West Control Solutions KS 50-1 - Manual (Page 18)

3.5.5 Optimization after start-up or at the set-point
The two methods are optimization after start-up and at the set-point.
As control parameters are always optimal only for a limited process range, vari-
ous methods can be selected dependent of requirements. If the process behaviour
is very different after start-up and directly at the set-point, parameter sets 1 and 2
can be optimized using different methods. Switch-over between parameter sets
dependent of process status is possible (see page ).
Optimization after start-up: (see page 18)
Optimization after start-up requires a certain separation between process value
and set-point. This separation enables the controller to determine the control pa-
rameters by evaluation of the process when lining out to the set-point.
This method optimizes the control loop from the start conditions to the set-point,
whereby a wide control range is covered.
We recommend selecting optimization method “Step attempt after start-up”
with
tunE = 0 first. Unless this attempt is completed successfully, we then re-
commend a “Pulse attempt after start-up”.
Optimization at the set-point: (see page 19)
For optimizing at the set-point, the controller outputs a disturbance variable to the
process. This is done by changing the output variable shortly. The process value
changed by this pulse is evaluated. The detected process parameters are conver-
ted into control parameters and saved in the controller.
This procedure optimizes the control loop directly at the set-point. The advantage
is in the small control deviation during optimization.
3.5.6 Selecting the method (
ConF/ Cntr/ tunE)
Selection criteria for the optimization method:
Step attempt after start-up Pulse attempt after start-up Optimization at the set-point
tunE = 0 sufficient set-point reserve is
provided
sufficient set-point reserve is not
provided
tunE = 1 sufficient set-point reserve is
provided
sufficient set-point reserve is not
provided
tunE = 2 Only step attempt after start-up
required
Sufficient set-point reserve:
inverse controller:(with process value < set-point- (10% of
rnGH - rnGL)
direct controller: (with process value > set-point + (10% of rnGH - rnGL)
inverse controller:
process value is (10% of
rnGH - rnGL) below the set-point
direct controller:
process value is (10% of
rnGH - rnGL) above the set-point
Operation
Self-tuning 18 KS50/52-1