use the feedback measurements of the actual controlled process value. The feedforward
control uses other measurements that have an effect on the controlled process value.
EXAMPLE 1:
You can control the water level of a tank with flow control. The target water level is set as a
setpoint, and the actual level as feedback. The control signal monitors the flow that comes
in.
The outflow is like a disturbance that you can measure. With the measurements of the
disturbance, you can try to adjust this disturbance with a feedforward control (gain and
offset) that you add to the PID output. The PID controller reacts much faster to changes in
the outflow than if you only measure the level.
+
+
A
B
C
LT
FT
PID
FFW
Fig. 71: The feedforward control
A. Level ref
B. Level control
C. Outflow control
P3.13.4.2 FEEDFORWARD GAIN (ID 1060)
Use this parameter to adjust the gain of the feedforward signal.
P3.13.4.3 FEEDFORWARD 1 SOURCE SELECTION (ID 1061)
Use this parameter to select the source of the PID feedforward signal.
P3.13.4.4 FEEDFORWARD 1 MINIMUM (ID 1062)
Use this parameter to set the minimum value of the feedforward signal.
P3.13.4.5 FEEDFORWARD 1 MAXIMUM (ID 1063)
Use this parameter to set the maximum value of the feedforward signal.
PARAMETER DESCRIPTIONS
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