E5EX–H
E5EX–H
13
Beginning Control Operation
Temperature control is begun for the set values as soon as the pow-
er is turned on, and temperature control is carried out according to
the parameters that have been input. To operate the Temperature
Controller after all the parameters are input, turn the power off once
and then on again.
Auto-tuning
When the AT key is pressed for 1 second or more, the Temperature
Controller automatically starts tuning the PID constants. While auto-
tuning is taking place, the auto-tuning indicator on the front panel will
flash. The Temperature Controller executes control based on the
set PID constants (factory set to P = 40
°
C, I = 240 seconds, and D =
60 seconds) until the temperature of the controlled system reaches
the set temperature. After that, the Temperature Controller automat-
ically adjusts the PID constants using the limit cycle method. After
the automatic tuning of the PID constants has been completed, the
auto-tuning display goes out.
Auto-tuning can be carried out regardless of whether the Tempera-
ture Controller is performing reverse (heating) or normal (cooling)
operation. To stop auto-tuning, hold down the AT key again for 1
second or more. Automatic tuning can be executed at any time: on
power up, while the temperature is rising, and after the control ac-
tion has stabilized.
Set
temperature
Old PID
constants
Limit Cycle Method
New PID constants
AT indicator blinks
AT key is pressed
Limit cycle method:
The optimum PID constants are calculated by this method by vary-
ing the control output variable and generating external oscillation.
Advanced PID Control
Advanced PID control with two degrees of freedom adds a feed-for-
ward (FF) loop to the conventional PID controller. Whereas the con-
ventional PID controller responds to disturbance (d) to quickly
achieve stability, it overshoots the target because it lacks sufficient
control, as shown below.
This is prevented in advanced PID control because the feed-for-
ward loop is not affected by disturbance. Here, the feed-forward
loop operates from the target value (r) to achieve fast response with-
out overshooting.
–
+
–
+
+
+
y
d
r
FF
PID
Control
object
Normal
PID
operation
E5EX–H
If response to target value improves, response to external
disturbances degrades.
If response to external disturbances value improves, re-
sponse to target value degrades.
Excellent response to both target value and external
disturbances.
