DocumentCode :
3139105
Title :
Quantification of valve stiction and dead band in control loops based on harmonic balance method
Author :
Araujo, Alancardek P. ; Munaro, Celso J. ; Filho, Moacir Rosado
Author_Institution :
Dept. of Math., Fed. Univ. of Espirito Santo, Vitoria, Brazil
fYear :
2011
fDate :
19-21 Dec. 2011
Firstpage :
1066
Lastpage :
1073
Abstract :
The presence of stiction in control valves often causes oscillations in control loops, with negative effects on quality and cost of goods. Step that follows diagnosis is to quantify this stiction, in order to decide about maintenance or to implement compensators that can improve control loop performance until next plant stop. The describing function method is a well known scheme to predict the period and amplitude of limit cycles in control loops, requiring the knowledge of linear and nonlinear parameters of system model. Here, a method is proposed to estimate these nonlinear parameters using the parameters of linear model and amplitude and period of limit cycle produced by nonlinearity. The result is a simple and efficient algorithm that can be easily extended to other nonlinearities. The conditions for existence and uniqueness of solution for dead band and stiction estimations are obtained. Also, the error from estimations is related to total harmonic distortion of control signal. The usefulness of the proposed method is demonstrated through its application to two examples.
Keywords :
compensation; control nonlinearities; linear systems; mechanical variables control; nonlinear control systems; stiction; valves; compensator; control loop; control signal distortion; control valves; dead band; harmonic balance method; linear parameter; nonlinear parameter; nonlinearity; valve stiction; Computational modeling; Equations; Frequency control; Mathematical model; Oscillators; Process control; Valves; Control valve; Deadband; Describing function; Stiction;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Control and Automation (ICCA), 2011 9th IEEE International Conference on
Conference_Location :
Santiago
ISSN :
1948-3449
Print_ISBN :
978-1-4577-1475-7
Type :
conf
DOI :
10.1109/ICCA.2011.6138040
Filename :
6138040
Link To Document :
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