .
The p lo t f i l e s
are
th e
id e a l
file s
to be u sed in t h is p r o c e s s ,
because o f i t s c a p a b ilitie s to rep resen t
a ll
th e
e n t i t i e s , w h ic h
ca n b e draw n on t h e s c r e e n .
A ls o , t h e s e f i l e s a r e w r it t e n in t e x t f i l e s , w h ic h
can
e a sily
be
read and t r a n s la t e d t o o th e r fo r m a ts .
O rCAD /SDT I I I h a s
th e
c a p a b i l i t y t o c r e a t e s e v e r a l t y p e s o f OrCAD
p l o t f i l e s . T h e s e f i l e s com m and p l o t t e r s
to c r e a te hardcopy o f th e
d r a w in g s.
H P -fo rm a tted p l o t f i l e h a s b een c h o se n t o b e u s e d a s a n e u tr a l f i l e
in t h is in te g r a tio n p r o c e ss.
T he m a in d r a w in g e n t i t i e s r e p r e s e n t e d i n t h i s fo r m a t a r e a s f o l l o w :
1 . T h e l i n e co m m a n d :
t h i s co m m a n d ,
ask
P A ( x l , y l ) ; P D ;P A (x2, y 2 )
H P -P lo tte r
to
draw
lin e
b etw een
p o i n t ( x l , y l ) and p o in t ( x 2 , y 2 ).
2 . T h e t e x t co m m a n d :
P A (x ,y );L B
t h i s co m m a n d ,
H P -P lo tte r
ask
text
to w r ite th e d e fin e d te x t a t
p o in t(x ,y ).
3 . T h e c i r c l e co m m a n d :
P A (x ,y );C I r
t h i s co m m a n d , a s k H P - P l o t t e r
97
to
draw
a
c ir c le
w ith
th e
ra d iu s r , a t p o in t ( x ,y ) .
4 . The
arc
com m and:
P A (x l,y l);A A (x ,y ),+ /- s t a r t a n g le , th e
a rc in d e x .
or:
A A (x l,y l),+ /- s ta r t
a n g le ,th e
arc
in d e x ;A A (x ,y ), + / -
s t a r t a n g le ,th e a rc in d e x ,
t h i s co m m a n d , a s k H P - P l o t t e r t o d r a w a n a r c ,
In th e
fir st
form at
P o in t(x l,y l)
(w h ere t h e p l o t t e r ' s p en
sta rt
d e fin e
d r a w in g
a t p o in t(x ,y ).
th e s t a r t p o in t
th e
a rc).
In th e
s e c o n d fo r m a t, w h ic h i s e n c o u n te r e d in t h e c a s e o f d r a w in g a
ch a in o f a r c s ( c o i l ) , p o i n t ( x l ,y l ) d e f in e th e
c e n tr e o f th e
p r e v io u s a r c .
+/ - d e fin e
t h e d i r e c t i o n o f t h e d r a w (+ f o r c l o c k w i s e / - f o r
u n ti-c lo c k w ise ).
A s o ftw a r e h as b een d ev elo p e d u s in g
g r a p h ic a l form at o f
th e
TURBO
C. C o m p ile r t o r e a d t h e
p l o t f i l e t o b e u s e d in E X P -T est
S ystem .
T h is s o f t w a r e i s d i v i d e d i n t o tw o m a in p a r t s . T he f i r s t p a r t o f t h e
program s e a r c h e s and e x t r a c t s a l l th e d a ta o f t h e d ra w in g e n t i t i e s .
A fte r m a n ip u la tin g and
m o d ify in g
th ese
d ata,
i t s a v e s th em in a
d a ta f i l e to be u sed la t e r .
The f u n c t io n o f t h e o t h e r p a r t o f th e s o f tw a r e i s t o r e a d t h i s d a ta
from t h e d a t a f i l e , an d p r e p a r e i t
s c r e e n . The s c r e e n
is
s c a le a c c o r d in g to
th e
set
so
t h a t i t ca n b e draw n on t h e
t o t h e g r a p h ic m ode u s i n g
d r a w in g .
a
s u ita b le
TURBO C . b u i l t - i n f u n c t i o n s h a v e
been u sed to c r e a te th e sc h e m a tic
d ia g ra m
on
th e
screen.
T hese
fu n c tio n s a r e :
1 . The l i n e f u n c t io n :
w h ic h draw
lin e
l i n e ( x l ,y l , x 2 ,y 2 )
on
th e
screen
p o in t(x 2 ,y 2 ).
98
b etw een p o i n t ( x l , y l )
and
2 . The t e x t f u n c t io n :
o u t t e x t x y ( x , y , text)
w h ic h w r i t e th e d e f in e d t e x t on t h e s c r e e n a t p o i n t ( x , y ) .
3 . The c i r c l e f u n c t io n :
w h ic h draw
c ir c le
c i r c l e ( x , y , r)
on th e s c r e e n a t p o i n t ( x ,y ) , w ith r a d iu s
r.
4 . The a r c f u n c t io n :
a r c ( x ,y ,s t a r t a n g le ,e n d a n g le ,r )
w h ic h draw a r c on th e s c r e e n a t p o i n t ( x , y ) , b e g in n in g a t th e
s p e c i f i e d s t a r t a n g le , and
fin ish in g
at
th e s p e c if ie d end
a n g le , w ith r a d iu s r .
S ev era l t e s t s have been c a r r ie d o u t u s in g th e s e program s,
r e s u lt b oth , th e
d r a w in g s
crea ted
by
O rC A D /SD T
and as a
I I I and th e one
e x t r a c t e d from t h e p l o t f i l e w e re i d e n t i c a l .
6.3.
Prnnr»ma
The s o f t w a r e w h ic h r e a d s t h e g r a p h i c a l
and draw s th e
g r a p h ic s
on
form at o f th e p l o t f i l e
th e scre en i s d iv id e d
in to
tw o
m a in
p a rts.
The f i r s t p a r t
is
c a lle d
th e
S e a r c h P rogram . The s e c o n d p a r t i s
c a l l e d th e S k e tc h Program .
F ig . 6 -2 show s th e flo w c h a r t o f th e S e a r c h Program .
The w ork o f t h e S e a r c h P rogram i s
to
search
and
e x tr a c t a l l th e
d a ta o f t h e d r a w in g e n t i t i e s , i n s i d e t h e p l o t f i l e . T hen t h e S e a r c h
Program w i l l s a v e t h e s e d a ta in a d a ta f i l e , a f t e r m a n ip u la t in g and
m o d ify in g th em .
I n t h e b e g i n n i n g t h e S e a r c h P r o g r a m o p e n s t h e OrCAD
read i t , and
opens
a
d ata
p lo t
file
to
f i l e to sa v e th e m o d ifie d d a ta in i t .
Then t h e S e a r c h P rogram m ak es c h e c k s
on
th e
p lo t
t h a t i t i s n o t em p ty. A t t h i s s t a g e i f t h e p l o t f i l e
s e a r c h p rogram w i l l p r in t on th e s c r e e n :
99
f i l e to ensure
is
em p ty t h e
SEARCH
/
I
P H O G R flM
START
1
“ I
t
'
OrCflD PLOT
('P E N OrCftl) H l . E
* 0 R R M D IN G .O P L N
W llA f I L E .
-fill
T
r '^ S\
PM T
\
FtLE IS
\
EMPTY /
\
/
sJno
YES
>------
f i g . 6 - 2 . The F lo w c h a r t o f th e S e a r c h P rogram
100
"ERROR: OPEN PLOT F I L E " . T h e n i t w i l l c l o s e t h e p l o t a n d d a t a f i l e s
and e x i t .
But i f th e p lo t f i l e c o n ta in s th e g r a p h ic a l in fo r m a tio n , th e S ea rch
P rogram w i l l s t a r t s e a r c h in g f o r t h e s t a r t p o in t o f t h e d a t a , w h ic h
i s f o r H P -fo rm a t, th e term (S P 1 ) .
A f t e r f i n d i n g (S P 1) i n s i d e t h e p l o t f i l e , t h e S e a r c h P ro g r a m
ch eck s th e p lo t f i l e to en su re th a t i t h a sn 't reach ed i t s end.
I f t h e S e a r c h P r o g r a m e n c o u n t e r e d (EOF) i n s i d e t h e p l o t f i l e
i t w i l l c lo s e th e p lo t and th e d a ta f i l e s , and e x i t .
T h is ch e c k fo r
th e
end
of
f i l e w i l l be a c c o m p lish e d a f t e r ev ery
s e a r c h f o r new d a t a i n t h e p l o t f i l e .
Now i f i t i s n o t t h e e n d o f t h e f i l e , t h e S e a r c h P r o g r a m w i l l s t a r t
to sea rch fo r th e f i r s t p a rt o f th e
g r a p h ic a l
d ata ,
w h ic h a lw a y s
has one o f th e fo llo w in g form ats:
1 . P A (x ,y ); (th e norm al c a s e ) .
2 . A A (x ,y ),+ /-
sta rt
a n g le , th e a r c in d e x ;
(in
th e
case
of
d ra w in g a c h a in o f a r c s ) .
T hen i t w i l l
save
th e
ca p tu red
d a ta
( F i r s t ) . A f t e r t h a t th e S e a r c h Program
on th e p lo t
in
an
array o f ch a ra cter
m akes th e end o f f i l e ch eck
f i l e . I f i t i s p a s s e d , th e S ea rch Program
s e a r c h in g fo r th e
second
part
of
w ill
sta rt
th e g r a p h ic a l d a t a , w h ic h w i l l
ta k e one o f th e fo llo w in g fo rm ats:
(1) P A (x ,y )
f o r d ra w in g l i n e .
( 2 ) LB t e x t
fo r w r itin g a t e x t .
(3) C l r
f o r d ra w in g a c i r c l e .
(4) A A ( x , y ) , + / - s t a r t a n g l e , t h e a r c in d e x
Then i t w i l l s a v e t h e c a p t u r e d d a t a
in
a n o th er a rra y o f c h a r a c te r
(S e c o n d ). A ls o th e S e a r ch Program w i l l ch eck f o r
p r e v io u s se a r c h .
101
f o r d ra w in g an a r c .
(E O F ),
a f t e r th e
Now t h e S e a r c h
P rogram
has
a
c o m p le te in f o r m a tio n f o r d ra w in g a
l i n e , a c i r c l e , an a r c , o r w r it in g
a
tex t.
To d e f in e th e ty p e o f
t h e c a p tu r e d d a ta t h e S e a r c h P rogram s c a n s t h e f i r s t tw o c h a r a c t e r s
in t h e a r r a y ( S e c o n d ) . The f i r s t tw o c h a r a c t e r s i n
th e second p art
o f th e d a ta , a lw a y s d e f in e s th e ty p e o f g r a p h ic a l in fo r m a tio n .
T hen t h e S e a r c h P rogram w i l l s a v e t h e s e tw o c h a r a c t e r s in c h a r a c t e r
a r r a y (C om p ). A f t e r
t h a t , th e S ea rch Program b e g in s t o e x t r a c t th e
m a in i n f o r m a t i o n a b o u t t h e c a p t u r e d
t e x t , a n g l e s ) . T hen
saves
th em
d a ta (d im e n sio n s, c o o r d in a te s ,
in tw o a r r a y s o f
ch a ra cter
((C )
c o n t a i n s t h e e x t r a c t e d in f o r m a t io n from t h e f i r s t p a r t o f g r a p h i c a l
d ata,
(D) c o n t a i n s
th e
e x t r a c t e d in f o r m a t io n from t h e s e c o n d p a r t
o f g r a p h ic a l d a t a ) .
By u s i n g s t r c m p O
f u n c t i o n i n TURBO.
com pare b etw een th e
co n ten t
(c o n ta in s th e f i r s t
tw o
C.
th e
Search
Program w i l l
o f (Com p) a n d a p o i n t e r
ch a ra cters
to
every
to
o p tio n s,
ex p ected g r a p h ic a l
e n t i t i e s , P A ,L B ,C l,A A ).
I f t h e c o n t e n t o f (Com p) a r r a y w a s
“PA"
th is
w ill
in d ic a te to a
l i n e com m and i n t h e H P - f o r m a t e d p l o t f i l e . I n t h i s c a s e , t h e S e a r c h
Program w i l l do th e s u i t a b l e m a n ip u la t io n an d m o d if ic a t io n
form at o f th e
ca p tu red
th e lin e ( ) fu n c tio n
in
d ata
to
th e
to p u t i t in th e s u it a b le form at fo r
TURBO. C .
(th e
new
form ated
x l , y l , x 2 , y 2 ; ) . Then t h e S e a r c h P rogram w i l l s a v e
th e
d ata:
L IN
new fo r m a te d
d a ta in th e d a ta f i l e .
I f th e co n ten t
of
(Comp)
a r r a y w a s "LB", t h i s w i l l i n d i c a t e t o a
t e x t com m and i n t h e H P - f o r m a t t e d p l o t
f i l e . A lso in t h i s c a s e , th e
s u it a b le m a n ip u la tio n and m o d ific a tio n w i l l ta k e
ca p tu red d a ta in
th e
s u ita b le
form at
part
to
put th e
f o r t h e t e x t () f u n c t i o n i n
TURBO. C . ( t h e n e w f o r m a t e d d a t a : TEX x , y , text ; ) .
T hen t h e S e a r c h P rogram w i l l s a v e t h e new fo r m a te d d a t a i n t h e d a t a
102
file .
I f th e co n ten t
of
(Comp)
array
is
c i r c l e com m an d i n t h e H P - f o r m a t t e d
“C l " ,
A lso
th e su ita b le
m a n ip u la tio n and m o d ific a tio n w i l l ta k e a p a r t to p u t
th e ca p tu red
d a ta in th e
p lo t
th is w ill sig n a l to a
file .
s u i t a b l e f o r m a t f o r t h e c i r c l e () f u n c t i o n i n TURBO. C .
( th e new fo r m a t t e d d a ta : C l x , y , r ; )•
T hen t h e S e a r c h P rogram w i l l
s a v e t h e new fo r m a tte d d a ta in t h e d a t a f i l e .
I f t h e c o n t e n t o f (Comp) a r r a y i s “A A " , t h i s w i l l s i g n a l
to an a r c
com m and i n t h e H P - f o r m a t t e d p l o t f i l e . I n t h i s c a s e , s o m e d i f f i c u l t
work h a s c a r r ie d
o u t t o m o d ify th e c a p tu r e d d a ta , t o p u t i t in th e
s u i t a b l e f o r m a t f o r t h e a r c () f u n c t i o n i n TURBO. C . .
T h e a r c com m and i n H P - f o r m a t t e d p l o t f i l e h a s t w o f o r m a t s :
(1) P A ( x l , y l ) ;A A ( x ,y ) , + / - s t a r t a n g l e , t h e a r c in d e x ;
(2) A A ( x l , y l ) , + / -
s ta r t a n g le ,th e
arc
in d e x ;A A (x ,y ), + /- s t a r t
a n g le ,t h e a r c in d e x .
