Danfoss VACON 100 FLOW Series Application Manual page 239

VACON® 100 FLOW
Application Guide
Parameter Descriptions
11.15.3 Feedback
11.15.3.1 (ID 333) Feedback Function
Location in the menu: P3.13.3.1
Use this parameter to select if the feedback value is taken from a single signal or combined from two signals. It is possible to select
the mathematical function that is used when the two feedback signals are combined.
11.15.3.2 (ID 1058) Feedback Function Gain
Location in the menu: P3.13.3.2
Use this parameter to adjust the gain of the feedback signal. This parameter is used, for example, with the value 2 in Feedback
Function.
11.15.3.3 (ID 334) Feedback 1 Source Selection
Location in the menu: P3.13.3.3
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.
The ProcessDataIn signals use 2 decimals.
If temperature inputs are selected, the values of parameters P3.13.1.5 Process Unit Min and P3.13.1.6 Process Unit Max must be set
to correspond to the scale of the temperature measurement board: ProcessUnitMin = -50 °C and ProcessUnitMax = 200 °C.
11.15.3.4 (ID 336) Feedback 1 Minimum
Location in the menu: P3.13.3.4
Use this parameter to set the minimum value of the feedback signal.
11.15.3.5 (ID 337) Feedback 1 Maximum
Location in the menu: P3.13.3.5
Use this parameter to set the maximum value of the feedback signal.
11.15.4 Feedforward
11.15.4.1 (ID 1059) Feedforward Function
Location in the menu: P3.13.4.1
Use this parameter to select if the feedforward value is taken from a single signal or combined from two signals. It is possible to
select the mathematical function that is used when the two feedforward signals are combined.
Accurate process models are 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 affect the controlled process value.
Example
It is possible to 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 can be measured. With the measurements of the disturbance, it is possible to try to adjust this
disturbance with a feedforward control (gain and offset) added to the PID output. The PID controller reacts much faster to changes
in the outflow than if the level is only measured.
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