1-2
<Toc> <Ind>
TI 05C01E02-01E
1st Edition : Oct. 31, 2001-00
■
Types of Temperature Control Action
ON/OFF action is the simplest action among the control actions. ON/OFF action of the
internal thermostat keeps the optimum temperature. But the temperature control
output fluctuates in the fixed cycle with ON/OFF action. If this temperature cycle
causes a problem, the control action that changes the output in proportion to the devia-
tion (the difference between the target setpoint and present value) can give a better
control performance. Thus the control action that moves the function part in proportion
to the deviation is referred to as a proportional action (P action). But a steady-state
deviation (offset) is inherently unavoidable with proportional action alone. Though the
manual reset can remove the offset, the same thing can be done using the control
action together with the Integral action (I action) that will integrate the deviation as long
as the deviation exists. This combination is referred to as a proportional-plus-integral
action (PI action). It is the popular control method among the process control actions.
On the other hand, the derivative action (D action) is the action that changes the output
in proportion to the rate-of-change of deviation. Since the output of derivative action
depends on not the amount of deviation but its rate-of-change, the larger the rate-of-
change is, the more intensive corrective action the controller takes to correct the pro-
cess response in advance. Setting each optimum value with the PID action consisted
of these three actions enables a stable control quickly.
■
Dynamic Auto Tune Control
The Dynamic Auto Tune Control is the function to automatically determine the optimum
PID constants for continuing a good control when the controller is turned on or the
control conditions are unstable. This control method is gentle to the controlled object
itself because a disturbance needs not to be set forcibly like Auto tuning.
In Dynamic Auto Tune Control, the controller automatically monitors the behavior and
determines the optimum PID constants when (1) at power on, (2) the output travels up
to 100% or down to 0% and remains there after changing a setpoint, (3) process begins
oscillating by disturbance and the like. The principle of Dynamic Auto Tune Control can
be relied on because it is based on Geglar/Nichols’s control method.
Refer to “6.5.1 Dynamic Auto Tune Control” on Page 6-6.
Summary of Contents for UT130
Page 2: ...Blank Page ...
Page 4: ...Blank Page ...
Page 8: ...Blank Page ...
Page 30: ...Blank Page ...
Page 48: ...Blank Page ...
Page 60: ...Blank Page ...
Page 72: ...Blank Page ...