5.3.2
Feedforward control to PID controller
In processes with very short response times it may be practical to apply the flow rate to the
controller, if the flow rate fluctuates, in order to optimise the control process.
Feedforward control is a multiplying function as depicted in the below figure (factory setting as
example):
1
0
20
40
60
80
100
Z7
Gain
K
influ
Current input
signal [%]
1.5
0.5
Fig. 5.5
Multiplying feedforward
control
HAUSER
LIQUISYS M
CAL
REL
REL 1
REL 1
ALARM
REL 2
REL 2
E
mg/l
25.0 °C
0.42
F
4 ... 20 mA
Oxidising
agent
Reducing
agent
COA 250 with
COS 21
Liquisys M COM 253 F
Static mixer
Injection points
Measuring water
extraction point
Flow meter
Fig. 5.6
Arrangement example for
feedforward control of the
flow rate in the main stream to
the PID controller(s)
Instrument configuration
Liquisys M COM 223 F / 253 F
26
Hauser