T h e a r c ( ) f u n c t i o n i n TURBO .C. h a s t h e f o r m a t :
a r c ( x ,y ,s t a r t a n g le ,e n d a n g le ,r )
T h e f i r s t f o r m a t o f t h e a r c co m m a n d , c o n t a i n s t h e
th e arc p o in t
sta rt
p o in t
of
P A ( x l,y l) , th e c e n tr e o f th e cu rren t arc p o in t ( x ,y ) ,
th e d ir e c tio n o f th e arc, th e s ta r t
se c o n d fo rm a t o f
th e
arc
co m m a n d ,
p r e v io u s a r c , p o in t A A (x l,y l)
in sid e th e f i r s t
d a ta c o n ta in s th e
part
of
cen tre
a n g le ,
and t h e a r c in d e x . The
c o n ta in s th e
cen tre
of
th e
(no m a t t e r w h a t t h e o t h e r in f o r m a t io n
d a ta , in t h i s c a s e ) . The s e c o n d p a r t o f
of
th e
current
arc
p o in t(x ,y ),
th e
d ir e c t io n o f th e a r c , th e s t a r t a n g le , and th e a r c in d e x .
W h i l e t h e a r c () f o r m a t c o n t a i n s t h e c e n t r e o f t h e
arc
p o in t(x ,y ),
th e s t a r t a n g le , th e end a n g le and th e r a d iu s r .
T h ere a r e tw o
w a y s, t o c a l c u l a t e t h e en d a n g le o f t h e a r c from t h e
c o m p o n e n t s o f t h e a r c com m and f o r m a t .
103
If
th e
a r c in d e x was eq u a l
(30) :
th e end a n g le = + / - s t a r t a n g le + 180
B ut i f th e a r c in d e x was e q u a l (1 5 ):
t h e e n d a n g l e = + / - s t a r t a n g l e + 90
To c a l c u l a t e t h e
r a d iu s o f th e a r c , from t h e co m p o n en ts o f t h e a r c
com m and:
xr = xl - x
yr = yl - y
f o r t h e f i r s t fo r m a t ( o f t h e a r c com m an d ):
r = s q r t(p o w (x ,2 .0 ) + p o w (y ,2 .0 ))
f o r t h e s e c o n d fo r m a t ( o f t h e a r c com m an d ):
r = ( 1 .0 /2 .0 ) * (s q r t(p o w (x ,2 .0 ) + p o w (y ,2 .0 ) ) )
T h e n e w f o r m a t t e d d a t a : ARC x , y , s t a r t a n g l e , e n d a n g l e ,
r
Then t h e S e a r c h P rogram w i l l s a v e
d a ta in th e
d ata f i l e . I f
th e
new
form atted
t h e c o n t e n t o f ( C o m p ), w a s n ' t o n e
c h a r a c te r s, th e Search
Program
w ill
p r in t
of
th e
on
p r e v io u s
th e
screen:
"ERROR: READING FROM PLOT F I L E " .
The t h r e e c h a r a c t e r s in th e b e g in n in g
was added to
sim p lify
of
e v e r y new fo r m a te d d a t a ,
th e r e c o g n itio n o f th e d ata
ty p e,
in
th e
secon d p a rt o f th e so ftw a re.
In th e end
of
th is
s e a r c h , t h e S e a r c h P r o g r a m w i l l m a k e a n (EOF)
t e s t . I f th e S e a r c h Program e n c o u n te r s
(EOF)
in s id e th e p lo t f i l e
i t w i l l c lo s e th e p lo t and th e d a ta f i l e s , and e x i t .
I f t h e S e a r c h P r o g r a m d o e s n ' t e n c o u n t e r (E O F ), i t
r e p e a t th e p r e v io u s
w ork.
So
it
w ill
seco n d p a r ts o f g r a p h ic a l in fo r m a tio n ,
search
th en
it
w ill
r e tu r n and
fo r th e f i r s t and
w ill
m a n ip u la te ,
m o d ify th em , and s a v e t h e new f o r m a t t e d d a t a in t h e d a t a f i l e .
The d a t a i s
o r g a n iz e d
in
lin e s in s id e th e d a ta f i l e ,
c o n t a in s in fo r m a tio n f o r d ra w in g o n e g r a p h ic e n t i t y :
104
each
lin e
L IN x l , y l , x 2 , y 2 ;
TEX x , y , f c e x t ;
CIR x , y , r ;
ARC x , y , s t a r t a n g l e , e n d a n g l e , r ;
The w ork o f
th e
S k etch
P rogram i s t o r e a d t h e new f o r m a t t e d d a t a
from t h e d a t a f i l e , an d p r e p a r e i t
so
t h a t i t ca n b e draw n on t h e
s c r e e n . The S k e tc h Program w i l l draw t h e s c h e m a tic (S k e t c h l) o r t h e
la y o u t d ia g ra m ( S k e t c h 2 ),
when i t i s c a l l e d from
in sid e
E X P -T est
S ystem . The d if f e r e n c e b etw een S k e tc h l and S k e tc h 2 i s t h a t , S k e tc h l
read s th e d ata
file ,
w h ic h c o n t a in s t h e g r a p h ic a l in f o r m a t io n f o r
d r a w in g t h e s c h e m a t ic d ia g ra m , w h i l e
w h ic h c o n t a in s t h e
g r a p h ic a l
S k etch 2
read s th e d ata f i l e ,
in f o r m a tio n f o r d ra w in g
th e
la y o u t
d ia g ra m . F ig . 6 -3 show s t h e f lo w c h a r t o f t h e S k e tc h P rogram .
In t h e b e g in n in g t h e S k e tc h P rogram i n i t i a l i z e s t h e g r a p h ic s s y s te m
and p u t s t h e s y s te m in t h e g r a p h ic s m ode. T hen i t s e l e c t s t h e s t y l e
o f th e lin e ,
w h ic h w i l l b e u s e d f o r w r i t i n g t h e t e x t . A ls o i t w i l l
s e t th e c o l o r o f th e c u r r e n t d r a w in g
and
th e
current
c o l o r . A f t e r t h a t th e S k e tc h Program w i l l o p en t h e
r e a d i t . Then
d ata
background
file
and
i t w ill check th e d ata f i l e to en su re th a t i t is n ot
em p ty. The S k e tc h P rogram w i l l p r i n t on t h e s c r e e n :
"ERROR: OPEN F I L E " , a n d e x i t , i f t h e d a t a f i l e i s e m p t y .
I f t h e d a t a f i l e i s n ' t em p ty , t h e
n ex t s ta g e . In
th e
S k etch
Program
n e x t s t a g e t h e S k e tc h Program
w ill go to th e
w ill
scan
th e
f i r s t th r e e c h a r a c te r s o f th e f i r s t lin e in th e d a ta f i l e , and sa v e
th em i n c h a r a c t e r
A lso by u s in g strcm p O
w i l l com pare b etw een
o p tio n s,
array
fu n c tio n ,
th e
(w h ic h c o n t a in s
in
co n ten t
th e
(C om p ).
TURBO. C . , t h e S k e t c h P r o g r a m
of
d iffe r e n t
(Comp)
ty p es
c h a r a c te r s fo r ev ery lin e in th e d a ta f i l e ) .
105
and
a
p o in te r
to
o f th e f ir s t th ree
SKETCH
TUE S C H E M A ! 1 C DIAGRAM
/
\
I START I
V
,
y
»
f i g . 6 - 3 . The F lo w c h a r t o f t h e S k e tc h P rogram
106
I f th e co n ten t
of
(Comp)
a r r a y i s " L IN " , t h i s w i l l i n d i c a t e t h a t
t h e d a ta f i l e , c o n t a in s d a ta f o r d r a w in g a l i n e . The S k e tc h P rogram
w ill scan th e
rest
o f th e cu rren t
d ata
lin e
put
in f o r m a tio n in a r r a y o f c h a r a c t e r (T em p ). T hen t h e
s c a n s (T em p ), s e p a r a t e s
its
co n ten t
to:
th e
g r a p h ic s
S k etch
x l,y l,x 2 ,y 2 .
Program
By
u sin g
c o n v e r t () f u n c t i o n , w h i c h c o n v e r t s t h e c o o r d i n a t e s f r o m t h e p l o t t e r
s c a le to th e s c r e e n s c a le , and u s in g
lin e ()
fu n c tio n ,
th e S k etch
P rogram w i l l draw a l i n e on t h e s c r e e n .
I f t h e c o n t e n t o f (Comp) a r r a y i s
procedu re w ill ta k e
p la c e .
( T E X ) , (C IR ) OR
But o u tte x tx y O
fo r w r itin g th e s p e c ifie d te x t, c i r c le ( ) ,
( A R C ),
t h e sam e
fu n c tio n , w ill be used
w i l l b e u s e d f o r d ra w in g
a c i r c l e , a n d a r c () f u n c t i o n , w i l l b e u s e d f o r d r a w i n g a n a r c .
T hen t h e S k e tc h P rogram w i l l m ake t h e en d o f f i l e
test,
to ensure
th a t th e f i l e h a s n 't reached th e end.
I f th e S k etch
Program
p a ss t h is t e s t , i t w il l re tu r n back to scan
a n o th er lin e o f d a ta in s id e th e d a ta
file .
But
i f i t d id n 't pass
th e end o f f i l e t e s t , th e S k e tc h Program w i l l c l o s e
At th is sta g e,
a
th e d ata f i l e .
c o m p le te s c h e m a tic w i l l a p p e a r on t h e s c r e e n . So
t h e S k e tc h P rogram w i l l draw a b l i n k i n g
r e c ta n g le
around th e t e s t
p o in t , t o draw t h e a t t e n t i o n o f t h e u s e r t o t h e w a n ted p l a c e .
T h is b lin k in g r e c t a n g le
S k e tc h Program w i l l
w ill
c le a r
c o n tin u e
th en
th e
t h e s c r e e n , a n d w i l l zoom o n t o t h e a r e a
in s id e th e r e c ta n g u la r . A lso th e t e s t
on th e s c r e e n
f o r 20 s e c o n d s ,
p o i n t w i l l b e show n b l i n k i n g
to n o tify th e u se r o f th e c o r r e c t
p o sitio n
of
th e
te st p o in t.
A fter a w h ile ,
in
a d d i t i o n t o t h e s c h e m a t i c d i a g r a m , a “ PRESS ANY
KEY TO CONTINUE" s e n t e n c e w i l l a p p e a r
S k e tc h Program t o
w a it
u n til
on
t h e s c r e e n , t o f o r c e The
th e u ser p r e sse s
keyboard.
107
any
key
on
th e
I f th e u ser
h a s p r e s s e d a n y k e y , t h e S k e t c h P ro g r a m w i l l s h u t down
t h e g r a p h i c s m ode a n d e x i t .
The c o n v e r t f u n c t io n c o n s i s t s o f
tw o
fu n c tio n s.
The f i r s t one i s
x _ c o n v ( ) f u n c t i o n , w h ic h c o n v e r t (x) v a l u e s fr o m t h e
to th e screen
sc a le .
w h ic h c o n v e r t (y)
The
secon d
fu n c tio n
v a l u e s from t h e
p lo tte r
p lo tte r sc a le
i s y ^ c o n v () f u n c t i o n ,
sc a le
to
s c a l e . In t h e b e g in n in g w hen t h e p l o t f i l e i s c r e a t e d ,
th e
screen
th e s iz e o f
t h e p a p e r , w h ich t h e p l o t t e r w i l l p l o t t h e s c h e m a t ic o n , i s d e f in e d
t o (A 4 ). The
lo c a tio n o f th e c o o r d in a te o r ig in
(0 ,0 p l o t t e r u n its )
and th e o r i e n t a t i o n o f th e X -an d Y- a x i s i s show n in f i g . 6 - 4 .
ty f
P2<110W,7?2I)
v
8.8 ORIGIN
f i g . 6 -4 . The L o c a tio n
+>'
o f th e (0 ,0 P lo t t e r U n its)
T h e (A 4) s i z e p a p e r a r e a i s d i v i d e d
to
(11000) in X -d ir e c tio n
and
t o (7721) in Y - d i r e c t i o n .
The i n i t i a l i z e o f
th e
g r a p h ic
sy stem d e f in e s th e s c r e e n
to be
d iv id e d t o (320) in X - d i r e c t i o n and t o (200) i n Y - d i r e c t i o n .
F ig . 6 -5 show s
th e
lo c a tio n
of th e c o o r d in a te o r ig in
(0 ,0 s c r e e n
u n i t s ) and th e o r i e n t a t i o n o f th e X -an d Y - a x i s .
8.8 ORIGIN________________________
t
1
)
i
'
I
i
+
P 2 (3 2 8 ,2 0 « >
*
f i g . 6 - 5 . The L o c a tio n o f t h e (0 ,0 S c r e e n U n its )
108
The x _ c o n v () f u n c t io n ,
m u ltip ly
th e
com e fro m t h e H P -fo r m a tte d p l o t f i l e
(x)
v a lu e , w h ic h o r i g i n a l l y
(th e c o o r d in a t e s show n in f i g .
6 -4 ), by x _ c o n v e r sio n r a te :
x _ c o n v e r s io n r a t e = 320 / 11000 = 0 .0 2 9
(x) v a lu e ( in s c r e e n s c a l e ) = x _ c o n v e r s io n
ra te
*
(x)
v a lu e (in
p lo tte r sc a le )
Then x _ c o n v ( ) f u n c t i o n , r e t u r n s t h e (x) v a l u e i n t h e s c r e e n s c a l e .
B ecau se th e o r ie n t a t io n o f Y -a x is in th e p lo t t e r s c a le i s o p p o s ite
th a t o f th e o r ie n t a t io n o f Y -a x is in th e s c r e e n s c a le .
The y _ c o n v () f u n c t io n ,
su b tracts
th e
com e from t h e H P -fo r m a tte d p l o t f i l e ,
in th e p lo t t e r
sc a le
(7 7 2 1 ).
(y) v a l u e , w h ic h o r i g i n a l l y
f r o m t h e m axim u m v a l u e t o ( y )
T hen
m u ltip ly
th e
r e su lt
by
y _ c o n v e r sio n r a te :
y _ c o n v e r s io n r a te = 200 / 7721 = 0 .0 2 6
(y) v a l u e ( i n s c r e e n s c a l e ) = y _ c o n v e r s i o n r a t e * (7 7 2 1 - (y ) v a l u e
(in p lo t t e r s c a le )
T hen y _ c o n v ( ) f u n c t i o n , r e t u r n s t h e (y) v a l u e i n t h e s c r e e n s c a l e .
6.4. Integrating OrC&D/SDT III System with EXP-Test System
Now t h e
S k etch
program
d ra w in g t h e s c h e m a tic
or
(S k e tc h l and S k etch 2 )
th e
la y o u t
c o n j u n c t io n w it h E X P -T est S y ste m ,
th e
d ia g ra m .
