Fine Tuning - Siemens SIMATIC S7-1200 Function Manual
Pid control
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Also See for SIMATIC S7-1200:
- Manual (364 pages) ,
- System manual (338 pages) ,
- Reference manual (89 pages)
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6.3.3
Fine tuning
Fine tuning generates a constant, limited oscillation of the process value. The PID
parameters are tuned for the operating point from the amplitude and frequency of this
oscillation. The PID parameters are recalculated from the results. PID parameters from fine
tuning usually have better master control and disturbance characteristics than PID
parameters from pretuning. You obtain the best PID parameters when you perform pretuning
and fine tuning.
PID_Temp automatically attempts to generate an oscillation greater than the noise of the
process value. Fine tuning is only minimally influenced by the stability of the process value.
The PID parameters are backed up before being recalculated.
PID_Temp offers different fine tuning types depending on the configuration:
● Fine tuning heating:
PID_Temp generates an oscillation of the process value with periodic changes at the
output value heating and calculates the PID parameters for heating.
● Fine tuning cooling:
PID_Temp generates an oscillation of the process value with periodic changes at the
output value cooling and calculates the PID parameters for cooling.
Temporary tuning offset for heating/cooling controllers
If PID_Temp is used as a heating/cooling controller (Config.ActivateCooling = TRUE), the
PID output value (PidOutputSum) at the setpoint has to fulfill the following requirements so
that process value oscillation can be generated and fine tuning can be carried out
successfully:
● Positive PID output value for fine tuning heating
● Negative PID output value for fine tuning cooling
If this condition is not fulfilled, you can specify a temporary offset for fine tuning that is output
at the opposing output.
● Offset for cooling output (PIDSelfTune.TIR.OutputOffsetCool) with fine tuning heating.
Before starting tuning, enter a negative tuning offset cooling that is smaller than the PID
output value (PidOutputSum) at the setpoint in the stationary state.
● Offset for heating output (PIDSelfTune.TIR.OutputOffsetHeat) at fine tuning cooling
Before starting tuning, enter a positive tuning offset heating that is greater than the PID
output value (PidOutputSum) at the setpoint in the stationary state.
The defined offset is balanced by the PID algorithm so that the process value remains at the
setpoint. The height of the offset allows the PID output value to be adapted correspondingly
so that it fulfills the requirement mentioned above.
To avoid larger overshoots of the process value when defining the offset, it can also be
increased in several steps.
If PID_Temp exits the fine tuning mode, the tuning offset is reset.
PID control
Function Manual, 03/2017, A5E35300227-AC
Using PID_Temp
6.3 Commissioning PID_Temp
185
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