Description
3.4 Mode of operation
SIPART PS2 with and without HART
Operating Instructions, 10/2013, A5E00074631-11
27
The control algorithm is an adaptive, predictive five-point controller.
In case of large control deviations, the valves are controlled using permanent contact. This
takes place in the so-called fast step zone.
In case of medium control deviations, valves are controlled using pulse-length modulated
pulses. This takes place in the so-called slow step zone.
Figure 3-11 Functional principle of five-point controller
Small control deviations do not send control pulses in the zone. This takes place in the so-
called adaptive deadband. The deadband adaptation and the continuous adaptation of
minimum pulse lengths in the automatic mode ensure the best possible control accuracy with
the smallest number of operating cycles. The start parameters are determined during the
initialization phase and stored in the non-volatile memory. The most important start
parameters are:
● The real actuator travel with mechanical end stops
● Actuating times
● The deadband size
The number of fault messages, changes in direction and the stroke number are continuously
determined during operation and saved after every 15 minutes. You can read and document
these parameters using communication programs such as PDM and AMS. By comparing the
old values with the current ones, you can draw conclusions about the wear and tear of the
control valve. You can use the diagnostics function for this.
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