FUZZY SELF--TUNING
E5CK
A--11
In order to prevent overshooting, the step controlled amount must be
imposed continuously only while the present deviation is the same as or
greater than the value obtained from the proportional band (P) x 1.27. The
step control will not be applied when the deviation becomes smaller than
this value.
If the step control amount is applied before the maximum temperature
slope (R) is obtained, SRT will not renew any PID constant. If the propor-
tional band obtained from the R and L values that were measured before
the imposition had been completed is larger than the present proportional
band, the PID constants will be renewed because the measured value is in
the direction towards the suitable proportional band value, and the set
point at that time will be the SRT-executed set point.
Temperature
Slope (R)
SP
Stable range
P x 1.27
Completion of SRT
Time
F
Stable Temperature Status
If the temperature is within the stable range for a certain time, it is deemed
that the temperature is stable. This time is called stability judgement time.
Like PID constants, stability judgement time is adjusted with fuzzy self-
tuning according to the characteristics of the object to be controlled. Fuzzy
self-tuning will not be activated if the temperature is stable because the
Temperature Controller deems that temperature control is smooth.
Stable
Stable range
Stable range
Stable
Stability judgement time
Set point
Shorter than the stability judgement time
(Set to 15.0
_
C
before shipping)
F
Imposition
Completion
Condition of Step
Control Amount
F
PID Constant
Refreshing
Conditions