Parameters State And Mode V2 - Siemens SIMATIC S7-1200 Function Manual
Pid control
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9.1.4.8
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_Compact 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_Compact starts in
the operating mode that is saved in the Mode parameter. To leave PID_Compact in
"Inactive" mode, set RunModeByStartup = FALSE.
Meaning of values
State / Mode Description of operating mode
0
Inactive
In "Inactive" operating mode, the output value 0.0 is always output, regardless of Config.OutputUpperLimit
and Config.OutputLowerLimit. Pulse width modulation is off.
1
Pretuning
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.
Pretuning requirements:
Inactive (State = 0), manual mode (State = 4), or automatic mode (State = 3)
•
ManualEnable = FALSE
•
Reset = FALSE
•
The process value must not be too close to the setpoint.
•
|Setpoint - Input| > 0.3 * | Config.InputUpperLimit - Config.InputLowerLimit| and
|Setpoint - Input| > 0.5 * |Setpoint|
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 compared to the noise.
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 the operating mode is dependent on ActivateRecoverMode.
The phase of pretuning is indicated with PIDSelfTune.SUT.State.
PID control
Function Manual, 03/2017, A5E35300227-AC
Instructions
9.1 PID_Compact
265
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