Landis & Staefa Division
CC1B7865E
February 10, 2000
49/56
9. Self-setting function
The optimum adjustment of the controller to the controlled system can be checked by
recording a startup sequence with the control loop closed. The following diagrams
indicate possible incorrect adjustments, and their correction.
The response to a setpoint change is shown here for a 3
rd
order controlled system for a
PID controller. The method used for adjusting the controller parameters can, however,
also be applied to other controlled systems.
A favourable value for «dt» is «rt» / 4.
«PB too small»
«PB too large»
t
x
w
7865d17/1099
t
x
w
7865d15/1099
«rt, dt» too small
«rt, dt» too large
t
x
w
7865d16/1099
t
x
w
7865d14/1099
Optimum adjustment
t
x
w
7865d18/1099
9.2 Checking the controller parameters
Example
