Parallel Tuning Of Controller Channels - Siemens SIMATIC S7-1200 Function Manual

Using PID basic functions
7.3 TCONT_CP
7.3.3.5

Parallel tuning of controller channels

Adjacent zones (strong heat coupling)
If two or more controllers are controlling the temperature, on a plate, for example (in other
words, there are two heaters and two measured process values with strong heat coupling),
proceed as follows:
1. OR the two outputs QTUN_RUN.
2. Interconnect each TUN_KEEP input with the output of the OR element.
3. Start both controllers by specifying a setpoint step change at the same time or by setting
TUN_ST at the same time.
The following schematic illustrates the parallel tuning of controller channels.
Advantage:
Both controllers output LMN0 + TUN_DLMN until both controllers have left phase 2. This
prevents the controller that completes tuning first from falsifying the tuning result of the other
controller due to the change in its manipulated variable.
NOTICE
Reaching 75% of the setpoint step change causes an exiting of phase 2 and resetting of
output QTUN_RUN. However, automatic mode does not start until TUN_KEEP is also 0.
Adjacent zones (weak heat coupling)
In general terms, tuning should be carried out to reflect the way in which the controller will
operate subsequently. If zones are operated together during production such that the
temperature differences between the zones remain the same, the temperature of the
adjacent zones ought to be increased accordingly during tuning.
Differences in temperature at the beginning of the tuning are irrelevant since they will be
compensated by the initial heating (-> initial rise = 0).
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Function Manual, 03/2017, A5E35300227-AC
PID control