NOVA541
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4-8. PID Group (G.PID)
▪ When On/Off mode, it is skipped. ON.OF = ON in G.CTL.
Anti reset wind-up (ARW)
.
▪ ARW is an effective function to minimize the influence of an external perturbation or disturbance.
▪ When I=0 in PID parameter, ARW will not work.
▪ MV estimation in PID control : MV = P (proportional ) + I (integration term) + D (derivative term)
과
적
분
방
지
기
능
이
없
는
경
우
When a perturbation occurs (ex. door open) PV decreases, and MV increases to fit PV to SP. If the
deviation keeps high for a long time, the integration value in I term remains for long time after the
termination of the perturbation. Consequently, a large overshoot may occur and it takes a long
time to get stable PV.
과
적
분
방
지
기
능
이
있
는
경
우
When current NPV approaches ±P BAND , the integration value in I term vanishes by the operation
of Anti-Reset-Windup. Therefore, overshooting is minimized and PV gets stable quickly.
▶ P BAND setting example
→ input range : 0.0~100.0℃ , P:10.0% , ARW : 200%
→
P BAND = 200% of P = 20.0%(P*2) = 20.0℃ (input range * 0.2)
SP
PV
Perturbation
After the termination of the external perturbation
MV
SP
PV
MV
Perturbation
After the termination of the external perturbation