8-66
IM 05P02C41-01EN
8.7
SuppressingIntegralAction(Anti-resetWind-up)
Description
Where there is a large deviation at the start of the control operation, for example, integral
outputs are accumulated and the PV exceeds the SP, thereby causing the output to
overshoot. To avoid this, the controller provides an anti-reset wind-up function for
suppressing an extreme integral output by stopping PID computations. Same applies to
the case of undershoot.
100
OH
0
SP
PID computations restart
OH: Output high limit
Time
PV
Deviation band (AR):
the ratio of (PV–SP) to
PV
The parameter AR sets the point (by deviation band (%)) to restart the PID computation
that is suspended by the controller’s anti-reset windup function. PID computation restarts
when the deviation band has decreased to the AR setpoint. When the parameter AR is
set to AUTO, the controller automatically determines the point at which to restart the PID
computation.
Deviation band (= Setpoint of AR) = × 100 (%)
Proportional band
| PV – SP |
SettingDetails
Parameter
symbol
Name
Display
level
Settingrange Menusymbol
AR Anti-reset windup STD AUTO, 50.0 to 200.0% TUNE
Note1: In Cascade control, the LP2 lamp is lit while the Loop-2 parameter is displayed.
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