Pid Example; Reference Array Initialization Using %M00006 - GE PACSystems RX7i Cpu Programmer's Reference Manual

7.7 PID Example

The following PID example has a sample period of 100ms, a Kp gain of 4.00 and a Ki gain of 1.500. The
set point is stored in %R0001, the control variable is output in %AQ0002, and the process variable is
returned in %AI0003. CV Upper and CV Lower Clamps must be set, in this case to 20000 and 4000,
and an optional small Dead Band of +5 and -5 is included. The 40-word reference array starts in
%R0100. Normally, user parameters are set in the reference array, but %M0006 can be set to
re-initialize the 14 words starting at %R0102 (word 3) from constants stored in logic (a useful
technique).
The block can be switched to Manual mode with %M1 so that the Manual Command, %R113, can be
adjusted. Bits %M4 or %M5 can be used to increase or decrease %R113 and the PID CV by 1 every
100ms solution. For faster manual operation, bits %M2 and %M3 can be used to add or subtract the
value in %R2 to/from %R113 every CPU sweep. The %T1 output is on when the PID is OK.
7.7.1

Reference Array Initialization using %M00006

For details on the contents of the reference array, refer to Reference Array for the PID Function.
Word Function
3 Sample Period
4 + Dead Band
5 - Dead Band
6 Kp
7 Kd
8 Ki
9 CV Bias
10 CV Upper Clamp
11 CV Lower Clamp
12 Minimum Slew Time %R111
13 Config Word
14 Manual Command
15 Control Word
16 Internal SP
GFK-2950C
Address Value
%R102 10
%R103 5
%R104 5
%R105 400
%R106 0
%R107 1500
%R108 0
%R109 2000
%R110 400
0
%R112 0
%R113 0
%R114 0
%R115 0
February 2018
Chapter 7. PID Built-In Function Block
363