6-10
<Toc> <Ind>
TI 05C01E02-01E 1st Edition : Oct. 31, 2001-00
6.7 Overshoot Suppressing Function “SUPER”
6.7.1 “SUPER” Operating Principles
•
The "SUPER" function monitors the
deviation for evidence that there is a
danger of overshoot, and on sensing such
danger automatically changes the setpoint
temporarily to a somewhat lower value
(sub-setpoint "SSP").
•
Once the danger of overshoot appears
diminished, the function returns the
effective setpoint gradually to the true
setpoint.
•
"Fuzzy inference" techniques are
employed in the algorithms used to
change the setpoint to the lower temporary
value, and to return it gradually to the true
setpoint.
OFF, ON
SC
Parameter Range
SP
Start of fuzzy inference
Time
PV
PV
Sub-setpoint (SSP)
SUPER ON
Operation Diagram
•
"SUPER" is effective in the following cases.
•
Overshoot must be suppressed.
•
Rise-up time needs to be shortened.
•
Load varies often.
•
SP is changed frequently.
•
The "SUPER" function is effective when used together with the Auto-Tune (AT) function.
6.7.2 Effects of “SUPER”
•
If the optimum PID values are being
used, then use of the "SUPER" function
yields stable control without overshoot
even on setpoint changes.
•
As a result, temperature up-ramps
follow the programmed pattern more
closely, giving more consistent product
quality.
•
"Overshoot" is not only a matter of
temperature exceeding the setpoint, but
also of prolonged instability and slow
settling resulting from the undershoot that
occurs in reaction to the overshoot.
Example of overshoot suppression control for setpoint changes
Process: Small electric furnace
P = 1.5% I =128 sec D = 32 sec
(from auto-tuning)
SUPER effects (1)
Time
Temperature
Time
Without SUPER
With SUPER
Temperature
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