YOKOGAWA UT55A - Feedforward Control

8-85
IM 05P01C31-01EN
Control Functions
8.2.8 Feedforward Control
Description
Using only the feedback control results in a delay in recovery of the control target to
normal status because PID action occurs only when the effects of disturbance appear on
a
PV.
If disturbance can be measured, a correction signal with respect to the disturbance can
be applied in advance to the controller’
s output (OUT) to cancel out the disturbance
before it affects the control target.
This is called feedforward control.
Improving
heatexchanger
controllability
For simple heat exchanger control, the addition of feedforward control enables
compensation to be made for variations in the inflow rate.
Gf
TIC
+ +
Product
Temperature
Heating medium
UT
Inflow rate (feedforward signal)
Heat exchanger
Note
For Feedforward control, it is necessary to use the controller (UT55A-x7) equipped with AIN2
aux. analog input or to build the function by LL50A Parameter Setting Software with unused
aux. analog input.
► Controller with AIN2 aux. analog input: 8.1 Setting Control Mode (CTLM), Function Block Diagram
8
8.2SettingControlType(CNT)