Parameters State And Mode V2 - Siemens SIMATIC S7-1200 Function Manual

Instructions
9.2 PID_3Step
9.2.4.8

Parameters State and Mode V2

Correlation of the parameters
The State parameter shows the current operating mode of the PID controller. You cannot
change the State parameter.
With a rising edge at ModeActivate, PID_3Step switches to the operating mode saved in the
Mode in-out parameter.
When the CPU is switched on or switches from Stop to RUN mode, PID_3Step starts in the
operating mode that is saved in the Mode parameter. To leave PID_3Step in "Inactive"
mode, set RunModeByStartup = FALSE.
Meaning of values
State Description of operating mode
0 Inactive
The controller is switched off and no longer changes the valve position.
1 Pretuning
The pretuning determines the process response to a pulse 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.
Pretuning requirements:
The motor transition time has been configured or measured.
•
Inactive (State = 0), manual mode (State = 4), or automatic mode (State = 3)
•
ManualEnable = FALSE
•
Reset = FALSE
•
The setpoint and the process value lie within the configured limits.
•
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 as compared to the noise. This is most likely the case in operating modes "Inac-
tive" and "manual mode".
The setpoint is frozen in the CurrentSetpoint tag. Tuning is canceled when:
Setpoint > CurrentSetpoint + CancelTuningLevel
•
or
Setpoint < CurrentSetpoint - CancelTuningLevel
•
Before the PID parameters are recalculated, they are backed up and can be reactivated with LoadBackUp.
The controller switches to automatic mode following successful pretuning. If pretuning is unsuccessful, the
switchover of operating mode is dependent on ActivateRecoverMode and ErrorBehaviour.
The pretuning phase is indicated with the SUT.State tag.
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Function Manual, 03/2017, A5E35300227-AC
PID control