Azbil SDC36 - 5-4 Auto Tuning (AT) Function

5-29
Chapter 5. DETAILED DESCRIPTION OF EACH FUNCTION
The auto tuning (AT) function is used when the PID constants are set automatically with the control method set at
“Fixed PID” ([
CtrL
= 1]).
The AT function can be used when the control method is set to “Fixed PID”.

Starting procedures
(1) Make sure that the PV input or operation end (heater power, etc.) is
controllable.
(2) Using the [
r- -r
] setup of the mode bank, multi-status display, and LED
monitor, make sure that the operation is in the RUN mode. If the indicator
[rdy] is lit and the operation is in the READY mode, change the mode to the
RUN mode.
(3) Make sure that the mode indicator [man] is off and the operation is in
the AUTO mode. If the indicator [man] is lit and the operation is in the
MANUAL mode, change the mode to the AUTO mode.
(4) Set the parameter setting [AT Stop/Start selection] to “AT start ([At] =
[
At.On
]) ”.

Stopping procedures
The AT function is completed automatically. To stop the AT function, which is
running, change the parameter setting [AT Stop/Start selection] to AT stop ([At]
= [
At.OF
]). Additionally, the AT function is stopped when changing the READY
mode to the MANUAL mode.

Display during execution of AT
The decimal point at the 1st digit of the upper display (right end digit) flashes twice
repeatedly while the AT function is running. When the AT function is completed
and the PID constants are changed, this LED goes off.
sp
out
pv
man rsp ev1 ev2 ev3 ot1 ot2
mode
display
enter
para
LED
para enter
display
mode
pv
out
sp
ot2
ot1
ev3
ev2
ev1
rsp
man
LED

Operation during execution of AT
The AT function calculates the PID constants using the limit cycle.
(1) When the AT function is started, a point, where the SP and PV deviations
are split to “2:1”, is determined as ON/OFF change point of the manipulated
variable (MV).
(2) When the limit cycle is judged as stable, the PID constants are changed and the
AT function is completed.
5 - 4 Auto Tuning (AT) Function