Commissioning Liquisys M CUM223/253
38 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. You apply this flow rate value
(0/4 to 20 mA) as feedforward control to the PID controller.
Feedforward control is a multiplying function as illustrated in the figure below (example
with factory setting):
C07-CPM2x3xx-05-06-00-de-003.eps
Fig. 22: Multiplying feedforward control
YGain K
infl
X Current input signal [%]
Z7 Input value, when gain K
infl
= 1
a0003169
Fig. 21: Arrangement example for feedforward control of the flow rate in the main stream to the PID controller(s)
1
2
3
4
Measuring water extraction point
Static mixer
Injection points
Flowmeter
5
6
7
Reagents
Liquisys M CUM253
CUA250 with CUS31
CAL REL
REL1
REL1
ALARM
REL2
REL2
E
NTU
25.0 ¡C
1.85
F
4 ... 20 mA
1
2
3
4
55
6
7
1
0 20 40 60 80 100Z7
1,5
0,5
Y
X
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