CALL
To
c la u se ,
V P - E x p e r t , s h o u l d b e u s e d . T h e CALL c l a u s e , s h o u l d
IF -T H E N r u l e s , i n
is
ready
do
th a t
fo r
in
from i n s i d e
be added to th e
th e s u it a b le p la c e t o in c r e a s e th e co m p eten ce o f
E X P -T est S y s te m . As show n i n t h e f o l l o w i n g e x a m p le :
109
RULE
POWER_SUPPLY
IF
CHECK_TRANSFORMER = YES
THEN
CALL \T C 2\SK E T C H 1
CALL \T C 2\SK E T C H 2
CALL \T C 2 \E X P _ T 1
LOADFACTS
F IL E 9
FIN D THE_TEST
THE_PROBLEM = FOUND;
In r e s p o n s e t o t h e p r e v io u s r u l e , E X P -T est S y s te m w i l l d i s p l a y :
TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM (J9).
THEN PUT THE OSCILLOSCOPE'S PROBE A T POINT (1).
TO LOCATE
POINT
(1) AND CONTINUE THE TEST, CHOOSE YES, AND
PRESS <ENTER>. OTHERWISE CHOOSE NO, AND PRESS < E N T E R > .
NO
YES
w h e n POWER_SUPPLY r u l e i s f i r e d ( b y
e n g in e w i l l c a l l
c h o o sin g
Y E S ),
f i r s t o f a l l t h e SKETCH1 f i l e ,
s c h e m a tic d ia g ra m o f
th e
la y o u t
d ia g ra m
The u s e r s h o u ld p u t th e p r o b e a t p o in t ( 1 ) , th e n
th e
keyboard
w h ic h
draw s
th e
c i r c u i t , th en th e in fe r e n c e e n g in e c a l l s
t h e SKETCH2 f i l e , w h i c h d r a w s t h e
any key on
th e in fe r e n c e
to
c o n tin u e
m a c h in e .
110
te stin g
o f th e c ir c u it .
he
th e
sh o u ld
p ress
broken_dow n
CHAPTER 7
IMPLEMENTATION
7.1. Introduction
E X P -T est S y ste m w as
d e v e lo p e d
as
a
sy stem
d ia g n o s is . I t h as an a d v a n ta g e th ro u g h
fo r e le c tr o n ic fa u lt
th e in c lu s io n o f b oth ty p es
o f k n o w led g e, s h a llo w an d d e e p k n o w le d g e ,
(T h e s h a l l o w k n o w l e d g e i s
t h e k n o w le d g e a b o u t f a u l t d i a g n o s i s an d th e d e e p
k n o w le d g e
is th e
k n o w led g e a b o u t e l e c t r o n i c c i r c u i t r y ) .
The s h a l lo w k n o w le d g e
in
E X P -T est
S ystem
was
rep resen ted
in a
n u m b e r o f t h e IF -T H E N r u l e s . T h e s e IF -T H E N r u l e s g i v e t h e s y s t e m a n
e a s y w ay o f r e p r e s e n t i n g t h e d o m a in
k n o w led g e o f t h e e x p e r t in th e
m a in ten a n ce, a ls o i t g iv e s th e sy ste m a h ig h s p e e d
e x e c u tio n
w ith
t h e a b i l i t y t o e x te n d t h e s y s te m e a s i l y , b y a d d in g som e r u l e s .
The d e e p k n o w le d g e
is
in c lu d e d
in
th e
u n io n
of
th e
G r a p h ics
f a c i l i t y , and th e i n t e l l i g e n c e o f th e te c h n ic ia n .
D ia g n o sis i s i n t r i n s i c a l l y a g o a l
g o a l b e in g to
prove
d ir e c te d
r e a so n in g
t h a t a p a r t i c u l a r m o d u le o r
process;
com ponent
in
a
a
c ir c u it is fa u lty [63].
The p r o c e d u r e f o r
te stin g
th e
p lo tte r 's
S ystem , w as d e f in e d in c o o p e r a tio n
w ith
c ir c u itr y ,
i n E X P -T est
th e m a in te n a n c e e x p e r t in
th e s c h o o l o f e l e c t r o n i c e n g in e e r in g a t D u b lin C ity U n iv e r s it y .
As m e n tio n e d , d i f f e r e n t
ex p erts
use
d iffe r e n t
str a te g ie s
for
so lv in g e le c tr o n ic fa u lt s .
I n NODAL, t h e
e x p e r t s y s te m w h ic h w as d e v e lo p e d in T r i n i t y C o lle g e
D u b lin f o r t e s t i n g
th e
sw itc h in g
m ode
pow er
su p p ly ,
s tr a t e g ie s w ere u sed fo r e le c t r o n ic fa u lt d ia g n o s is .
Ill
d iffe r e n t
" T he m o d e l w i t h i n
NODAL
is
h ie r a r c h ic a l
l e v e l s ; a m o d u le l e v e l an d a co m p o n en t
la r g e o r c o m p lex
c o n t a i n i n g a t l e a s t tw o
le v e l.
If
t h e m o d u le s a r e
t h e n t h e y m ay b e s u b d i v i d e d i n t o
su b -m o d u le s
in
th e m o d e l” [ 6 3 ].
"A t a m o d u l e
le v e l
th e
fu n d a m e n ta l p r i n c i p l e i s t h a t i f a m o d u le
h as good s i g n a l s a t i t s in p u t and
o u tp u ts th en i t i s fa u lty "
a
bad
at
to
tra ce
one
of
its
[3 5 ].
The s t r a t e g y , w h ic h
E X P -T est
S ystem
f a u lt s , depends on
r e g r e ssin g
a lo n g
sim ila r to th a t
sig n a l
uses
a
w h ich th e t e c h n ic ia n
e le c tr o n ic
f a u l t y l i n e . T h is i s v e r y
does
in
th e
e l e c t r o n i c f a u l t s . So f o r ex a m p le a 'b a d ' s i g n a l
d ia g n o sis
is
fo u n d
of
a t th e
(5V ) o u t p u t o f t h e p o w e r s u p p l y , t h e E X P - T e s t S y s t e m w i l l t r a c e a l l
th e s ig n a ls on
th a t
lin e ,
w ith
th e
in te n tio n
of
d e fin in g th e
dam aged c o m p o n e n ts .
7.2. U.U.T. description
As m e n tio n e d ,
E X P -T est S y ste m
was
d e v e lo p e d
fo r
e le c tr o n ic
f a u l t d i a g n o s i s i n CNC m a c h i n e s . B e c a u s e o f t h e u n a v a i l a b i l i t y o f a
CNC m a c h i n e i n t h e e l e c t r o n i c s c h o o l , t h e HP 7 4 7 5 A G r a p h i c s p l o t t e r
has been u sed
a s U . U . T . ( u n i t u n d e r t e s t ) . T h e HP
7475A
G r a p h ic s
p l o t t e r h a s t h e s a m e p r i n c i p l e o f t h e CNC m a c h i n e s .
F i g . 7 - 1 , s h o w s t h e b l o c k d i a g r a m o f HP 7 4 7 5 A G r a p h i c s p l o t t e r .
T h e HP 7 4 7 5 A
G r a p h ics
p lo tte r
con vert d ig it a l in str u c tio n s
u se s m icr o p ro c esso r-b a sed lo g ic to
in to
a g r a p h ic
m ic r o p r o c e s s o r r e c e i v e s i n s t r u c t i o n s from e i t h e r
( r e a d o n l y m em ory)
program
or
The
i n t e r n a l ROM
an e x te r n a l c o n tr o lle r th rou gh th e
I/O ( i n p u t /o u t p u t ) c i r c u i t s . I t t h e n
and paper d r iv e
an
p lo t.
m otor s e r v o s y ste m s
produce th e p l o t .
112
is s u e s d a ta t o th e pen d r iv e
and th e pen
down
c ir c u it to
S IX PEN
caro usel
DOW N
D R IV E R
CONTROLLER
s
PEN D R IV E
MOTOR
&OQRESS BUS
J----
I/O
carousel
M O TO R
D R IV E R
M ICROPROCESSOR
H P - lt
RS 7 22C
GATE
ARRAYS
hS'
SERVO
O P T IC A L
EN C O D ER
1C
ROM
24K X 8
.
PAPER D R IV E
M O TO R
REA R PANEL
S W ITC H ES
-5V
-5V
• 12V
--S V
SUPPLY
POWER
L.
R AM
2K X 8
M OTOR
I D R IV E R 1—
F R O N T PA N E L
C O N T R O L ft
IN D IC A T O R S
♦ 2?V
H
ÌÌ
0
I
E N C O D ER 1
SERVO
IC
o p t ic a l
- ■ I 2V ¡RS 232-C O N L Y l
o
f ig . 7-1
7 47 5A S i m p l i f i e d B l o c k D i a g r a m
T he tw o d r i v e
m otors
are
r e v e r sib le
dc m o to r s . E n co d ers on e a c h
m o t o r t r a n s m i t r o t a t i o n d a t a b a c k t o t h e i r r e s p e c t i v e s e r v o I C . O ne
m o t o r d r i v e s g r i t w h e e l s w h i c h m o v e s t h e p l o t t i n g m e d iu m , w h i l e t h e
o t h e r m otor m oves th e p en a c r o s s th e p l o t t i n g s u r f a c e .
The m ost o f
th e p lo t t e r 's f a u lt s ,
su p p ly , m otors and
in
th ese
happen
in
th e
pow er
of
th at,
th e m otor s e r v o s y s te m s . B e c a u se
E X P -T est S y ste m a t t e m p t e d ,
cop e w ith a l l
u su a lly
in
its
f a u lt s , and
e le c tr o n ic fa u lt d ia g n o sis, to
d e fin e
th e
dam aged
co m p on en ts
in sid e th ese u n its .
Two i d e n t i c a l s e r v o s y s t e m s a r e u s e d t o d r i v e t h e m o t o r s .
F i g . 7 - 2 , sh ow s t h e b l o c k d ia g r a m o f a m o to r s e r v o s y s t e m .
113
FROM
PROCESSOR
THROUGH 1
GATE A R R A Y
X *|
S ER VO
C O N D IT IO N
C IR C U IT
{P A R T OF
G ATE A R R A Y »
PULSE
1
r
S TR E T C H E D f
PULSE
1
D IG IT A L
G A IN A D J U S T
IP A R T OF
GATE A R R A Y )
P U LS E W ID T H
D A T A FROM
PROCESSOR
O P T IC A L
ENCODER
D R IV E R S
♦ 1 8 /3 6 V
UNREG ULATED
!
f i g . 7-2
M o to r S e r v o S y s te m B lo c k D ia g r a m
D i g i t a l m o v e co m m a n d s
are g e n e r a te d and s e n t by th e m ic r o p r o c e s so r
th ro u g h t h e g a te a r r a y s t o th e s e r v o c h ip s . The s e r v o c h ip s p r o v id e
th e in t e r f a c e to th e m ic r o p r o c e sso r ,
su m s p o s i t i o n e r r o r s ,
tran sform s th e servo
e stim a te s
error
decodes
v e lo c ity
th e en cod er s ig n a ls ,
and
sum s
it,
and
t o a p u ls e - w id t h - m o d u la te d o u t p u t . The
s e r v o c h ip s o u tp u t th e p u lse _ w id th _ m o d u la te d
sig n a l
back
to
th e
g a t e a r r a y w h ere th e m otor d r iv e p u ls e s a r e s t r e t c h e d t o th e p r o p e r
w id th in th e d i g i t a l g a in c i r c u i t . The s e r v o c o n d i t i o n i n g
a ls o in th e
g a te
array,
d r iv e r s th rou gh e it h e r
th en
th e
passes
XA
or
XC
th e p u ls e s on t o th e m otor
lin e ,
d e p e n d in g
d ir e c tio n o f r o ta tio n in d ic a te d by th e sig n v o lta g e
c h ip . As th e
m e c h a n ic a l
c ir c u it,
on
th e
from t h e s e r v o
s y s te m m oves, o p t i c a l e n c o d e r s m ou n ted on
th e s h a f t o f e a c h m otor sen d b a ck
d i g i t a l p u ls e s to th e s e r v o c h ip
to c lo s e th e se r v o lo o p .
To m a i n t a i n a c o n s i s t e n t a n d p r e d i c t a b l e m o v e m en t,
to c o n tr o l th e
it is e sse n tia l
am ount o f p ow er a p p lie d t o t h e m o to r b y e a c h p u l s e .
114
The pulse amplitude
depends
on
the
actual voltage output of the
motor drive power supply. The pulse width is modified to compensate
for pulse amplitude so that the pulse
represents the proper amount
of power.
Five major voltages
are
current linear supplies
generated
provide
by
the 7475A
circuitry.
the +12V and -5V required for the
servo IC's. The +5V supply provides
the
power
for
the remaining
logic circuitry. Regulation for the +5V linear supply
The unregulated 18/26V
supplied
to
pen carousel drive motor. The fifth
in conjunction with
(input/output)
Fig. 7-3 shows
the
+12V
Low
is provided.
the main drive motors and the
supply is the -12V source used
supply
to
operate
the
I/O
line drivers.
the
7475A
Graphics
115
plotter's
power
supply.
. II Oil
Üi«Odl
A l*i.i \
Ûi» flOi
iiti
£ ig .
i
3 . The 7475A G r a p h ic s P l o t t e r ' s Pow er S u p p ly
116
7.3. Approach Adopted
The d e v e lo p m e n t o f t h e E X P -T est S y s te m p r o c e e d e d i n tw o s t a g e s .
The F i r s t s t a g e
was
to
s t u d y t h e d o m a in , w h ic h w as t h e d e s i g n o f
t h e 7475A G r a p h ic s p l o t t e r , i t s c o n s t r u c t io n an d t h e p ro b le m s w h ic h
m ig h t b e e n c o u n te r e d d u r in g i t ' s
use.
A
deep
stu d y to th e 7475A
G r a p h ics p l o t t e r ' s c i r c u i t r y w as d o n e.
The c o n t a c t w it h th e m a n u fa c tu r e r 's s e r v i c e b o a rd ,
l i s t o f som e
c o n clu d e d
by a
p r e v io u s f a u l t s , w h ic h h a p p en ed d u r in g t h e h i s t o r y o f
th e p lo t t e r .
