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Self-tuning Control
7-4
Self-tuning Control is a control which automatically calculate the value of PID, under the condi-
tion that the control target or set value (SV) changes.
Self-tuning is especially effective for situations when a high level of control is not needed, but
auto-tuning cannot be run due to frequent changes in the control target conditions.
When a high level of control is required, choose PID control, fuzzy PID
Point
control, or PID2 control.
Conditions where self-tuning can be used
Self-tuning is used in the following situations:
When temperature rises when the power is turned on
•
When temperature rises when SV changes (or when the controller decides it is necessary)
•
When the controller decides it is necessary because the controls have become unstable
•
Conditions where self-tuning cannot be used
Self-tuning cannot be used in the following situations:
During control standby
•
•
During ON/OFF (2-position) control
During auto-tuning
•
•
During ramp soak progress
When there is error input
•
•
When set for dual output
When any of the P, I, D, Ar parameters are set to manual
•
•
During manual mode
During soft start progress
•
Conditions to halt self-tuning
Halt self-tuning in the following situations:
When there is a change in SV (This includes the case where SV changes because of the
•
ramp soak function, remote SV function, or ramp SV.)
When self-tuning has not finished after running for nine or more hours
•
Setting self-tuning
Turn on power of the controller and set the SV.
1
Display the system menu ("
SYS [h 7
2
Display the controller parameter ("
3
Press the
key to set the value.
4
Turn off power of the controller.
5
Turn on power of the control target equipment and the controller. Turn on
6
power of the control equipment first.
Self-tuning will begin.
process value
SV
tuning
dead time
lag time
•
The equipment will not tune correctly if power of the controller is
Point
turned on first.
•
To reset self-tuning, set the control method to PID ("PiD") once
before changing back to self-tuning.
PID2 Control
7-5
In case which the power supply of the control target goes ON → OFF → ON, this PID2 control
can suppress the amount of overshoot.
This control introduces an algorithm to prevent the calculated PID result from becoming a mis-
calculation, even when the control loop is open.
You will need to run auto-tuning to set the Pid parameter when using Pid2 control.
●
Features of PID2 Control
process value
control equipment power
control loop
Setting PID2 control
Display the system menu ("
SYS Ch 7
1
Display the control parameter ("
2
Press the
key to set the value.
3
").
[trL
") and choose self-tuning ("
t
suppress overshoot
SV
PV
t
ON
OFF
close
close
open
").
CTrL
") and choose PID2 ("
Pid2
").
7-6
Run auto-tuning to set the PID parameter automatically.
At
"
" set value
oFF
"
"
on
"
"
"
Lo
"
●
Normal type
process value AT start
SV
Point
Running auto-tuning
Display the operation menu ("
1
Display auto-tuning ("
2
Choose the standard type ("
Press the
3
A decimal point will blink at the bottom of the display during auto-tuning.
When auto-tuning has successfully competed, blinking decimal point will turn off and
overwrites the PID.
Point
SELF
").
7-7
Valve controls adjust and control the valve position according to [OPEN] and [CLOSE] of the
contact signal.
Turn on the contact outputs in manual mode, so that pressing the
pressing the
Servo control 1 and servo control 2 have the following differences.
Servo Control 1: No valve position display
•
•
Servo Control 2: Has valve position display
Neither control can be used to control the valve position itself.
Setting Servo Control 1 or Servo Control 2
Display the system menu ("
1
Display the control parameter ("
2
This chooses "Servo Control 1".
Press the
3
Point
Caution
– 11 –
Auto-tuning
Behavior
Function
Stop/Finish
Stops or finishes auto-tuning.
Normal type
The standard auto-tuning for SV reference. Choose this
auto-tuning in most situations.
Low PV type
Auto-tuning for SV-10% reference. Choose this when you
want to suppress the overshoot when tuning.
●
Low PV type
process value AT start
AT calculating
PID control
PV
t
Set the following parameters before running auto-tuning.
PV input type / PV input upper limit / PV input lower limit / Decimal
•
position / PV input filter in the setup channel menu ("
OUT1 proportion cycle (OUT2 proportion cycle) in the PID channel
•
menu ("
Pid Ch 2
").
oPE [h 1
").
At
") and choose the tuning type.
") or low PV type ("
on
key to start auto-tuning.
PID parameter which is set after auto tuning has finished normally
•
will be maintained even when the power is turned off. However, the
PID value will not be changed if the power is turned off during auto-
tuning. In this case, rerun auto-tuning.
•
The equipment will use ON/OFF (2 position) control during auto-
tuning, so there may be a large change in PV according to the pro-
cess. Do not use auto-tuning for processes that do not permit a
large change in PV. Do not use auto-tuning for processes such as
pressure control and flow control that have a fast response.
Auto-tuning is not behaving normally if it has not finished after four
•
or more hours have passed. In these cases, recheck parameters
such as input/output wiring, control output behavior (normal/
reverse), and input sensor type.
•
Rerun auto-tuning if there is a large change in SV, a change in the
PV input type, or a change in the control target conditions that
reduces the effectiveness of the controls.
•
You can run auto-tuning when the control type is set to "fuzzy" or "PID2".
You cannot run auto-tuning in manual mode.
•
•
When using the PID selection function, the auto-tuning result for
the selected PID group is stored.
Auto tuning is forcibly terminated when SV changes because of
•
the ramp soak function, remote SV function, or ramp SV.
Valve Control (Servo Control 1 / Serve Control 2)
key means "CLOSE"
OPEN contact output
CLOSE contact output
Valve motor
(servo 1)
Valve opening
(servo 2/PFB)
Valve
SYS Ch 7
").
PrCS
") and choose servo control 1 ("
key to set the value.
Adjustments must be made to display the valve opening position.
•
"7-8 Position Feedback Control (PFB Control) (page 12)
•
An interlock function is built in.
Chattering may occur if the dead band ("
is set too small.
AT calculating
SV-10%FS
SV
PID control
PV
t
SET Ch 6
")
") according to the control target.
Lo
key means "OPEN", and
set value input
(temperature)
boiler
Srv1
").
PGAP
") in the PFB menu ("
PFB Ch10
")
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