9.12.1 FEEDFORWARD
P3.13.4.1 FEEDFORWARD FUNCTION (ID 1059)
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.
PID
+ +
LT
FT
FFW
Level ref
Level control
Outflow
control
Fig. 70: The feedforward control
9.12.2 SLEEP FUNCTION
P3.13.5.1 SP1 SLEEP FREQUENCY (ID 1016)
The drive goes to sleep mode (that is, the drive stops) when the output frequency of the drive
is less than the frequency limit that is set in this parameter.
The value of this parameter is used when the signal of the PID controller setpoint is taken
from the setpoint source 1.
PARAMETER DESCRIPTIONS VACON · 291
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