SuperNova PD500 PID Process & Temperature Controllers
Instruction Manual
45
Auto-Tuning Mode (AT.MD)
There are two types of auto-tuning (AT): standard
type and low PV type.
Standard type auto-tuning is auto-tuning based on set
value (SV).
Low PV type auto-tuning is auto-tuning based on a
value 10% lower than set value (SV).
When low PV type auto-tuning is performed, the
selected SV is displayed on the device, but the actual
operation executes the auto-tuning at SV minus 10%.
For example, if the SV is set to 200°C with a type k
thermocouple input type, and the low PV type auto-
tuning is performed, the SV displayed on the device
remains 200°C, but the actual auto-tune operation
executes the auto-tuning at 160°C.
The calculation formula is as follows.
Target value of low
PV mode auto-tune = (SV – FRL) x 0.9 – FRL
= (200 – (-200)) x 0.9 – FRL
= 160
Figure 33. Standard and Low PV Auto-Tuning SV
Auto-Tuning (AT)
This parameter is used to activate the auto-tuning
mode.
If AT is set to ON, or if the front panel SET and UP
keys are held together for 3 seconds when in run
mode, auto-tuning starts.
The AT sequence is as follows:3
1. Select the set value number (SV.NO) to
execute the auto-tuning on. In many
applications, only one SV number will be
used, and the default set value number of
one is used
2. Set the desired set value for the selected set
value number. It is best to auto-tune to a SV
that is in the range the application normally
requires.
3. Select from standard or low PV type in
parameter AT.MD.
4. Verify the controller is set to run mode. RUN
will appear as one of the front panel display
indicators.
5. Begin the auto-tuning process with one of
the following methods:
a. Set the Control Group (G.CTL)
parameter Auto-Tune (AT) to ON.
b. Press and hold the front panel keys
SET and UP for 3 seconds.
6. When auto-tuning process has started, the
TUNE or [T] indicator will blink. This indicator
will turn off when the auto-tuning process is
completed.
7. To end the auto-tuning process before it is
automatically completed:
a. Set the Control Group (G.CTL)
parameter Auto-Tune (AT) to OFF.
b. Press and hold the front panel keys
SET and UP for 3 seconds.
If the auto-tuning process is completed successfully,
the P, I, and D values are automatically set. The P, I,
and D parameters are set in the PID group number
that matches the selected set value number during
the auto-tuning process.
For example, if the set value number selected is set
value number 1, then the PID group P, I, and D
parameters set are also from PID group number 1.
If the remove SV input is selected for the set value
number selected, the P, I, and D values will be set in
PID group number 4.
The P, I, and D values are not changed if auto-tuning
process is cancelled, fails, or is otherwise ended
early.
Anti-Reset Wind-Up (ARW)
When the control output value (MV) reaches the limit
value (OLH, OLL), it executes the anti-reset wind-up
operation to prevent over-integration.
Alpha (ALPA)
The response in a typical closed loop control system
can be broadly divided into response to set value
change and response to disturbance. The normal PID
(one-degree-of-freedom) algorithm has the limitation
that it can only optimize one response for these two
issues. To overcome this limitation, with the
application of the two-degree-of-freedom PID
algorithm, you can optimize the response to the set
value change and obtain an appropriate response to
disturbances.
The ALPHA parameter is used to adjust the response
characteristics to the set value (SV) changes.
If ALPHA is set to 0%, it is the same as the normal
PID control response.
If ALPHA is set to 100%, it may take a long time to
reach a normal state, but overshoot and undershoot
will be minimized.