Commissioning Pid_3Step V2; Pretuning V2 - Siemens SIMATIC S7-1200 Function Manual

5.2.2

Commissioning PID_3Step V2

5.2.2.1

Pretuning V2

The pretuning determines the process response to a pulse of the output value and searches
for the point of inflection. The tuned PID parameters are calculated as a function of the
maximum slope 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.
The setpoint is frozen during pretuning.
Requirement
● The PID_3Step instruction is called in a cyclic interrupt OB.
● ManualEnable = FALSE
● Reset = FALSE
● The motor transition time has been configured or measured.
● PID_3Step 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
settings" configuration).
PID control
Function Manual, 03/2017, A5E35300227-AC
Using PID_3Step
5.2 PID_3Step V2
129