Commissioning Pid_Compact V2; Pretuning V2 - Siemens SIMATIC S7-1200 Function Manual

Using PID_Compact
4.2 PID_Compact V2
4.2.2

Commissioning PID_Compact V2

4.2.2.1

Pretuning V2

The pretuning determines the process response to a jump change of the output value and
searches for the point of inflection. The PID parameters are calculated from the maximum
rate of rise and dead time of the controlled system. You obtain the best PID parameters
when you perform pretuning and fine tuning.
The more stable the process value is, the easier it is to calculate the PID parameters and the
more precise the result will be. Noise on the process value can be tolerated as long as the
rate of rise of the process value is significantly higher compared to the noise. This is most
likely the case in operating modes "Inactive" and "manual mode". The PID parameters are
backed up before being recalculated.
Requirement
● The "PID_Compact" instruction is called in a cyclic interrupt OB.
● ManualEnable = FALSE
● Reset = FALSE
● PID_Compact is in one of the following modes: "Inactive", "Manual mode", or "Automatic
mode".
● The setpoint and the process value lie within the configured limits (see "Process value
monitoring" configuration).
● The difference between setpoint and process value is greater than 30% of the difference
between process value high limit and process value low limit.
● The distance between the setpoint and the process value is > 50% of the setpoint.
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Function Manual, 03/2017, A5E35300227-AC
PID control