A New Methodology to Compensate Stiction in Pneumatic Control Valves
S. Sivagamasundari1, D. Sivakumar2

1S.Sivagamasundari, Dept. of Electronics and Instrumentation Engg., Annamalai University, Annamalai Nagar, Tamil Nadu, India.
2D.Sivakumar, Dept. of Electronics and Instrumentation Engg. Annamalai University, Annamalai Nagar, Tamil Nadu, India.
Manuscript received on January 01, 2013. | Revised Manuscript received on January 02, 2013. | Manuscript published on January 05, 2013. | PP: 480-484 | Volume-2, Issue-6, January 2013. | Retrieval Number: F1203112612/2013©BEIESP
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© The Authors. Published By: Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Abstract: Industrial surveys reported that, almost one third of poorly performing control loops are caused by nonlinearities present in the control valves, one of which is static friction. The effect of this nonlinearity is usually observed as oscillations in process variable. Since industrial plants include numerous interacting loops, the oscillations will be propagated to the entire system. Doubtlessly, repairing the faulty valves will be the only solution to this problem, which is possible only during process shut down. But, as shutting down the process to isolate the faulty valve for maintenance purposes is not economical, this solution does not count as the primary one. So, there is a need for a method to compensate the destructive effect of the stiction phenomenon in the control valve, especially when maintenance is not available. This paper focuses on existing compensation issues, followed by a proposal of a new model-based compensation approach for the stiction nonlinearity present in control valves. Performance of this method is validated by both simulation and laboratory data. 
Keywords: Pneumatic control valve, stiction, Stick band, stiction compensation, knocker.