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6-15
Chapter 6. OPERATION
• During execution of auto-tuning, progress of program operation time stops.
Accordingly, the DCP32 is in a similar state to the HOLD mode even in the
RUN or FAST modes.
• Auto-tuning in all instances involves calculating the downtime and critical
sensitivity of the control system according to two limit cycles and PID values
according to suitable characteristic equations for each, and automatically writing
these PID values.
• During execution of auto-tuning, PV fluctuates according to fluctuations in MV.
Before executing auto-tuning, make sure that fluctuations in PV will not cause
controller trouble.
• Normally, suitable values are written by setting variable parameter At setting to
1 or 3. However, when executing auto-tuning on a control system that easily
overshoots, either set to 2, or also use smart-tuning for carrying out overshoot
inhibit control. Setting to 3 executes AT by neural net so that suitable values are
calculated for wider range applications.
• The point at which output at auto-tuning is inverted (lower limit to upper limit,
and vice versa) is determined as follows from SP and PV at start of auto-tuning.
• Auto-tuning can be started by the
AT
key, external switch inputs and
communications. The
AT
key functions on the currently displayed channel.
During auto-tuning, the
AT
LED on the currently displayed channel blinks.
• If one or more of the following conditions occurs during auto-tuning, auto-
tuning is canceled without PID constants being written, and the
AT
LED goes
out.
- Cancellation by the
AT
key (when the displayed channel indicates auto-tuning
in progress)
- Cancellation by external switch input
- Cancellation by communications
- Change in mode (move to MANUAL mode or READY mode)
- Execution of automatic motor valve opening adjustment on 2G output models
- When variable parameter
At
(for CH1) setting is changed to “0”
- When variable parameter 2
At.2
(for CH2) setting is changed to “0”
- When PV becomes out-of-range
Handling Precautions
• Auto-tuning will not function properly unless the control target is
connected.
• The time from start to end of auto-tuning varies according to the control
target.
SP
AT start
Normal end
Time
PV > SP
PV < SP
SP
≠
PV
2/3
2/3
1/3
1/3
SP
AT start
Normal end
Time
SP = PV operation
PV
PV