The s e c o n d p h a s e o f th e p r o j e c t , w h ic h
r e q u i r e d m uch m ore o r i g i n a l
th o u g h t and w ork,
was t o d e s ig n and b u i l t th e su p p o r tin g
( i n T U R B O .C .) a n d
th e
fin a l
expert
d e s ig n s t r u c t u r e im p o sed b y V P -E x p ert
sy stem
m eant
w ith
program s
V P -E x p ert. The
th a t, in g e n e r a l, th e
s y s te m w o u ld h a v e k n o w le d g e a b o u t w h at s h o u ld b e
h a p p en in g
i f th e
p l o t t e r w ere in p e r f e c t w o rk in g o r d e r . So t h e s y s te m lo o k s f o r w h at
sh o u ld be th e r e
and
w hen
th ere
e x p e c te d b eh a v io u r and th e a c tu a l
is
a
d isc r e p a n c y
b e h a v io u r
of
t r ie s to lo c a liz e th e so u rce o f t h is d isc r e p a n c y .
has done th is
th e
b etw een
th e
p lo tte r ,
it
W hen
th e sy stem
i t th en p ro p o ses a h y p o th e s is ab ou t th e ca u se o f th e
f a u lt b a sed on th e lo c a t io n o f th e d is c r e p a n c y .
T h ere fo re th e f a u lt i s d ia g n o se d
not
b y w h at i s h a p p e n in g , b u t by
w hat i s n o t h a p p en in g in th e p l o t t e r ' s c i r c u i t r y .
7.4. Design and Development
7.4.1. Introduction
O nce V P -E x p e r t
sy stem
S ystem , th e a p p e a ra n ce
of
was a d o p ted a s th e s h e l l
for
E X P -T est
th e sy stem to th e u s e r and th e s t y l e o f
c o n s u lta tio n had a ls o been d e c id e d
117
as
V P -E xp ert
sy stem
d ic ta te s
th is to th e
b u ild e r o f th e e x p e r t sy ste m . T h is i s due t o th e r i g i d
q u e s t io n and a n sw er fram ew ork w h ic h
V P -E x p ert
sy stem
p r o v id e s as
i t s o n ly m eans o f co m m u n ica tio n w it h t h e u s e r .
V P -E x p ert sy ste m was
s e l e c t e d a s th e d ev elo p m e n t
E X P -T est S y ste m , b e c a u s e
it
was
th e
a v a ila b le in th e e le c t r o n ic sc h o o l
o n ly
at
en v iro n m e n t
expert
sy stem
fo r
sh e ll
th e tim e o f im p le m e n ta tio n .
V P -E x p ert sy ste m h as s p e c ia l f e a t u r e s in c lu d in g :
( 1 ) An
" in fe r e n c e
e n g in e"
th a t
uses
backw ard
and
forw ard
c h a in in g f o r p ro b lem s o l v i n g .
(2) O p t io n a l
d e v e lo p m e n t w in d o w s t h a t l e t t h e u s e r o b s e r v e t h e
b e h in d -th e -sc e n e s p ath
n a v ig a te s th e
of
k n o w led g e
th e
in fe r e n c e
e n g in e
b a s e t o s o lv e p ro b lem s
as
it
d u r in g
a
c o n su lta tio n .
(3) C o n fid e n c e
fa c to r s th a t l e t th e u se r a cco u n t fo r u n c e r ta in
in f o r m a tio n in a k n o w le d g e b a s e .
(4) S im p le E n g lis h r u l e c o n s t r u c t i o n .
(5) The a b i l i t y t o e x p l a i n i t s a c t i o n s d u r in g a c o n s u l t a t i o n .
(6) K n o w led g e
b a s e " c h a in in g " ,
w h ic h
le ts
th e
user
crea te
k n o w le d g e b a s e s t h a t w o u ld o t h e r w i s e b e t o o l a r g e t o f i t in
m em ory.
(7) A b u i l t in t e x t E d i t o r .
(8) A u to m a tic q u e s t i o n g e n e r a t i o n .
(9) The
a b ility
to
record
and
g r a p h ic a lly
d isp la y
th e
r u le - b y - r u le s e a r c h p a t t e r n u se d b e h in d th e s c e n e s d u r in g a
c o n su ltâ t io n .
(1 0 ) R a p id e x e c u t i o n o f t h e k n o w le d g e b a s e .
( 1 1 ) T h e a b i l i t y t o e x e c u t e e x t e r n a l DOS p r o g r a m s .
(1 2 ) F l o a t i n g p o i n t m ath f u n c t i o n s .
O ne o f t h e
m a in
p ro b lem s
[66]
a t th e o u t s e t o f d e s ig n an d d e v e lo p m e n t
118
w as th e co m p le te
la c k
of
a n y e x a m p le s, o r p r e v i o u s l y im p le m e n te d
s y s t e m s e i t h e r i n EMYCIN o r i n a n y
sim ila r
expert
sy stem
sh e ll.
A lth o u g h t h e r e i s a la r g e am ount o f in fo r m a tio n in p a p e r s and b o o k s
about ex p ert sy stem s,
anyw here on a c tu a l
th ere
d e sig n
i s v e ry l i t t l e in fo r m a tio n
and
im p le m e n ta tio n
a v a ila b le
o f w o r k in g s y s te m s
[6 4 ] .
7.4.2. Structure
The g o a l o f E X P -T est S y ste m th r o u g h o u t a r e t o d e t e c t ' f a u l t s '
and
fin d 's o lu t io n s '.
To
a u to m a tic t e s t sy ste m ,
approach
su p p o r tin g
th e se g o a ls
so ftw a re
and
b u ild th e
h a s b een d e v e lo p e d in
TURBO.C. w i t h E X P - T e s t S y s t e m .
T h is s o f t w a r e r e d u c e s t h e d e p e n d e n c y on t h e u s e r o f E X P -T est S y ste m
in d e fin in g
I n NODAL
sy stem ,
th e q u a lity o f th e s ig n a ls .
i t i s v e r y im p o r ta n t t h a t
th e
user
g iv e
i n d e f i n i n g t h e f a u l t . NODAL u s u a l l y a s k s
th e n a tu re
o f th e
sig n a ls
at
h e lp
th e
user
to
th e
about
v a r io u s p o in t s in th e pow er su p p ly
c ir c u it.
"In o r d e r t o p r o v e t h i s t h e c l a u s e s
in th e r u le p r e m ise h a v e t o be
p r o v e d t r u e . The in f o r m a t io n t h a t t h e m o d u le i s o f
a v a ila b le in th e
th e
m o d u le
fra m e. The u s e r w i l l h a v e t o b e a s k e d fo r
o t h e r in f o r m a tio n . The o u tp u t
is
fo u n d
to
be
asked fo r th e q u a lity o f
co n n ected
so th e
user
N od e-12
and a t
A t o w h ic h th e in p u t i s c o n n e c t e d . I f t h e s i g n a l on
o u tp u t i s bad and th e s ig n a l
on
m o d u le i s c o n c lu d e d t o b e f a u l t y .
S etu p fo r T e st V e c to r 1
W hat
i s t h e SIGNAL o f A? G o o d
W hat
i s t h e SIGNAL o f B? G o o d
119
th e in p u t
th e
is
sig n a l
to
N od e-12
th e
is
ty p e o n e-o n e is
at
good th en th e
What is the SIGNAL of MO D E - 12? Good"
[S3]
E X P -T est S y ste m u s u a l l y ,
t e s t p o in t to
a n o th er,
asks
th e u s e r t o m ove t h e p r o b e from on e
and
it
w ill
ask
h im
for
som e
ex tra
in fo r m a tio n ab o u t th e q u a lit y o f th e s ig n a ls in a few p l a c e s .
F ig . 7 -4 show s
th e
co m p le te
so ftw a re,
w h ic h
was
d e v e lo p e d
to
a c h ie v e th e p r o je c t 's g o a ls .
O ï'C A D F L O T
im i
D R A M S C H E M A T IC
3
S L A V (M IT D IA G R A M S ?
ON T H E S C R E E N
S
THE P . C .
OF
I
SEARCH
PROGRAM
D ATA
-M l! !
“t
■M GETTING
EVP J E S T
SVSTEM
H-
H
I
and
C O r t P A R lN ii T H E
T E S T S IG N A L S
i n
■Vi
G E T T I N G A N I»
I
PH O M IN G
-Î
IN P U T = O U T F U T
t____________________
I
i SENDING SFTäiF
INFORMATION fO
[HE <L. A. y
I ret*fenc
G E T T IN G H I E
i
R E F E R E N C E S IG N A L S I
FRO M 1 H E t l l . ü . r . ) I
L ------------------------------------------ i
I
|
!*•
I
I G E T T IN G T H E S E T U P i
i I N f O RM AT I ON FRO M I
I
THE
(L.A.)
I
I______
f i g . 7 - 4 . The C o m p le te S o ftw a r e C o n f ig u r a t io n
1
F i r s t o f a l l , E X P -T e st S y s te m a s k s t h e u s e r t o c h e c k t h e m a in p o w er
s u p p ly . T h is w ork
sh o u ld
be
done b e fo r e t e s t in g any p o in t in th e
p lo tte r 's c ir c u itr y .
A f t e r t h a t E X P -T est S y s te m w i l l a s k
th e
user
to p u t th e probe o f
th e o s c i l l o s c o p e (fo r t e s t i n g th e a n a lo g u e s i g n a l s in th e p l o t t e r ' s
c ir c u itr y ) or o f
th e
lo g ic
a n a ly ze r
(fo r
te stin g
th e
d ig ita l
s ig n a ls in th e p l o t t e r ' s c i r c u i t r y ) , on one o f t h e t e s t p o in t s .
Im m e d ia te ly a f t e r t h a t
w h ic h w i l l draw
th e
E X P -T est
S ystem
sc h e m a tic and
th e
w i l l c a l l SKETCH p r o g r a m ,
la y o u t
d ia g r a m s
on
th e
probe
at
screen.
E X P -T est S y s te m w i l l a s k t h e u s e r now i f h e h a s p u t
t h e w a n ted t e s t
p o in t.
W hen
th e
th e
u s e r c h o o s e YES f r o m t h e c h o i c e
l i s t , E X P -T est S y ste m w i l l c a l l t h e
G e t t i n g a n d C o m p a rin g t h e T e s t
s ig n a ls program .
The w ork o f t h i s p ro gram i s t o g e t t h e s i g n a l from
and com pare i t
w ith
th e
referen ce
sig n a l.
th e
t e s t p o in t
T hen c a l c u l a t i n g th e
d i f f e r e n c e an d t h e a l l o w a b l e t o l e r a n c e an d s a v e th em in a t e x t f i l e
c a l l e d RESULT.
E X P -T est S y ste m w i l l t a k e t h e s e tw o
v a lu e s
from
RESULT, a n d w i l l
com p are th em t o d e f i n e t h e p r o b le m an d t h e s o l u t i o n .
In th e c a s e
o f u s in g th e lo g ic a n a ly z e r to g e t th e
E X P -T est S y ste m w i l l
c a ll
th e
w h ic h g e t s t h e s e t u p in f o r m a tio n
test
sig n a ls.
S en d in g S e tu p I n fo r m a tio n program ,
from
th e s e tu p f i l e and sen d s i t
to th e lo g ic a n a ly z e r .
E X P -T est S y ste m w i l l
program fo r t e s t i n g
c a ll
th e
G e ttin g
c o n d itio n
and
of
P ro v in g
in p u t
=
ou tp u t
t h e i n v e r t e r s in t h e m otor
servo sy stem s.
To t e s t t h e o u t p u t o f t h e e n c o d e r s ( t h e f e e d b a c k s i g n a l s ) , E X P -T est
S ystem w i l l a sk th e u s e r t o p u t th e o s c i l l o s c o p e ' s p ro b e a t th e
121
e n c o d e r 's o u tp u t and d e f in e th e q u a lit y o f t h e s i g n a l s . T h is i s th e
o n ly c a s e w h ic h
E X P -T est
S ystem
ask s th e u ser fo r th e q u a lity o f
th e s ig n a l. That i s b eca u se o f th e
c a u se s d u r in g t e s t i n g
c o n fu sio n
w h ic h
t h e m otor s e r v o s y s te m s . The
th e
feed b ack
m otor
u su a lly
s to p s in th e c a s e o f an y f a u l t in th e m otor s e r v o sy ste m , t h a t w i l l
ca u se th e feed b ack
sig n a l
G e t t i n g a n d C o m p a rin g
to
v a n is h . So i f E X P -T est S y ste m c a l l s
th e T est S ig n a ls
program ,
to
com pare
feed b a ck s ig n a l w ith a r e fe r e n c e s ig n a l i t w i l l c o n c lu d e
p ro b lem i s a lw a y s
in
th a t
th e
th e
th e e n c o d e r , w h erea s i t m ig h t b e in an y p a r t
o f th e m otor s e r v o s y s te m .
7.4.2.1. Supporting Software
The s u p p o r tin g s o f tw a r e w as d e v e lo p e d
w ork o f E X P -T est
S ystem .
each ty p e su p p o rts
t o en h an ce th e a u to m a tic
I t is d iv id e d in to s ix d if f e r e n t
E X P -T est
S ystem
t e s t . A b r i e f e x p la n a tio n on ea ch
in
typ e
typ es,
on e s id e o f th e a u to m a tic
w ill
be
m en tio n e d . T h ese
ty p es are:
(1) S e a r c h and S k e tc h p ro g ra m s
An e x p a n d e d e x p l a n a t i o n h a s b e e n a l r e a d y g i v e n
tw o p r o g r a m s
w h ic h
support
th e
about th ese
g r a p h ic s
fa c ility
a c co m p a n y in g E X P -T est S y ste m .
(2) G e t t i n g t h e R e f e r e n c e S i g n a l s from t h e ( U .U .T .)
T h is s o f t w a r e w as d i v i d e d i n t o tw o p r o g r a m s . The f i r s t o n e ,
g e t th e r e fe r e n c e a n a lo g u e
t h e IEEE
In terfa ce
program w i l l
convert
C ard
th e
s ig n a ls
from
(U .U .T .) th r o u g h
by u sin g th e o s c illo s c o p e .
ca p tu red
T h is
d a ta (th e raw d a ta in
A SC II c o d e ) t o a u s e f u l i n t e r p r e t a t i o n .
A fter th a t i t w ill
s a v e t h e p r o c e s s e d d a t a i n a t e x t f i l e , c a l l e d REFERENCE.
The s e c o n d
one,
get
th e r e fe r e n c e d ig it a l
122
sig n a ls
from
( U . U . T . ) t h r o u g h t h e IEEE I n t e r f a c e C a r d b y u s i n g t h e L o g i c
A n a ly z e r . T hen
t h i s program w i l l c o n v e r t th e c a p tu r e d d a ta
( t h e ra w d a t a i n A SC II c o d e )
to
a
u se fu l in te r p r e ta tio n .
A fter th a t i t w ill save th e p r o c e sse d d a ta
in
a text file
a l s o , c a l l e d REFERENCE.
( 3 ) G e t t i n g a n d C o m p a r in g t h e T e s t S i g n a l s
T h is s o ftw a r e
was
d iv id e d
i n t o tw o p a r t s . The f i r s t p a r t
g e t s th e t e s t a n a lo g u e s ig n a ls
IEEE I n t e r f a c e
program w i l l
from
(U .U .T .)
