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Compensator for constant relative stability in process control systems

Madhuranthakam, Chandra Mouli R and Elkamel, Ali and Govindarao, Venneti MH (2011) Compensator for constant relative stability in process control systems. In: Chemical Engineering Communications, 198 (3). pp. 344-359.

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Abstract

Process control systems are designed for a closed-loop peak magnitude of 2dB, which corresponds to a damping coefficient () of 0.5 approximately. With this specified constraint, the designer should choose and/or design the loop components to maintain a constant relative stability. However, the manipulative variable in almost all chemical processes will be the flow rate of a process stream. Since the gains and the time constants of the process will be functions of the manipulative variable, a constant relative stability cannot be maintained. Up to now, this problem has been overcome either by selecting proper control valve flow characteristics or by gain scheduling of controller parameters. Nevertheless, if a wrong control valve selection is made then one has to account for huge loss in controllability or eventually it may lead to an unstable control system. To overcome these problems, a compensator device that can bring back the relative stability of the control system was proposed. This compensator is similar to a dynamic nonlinear controller that has both online and offline information on several factors related to the control system. The design and analysis of the proposed compensator is discussed in this article. Finally, the performance of the compensator is validated by applying it to a two-tank blending process. It has been observed that by using a compensator in the process control system, the relative stability could be brought back to a great extent despite the effects of changes in manipulative flow rate.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Taylor and Francis Group.
Keywords: Control valve; Mathematical modeling; Process control; Relative stability
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Depositing User: Id for Latest eprints
Date Deposited: 03 Jan 2011 06:53
Last Modified: 03 Jan 2011 06:53
URI: http://eprints.iisc.ac.in/id/eprint/34764

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