Siemens SIMATIC S7-1200 Function Manual page 332

Instructions
9.2 PID_3Step
State Description of operating mode
4 Manual mode
In manual mode, you specify manual output values in the Manual_UP and Manual_DN parameters or Man-
ualValue parameter. Whether or not the actuator can be moved to the output value in the event of an error
is described in the ErrorBits parameter.
You can also activate this operating mode using ManualEnable = TRUE. We recommend that you change
the operating mode using Mode and ModeActivate only.
The switchover from manual mode to automatic mode is bumpless. Manual mode is also possible when an
error is pending.
5 Approach substitute output value
This operating mode is activated in the event of an error, if Errorbehaviour = TRUE and ActivateRecover-
Mode = FALSE..
PID_3Step moves the actuator to the substitute output value and then switches to "Inactive" mode.
6 Transition time measurement
The time that the motor needs to completely open the valve from the closed condition is determined.
This operating mode is activated when Mode = 6 and ModeActivate = TRUE is set.
If endstop signals are used to measure the transition time, the valve will be opened completely from its
current position, closed completely, and opened completely again. If GetTransit-
Time.InvertDirection = TRUE, this behavior is inverted.
If position feedback is used to measure the transition time, the actuator will be moved from its current posi-
tion to a target position.
The output value limits are not taken into consideration during the transition time measurement. The actua-
tor can travel to the high or the low endstop.
7 Error monitoring
The control algorithm is switched off and no longer changes the valve position.
This operating mode is activated instead of "Inactive" mode in the event of an error.
All the following conditions must be met:
Automatic mode (Mode = 3)
•
Errorbehaviour = FALSE
•
ActivateRecoverMode = TRUE
•
One or more errors have occurred in which ActivateRecoverMode (Page 338) is effective.
•
As soon as the errors are no longer pending, PID_3Step switches back to automatic mode.
8 Approach substitute output value with error monitoring
This operating mode is activated instead of "approach substitute output value" mode when an error occurs.
PID_3Step moves the actuator to the substitute output value and then switches to "error monitoring" mode.
All the following conditions must be met:
Automatic mode (Mode = 3)
•
Errorbehaviour = TRUE
•
ActivateRecoverMode = TRUE
•
One or more errors have occurred in which ActivateRecoverMode (Page 338) is effective.
•
As soon as the errors are no longer pending, PID_3Step switches back to automatic mode.
10 Manual mode without endstop signals
The endstop signals are not taken into consideration, even though Config.ActuatorEndStopOn = TRUE.
The output value limits are not taken into consideration. Otherwise, PID_3Step behaves the same as in
manual mode.
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Function Manual, 03/2017, A5E35300227-AC
PID control