C ard b y u s in g t h e o s c i l l o s c o p e .
convert
th e
ca p tu red
th is
A fter th a t i t w ill
c a l l th e r e fe r e n c e f i l e , and com pare b etw een
sig n a ls
T hen
d a t a ( th e raw d a ta in
A SC II c o d e ) t o a u s e f u l i n t e r p r e t a t i o n .
th e re fe re n c e
th rou gh th e
th e
t e s t and
to c a lc u la t e th e d i f f e r e n c e . In th e
end i t w i l l d e f in e th e a llo w a b le t o le r a n c e and s a v e i t w ith
t h e d i f f e r e n c e i n a t e x t f i l e c a l l e d RESULT.
The s e c o n d p a r t , g e t t h e t e s t d i g i t a l s i g n a l s from (U .U .T .)
th rou gh th e
IEEE
In terface
C ard
by
u sin g
A n a ly z e r . T hen t h i s p rogram w i l l c o n v e r t th e
(th e raw
d ata
in
th e
L o g ic
ca p tu red d a ta
A SC II c o d e ) t o a u s e f u l i n t e r p r e t a t i o n .
A fter th a t i t w ill c a ll
th e
re feren ce
file ,
and com pare
b etw een th e t e s t and th e r e fe r e n c e s ig n a ls t o c a lc u la t e th e
su m o f
th e
p lo tte r is
to ta l
in
d if f e r e n c e , w h ic h e q u a ls
zero
if
th e
good c o n d it io n . In th e end i t w i l l sa v e th e
sum o f t h e t o t a l d i f f e r e n c e
v a lu e
in
a
te x t f i l e c a lle d
R ESU LT.
(4) G e t t i n g an d P r o v in g I n p u t = O u tp u t
T h is program
w ill
get
th e
test
d ig ita l
sig n a ls
from
( U . U . T . ) t h r o u g h t h e IEE E I n t e r f a c e C a r d b y u s i n g t h e L o g i c
A n a ly z e r . The in p u t and t h e o u tp u t s i g n a l s o f t h e i n v e r t e r
123
can be
ca p tu red ,
by
u sin g
th e m u lti-c h a n n e ls pod o f th e
L o g ic A n a ly z e r . T hen t h i s program w i l l c o n v e r t t h e c a p tu r e d
d a ta (th e
raw
d ata
in te r p r e ta tio n . A fter
sig n a l is
in
A SC II
code)
th a t i t w ill check
to
a
u sefu l
th a t th e
in p u t
o p p o site to th e ou tp u t s ig n a l (to prove th a t th e
i n v e r t e r i s o k ) , a n d s a v e t h e r e s u l t i n RESULT.
(5) G e t t i n g t h e S e tu p I n f o r m a t io n from t h e L o g ic A n a ly z e r
T h is program w i l l j u s t g e t
th e
s e t u p in f o r m a t io n from t h e
L o g ic A n a ly z e r and sa v e i t in a s e tu p f i l e .
(6) S e n d in g t h e S e tu p I n fo r m a tio n t o t h e L o g ic A n a ly z e r
T h is program w i l l c a l l
th e setu p f i l e and sen d th e
setu p
in fo r m a tio n t o th e L o g ic A n a ly z e r .
The flo w c h a r ts
of
a ll
th e
p r e v io u s
m e n tio n e d
program s a r e in
a p p e n d ix A.
7.4.2.2. Designing the Rule Set
D e v elo p in g th e r u le s t o b e u sed
l a r g e s t d e v e lo p m e n t t a s k
w ork w h ic h form ed
by
r e p r e se n tin g
E X P -T est
S ystem
a p p r o x im a te ly
fo u r
was
th e
m on th s
th e c o r e o f th e p r o j e c t . The r e s u l t i s ab o u t one
hundred r u le s . A f u l l e r d e s c r ip t io n i s p ro v id ed in s e c t io n 4 .1 0 .1 .
A t y p i c a l r u l e from t h i s e x p e r t s y s t e m i s show n h e r e :
RULE POWER_SUPPLY12
I F CHECK_PEN_SUPPLY = YES
THEN C A L L \T C 2\SK E T C H l
CALL\TC2\SK ETCH 2
CALL\TC2 \E X P _ T 10
LOADFACTS
F IL E 9
FIN D THE_PEN_SUPPLY
T H E _12V _TE ST = FOUND;
124
RULE P0WER_SUPPLY13
IF d e l t a l >= ( s t a n d e r l )
THEN WOPEN 4 , 1 5 , 1 , 8 , 6 0 , 1 4
ACTIVE 4
DISPLAY
"THERE I S
A
PROBLEM
IN
THE
PEN
CO IL S U P P L Y 'S OUTPUT, TO
DEFINE WHICH COMPONENTS CAUSE
THE
PROBLEM, YOU SHOULD MAKE
TEST TO ANOTHER P O IN T . <PRESS ANY KEY> TO C O N T IN U E .-"
WCLOSE 4
RESET d e l t a l
RESET s t a n d e r l
THE_PEN_SUPPLY = FOUND
FIN D MOR_PEN_SUPPLY
ELSE CLS
DISPLAY
“THE PEN
COIL
SUPPLY
I S OK, <PR E SS ANY KEY>
TO
CONTINUE
TESTING T H IS D E V IC E .-"
RESET d e l t a l
RESET s t a n d e r l ;
7.4.2.3. Domain expertise
T h ere w e r e tw o c l e a r s t a g e s in d e v e lo p i n g t h e r u l e s e t .
F ir s t th e r e was
t h e t a s k o f d e v e l o p i n g " d o m a in e x p e r t i s e " i n o t h e r
w o rd s b ec o m in g f a m i l i a r
w ith
v a r io u s
a sp ects
of
th e
p lo tte r 's
e le c tr o n ic c ir c u itr y .
I t was im p o r ta n t
to
p lo tte r 's c ir c u itr y as
u n d ersta n d
w ill
th e
as
a c tu a l c o n str u c tio n
u n d e r sta n d in g
th e
of
th e
c ir c u itr y 's
w o rk in g a t a l o g i c a l and d i g i t a l l e v e l .
T h is in c lu d e d a
w id e
k n o w le d g e
about
125
th e
p r o b le m s
and
th e
components which would be most likely to be at fault.
A great deal
of
th e
in fo rm a tio n
o r “k n o w l e d g e " g a t h e r e d a t t h i s
s ta g e o f th e p r o j e c t seem ed e x tr e m e ly
d iffic u lt
to
put in to r u le
fo r m a t. D e t a i l s o f th e p a r t i c u l a r t h in g s w h ic h c o u ld
b e w rong w ith
t h e p l o t t e r , an d how t h e y m ig h t b e c h e c k e d , c o n fir m e d an d f i x e d .
The s e c o n d s t a g e
of
th e
d ev elo p m e n t c o n s i s t e d o f o r g a n iz in g t h i s
in f o r m a tio n an d c o n s t r u c t in g r u l e s from i t .
7.4.2.4. Knowledge Engineering
One a p p r o a c h t o d e s i g n r u l e s
c o n s u l t a t i o n “t r e e s " o n
q u e s t io n s w h ic h c o u ld
is
paper,
be
by
asked,
by
w r itin g ou t
and
r e p r e s e n t in g t h e o r d e r in w h ich
a tte m p tin g
th ey
lin k in g
sh o u ld
th em
be
(eg.
YES
co n stru ct
lists
of
u sefu l
w ith
arrow s
p resen ted to th e
u s e r s o t h a t t h e y w o u ld b e m o st i n t e l l i g i b l e t o h im .
tw o p o s s i b l e a n sw e r s
to
A
r u le
w ith
o r N O ), w o u ld h a v e tw o a r r o w s fro m
i t , f o r t h e tw o p o s s i b l e a n s w e r s .
T hese
arrow s
w o u ld
g o t o m ore
q u e s tio n s , o r i f enough in fo r m a tio n had b een c o l l e c t e d
th en ,
th ey
w o u ld p o i n t t o a f a u l t an d a s s o c i a t e d s o l u t i o n .
The a p p ro a ch w h ic h
used
to
d e sig n
d r a w in g t h e i n i t i a t i v e f lo w c h a r t
of
r u le s
in t h i s p r o je c t was by
E X P -T est
S ystem .
c h a r t w as c o n t a in in g th e u s e f u l q u e s t io n s w h ic h c o u ld
T h is flo w
be
asked to
th e u s e r and th e e x p ected a n sw e r s.
T h is was fou n d
to
be
a
very
u s e fu l approach fo r d e v e lo p in g th e
o v e r a ll s tr u c tu r e and a ls o fo r v i s u a l i z i n g
how
th e
sy stem
w o u ld
appear to th e u ser.
The f i r s t s t a g e o f t h e k n o w le d g e e n g in e e r in g p r o c e s s w as t o d e v e lo p
th e o v e r a ll stru ctu re
of
th e
sy stem ,
th is
was
done
a lo n g
c o n v e n t io n a l k n o w led g e e n g i n e e r i n g l i n e s .
The l o c a l i s a t i o n te c h n iq u e
i s v e r y s i m i l a r t o t h a t w h ic h an e x p e r t
126
would be expected to t a k e .
7.5. Certainty Factors
E X P -T est S y s te m
d id n 't u s e c e r t a in t y f a c t o r s in i t s r u l e s . The
reason s fo r th is are very in te r e stin g
and
a r e a r e f le c t io n on th e
f a u l t d o m a in . In m o st i n s t a n c e s t h e s y s t e m a s k s t h e
t h e p ro b e from
to
m ove
one t e s t p o in t to a n o th er, or i f th e r e is a s ig n a l,
i n som e t e s t p o i n t ( fe e d b a c k s i g n a l s ) ,
th is
is
query w here th e r e i s v ery l i t t l e v a g u e n e ss. T here
th e r e is n ot!
user
a
sim p le
is
a
Y E S/N O
sig n a l or
I f th e ex p ected s ig n a l i s n o t th e r e , th en th e r e i s a
f a u l t o r p r o b le m in t h e c i r c u i t w h ic h p r o d u c e s o r u s e s t h a t s i g n a l ,
so th e sy stem
lo c a liz e s
to
th at
part
of
th e c i r c u i t and t e s t s
an o th er p o in t o r s e c t io n o f th e c i r c u i t .
T h e r e i s v e r y l i t t l e room f o r u n c e r t a i n t y
e s p e c ia lly in d i g i t a l
in
e le c tr o n ic c ir c u its ,
c ir c u it s . A lin e is g e n e r a lly
e ith e r
h ig h ,
lo w o r c a r r y in g a s i g n a l ! The n a tu r e o f d i g i t a l t e s t e q u ip m en t a l s o
le a d s to p r e c is e r e s u lt s o f t e s t s , th e u s e r e it h e r s e e s a s ig n a l on
an o s c i l l o s c o p e s c r e e n o r h e d o e s n 't . T h is i s v e r y d i f f e r e n t t o th e
s it u a t io n in m e d ic a l
d ia g n o sis
w here
e stim a te s
and
q u a lita tiv e
ju d g e m e n ts m u st b e m ade w it h o u t c l e a r q u a n t i t a t i v e r e s u l t s [ 6 4 ] .
7.6. EXP-Test Svatem in Operation
To t e s t t h e p e r fo r m a n c e o f E X P -T e st
S ystem
a b ilit y in e le c t r o n ic
fa u lt
d ia g n o sis,
a p p lie d on i t .
th at,
w ir e s
To
do
p o in t s (A ,B ,C ,D ,E ,F ,G ,H ,I ,J ,K ,L ,M )
an e x te r n a l b read b oa rd
th a t p o in t s . But
it
w ere
on
som e
an d t o im p ro v e i t s
e x p e r ie n c e s
c o n n e c t e d from t h e t e s t
th e m otor s e r v o s y s te m s, t o
to s im p lify g e ttin g th e t e s t
was
w ere
sig n a ls
from
v ery d i f f i c u l t to rea ch th e d e fin e d t e s t
p o in t s in s id e th e p l o t t e r ' s pow er su p p ly , and c h a n g in g th e s i g n a l ' s
127
c h a r a c t e r is t ic s to s im u la te th e f a u l t s . So a fu n c tio n g e n e r a to r and
a pow er su p p ly
was
used
to sim u la te th e s ig n a ls o f th e p lo t t e r ' s
pow er s u p p ly .
The f u n c t io n g e n e r a t o r 's
sig n a ls
w ere
used
to
sim u la te
th e
t r a n s f o r m e r ' s o u t p u t ( t o g i v e 1 0 . 5 A C V ).
The pow er s u p p ly 's s i g n a l s w ere u s e d t o s im u la t e a l l t h e c o n tin u o u s
v o lt a g e s a p p e a r in g on th e p l o t t e r ' s p ow er s u p p ly b o a r d .
So by u s in g
th e
fron t
p a n e ls o f th e fu n c tio n g e n e r a to r
and
th e
pow er su p p ly , th e a m p litu d e o f th e s ig n a ls ca n be ch a n ged (in c r e a s e
or d e c re a se th e v o lt v a lu e s) to sim u la te th e f a u lt c a s e s .
The f o l l o w i n g e x a m p le s
w ill
e x p l a i n how E X P -T est S y s te m d ia g n o s e s
th e e le c t r o n ic f a u lt s to a c h ie v e th e s o lu tio n :
The f i r s t f a u l t w as s im u la t e d b y
i t l e s s th an
d e c r e a sin g
( - 5 V ) DCV, a n d m a k i n g
th e a llo w a b le t o l e r a n c e . The p l o t t e r ' s
pow er
su p p ly
f a i l s t e s t POWER_SUPPLY4.
The d ia lo g u e w as
as
fo llo w s
(th e
u n d e r lin e d
tex t
is
th e u ser
c h o ic e ):
WELCOME TO
EXP-Test SYSTEM
SYSTEM FOR TESTING CNC MACHINE
<PRESS ANY KEY TO CONTINUE»
(T h e u s e r s h o u l d p r e s s a n y k e y )
CHECK THE MAIN POWER PLUG (220) ACV.
IF THE MAIN POWER IS OFF,
<ENTER»,
(MOVE
IF ON PRESS <E N T E R » .
OFF
ON
128
THE
CURSOR TO OFF AND PRESS
TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM (J9).
THEN PUT THE OSCILLOSCOPE'S PROBE A T POINT
TO LOCATE
POINT
(1)
(1).
AND CONTINUE THE TEST, CHOOSE YES, AND
PRESS <ENTER>. OTHERWISE CHOOSE NO, AND PRESS < E N T E R > .
YES
NO
THE TRANSFORMER IS OK, <PRESS
A NY
KEY>
TO CONTINUE TESTING
THIS DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT
(2),
IF YOU ARE READY, CHOOSE YES, AND PRESS <EN T E R >.
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
YES
NO
THE (5V) OUTPUT IS OK, <PRESS ANY KEY>, TO
CONTINUE
THIS
TESTING
DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT (5).
