8 Actuator and feedback
52 Positioner DC 6-06
8.2 Limiting the actuator stroke
Absolute limiting of the actuator's control path is also provided to protect the actuator from
mechanical and thermal overload. This limiting provides a safety distance ahead of the
actuator's mechanical limit stops.
The minimum position of the control path is limited by parameter 310 ActPosSecureMin.
Param
eter 312 ActPosS
ecureMax limits the maximum position of the control path. The
following values are usually used for these two parameters:
Number Parameter Value Unit
310 ActPosSecureMin 3.0 %
312 ActPosSecureMax 97.0 %
8.3 Servo loop
The control unit specifies a filling setpoint 2350 FuelQuantity from which a set position
for the actuator has to be calculated. Because 2350 FuelQuantity is provided as a
percentage, with a linear linkage the actuator setpoint 2330 ActPosSetpoint c
an be taken
directly from 2350 FuelQuantity.
In certain cases however it may be necessary to take the actuator setpoint from a filling-
dependent curve. This is especially useful with nonlinear linkages or throttles, or if the
actuator is mounted directly without any linkage (
4.2 Determining the actuator setpoint).
8.3.1 Servo control loop
The task of the servo or position control loop is to approach the selected set position
2330 ActPosSetpoint for the actuator. Parameters for P, I and D components are
available for this control loop. There is also an additional parameter which counteracts
the actuator's acceleration. This parameter is used primarily with the particularly fast
actuators in the 2000 series.
1911 ServoGain
P component for the servo loop of the actuator
1912 ServoStability I com
ponent for the servo loop of the actuator
1913 ServoDerivative
D component for the servo loop of the actuator
1914 Servo
Acceleration DD component for the servo loop of the actuator
2300 ActPos
Current value of the actuator
2330 ActPosSetpoint Set position for the actuator
A simple correction of the PID parameters of the servo loop in the static state which is
defined by the range 1906 ServoCorrRange is possible:
If the actuator position deviation between target and actual position is within the range
1906 ServoCorrRange, then
the PID parameters are corrected with the value 1905
ServoCorrFactor, i.e. they are usually reduced.
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