Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 5)

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IM 04L31A01-02E
PID Parameter Selection Method
You can select the method for switching PID parameters from the following:
• Target setpoint selection: By specifying the SP number.
• Zone PID selection:
By dividing the measurement span in to multiple zones and
determining in which zone the PV resides.
• Segment PID selection: Using the program pattern segment when in program
control.
Tuning
There are two methods: auto tuning of PID constants using the limit cycle method, and
manual tuning that allows PID parameters to be set individually during operation.
Control Suppression Function
Anti-Reset Windup (Over-Integration Prevention)
Overshoot may occur if the deviation between the SP and PV continues for an extended
time and the control output reaches the output high-limit through the integration process.
To prevent this from happening, the anti-reset windup function is used to pause the
integration process when the manipulated output reaches the high limit of the output
limiter.
Stop PID
computation
Start PID
computation
Output
value
PV
Time
Time
100%
Output
high limit
0
SP
Overshoot Suppression Function (“Control Output Suppression” in the Settings)
The deviation is monitored to detect the danger of overshooting and automatically
changes the SP to a slightly lower tentative value referred to as the “auxiliary target
setpoint” and continues control. Then, when the process value enters a range in which
overshooting is no longer a danger, the auxiliary target setpoint is gradually returned to
the original SP.
Original SP
Start fuzzy logic
Time
PV
PV
Auxiliary SP
Control output
suppression function On
Control Output Limiter
You can set high and low limits of the control output range (“output high-limit/low-limit” in
the settings) regardless of the operation mode.
Shutdown
This function is used to close the control value fully (set the output to 0) exceeding the
dead band of the control valve positioner.
Output Velocity Limiter
This function is used to prevent radical changes in the control output to protect the
control element and object of control.
Introduction to Control Functions