P3.12.3.2 FEEDBACK FUNCTION GAIN (ID 1058)
Use this parameter to adjust the gain of the feedback signal.
This parameter is used, for example, with the value 2 in Feedback Function.
P3.12.3.3 FEEDBACK 1 SOURCE SELECTION (ID 334)
Use this parameter to select the source of the PID feedback signal.
The AIs and the ProcessDataIn are handled as percentages (0.00-100.00%) and scaled
according to the feedback minimum and maximum.
NOTE!
The ProcessDataIn signals use 2 decimals.
If temperature inputs are selected, you must set the values of parameters P3.13.1.7 Process
Unit Min and P3.13.1.8 Process Unit Max to correspond to the the scale of the temperature
measurement board: ProcessUnitMin = -50 °C and ProcessUnitMax = 200 °C.
P3.12.3.4 FEEDBACK 1 MINIMUM (ID 336)
Use this parameter to set the minimum value of the feedback signal.
P3.12.3.5 FEEDBACK 1 MAXIMUM (ID 337)
Use this parameter to set the maximum value of the feedback signal.
10.12.4 FEEDFORWARD
P3.12.4.1 FEEDFORWARD FUNCTION (ID 1059)
Use this parameter to select if the feedforward value is taken from a single signal or
combined from two signals.
Accurate process models are usually necessary for the Feedforward function. In some
conditions, a gain and offset type of feedforward is sufficient. The feedforward part does not
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.
VACON · 170
PARAMETER DESCRIPTIONS
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