Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 48)

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IM 04L31A01-01E
1.8 Control Output Suppression Settings
Anti-Reset Windup (Over-Integration Prevention)
There are certain cases in which a large deviation between the SP and PV is present for
an extended time such as when control operation is started. In such cases, the control
output may reach the high limit of the output limiter and become saturated due to the
integral action. In the end, an overshoot may occur. To prevent this from happening, the
anti-reset windup function is used to pause the integral action when the manipulated
output reaches the high limit of the output limiter.
Stop PID
computation
Start PID
computation
Output
value
PV
→Time
→Time
100%
Upper limit of the
output limiter
0
SP
The function can be set automatically or manually. When manually setting the function,
the point at which the integral computation is resumed is set in terms of a deviation width
(%). The deviation width is derived using the following equation.
Deviation width (%) = |PV – SP|/proportional band × 100
Selectable range of deviation width: 50.0 to 200.0%
Control Output Suppression
You can use the overshoot suppressing function that uses fuzzy logic. The overshoot
suppression function works only during PID control when all PID constants are specified.
When the overshoot suppression function is used, the deviation is monitored to detect
the danger of overshooting. If danger is detected, the SP is automatically changed to a
slightly lower tentative value referred to as the “auxiliary SP”, and the control continues.
Then, when the PV enters a range in which overshooting is no longer a danger, the auxiliary SP
is gradually returned to the original SP.
The following cases are examples in which this function is effective.
• When you wish to suppress overshooting.
• When you wish to shorten the rise time.
• When load fluctuation is frequent
• When the setpoint is changed frequently.
PV
Auxiliary SP
Control output
suppression function ON Start fuzzy logic
Time
PV
Original SP