IF YOU ARE READY, CHOOSE YES, AND PRESS <E N T E R >.
OTHERWISE CHOOSE NO, AND PRESS < ENTER>.
YES
NO
THE (-12V) OUTPUT IS OK, <PRESS A NY KEY>, TO CONTINUE TESTING
THIS DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
129
PUT THE OSCILLOSCOPE'S PROBE AT POINT (7).
IF YOU ARE READY, CHOOSE YES, AND PRESS <ENTER>.
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
THE PROBLEM IS DEFINED, THE EXPECTED DAMAGED COMPONENTS ARE:
(1) C3.
(2) VR2
PRESS <ENTER>, THEN <Q>, TO EXIT.
The E X P -T est S y ste m
C 3, VR2. A ll
what
h a s d e f in e d th e f a u l t c a n d id a t e l i s t , w h ic h i s
is
w a n te d from
th e
user
is
to
test
th ese
co m p on en ts and ch a n g e th e f a u l t y o n e .
The p r e v io u s t e s t
was
one
o f m any t e s t s , w h ic h
a p p lie d
on
th e
E X P -T est S y s te m t o im p ro v e i t s c a p a b i l i t y in t r o u b l e s h o o t i n g f a u l t s
in th e p l o t t e r ' s pow er su p p ly .
The s e c o n d f a u l t
was
s i m u l a t e d b y g e t t i n g t h e i n p u t ( p o i n t A) a n d
t h e o u t p u t ( p o i n t E) s i g n a l s o f t h e
from t h e in p u t
o n ly .
T h is
w ill
in v e r t e r (p ap er m otor d r iv e r s )
in d ic a te
th a t th e
paper
m otor
d r i v e r s , w h ic h i n v e r t th e in p u t s i g n a l s , i s f a u l t y . T h is i s b e c a u s e
t h e in p u t an d t h e o u t p u t s i g n a l s w i l l b e t h e sam e (tw o s i g n a l s from
t h e sam e s o u r c e ) .
T h is ex a m p le w i l l
show
th e
d e f i n i n g t h e dam aged co m p o n en ts
s e r v o s y s t e m ) . The
c a p a b ility
in
th e
of
E X P -T est
d ig ita l
m otor s e r v o sy ste m f a i l s t e s t
S y stem
c ir c u its
(m otor
P-D -M O T O R 5.
d ia lo g u e was a s f o llo w (th e u n d e r lin e d t e x t i s th e u s e r c h o i c e ) :
130
in
The
WELCOME TO
EXP-Test SYSTEM
SYSTEM FOR TESTING CNC MACHINE
<PRESS A NY KEY TO CONTINUE»
(T h e u s e r s h o u l d p r e s s a n y k e y )
CHECK THE M A I N POWER PLUG (220) ACV.
IF THE
<ENTER>,
MAIN
POWER IS OFF,
(MOVE THE CURSOR TO OFF AND PRESS
IF ON PRESS <ENTER>.
OFF
ON
TO CHECK THE TRANSFORMER:
DISCONNECT THE TRANSFORMER'S OUTPUT FROM (J9) .
THEN PUT THE OSCILLOSCOPE'S PROBE AT POINT
TO LOCATE POINT (1) AND CONTINUE
THE
(1).
TEST,
CHOOSE YES, AND
PRESS <ENT E R > . OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
NO
YES
THE TRANSFORMER
IS
OK, <PRESS ANY KEY> TO CONTINUE
THIS DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT
(2),
IF YOU ARE READY, CHOOSE YES, AND PRESS < ENTER>.
OTHERWISE CHOOSE NO, AND PRESS < ENTER>.
YES
NO
131
TESTING
THE (5V)
OUTPUT
IS OK, <PRESS A NY KEY>, TO CONTINUE TESTING
THIS
DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT (5).
IF YOU ARE READY, CHOOSE YES, AND PRESS <E N T E R > .
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
THE (-12V) OUTPUT IS OK, <PRESS A NY KEY>, TO CONTINUE TESTING
THIS
DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE A T POINT
(7).
IF YOU ARE READY, CHOOSE YES, AND PRESS <ENTER>.
OTHERWISE CHOOSE NO, AND PRESS < ENTER>.
NO
YES
THE (-5V)
OUTPUT IS OK, <PRESS AN Y KEY>, TO CONTINUE TESTING
THIS
DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT
(8).
IF YOU A RE READY, CHOOSE YES, AND PRESS <E N T E R > .
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
THE (+18/26V)
OUTPUT
IS
OK,
TESTING THIS DEVICE.
132
<PRESS ANY KEY>,
TO
CONTINUE
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT (11).
IF YOU ARE READY, CHOOSE YES, AND PRESS < E N T E R > .
OTHERWISE CHOOSE NO, AND PRESS <ENTER>.
NO
YES
THE
(+12V) OUTPUT IS OK, <PRESS ANY KEY>, TO CONTINUE TESTING
THIS DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE OSCILLOSCOPE'S PROBE AT POINT
(12).
IF YOU ARE READY, CHOOSE YES, AND PRESS <E N T E R > .
OTHERWISE CHOOSE NO, AND PRESS <E N T E R » .
NO
YES
THE
(PEN
COIL
SUPPLY)
OUTPUT
IS
OK,
<PRESS A NY KEY>, TO
CONTINUE TESTING THIS DEVICE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
SWITCH THE PLOTTER (U.U.T.)
OFF,
AT LEAST,
(PI) & (P2), AT
(NOl). THEN PRESS
PUT A BLANK PAPER, ONE PEN
THE
SAME
TIME
SWITCH ON THE PLOTTER. THE TEST PROGRAM WILL RUN, TESTING THE
OPERATION OF
EVERY
MOTOR,
THAT
P R O GRAM). BY LOOKING CAREFULLY
CALLED
(THE INTERNAL TEST
TO THE MOTORS,
PRESS <ENTER>,
IF ALL OF THEM W ORK PERFECTLY, OR MOVE THE CURSOR
AND PRESS <ENTER>.
NO_PROBLEM
PROBLEM
133
TO PROBLEM
ONE OF
THE
DRIVE
MOTORS
DOESN'T
WORK,
<PRESS AN Y KEY> TO
DEFINE WHICH ONE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
MOVE THE CURSOR TO THE SUITABLE DRIVE MOTOR WHICH YOU NOTICED
DOESN'T WORK AND PRESS <ENTER>.
PEN_DRIVE_MOTOR
PAPER DRIVE MOTOR
PEN_SOLENOID
CAROUSEL_STEPPER__MOTOR
<PRESS ANY KEY>, TO DEFINE THE DAMAGED COMPONENTS.
(T h e u s e r s h o u l d p r e s s a n y k e y )
PUT THE
OSCILLOSCOPE'S PROBE AT POINT
THEN ROTATE
THE
(ENCAX),
OR
(ENCBX).
MOTOR MANUALLY (BY USING ONE OF THE BUTTONS
ON THE FRONT PANEL OF THE
SIGNAL PRESS <ENTER>,
PLOTTER).
IF
THERE
IS
A SQUARE
IF THERE IS NO SIGNAL:
MOVE THE CURSOR TO NO, AND PRESS <ENTER>.
NO
YES
THE ENCODER IS OK, <PRESS ANY KEY>, TO CONTINUE
TESTING THIS
UNIT.
(T h e u s e r s h o u l d p r e s s a n y k e y )
SWITCH ON
THE
LOGIC
ANALYZER,
THEN
CHOOSE YES, AND PRESS
<ENTER>. OTHERWISE CHOOSE NO, AND PRESS < ENTER>.
YES
NO
134
CONNECT POD
(0), CHANNEL
BUTTON, ON
THE LOGIC
(0),
TO POINT
ANALYZER
ANALYZER GET DATA ON IT'S SCREEN,
(A), AND PRESS
(START)
FRONT PANEL. WAIT TILL THE
THEN CHOOSE YES, AND PRESS
< ENT E R > . OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
YES
NO
THE INPUT OF THE PAPER MOTOR DRIVERS IS OK,
TEST TO
ANOTHER
POINTS,
TO
YOU
SHOULD MAKE
DEFINE THE DAMAGED COMPONENTS,
<PRESS A N Y KEY>, TO CONTINUE.
(T h e u s e r s h o u l d p r e s s a n y k e y )
CHOOSE YES, THEN PRESS <ENTER>, TO SEND THE SUITABLE SETUP.
OTHERWISE CHOOSE NO, AND PRESS <E N T E R > .
YES
NO
CONNECT POD (0), CHANNEL
CHANNEL
(0),
TO
POINT
(A),
AND
POD (0),
(1), TO POINT (E), AFTER THAT RUN (THE INTERNAL TEST
PROGRAM), AND
FRONT PANEL.
PRESS
(START)
BUTTON,
ON THE LOGIC ANALYZER
WAIT TILL THE ANALYZER GET DATA ON IT'S SCREEN,
THEN CHOOSE YES, AND PRESS <E N T E R > .
OTHERWISE CHOOSE NO, AND PRESS < ENTER>.
YES
NO
THE PROBLEM IS DEFINED, THE EXPECTED DAMAGED COMPONENTS ARE:
(1) U2.
(2) Q4,Q8
(3) CR5
PRESS <ENTER>, THEN <Q>, TO EXIT.
135
The p r e c e d in g e x a m p le s a r e j u s t som e o f t h e e x a m p le s o f f a u l t c a s e s
w it h w h ic h E X P -T est S y ste m h a s b e e n t e s t e d .
T hese t e s t s in d ic a te
th a t
i t i s r e a s o n a b le t o e x p e c t t h e E X P -T est
S ystem t o be a b le t o d ia g n o s is b e t t e r
t h a n 70% o f f a u l t s i n t h e HP
7 47 5A G r a p h ic s p l o t t e r .
The f lo w c h a r t o f E X P -T est S y ste m i s sh ow n i n a p p e n d ix A .
S om e c o n c l u s i o n s o n t h i s r e s e a r c h a n d s o m e d i r e c t i o n s
r e se a r c h w i l l be g iv e n in th e n ex t c h a p te r .
136
fo r
fu rth er
CHAPTER 8
CONCLUSION
F a u lts due
m ajor c a u se o f
t o e le c t r o n ic sy stem f a i l u r e o r m a lfu n c tio n a re th e
d o w n tim e
in
h ig h ly
w orkshops. F a ilu r e d e te c tio n
s k i l l e d and w e ll
tr a in e d
c o n sta n t su p p ly . In
ra te
lo c a l
of
le v e l,
CNC
m a c h in e
and r e p a ir i s p r o b le m a tic
m a in te n a n c e
th is d isse r ta tio n
enhancem ent o f th e
about th e s k i l l
au tom ated
r e p a ir ,
it
sta ff
is
if
are
proposed
n o tw ith sta n d in g
to o l
h ig h ly
not
th a t
in
th e
u n c e r ta in ty
i s p o s s ib le w ith an e x te n s io n o f th e b a s ic
' t o o l k i t ' s o t h a t e x p e r t k n o w le d g e i s a v a i l a b l e in an i n t e l l i g e n c e
b ased w o r k sta tio n .
B a s e d o n t h e c o n c l u s i o n t h a t t o t a l m a i n t e n a n c e r e p a i r k n o w l e d g e m ay
n ot be e n c a p su la te d a p r io r i, th e
r e n d e r e d l i m i t e d . H ow ever
e le c tr o n ic c ir c u itr y is
r o le
of
n o r m a lly
in fo r m a tio n
w h ils t p r o c e e d in g w ith
expert
a c k n o w le d g in g t h a t 'd e e p '
d ocu m en ted
s y s te m h a s b e e n p r o p o s e d and im p le m e n te d
c a l l on g r a p h ic a l
an
(a v a ila b le
sy stem
is
k n o w le d g e
of
in g r a p h i c a l form , a
th a t
a llo w s
from a
CAD
th e u ser to
d a ta-b a se)
l i n g u i s t i c , d i a g n o s t i c i n s t r u c t i o n from t h e
ex p ert sy stem . I n te g r a tin g
g r a p h ic a l
c ir c u it
k n o w le d g e
and
f a c i l i t a t i n g in t e r r o g a t i o n o f t h e p ro b lem a g a i n s t t h e b a ck g ro u n d o f
a w o r k sta tio n d e fin e d
r e f le c t s th e norm al
in e le c t r o n ic s i s
in
r e p a ir
th is
way e s t a b l i s h e s
th e
co n tex t
and
s i t u a t i o n . The norm al r e p a ir s i t u a t i o n
c h a r a c te r iz e d
by
u n c e r ta in ty ,
in co m p lete
k n o w le d g e , m ix e d c a u s a l i t y and in c o n s e q u e n c e a r a t e o f c o n v e r g e n c e
to f a u lt d ia g n o s is v a r y in g w id e ly .
In t h i s p r o j e c t
th e
r o le
of
e x p e r t sy stem s in e le c t r o n ic
fa u lt
d ia g n o s is h as b een re v ie w e d , th e s i g n i f i c a n c e o f e l e c t r o n i c sy ste m s
137
f a i l u r e i n CNC
m a c h in e
d o w n tim e
d e te r m in a tio n h a s b een s ta te d , a
w orkshop f a c i l i t y s u it e d to r e p a ir
d e fin e d , and an
e x a m p le
w ith
w o r k sta tio n
m axim u m
support has been
im p le m e n te d
based
on
an
in t e g r a t io n o f hardw are and so ftw a r e w ith in str u m e n t in t e r r o g a t io n
co m p lem en tin g i n s t r u c t i o n o r
d ir e c tio n
from
an e x p e r t sy stem and
c i r c u i t d a t a r e p r o d u c i b l e o n r e q u e s t f r o m a CAD d a t a - b a s e .
S u b s t a n t ia l a d d it io n a l w ork i s r e q u ir e d
u s a b le sy stem th a t
w ill
t h a t w i l l acco m m od a te
th e
to
p ro d u ce a f l e x i b l e and
e n a b le t h e d ev elo p m e n t o f
u p d a tin g
n ecessary
to
a
w o r k sta tio n
cope
w it h new
r e p a i r s i t u a t i o n s . H o w e v e r w i t h CAD d a t a - b a s e i n f o r m a t i o n a v a i l a b l e
from m a c h in e m a n u fa c tu r e r s
it
is
c o n c e iv a b le
in t e llig e n t r e p a ir s ta tio n can be produced.
136
th at
a
fle x ib le
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of
A u tom atic
c o n t r o l , P P .: 8 7 5 -8 8 0 , V o l. 2, Aug. 1981
[2 9 ] A. R.
