West Control Solutions KS98-1 - Manual (Page 254)

In the course of dynamic process control, the control algorithm can temporarily determine values below 0 or above 100
for the correcting variable. If necessary, however, these values can be reset to the limits by means of accelerated inte -
gral behaviour (Tsat).
Tsat time constant for integral action in Y limiting (anti-reset wind-up).
Self-tuning
r controller adaptation to the process (PIDMA)
Self-tuning can be started to determine the optimum parameters for a process. The function is applicable for the follo -
wing processes.
Preparation
w Adjusting the required control behaviour.
P-controller:
Tn = 0.0 Tv = 0.0
PD-controller: Tn = 0.0 Tv > 0.0
PI-controller: Tn > 0.0 Tv = 0.0
PID-controller: Tn > 0.0 Tv > 0.0
Parameters Tn or Tv can be switched off by setting = 0.0. I.e. these parameters do not participate in self-tuning.
w Correcting variable step change dYopt must be determined. This is the value by which the correcting variable
changes from the actual value. The step change can be positive or negative.
w Xlimit must be determined. It should be set to roughly half of the expected process value change.
‘Process at rest’ monitoring:
The PIDMA does not provide monitoring for the rest condition. The commissioning engineer is responsible for selection
of a suitable start time. Optimum results are only achieved, if the process is lined out, i.e. all dynamic actions have de -
cayed. Only in few cases in which parameter determination is imposssible due to decaying dynamics the algorithm pro -
vides a “restart” error message.
Self-tuning start
Self-tuning can be started and stopped from automatic or manual operation on the self-tuning page.
Select the self-tuning page by marking and confirming the two arrows. Select function Stat: OFF/OK (inverse
display) and confirm it with M.
Stat: OFF/OK blinks and can be switched over to Stat: Start by pressing I.
Pressing key M starts the self-tuning attempt. The setpoint can be changed at any time. However, this is not necessa -
ry as opposed to CONTR. A change after starting from automatic mode would even cause faulty process evaluation.
Self-tuning cancelation
Self-tuning can be stopped at any time by pressing key manual/automatic H on the controller front, provided that key
H was not disabled (1-signal on input
oplook).
Moreover, cancelation is possible on the self-tuning page of the required controller. For this purpose, select the Stat:
line (inverse display) on the self-tuning page, press M, Stat: line blinks. Press I until
Stat: Stop blinks. Press
M, the self-tuning attempt is stopped and the controller continues operating in automatic mode.
9499-040-82711
III-254 Controller characteristics and self-tuning with PIDMA
Fig. 69 Self-tuning page