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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 REFERENCES [1] B e r u t t i, A .: "D e c e n t r a l i z e d M a i n t e n a n c e f o r A u t o m a t e d P l a n t " . E l e c t r . C o n s t r . a n d M a i n t . 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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 APPENDIX (A) 3 E fi IR C H ? '« o G R f i m SV*RT t 1 OPEN OpCAS ifL E -on m v m Æ m {*MIA f i LE. ì ï w f \ / PI.Oi V ÏËS C VILE £S v---x EMPTY y % / 0r m ■i i l i PLOT % r ---------- 1 1SEsW-i! FOR THE i fS îflK Ï <>F IN * l THE PLttHit.. î - : , SEARCH FOR FIRST ! | PtìRT OF rtftïA.üiiUE I î in ARRv o f am. ; L j f .- 'X / x m c EOF >------- V 7 MO ! s \ y' s VES CX EOF >y* V ' à >SEARCH FOR SECOND ■ ; PART OF M i A. SAME 1 IN ARRY Of CHAR. 1 ? „ 'V / x m C EOF j— \ V ' MO 7 DEFI NE THE ï ï PE OF DATA Ì 1 1 J f -”N / \ VES < LIHE )-----------X / ’¡MO ? 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FROH REMO Í F. i 1 ? >X t* ir îfTiAîï i X S i 1 S 1 / HO ■ f t ‘’FT S E T U P 1 I N F O I T I O rí ( ŸM» i • n ifi flNftLVZER i ï ✓v VES / -V ' V Ciivlwii J X -V / NO »1 1 ! Q IM T H E C O N T R O L Ì 1 8 A C X T O I . O C f lL , j ( F R O N T P ftN E L ) f VES / ' ^ ^ X :•-------------------- -------------------------------------< E R R O R 3 X/ HO » F 1 í SAUE THE ¿<r™\ f ill WH SETUP INFORMATION! U N fl Hfl SS MEMORY » 1 £ND ON G ET T i H G THE A NS COWPftRINQ OSCILLOSCOPE SIGNAL iT R P .T i ' • NITJALiSE TK? bUS ■ < ' !<ST ?IÎHKNÎ . jW K K -itÇ .»NTJWL s' m PEMOTÎt, ) A m ? s- ■ íRROR X i i i ) »> } Xo T SET !¡a T ft FROM THE j CRU M EN T L-. k-c. /" A I 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 j SCHEMATIC 81AG8AN1 ? K ftU * : SKETCH THE! ! LAYOUT CIRCUIT ' ; ; ZOOM P Ô IN TSiB .i > Í ! 1 _____________ 7 k m : DETTINO* \ 5 '"ÎO IJ IH C :------------ 1 i ' 8 : F 1 • t i ? À / s il« C B : f 'J—---X S V VES I ? S THE Pope» I ¡>81UF HOTOR I (S DAMAGED. \ I 1 i 1 ( ! Í EXPECTED S ! ÜAMAGED | COHPOWENÏ j m > <>?. I< 2 ) 03,117 t 13 > CR4 I____________