West Control Solutions KS98-1 - Manual (Page 248)

The most important differences compared to controller functions CONTR and CONTR+ are:
w Integrated, front-panel operated optimization method like PMA tune
This function permits optimization also for difficult processes with Tg/Tu < 3 without engineering tool and laptop,
which was not possible with previous PMA (and competitor) controllers.
w Parallel controller structure unlike all other PMA controllers with “serial structure”.
w Distinction of “ behaviour” and “disturbance behaviour” by adjustable factors, which can be used for individual
attenuation of P (proportional action) and D (differential action) control effect on changes.
w The adjustable derivative gain VD of the D action, which is adjusted and matched to the process dynamics auto -
matically by self-tuning. Purposeful values for VD are within 2…10, whereby all previous PMA controllers are
fixed to VD=4 (empirical value for serial structure).
Using a PIDMA control block is purposeful where conventional PMA self-tuning methods are not satisfactory. PIDMA
should not be used for processes where PMA self-tuning has always been and still is unrivalled:
w Processes with a ratio Tg/Tu > 10
w (2nd order processes; with 2 [...3] energy storing elements!).
Roughly, these are applications in the plastics processing industry (extrusion, ...), where no improvements related to
quick line-out without overshoot are possible (unless a “robust” controller design with stable results also with variable
process dynamics and non-linearities is required)!
With classic thermal processes (ovens of all types, dryers, ...) air conditioning, level, flow, etc., however, a consider -
able number of difficult cases require the expenditure of many hours spent with hotline support or even at the site, in
order to make a plant operate properly.
The various types of control behaviour are not explained in detail in this section, because there are no differences com -
pared to controller blocks CONTR and CONTR+ (see from page ).
Only the additional parameters explained at the beginning of chapter "PIDMA control characteristics” have to be des -
cribed.
The difference between split-range and 3-point behaviour is that PIDMA does not provide parameter distinction of hea -
ting and cooling.
+ PIDMA does not permit the adjustment of the signaller control behaviour.
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III-248 PIDMA (Control function with particular self-tuning behaviour (No. 93)