E5CK
E5CK
17
Fuzzy Self-tuning
Fuzzy self-tuning is a function that enables the E5CK to calculate
the most suitable PID constants for the controlled object.
Features
· The E5CK determines by itself when to perform fuzzy
self-tuning.
Fuzzy Self-tuning Function
The fuzzy self-tuning function has three modes.
In SRT(step responsetuning) mode,the PID constants aretuned
using a stepresponse methodat thetimethe setpointischanged.
In DT (disturbance tuning) mode,the PIDconstants areamended
so that the controlled temperature will be within the target range
set in advance when there is external disturbance.
In HT (hunting tuning) mode, when hunting occurs, the PID
constants are amended to suppress the hunting.
Note: Be sure to turn onthe power supplyto the loadeither before
or simultaneously with the start of Temperature Controller
operation.
Dead time will be measured from the time the Temperature
Controller starts operating. If a load such as a heater is
turned on after the Temperature Controller is turned on,
dead time longer than the actual value will be measured
and inappropriate PID constants will be obtained. If an ex-
tremely large amount of dead time is measured, the control
amount will be set to 0% for a short period of time before
being returned to 100%, and the constants will then be re-
tuned. Retuning is performed only for large amounts of
dead time, so be sure to follow the precaution given above
when starting operation.
Startup Conditions of SRT
SRT will start if the following conditions are satisfiedsimultaneously
when the E5CK is turned on or the set point is changed.
At the time the E5CK starts
operating
At the time set point is
changed
1. The set point at the time the
E5CK starts operating is
different from the set point
used at the time SRT was
last executed (see note).
2. The process value at the
time the E5CK starts oper-
ating is smaller than the set
point in reverse operation
and larger than the set point
in normal operation.
1. The new set point is differ-
ent from the set point used
at the time SRT was last
executed (see note).
2. The process value is in
stable condition before the
set point is changed.
3. A larger set point value is
set in reverse operation and
a smaller set point is set in
normal operation.
Note: The last SRT-executed set point is set to 0 before shipping
and when changing from advanced PID control to ad-
vanced PID control with fuzzy self-tuning.
PID Constant Refreshing Conditions
If the step control amount is applied before the maximum tempera-
ture slope (R) is obtained, SRT will not renew any PID constant. If
the proportional 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)
Stable range
Time
SP
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 ad-
justed 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.
Shorter than the stability judgement time
Set
point
Stable
range
Stable
range
(Set to
15.0_C
before
shipping)
Stability judgement time
Stable Stable
Balanced Status
If the process value is within the stable range for 60 s when there is
no output, it is deemed that the the temperature is balanced.
Startup Conditions of DT
1. DT will startif the temperaturethat hasbeenstable variesdue
to external disturbance and the deflection of the temperature
exceeds the stable range, and then the temperature
becomes stable, provided that the number of maximum
temperature values is less than four.
2. DT will startif the setpoint ischanged underthe conditionthat
SRT does not start and the temperature becomes stable,
provided that the number of maximum temperature values is
less than four.
If there are four or more maximum temperature values, HT
will start.
SP
Temperature
Extreme value 2
Set point change
Time
Extreme value 1
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