E5CK Datasheet, PDF (20/22 Pages) Omron Electronics LLC – Advanced, Compact Digital Controllers

I 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 response tuning) mode, the PID constants are tuned
using a step response method at the time the set point is
changed.
In DT (disturbance tuning) mode, the PID constants are amended
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 con-
stants are amended to suppress the hunting.
Note: Be sure to turn on the power supply to the load either before or
simultaneously with the start of Temperature Controller opera-
tion.
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 inappropri-
ate PID constants will be obtained. If an extremely 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 retuned. Retuning is per-
formed 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 satisfied simultaneously
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 1. The new set point is different
E5CK starts operating is dif- from the set point used at the
ferent from the set point used time SRT was last executed
at the time SRT was last exe- (see note).
cuted (see note).
2. The process value is in stable
2. The process value at the time condition before the set point
the E5CK starts operating is is changed.
smaller than the set point in _{3. A larger set point value is set}
reverse operation and larger _{in reverse operation and a}
than the set point in normal _{smaller set point is set in nor-}
operation.
mal operation.
Note: The last SRT-executed set point is set to 0 before shipping and
when changing from advanced PID control to advanced 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 mea-
sured 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.
Slope (R)
Temperature
SP
Stable range
Time
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.
Shorter than the stability judgement time
Set
point
Stable
range
Stable
range
Stable
Stability judgement time
Stable
(Set to
15.0°C
before
shipping)
Balanced Status
If the process value is within the stable range for 60 s when there is
no output, it is deemed that the temperature is balanced.
Startup Conditions of DT
1. DT will start if the temperature that has been stable varies due 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 start if the set point is changed under the condition that
SRT does not start and the temperature becomes stable, pro-
vided that the number of maximum temperature values is less
than four.
If there are four or more maximum temperature values, HT will
start.
Temperature
SP
Extreme value 2 ^{Set point change}
Extreme value 1
Time
I-82
Digital Controller E5CK