6-15
Chapter 6. OPERATION
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Auto-tuning (AT)
When operating in the AUTO mode in either of the RUN, HOLD,
FAST or END modes, setting values can be automatically written
to the PID set in use by auto-tuning (AT). The following can be
selected by variable parameter
A
t
setting.
0: AT is disabled.
1: General AT is executed.
2: Overshoot-inhibited AT is executed.
3: AT by neural net is executed.
• Auto-tuning does not function when programmer functions are
selected on 3D or 5K heat/cool output models and 5G output
models.
• During execution of auto-tuning, progress of program operation
time stops. Accordingly, the controller 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 line 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 param-
eter At setting to 1 or 3. However, when executing auto-tuning
on a line 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 the suitable value is 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.
