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Automatic Tuning of PID Controllers based on Asymmetric Relay Feedback

Berner, Josefin LU (2015)
Abstract
This thesis presents an improved version of the classic relay autotuner. The proposed autotuner uses an asymmetric relay function to better excite the process in the experiment phase. The improved excitation provides the possibility to obtain better models and hence better tuning, without making the autotuner more complicated or time consuming.

Some processes demand more accurate modeling and tuning to obtain con-
trollers of sufficient performance. The proposed autotuner can classify these processes from the experiment. In an advanced version of the autotuner an additional experiment could be dhttps://localhost/admin/login.phpesigned for these processes, in order to further increase the possibilities in modeling and tuning.... (More)
This thesis presents an improved version of the classic relay autotuner. The proposed autotuner uses an asymmetric relay function to better excite the process in the experiment phase. The improved excitation provides the possibility to obtain better models and hence better tuning, without making the autotuner more complicated or time consuming.

Some processes demand more accurate modeling and tuning to obtain con-
trollers of sufficient performance. The proposed autotuner can classify these processes from the experiment. In an advanced version of the autotuner an additional experiment could be dhttps://localhost/admin/login.phpesigned for these processes, in order to further increase the possibilities in modeling and tuning. The experiment design would then rely on information from the relay experiment. A simple version of the autotuner could instead make a somewhat better model estimation immediately, or suggest that some extra effort may be put in modeling if the control performance of the loop is crucial. The main focus in this thesis is on the simple version of the autotuner.

The proposed autotuner uses the process classification for model and controller selection also in the simple version. The processes are classified according to their normalized time delays. In this thesis a simple method of finding the normalized time delay from the asymmetric relay experiment is presented and evaluated.

Research presented on different versions of the relay autotuner is often based solely on simulations. In large simulation environments, the ability to automatically tune the large amount of PID controllers is practical and time-saving. However, the ability to use the autotuner in an industrial setting, requires considerations not always present in a simulation environment. This thesis investigates many of these issues, regarding parameter settings and possible error sources. The proposed autotuner is implemented, tested and evaluated both in a simulation environment and by industrial experiments. The simple version of the autotuner gives satisfactory results, both in simulations and on the industrial processes. Still, there is a possibility to further increase the performance by an advanced version of the autotuner. (Less)
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author
supervisor
organization
publishing date
type
Thesis
publication status
published
subject
pages
92 pages
publisher
Department of Automatic Control, Lund Institute of Technology, Lund University
language
English
LU publication?
yes
id
44d2f23c-f801-4fc1-9298-a74d1c252e3d (old id 5463946)
date added to LUP
2015-06-29 11:09:46
date last changed
2017-02-01 12:45:10
@misc{44d2f23c-f801-4fc1-9298-a74d1c252e3d,
  abstract     = {This thesis presents an improved version of the classic relay autotuner. The proposed autotuner uses an asymmetric relay function to better excite the process in the experiment phase. The improved excitation provides the possibility to obtain better models and hence better tuning, without making the autotuner more complicated or time consuming.<br/><br/>Some processes demand more accurate modeling and tuning to obtain con-<br/>trollers of sufficient performance. The proposed autotuner can classify these processes from the experiment. In an advanced version of the autotuner an additional experiment could be dhttps://localhost/admin/login.phpesigned for these processes, in order to further increase the possibilities in modeling and tuning. The experiment design would then rely on information from the relay experiment. A simple version of the autotuner could instead make a somewhat better model estimation immediately, or suggest that some extra effort may be put in modeling if the control performance of the loop is crucial. The main focus in this thesis is on the simple version of the autotuner.<br/><br/>The proposed autotuner uses the process classification for model and controller selection also in the simple version. The processes are classified according to their normalized time delays. In this thesis a simple method of finding the normalized time delay from the asymmetric relay experiment is presented and evaluated.<br/><br/>Research presented on different versions of the relay autotuner is often based solely on simulations. In large simulation environments, the ability to automatically tune the large amount of PID controllers is practical and time-saving. However, the ability to use the autotuner in an industrial setting, requires considerations not always present in a simulation environment. This thesis investigates many of these issues, regarding parameter settings and possible error sources. The proposed autotuner is implemented, tested and evaluated both in a simulation environment and by industrial experiments. The simple version of the autotuner gives satisfactory results, both in simulations and on the industrial processes. Still, there is a possibility to further increase the performance by an advanced version of the autotuner.},
  author       = {Berner, Josefin},
  language     = {eng},
  note         = {Licentiate Thesis},
  pages        = {92},
  publisher    = {Department of Automatic Control, Lund Institute of Technology, Lund University},
  title        = {Automatic Tuning of PID Controllers based on Asymmetric Relay Feedback},
  year         = {2015},
}