Catalog ST PCS 7.1 - September 2005

■ Overview
In practice, conventional PID controllers are often operated in
the manual mode because the control quality achieved does not
match the expectations. The reason for this is that the controllers
are either badly adjusted or the processes are difficult to control
with PID controllers, e.g. temperature systems, processes with
any proportion of dead time component, or processes that
change depending on time or operating point. In addition, the
optimum setting of PID controllers demands special experience
and is very time-consuming.
A recommended alternative for solving these problems is the adaptive
ADCO controller. It works on the basis of a process model
that is determined in the background during the setting procedure.
With the aid of this process model, ADCO can predict the
consequences of an intervention in the process (predictive controller),
e.g. what effect the opening of a steam valve up to a certain
extent has on the process temperature. Conversely, it is also
in a position to determine the valve setting required for achieving
or maintaining a defined temperature. With the process model,
ADCO has more process information at its disposal than conventional
controllers and uses this to improve the quality of control.
Multi-range controller for non-linear systems
ADCO is also available as a multi-range controller (ADMR). The
special feature of this type of controller is that the control range
can be divided into as many as 8 zones which can be individually
optimized. The switchover between the zones can be automatic
or event-based.
ADCO faceplate with detail area for alarm limits / batch
Advanced Process Control
ADCO: Adaptive controller
■ Application
The adaptive controller ADCO can be used as a better alternative
to the conventional PID controller, in particular for processes
that are difficult to control. This has the following advantages:
• about 10 to 20 % saving of time in the commissioning phase
due to the fast and robust controller setting
• significantly better control quality for difficult processes
• very good adaptability, especially where there are changes to
the process characteristics
• significant reductions in transmission times in the case of status
transitions in batch processes (e.g. heating a product from
temperature level A to level B)
■ Technical specifications
Hardware requirements SIMATIC PCS 7 V5.x with AS 41x
automation systems
Memory requirement 21 KB (once only)
+ 5 KB (per controller)
Computing time about 2 ms (S7-416)
■ More information
i.p.a.s.-systeme
An der Landwehr 6
60437 Frankfurt, Germany
Tel.: +49 69 950418-0
Fax: +49 69 950418-19
E-mail: service@ipas-systeme.de
Additional information is available in the Internet under:
http://www.ipas-systeme.de
Siemens ST PCS 7.1 · September 2005
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