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Controlling
7.1
Overview
7.1.1
Concept of Integrated Controlling
7
Overview
The following SFBs are available to you for controlling with the CPU 313C, CPU 313C-2 DP,
PtP and CPU 314C-2 DP, PN/DP, PTP:
● SFB 41 for continuous control (CONT_C)
● SFB 42 for step control (CONT_S)
● SFB 43 for pulse width modulation (PULSEGEN).
The SFBs are compatible to FBs 41 through 43. This software control block solution offers
full controller functionality in every block. Data required for periodic calculation are stored in
the assigned DBs (Instance DBs). This allows you multiple calls of the SFBs. SFB
PULSEGEN in combination with SFB CONT_C used to obtain a controller with pulse output
for proportional actuators (e. g. for heating and cooling aggregates).
Basic Functions
A controller created with the help of SFBs consists of a number of units you can configure.
Functions for preparing setpoint and actual values as well as for post-processing the
calculated manipulated variable are integrated, in addition to the actual controller with its PID
algorithm.
Applications
Principally, the controls created with the two control blocks are neutral related to the field of
application. The controlling efficiency, and therefore processing speed, depends exclusively
on the performance of the CPU you are using. With the given CPU, a compromise must be
found between the number of controllers and the processing frequency required for the
controllers. The faster the connected control circuits are, that is, the more often the
manipulated values have to be calculated per time unit, the lower the number of installable
controllers. There are no restrictions with regard to the type of controllable processes. Slow
(temperatures, filling levels etc.) as well as fast controlling systems (flow, speed etc.) can be
controlled.
CPU 31xC: Technological functions
Operating Instructions, 03/2011, A5E00105484-05
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