E5CNH E5AN-H E5EN-H Digital Controllers User's Manual - OMRON

Determining PID Constants (AT, ST, Manual Setup) Section 3-8
ST Stable Range
Operating Procedure The ST stable range determines the condition under which ST (self-tuning)
functions.
This procedure sets the ST stable range to 20°C.
Advanced Function Setting Level 1. Select the ST Stable Range parameter by pressing the M Key in the ad-
ST Stable
Range
vanced function setting level.
3-8-3 RT (Robust Tuning)
64
C
st-b
1%0
C
st-b
2*0
rt
2. Use the U Key to set the parameter to 20°C.
When AT or ST is executed with RT selected, PID constants are automatically
set that make it hard for control performance to degenerate even
when the characteristics of the controlled object are changed.
RT can be set in the advanced function setting level when PID control has
been set.
The RT mode cannot be selected while an analog input is set.
Selecting the RT mode in the following cases will help to prevent hunting
from occurring.
When the set temperature is not constant and is changed in a wide
range
When there are large variations in ambient temperatures due to factors
such as seasonal changes or differences between day and night temperatures
When there are large variations in ambient wind conditions and air flow
When heater characteristics change depending on the temperature
When an actuator with disproportional I/O, such as a phase-controltype
power regulator, is used
When a rapidly heating heater is used
When the control object or sensor has much loss time
When hunting occurs in normal mode for any reason
PID constants are initialized to the factory settings by switching to RT
mode.
When the RT mode is selected, the derivative time setting unit becomes
the second.
RT Features Even when hunting occurs for PID constants when AT or ST is executed
in normal mode, it is less likely to occur when AT or ST is executed in RT
mode.