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ISRN Chemical Engineering
Volume 2012 (2012), Article ID 693545, 11 pages
Research Article

Tuning and Retuning of PID Controller for Unstable Systems Using Evolutionary Algorithm

1Department of Electronics and Instrumentation Engineering, St. Josephโ€™s College of Engineering, Chennai 600 119, India
2Department of Aerospace Engineering, Division of Avionics, MIT Campus, Anna University, Chennai 600 044, India

Received 9 January 2012; Accepted 26 February 2012

Academic Editors: B. Grgur and S. Rodrรญguez-Couto

Copyright © 2012 V. Rajinikanth and K. Latha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Proportional + integral + derivative (PID) controllers are widely used in industrial applications to provide optimal and robust performance for stable, unstable, and nonlinear processes. In this paper, particle swarm optimization (PSO) algorithm is proposed to tune and retune the PID controller parameter for a class of time-delayed unstable systems. The proposal is to search the optimal controller parameters like ๐พ ๐‘ , ๐พ ๐‘– , and ๐พ ๐‘‘ by minimising the cost function. The integral of squared error (ISE) criterion is considered as the cost function, which guides the PSO algorithm to get the optimised controller parameters. The procedure for PID parameter tuning and retuning is presented in detail. A comparative study is done with the conventional PID tuning methods proposed in the literature. The simulation results show that the PSO-based PID controller tuning approach provides improved performance for the setpoint tracking, load disturbance rejection, error minimization, and measurement noise attenuation for a class of unstable systems.