West Control Solutions N8840 - Manual (Page 16)

ti2 - Integral time 2 (cooling) in [s]
r only, unless set to OFF
td2 - Derivative time 2 (cooling) in [s]
r only, unless set to OFF
t2 - Minimum cycle time 2 (cooling) in [s]
r only, unless Adt0 was set to “no self-tuning” during
configuration by means of 8800/8840 Configurator .
Parameter set 2: analogous to parameter set 1 (see page 25)
3.5.1 Preparation for self-tuning
w Adjust the controller measuring range as control range limits. Set
values rnG.L and rnG.H to the limits of subsequent control.
(Configuration rControllerr lower and upper control range limits)
ConF r Cntr r rnG.L and rnG.H
w Determine which parameter set shall be optimized.
- The instantaneously effective parameter set is optimized.
r Activate the relevant parameter set (1 or 2).
w Determine which parameter set shall be optimized (see tables above).
w Select the self-tuning method
see chapter 3.5.3
-Step attempt after start-up
- Pulse attempt after start-up
- Optimization at the set-point
3.5.2 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,
various 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 25).
Optimization after start-up: (see page 17)
Optimization after start-up requires a certain separation between process value
and set-point. This separation enables the controller to determine the control
parameters 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
recommend a “Pulse attempt after start-up”.
Operation
Self-tuning 16 8840 profiler