Dormer:
"R e a l T i m e P r o c e s s O p t i m i s a t i o n " . F a c t o r y 2 0 0 0
I n te g r a tin g In form ation and
M aterial
F low (P u b l. No. 8 0 ) , 31
Aug- 2 Sep 1988
[ 3 0 ] P a t t i p a t i , K. R . ; S h a w , J . J . ; D e c k e r t , J . C . ;
A l e x a n d r i d i s , M .G .;
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W .P .:
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L. K . ;
"C o n f i d a n t e :
A
Com puter B ased D e s ig n A id f o r
th e O ptim al S y n t h e s is , a n a l y s i s
and o p e r a tio n
f a c i l i t i e s ",
A u t o t e s t Con.84
o f m ain ten an ce
(C at.
P roceed in gs
No. 84 C H 1 9 2 1 -6 ), P P .:
of
3 9 0 -4 0 4 , Nov.
1984
[ 3 1 ] S m i r n o v , A . N . : “E x p e r i e n c e i n
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[ 3 2 ] M i k h a i l o v , O. p . ; V e s e l o v , O. V . : "P r o m i s i n g
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(f o r
M achine
D evelop m ents
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in
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[33] C h a p u rla t, A .; de B o n n ie r e s ,
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T r o u b l e D i a g n o s i s ".
an
P .;
Expert
P roceed in gs
K retzschm ar,
System
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M ach ine-T ool
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I n t e r n a t i o n a l S e m in a r - E x h ib it io n , A p r il 1987
[ 3 4 ] K e l l e r , A.
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U .D .:
"R e l i a b i l i t y
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[3 5 ] P a d r a ig Cunningham ;
fo r F au lt
M i c h a e l B r a d y : "K n o w l e d g e
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AICS,
142
Irish
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[3 6 ] Brown J . S . ;
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In tellig en t
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“A _ T a x o n o m y
F o r m a l i s m s 11. T r i n i t y C o l l e g e
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[ 4 4 ] G e n e s e r e t h M . R . : “T h e U s e o f D e s i g n D e s c r i p t i o n s
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[45] G io v a n n in i F .; M a la b o c ch ia F .:
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"R e d u c i n g
C o n s u lta tio n M odel
as
C om plexity
a
B asis
for
4, O ct. 1985
by
the
R ejectin g
D esign
of
the
Expert
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[ 5 2 ] M i c h a e l D . R y c h e n e r : "E x p e r t S y s t e m s f o r E n g i n e e r i n g
D e s ig n ".
E xp ert S y stem s, V o l. 2, No. 1, Jan 1985
[ 5 3 ] M. H o f m a n n ;
J.
C avied es;
B r o d e r s e n : 11B u i l d i n g
J.
Expert
Bourne;
System s
for
G.
B eale;
R epair
A.
D o m a i n s ".
E xp ert S y stem s, V o l. 3, No. 1, Jan 1986
[54] M ic h a e l R.
G enesereth:
"D i a g n o s i s U s i n g H i e r a r c h i c a l
D esign
M o d e l s ” . AA AI, P P . : 2 7 8 - 2 8 3 , A u g . 1 9 8 2
[55] Jo h a n de
K leer;
B r i a n C. W i l l i a m s : "R e a s o n i n g A b o u t M u l t i p l e
F a u l t s " . AA AI, P P . : 1 3 2 - 1 3 9 , 1 9 8 6
[ 5 6 ] H a l S h u b i n ; J o h n Wade U l r i c h :
"I D T : An I n t e l l i g e n t D i a g n o s t i c
T o o l " . AA AI, P P . : 2 9 0 - 2 9 5 , A u g 1 9 8 2
[57] Ramesh S .
P a til;
Peter
"C a u s a l U n d e r s t a n d i n g
S zo lo v its;
of
P atien t
W illiam
Illn ess
B.
Schw artz:
in
M ed ical
D i a g n o s i s " . IJCA I, P P .: 8 9 3 - 8 9 9 , Aug 1981
[58] T .R . A d d is:
"T o w a r d s
an
'Expert *
144
D iagn ostic
System ".
ICL
T e c h n i c a l J o u r n a l , V o l . 2 , May 1 9 8 0
[59] S a n ja y M i t t a l ;
B.
Chandrasekaran;
K n ow led ae-D irected D atabase
for
Jon
S t i c k l e n : “P a t r e c ; &
a D i a g n o s t i c E x p ert S y s te m ".
Com puter, S ep . 1984
[ 6 0 ] L . F . P a u : "S u r v e y o f E x p e r t S y s t e m s f o r F a u l t
G en era tion and
M a in te n a n c e ".
Expert
D etection . T est
S ystem s, V o l. 3, No. 2,
A p r il 1986
[ 6 1 ] D a n a S . N a u : "E x p e r t C o m p u t e r S y s t e m s “ . C o m p u t e r , F e b . 1 9 8 3
[62] R a n d a ll D a v is;
Howard
Shrobe:
“R e p r e s e n t i n g
S tru ctu re
and
B e h a v i o u r o f D i g i t a l H a r d w a r e ". C o m p u t e r , O c t . 1 9 8 3
[63] P a d r a ig Cunningham :
K now ledge
rep resen tation
in
E lectro n ic
F a u l t D i a g n o s i s . P.H D. T h e s i s , T r i n i t y C o l l e g e D u b l i n , 1 9 8 9
[ 6 4 ] G l e e s o n J . F . J . : _ An
F au lt D ia g n o sis.
EMYCIN B a s e d E x p e r t S y s t e m f o r E l e c t r o n i c
M .Sc. T h e s i s ,
D ept.
of
Com puter
Scien ce,
V P-E xpert,
W ordware
T r in it y C o lle g e D u b lin ,1986
[ 6 5 ] W a l l y W ang;
John
M ueller:
Illu stra ted
P u b ., I n c ., 1989
[ 6 6 ] P a p e r b a c k S o f t w a r e : V P - E x p e r t . 19 87
[67] J . L.
A lty ;
M.
J.
Coombs:
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a n d E x p e r t S y s t e m s . (USA) 1 9 8 7
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1ENK:
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[71] S . J . C a h i l l : D e s ig n in g M ic r o p r o c e s s o r -B a s e d D i g i t a l C iy c u j t r y ,
PHI 1 9 8 5
[7 2 ] P a u l C.
Barr;
R onald
C h r i s t o p h e r S t a m m e n : _ CAD
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K rim per;
P rin cip les
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and
R.
Lazear;
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C a r b e r r v : CAD/CAM w i t h P e r s o n a l C o m p u t e r s . TAB B o o k
In c . 1985
[74] Joe Rooney;
P h ilip
S t e a d m a n P rin cip les
of
C om puter-A ided
D e s i g n .O pen U n i v e r s i t y 1987
[ 7 5 ] S p y r o s G.
T zafestas:_
K now ledge-B ased
System
D ia gn osis.
S u p e r v i s i o n , a n d C o n t r o l . P l e n u m P r e s s , New Y o r k 1 9 8 9
[76] B a rry B.
Brey:
M icrop rocessor/H ard w are
In terfacin g
and
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Expert
System s",
Kogan
Page, 1986
[78] F. H ay se-R oth ;
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W aterm an;
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[79] B .G . B u ch an an ;
E .H .
S h o rtliffe:
"R u l e - B a s e d E x p e r t S y s t e m s ".
A d d ison -W esly P u b lis h in g C o ., I n c ., 1984
[ 8 0 ] M .R . G e n e s e r e t h :
"An
O verview
of
MRS
for
AI
E x p e r t s ",
S t a n d f o r d H e u r i s t i c P r o g r a m m i n g p r o j e c t . Memo H P P - 8 2 - 2 7 , D e p t ,
o f Com puter S c i e n c e , 1982
[ 8 1 ] C . L . F o r g y : ”0 P S 5 U s e r ' s M a n u a l ". C a r n e g i e - M e l i o n
U n iv ersity ,
1981
[82] L o t f i A.
Zadeh:
“F u z z y
L o g ic ".
1988
146
Com puter, P P .: 8 3 - 9 2 , A p r il
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I
?
X
ERROR
)
V
i
,--------------------Ii
i
W’OCESS THE
!_
> .A P Ï* I F £ D
!
iflU E
DMA
THE
i PROCESSO) DAVA I N i -
i
3
IE H P O R f lR Y
F IL E i
I G IM E T H E C O N T R O L
! ö ftC K T O L O C A L ,
I (F R O N T P 3 N E L )
«
vï?s X
a
> 'V
X
C ERRO R
|
1
}
V /
INO
?
/■“ N
!+■
■ /7Ù
iW
tCALCULAIE THE 1
! ‘MFFEREWCt- I
! ÖEFINE THE
i
! üLLOÍWBLE
iTOLERANCE
i ____________________________!
5AU F. TH E
m m
,
1
üfl(iiJES INO )ÜCÍ t
F IL E
----------1* i
?
END
i-'S T
f S
■■«Mit
X s
G E T T I MG
TH E L O G IC
3 N ls C O M P A R I MG
.iN flL Ì’ Z E R 3 I G N * L
iv ________
ìTftBI
?
-
iIH IT 1 A L IS S THE *
1iHftXfc
BUS - r:*E1NSTW
W ÌNT. ».
CONTRO».
1 m * FiSHOTE
J
9
/
I
*
A
\
cFROfi >
SS
HO
¥
1
M itT CATft ['« OH tilt; i
1;
NSTRUHENT *
m
¥
A
y' V
rp.ROR ì
n/
PHOCESS THE
CAPIURED MTA
;___________________________
'
SAUE THE
PROCESSE» ì/ATft U'4 Ji A TEKPòRARV F I L E )
t
1
i
*
GIUE THE CONTROL }
BACK TO LOCAL.
■FRONT PfiNEL) |
YES /
»
ys,
N
(T -RROR ì
V
\
( ì l i !--fri
Pr
?
*-
HM
Hf il l
f 5 f 'J
CALCOLATE THE i
SUN OF THE
TOTAL
GlFìTRENCE.
SAUE THE RiSU LI
»»LUE IH « 1E5ÌT
f i LE
i
lH!)
'¡tÌ%
/~ N
-H t I l I
G ST T IN G
AND
S IG N A L S
P R O U ÏN G
FROM T H E L OG I G A HALS’ £
T H A T ;IN P U T
- O U TPU T
iiAHl
! ! H Ií I ALIZE W
í
j BUS f> INSTW íM íHf. i
! « rjíE THE '.'»MT«OL «
i FROH REMOTE
í
VÏS <X íí'.kokX
\
N
f
XHO
?
T
i íiET DATA FROM THE I
INSTRUMENT
I
j
?
m
< ERROR 1
N.
X
X INO
X
¥
1 PROCESS THE
! CAPTURE» PATA
1
i
I
1
t
p m BE PROCESSES Ï
DAT# TO t2 )S IG N ftU
INFORMATIONS.SÄUE »EfiCH ONE IN A
«
TEMPORARY i'\ LE. Î
}______________ï
-------------------------------------
■GUÍE THE CONTROL
t BACK TO LOCAL, |
i (FRONT PANEL)
!
?
f
END
y
¡ i
1f t i >
XX
■-Mporar-'j
[ADDÌVALUE >S) t
[ TO THE RESULT I
I UflKi HilLlí.
i
=><rVt*0f?f U
ADD <0>, TO
THE RESULT
VARIABLE
(*■(
V
-------- 1
r
I
SiWt>ít|g
!
! VALUE ÍM A ÍEVT tJt_____________
FIL E
!
r
-H t i ! I
yr
■LA c* _.T i l S
T
i V b T £3**
i ' i i O W C H fl
T
• raid
HM
?
1
o n th e I
MH
i W IN POWER >
<
‘
J SWITCH
y
<HAIN POWER )
>f’F / CHECK N
\
/
Xu
t iilSCOHNECT THE
! TRANSFORMER <H
} i.!°>
PHI THE PROB AT
P^IHT CD
.
11.hUL.
j
f
j C ALL
sketch me i
S
7
* s k e tc ti 1
t
; lawwt c w i > h i
t7 o « > H
u (j i n
f
1 1 ) ,
j
f CALL ! GETTING
!
i AMD COMPARING i
\
SfGNAL ( D
CHANGE THE i
t+TRflNSFORMER !
DIFFERENCE’'*
X ALLOWABL
YES
i
i
r"
10LERA
\ N ( 'I /
y '
NO
i
¥
exit
r
PUT THE PROB AI
POINT '?.)
>----------------------------------- !
{ CALL isk etch
j
i the <;i rcw i t *
?
Jz?»ok v*oint
i
I
1
,
__________________________________
I CALL : SETT INS >
{
i
AND COMPARING
r
SIGNAL iI)
j
YES ✓
-
i i
¡4 -
<
S
/
?
yv
x
v
»1FFEREN C EX
>V ALLOHABL
y
X TOLER A /
X nce y
XI
#
i' T
W
)
5
i
— ——
— ——1
! PROBLEM IN THE 5'J f
OUTPUT, BETWEEN 1
P 0 ïfiïin * P 0 lH T i2 ) 1
i
i
r
---------* PUT THE PROB AT
i
POINT (3>
Î_____________ !
CALL ¡ sketch
j
f he circuii S i
( ïoo-M p o in t í.3>. j
i
r ------------------I CALL ; «ETTïNQ
S ANI) COMPARING i
SIGNAL (3 )
}
!-----------------------i
NO /
<
X
i THE EXPECTED
! DAMAGED
COMPONENTS
<n ysi
(2) USi
¡3 ) C28, tJ30 i
(4 ) C5_7
t
i
:
em
/
DIFFERENCE^
}
ALLÛMABL y "
S ! OLERA y
NNCE/
N /l
¥tS
i PROBLEM BETHEEH
«
I
j POI NT <3 ) &P01NT <1 > \
r
I REMOVE (F3)
f PUT THE PPOB AT
POINT (A)
i
!
CALL : sk e tc h
the c ir c u it &
zoom p o in t i.4 ), î
f
I CALL ; GETTINO
i AND COMPARING
SIGNAL m)
!
1
»
?
■
jf
i
!
!
J
I
j
j
THE e xpec ted
DAMAGES)
COMPONENTS
c i) Ü9
>3) 826
i 3) € 3 4 ,Co5
<4> F3
HO / D IF F S W IC E X ÏES
N tìLLOltìBL y
\ SOLERA f
XNCE y "
¥
-.................. 1
fHE EXPECTED (
DAMAGED
COMPONENTS 1
<1) C32
(3) C37
j
1
à
*
<—
i r 'lT
T H E P W Ö (ÌT
i
3
»
¡
POINT ■ (
1_____________ i
9
r
\ <:*LL : SWITCH Í
![HE CISC#!7 £
(
i ZOOM PO»NF ( 5 ) .
?
f—
i CffLL : QITTUKi ¡
*
ft'M D < .0 H P û R ÎN ( 3 1
1
SIGNftL
I
1_____________ 1
✓N
:
x
V
y niF F E R IN O rv v is
\
>-
ALLOMÖL X
XîOI.tRfi y
X. MCE ÿ
MO
?
î-----------------------!
