Robust control of isopropyl benzene production process using H_∞ loop shaping control scheme

Abstract

This paper discusses robust control strategy for isopropyl benzene production process using the method of loop shaping $H_{\mathrm{\infty }}$ technology. This cumene production process is a part of phenol plant in HOCL, Kochi. $H_{\mathrm{\infty }}$ control of the propylene concentration is done here. The $H_{\mathrm{\infty }}$ controller is derived from the linearised model of the reactor. The optimal $H_{\mathrm{\infty }}$ controller is obtained by simplifying two algebraic Riccati equations. The proposed PID-like $H_{\mathrm{\infty }}$ controller provides a single tuning parameter which makes the controller design more accurate. The proposed controller has been compared with other robust controllers like $H_2$ and LQR. The $H_{\mathrm{\infty }}$ controller is found to be superior in a wide frequency range and has a feature of low distortion and good regulating performance. The reactor model has been developed in COMSOL Multiphysics with the parameters obtained from HOCL plant, Kochi. The model extracted is reduced using model order reduction for the controller design.

KEYWORDS:

• Cumene reactor
• $H_{\mathrm{\infty }}$ loop shaping
• model order reduction
• Riccati equation
• PID control
• stability
• robustness

Acknowledgements

The authors are grateful to the HOCL in Kochi, Kerala, for their prompt assistance in completing the work. Authors are grateful to Chief General Manager (Production & Engineering) Mr. K. K. Kunjumon, General Manager (Production) Mr. T. P. Sachidandan, and their team especially Mr. Ramesh Kumar P. for the timely advice and suggestions. The authors extend their gratitude to the anonymous referees for their support for improving this paper.

Disclosure statement

No conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Vinila Mundakkal Lakshmanan

Vinila Mundakkal Lakshmanan completed her Ph.D. from National Institute Technology, Calicut. She did her Masters from College of Engineering, Guindy, Chennai, and B. Tech. from University of Calicut, Kerala. She is working at Adi Shankara Institute of Engineering and Technology, Kalady, India. Her research interests include mathematical modelling, multiscale modelling and process control.

Aparna Kallingal

Aparna Kallingal did her B. Tech. and M. Tech. from Government Engineering College, Thrissur, and her Ph.D. from IIT Madras. She is working in the Department of Chemical Engineering, NIT Calicut, from 2007. Her research interests include process design and control, biomass and biofuels.

Sreepriya Sreekumar

Sreepriya Sreekumar did her B. Tech. degree from Cochin University of Science and Technology, Kerala, M. Tech. degree from Anna University, Chennai, India, and Ph.D. degree from National Institute of Technology, Calicut. She is working in Adi Shankara Institute of Engineering and Technology, Kalady, India. Her research interests include nonlinear control, application of evolutionary algorithms, soft computing in control and system optimisation.