Pid Control - Siemens S7-1200 System Manual
Hide thumbs
Also See for S7-1200:
- Operating instructions manual (132 pages) ,
- Programming manualline (74 pages) ,
- Manual (46 pages)
Table of Contents
Technology instructions
9.2 PID control
After enabling the HSC, configure the other parameters, such as counter function, initial
values, reset options and interrupt events.
For additional information about configuring the HSC, refer to the section on configuring the
CPU (Page 142).
9.2
PID control
STEP 7 provides the following PID instructions for the S7-1200 CPU:
● The PID_Compact instruction is used to control technical processes with continuous
input- and output variables.
● The PID_3Step instruction is used to control motor-actuated devices, such as valves that
require discrete signals for open- and close actuation.
Note
Changes that you make to the PID configuration and download in RUN do not take effect
until the CPU transitions from STOP to RUN mode. Changes that you make in the "PID
parameters" dialog using the "Start value control" take effect immediately.
Both PID instructions (PID_3Step and PID_Compact) can calculate the P-, I-, and D-
components during startup (if configured for "pre-tuning"). You can also configure the
instruction for "fine tuning" to allow you to optimize the parameters. You do not need to
manually determine the parameters.
Note
Execute the PID instruction at constant intervals of the sampling time (preferably in a cyclic
OB).
Because the PID loop needs a certain time to respond to changes of the control value, do
not calculate the output value in every cycle. Do not execute the PID instruction in the main
program cycle OB (such as OB 1).
The sampling time of the PID algorithm represents the time between two calculations of the
output value (control value). The output value is calculated during self-tuning and rounded to
a multiple of the cycle time. All other functions of PID instruction are executed at every call.
418
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
Table of Contents
