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Relay autotuning: an overview and alternative approach

journal contribution
posted on 2023-06-08, 08:58 authored by Derek P Atherton
This paper discusses the use of relay-produced limit cycles for selecting the parameters of fixed controllers, with particular reference to the proportional-integral-derivative (PID) controller. This work shows how the current ideas relate to the early work of Ziegler and Nichols, particularly their loop cycling test. The evaluation of limit cycles in relay feedback systems is discussed, and details of their possibilities for determining parameters of an assumed plant transfer function or the value of the plant critical point are given. To conclude, it is shown how the approximate value of points on the plant frequency response locus can be determined from using the relay in parallel with the controller, which can be done without opening the control loop.

History

Publication status

  • Published

Journal

Industrial and Engineering Chemistry Research

ISSN

0888-5885

Publisher

ACS Publications

Issue

12

Volume

45

Page range

4075-4080

Pages

6.0

Department affiliated with

  • Engineering and Design Publications

Notes

The paper was invited for a special edition on relay autotuning of PID controllers. The paper first reviews the loop cycling method and exact methods for finding limit cycles in relay feedback systems, on which the author is an acknowledge world leader (see his 1975 book). One disadvantage of the autotuning method, suggested by Astrom, is that the loop must be opened to convert the controller to a relay. The paper then presents a new contribution showing how this can be avoided by obtaining results for a limit cycle when the relay is placed in parallel with the controller.

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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