\ PUT
T H E P fiO B A T
;
\
POINT (? )
>_____________ i
i
»
¡“
t
-
—
CALÍ, ; SKETCH j
‘ HE Cl«CUIT &
!
ÏOÔH POINT ' ■» . i
_______________________i
i -ilLL : GETTING
itNl) COHPflRING
SIGNAL (VI
V
yv
VES /
—
EXPECTED i
DANAtiEB
COMPONENTS
C3
'2) !IR2
<\)
___________i
?
<
/
X
DI FFEP.ENCÉX
■=
% SLLÜUftliL /
V T Nhce
£ » Iy y
Y
ho
^
V_
)------- w 3
)
*
i
P R O B L E M ( H < - l2 V > i
, O U TPU T, BETU EEN
i
|? 0 1 H M > S P 0 IN I< 5 > i
t
t
V
i*
!
i f t ï P 0 1 N T Í6 ),
• P U T ' ilF , P R O B H T
I
¡
1 e a u . -ì KEIC ìì
< iKi ; 1H0H1 4
>
i &t 3C0NHEC1 ÍR23) !
ÏKE fSEE EDGE 10 1
< fh23).
I
;
:
#
—
,
ï SOOH f« H iT
■
« t* .
f
:
_____________ i
I »ALL : üETTIWi
¡1NÍ) rONPftRING »
s ifiitàL
1è
)
V
/
X
/■
X
y W lfg R E H C S V VIS
c
■3— ■
V aLtÔHABL f
'S ÏôL
X NE CR ftE / y
\y
'« 0
I EXPECTED DAMAGED I
1
! '1 ) C 3 6 ,C 3 8 .C 3 9 .C 4 8 \
j COMPONENTS :
r
!
* PROBLEM BETWEEN I
i t 'O t M r .i) .A N lX - liV I
‘ C?i -:■!<> v'JJTI^J i .
-
i'fECOHNF.CT •: i!23>.
i>isri>MECT<rdl>fif 1
POiNf<6>,
I POT THE ?BOB UtifllM
! hI ?'MHT<5>.
\
i
i CF4L SKETCH
} HIE CIRCUIT £
i aOOM P'JlKT ( 5 ) .
CSlL : GETTING -!
PHI* COMPftRIH(i
I
SIONftL <5>. i
¥
.'V
VE3 y MITEtiEMOEX
)r
f
X
!
!lX P E C T E 9
O ftM A G E D
"C M P O N E H T S
it L K H W B I ,
v roLiiRA y
> NOE/
\ /
NO
T
i
1
|
( L> 031,Cl4 !
UP.'J.^IW i
s2)
j
i
i
:
EXPECTED
iM N fM iE D
CO M PO H EM TS
I M> C3
) (2) V«2
E X IT
I
E X IT
1
y
J
*
i
í FUT I t'S' HflOB aî'
t
i
PftiHT *Si
¡
“ 1
f
F
iJfiLL : SKETCH
! LlîK '"IECU IT *
300N POINT Ui) «
)!
î
i
1 Cftliï, 5 TtKXT ^NÍj
1 8NÖ COaPâRÜfê
K Æ L (S)
!
1
s 'k
Xy'
ES y DIFFERENCES.
—f V ALLôMABL
X)
X I OLERA
x n c iV
i
i
<f
r
i
i
i
i
t
•" “) ’■
i-“— ----------- — --------------—
i HROSLEH s EWEEN
ipoum m poiw a)
1
________
!
I
i
I
1HEHOi7r ~
1 PUT THE PSOB ST
1
i'Q lM ( 9 ! ,
i
?
"’
'M l ■ SKETCH
THE CUÏCIUT %
SêOfl POINT m
,r!
!
i
:
?
Î
(---------! i.sLL ! >iiTT!NQ i
;
t îHpftRlt«i î
SKiHAl* ‘ :-f>
1
I ______________________ j
?
s\.
y
v
. y iMtFEKEHCEX WO
f
;—
Ai.LOWAHL y
v fO t.E R A
x
V ft‘.,£ y
w
: ÏES
*
r------{ T>l 3 CONNECT'
î
(R2Ô)flT FOI NT 1
( 1 0 ) . PUT THE i
PHOB AT THE !
SftHE POINT. !
I
1
! CALL ! 5KETCH )
i THE CIRCUIT <k 1
< ZOOM POINT ( 1 8 ) . I
J______________I
!
C ALL
: G E T T ! HO
î 4ND COMPARU«
I
S IG N A L ( 3 )
}
A
EXPECTED I
DAWAGEI)
!
COMPONENÏS i
I
( l > C1W.CR10!
<2? CRU
I
(3> CR12.C2 I
1
i
?
^
1
I
EXIT
I
/
N
r'ES > D lE S lR E W E X
— f.
V ALLOHftBi. ^
\ TOLERA /
V HCE y
■’sy
NO
t
EXPECTED
IMAGED
COMPONENTS
(1) ¡JHS.MRb
¡ I ) r 33
(3 ) C4.17
r
\
j
*
|
1
—
CHANGE
I ________
----- *
I
1
(?1)
1.
?
f — —
N
i
TO T
\
------------------- /
i»HT THE PR03 ftî
POINT M l)
t
I • HLL : SKETCM
i
I
—
i
l
!
!
........................
a u c u n &
ÜOO M P O IN T Ù l ) . i
i
tm e
«ÎEITING
I C ALL :
J
A N » C O M P A R IN G
i
5 1 < ÎN ftL C i )
!
5
t
>
?
X
/ '
V
/
yv
\
V
ALLO H ABL
TO LERA . /
NNCEX
X -"'
< EXPSCTE»
OAMAüED
¡N O
_________________
1
¡P U T T H E PRO B A ?
C O M PO N EN TS
( 1 ) U R 5 .M M
i. <2> C33 ?
0 4 .1 ?
j
j (3 )
<i 2 >
? O IN T
C ALL
j
I
: SKETC H
I
.............................................
t
?yi r
i.tt£ r ! RCU5 T * ?
ZOOM POINT '1 2 ) , |
CALL ; 'iETTINO I
? AND CONPAKim i
SIGNAL (1 8 )
f
/
X
VES y DIFFERENCES.
— c.
>=
X
ALLoU ABL
TO LERA
X .N C E /
/
/
■>
NO
7
!-----------------------1
I «U N ÏH E E N T E R N A L i
I I E S T PRO CRAM TO
i
t TH E P L ü ïT E R .
i M A T C H T H it F L O T T E R !
!;_MOT
_ _ _ORS
_ _ _ _CAREFULÏ.
_ _ _ _ _ _ _ _ _ ;t
?
✓
/
/
\
ALL
X
; M O TO RS W ORK
X
X
X
V
T
I
y
/
\
y
VES
EXIT
l
NO
>
H
9
\ __
\
«
I
i
ï
¡H ÏHt
> • F E N »: > IÏ! « H PUT.
> U P P ! iÿ )
(üEHíHfü: t.tt'*! PUT THE MfOB m
t
“ O IN T
i
I
.13)
>
? _________
•C PU . i KETCö IHEI
!
I
(SCHEMATIC
;__ _ _ _ _ _ _ _ _ _ó_fA_ _tìM
_ _ _* !¡
I CALL : SKETCH THE!
! LAYOUT CIRCUIT ■ )
». 200« POINT * Ì 3 ) . 1
;
!
I CALL ; GETTING i
} ‘«(HD COMPARING I
SIGNAL < 18) !
A
y
/
/
V
DIFFERENCES, NO
3 I .L Ô H 3 B L
N ío im y
/
VNCE y
'v "
TO
■US
I“
\
i
?
!
!
t tXPECTEB I
Î ÖAMAGED 1
iCOMPONENT «
i(l> c8? ¡
1(2) 0R8 ¡
I _______ ;
i
-
7
<------------a
mi
*
l_
'„HAWSE
<F2>
!
?
?
!
15 motor
"SFIN E wmw
HITCH T !j
WORK
i
L-______________ 1
í
0
A
/
V
x ' c a r o u s e l ' X no
r STEPPER MOTOR
s.\
/ X
X
X
NX
'YES
( 10 1
(
XX
y \
/N
' HO y
PEN
ORUJK MOTOR )
YES
i
1
12»
X
?
XV
/
V
X
\
X
\
rjAPER
X . H O HO y
>'EN
X
sos «rtofl >—»■-» - <. ^ysNOii)
)
X
x
X
X
V
✓
X X
XX
X/
YES
I YES
¥
1
- •'—s
i
15 I
V _X
> M i
- .X
I CALL : $SUD!WS !
;SET>iP 1^FORMATION \
ITO !HE < !,.*.
I
!
|
?
DISCONNECT THF INPUT
A I POINTS
.
CONNECT THE
(W A LTER 'S POD, ¡0
» •j.ii.L .M ) .uN THE
INPUT LINE SIDE.
1 CALI : SKETCH
!
\ THE CIRCUIT ¿ZOOMI
! P O IN T S U X L .H ) >
i
1
r
*-------
\ CALL : SETTING
{ AMD COMPARII«
SIQNAL *1b'i
/
Ì
/ \
\
HO X
N YES
— < DIFFERENCE > 8 )-------Né
y
v
/
\
/
EXPECT ED PAMnGED
COMPONENTS :
(1 ) 1*19
>2) CR1?,CR18,CR1?
CR28
(3 ) THE CAROUSEL
DRIVE STEPPER
MOTOR.
PROBLEM IN THE
CONTROL CIRCUIT.
' Ü I
I-----------------------------------------1
> CALL : SB ® UW !
{ SOIJ? UFOUHflHCMi
i TO ÍHE '.L.r) . )
!
— 1
} DISCONNECT THE ÍNPUT
iftT POINTS ( n .
CONNECT THE
i ANALYSER'S POD, ÍO
! ? O l N T ( l ) . ON THE
j PEN LiM E.
!
!
I
1
I CALL ! SKETCH
Í THE CIRCUIT S
I ZOOM POINT i l ) .
i
I
1 CALL ; '■ÏÎTING t
! rtf® COMPARING !
\
SiGNAL O S ) 1
L_____________ i
?
/
S
A
X
\
HO /
V VES
— < DIFFERENCE > «>-----V
/
V
EXPECTED
DAMAGLI)
COMPONENTS !
a> D1
K¿) CB1
Í 3 ) THE PEN
PROBLEM IN THE
i < U 6 > GAI ARRAY.
SOLENOID
7
1
I
1
r----------------------------------- !
! CHECK :Y ENCODER I
i NAMIALIA' '<?¥ ¡Hfc I
) ■ist.tuoscoPE
!_____________ i
%
/H
N. WJ
r s i g n a l >---\
s
ViS
f
1
:
SWITCH OH TWE
LOGIC «NrtLYSEP. I
1 CALL: SENDING
fSETUP INFORMATION!
* 10 THE L . A . ) 1
»THE ENCODER
'
is
t DAMAGED
_X1T
i CONNECT POD ( « ) , I
! CHANNEL < 8 ). TO i
POINT ( C>.
1
CALL : SKETCH
THE CIRCUIT «
200H POINT (C)
L
CALL : GETTING
■m COMPARING
SIGNAL <13)
1
(
!
?
/*
A
v
/
X "n YES
/
< DIFFERENCE > #Y—
X
X
A
?
r¡PROBLEM IN
¡THE <U5).GAT
ARRAV.
'
•
I
i Oí Li, , SENDÍN'3 ;
I SETUP iNFOP.HttTíoM í
ITO )HE
1
;
7
í CONNECT PO[) í 8) - i
¡ OWNNEL '0>.TO ¡
P'M.NT <C). ¿nd i
FOD («>. CHANNEL î
( i ) .10 P O iK K G ). *
A l l ; ^KETCH i
î THE Ci PCI! IT * !
; 200MPOINTStC. í > (
L_____________ ;
i ‘jflLL: ‘iüTTING -5
1 PJKWIN<i: —
< C : >i )
X
—v. «O
V/
VES
?
■ 14 I
?
f ------------------------------------- !
î EXPECTS»
i DAM AGES
COMPONENT
U> U8
(3 ) 01.1)5
(3 ) CIÌ2
f
!
j
i
I
•
~ '
—
',OHfJ£CT POD 1 rV), 1
'^HNEL
i
.
>.)). ?jffi •
( POD >i»>. CSifiNNEM
■ M J.TO POtHT<H>. •.
t_____________ t
¡CALL ; SKETCH THE I
I'jCftV’tiA flC DIllGRii# }
L
r----------------------i'^ L L ! SKETCH THE I
iL i i f
(KCUlT v t
i ¿OOH POlNtStD.H> 1
CALL; GETTING 4
i-BOMING; —
( D- W)
?
XV
S —vN©
c P - H >-----v
/
•iE3
?
i THE PEN DRIUE!
! MOTOK iS
j
DAMAGED. 1
1___________I
I
[Expected
I DAMAGED
I COMPONENT I
Id ) U8
a ) 02,06
<3> CSa
*i
i
EXIT
I
i
I
CHECK
ENCODER*
M A N U A LLY BY T H E t
O SCELLO SCO PE
I
A
/
N HO
(SIGNAL
')-------VFS
1
I
? S W IT C H O N IM F .
fL O G IC A N A L Y Z E R .
}
( C A L L : S E N D fN G
I S E T U P I M O H M A ltO M I
t ro i m e c l . a . > ;
L __________________________________!
t
I
!
< • ONNECT POD ' V*|. !
1 ch a nn e l <0>, rO ■
fo H lf < A K
1_____________ 1
i
!-----------------------!
I C ALL
: SK ETC H
S C H E M A T IC
D IA G R A M !
f
!
;
I CALL : SKETCH THE I
I LAYOUT C1RCUII * i
dOQM POINT ( A ) . |
?
1 C A L L ; G E T T IN G
1
A N D C O M P A R IN G
j
S IG N A L i l l )
i
/
>•
/
/
A .
S.
\
V YES
S
i W FFFSEHCE > « 1 -----
< r.aLL
, END I NO
'N F O w iA ilW
ro \ui n.a.)
15ETU P
i
I
I
i
i
CONNECT TOD <v»>. »
channel ikoao t
PO»NT <«>, ¿N£> i
?0& (0). CHANNEL »
\ I ) . {() rO f MT ( E ). »
CALL • SKETCH
THE CIRCUIT *
•
I ZOOM POINTS«»-h> i
I CALL; GETTING ft
i PROUIWi; —
<A = E '
•
I
*
f
>■%
^
NO
M : t )—
N /
VE3
f
I-------------!
I EXPECTED I
I DAMAGED
jCOMPONENT i
1(1) (12
1(2) 04.Q8 !
1 <3) CH5 I
<" 17 I
v
I
EXIT
')
t ÇüHNECT m 'li) , j
i OiANHEL
: i; I
i WiHI ’ A). '.NI) !
î eoô <«)- H AM ELi
ì <D,rO POIHKÏ). î
t______________;
¥
! ’
'
I CALI. : SKETCH THE i
I
t
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