Endress+Hauser Liquisys M CLM223/253 - Page 40

Commissioning Liquisys M CLM223/253
40 Endress+Hauser
Feedforward control to PID controller
For control systems with very short reaction times, you can optimize the control.
Additionally you measure the flow rate of the medium. This flow rate value (0/4 to 20 mA)
you apply as feedforward control to the PID controller.
Feedforward control is a multiplying function as illustrated in the figure below (example
with factory setting):
a0008942
Fig. 26: Multiplying feedforward control
YGain K
infl
X Current input signal [%]
Z7 Input value, when gain K
infl
= 1
1
0 20 40 60 80 100Z7
1.5
0.5
Y
X