Experimentally verified optimal bi-loop re-located IMC strategy for unstable and integrating systems with dead time

Abstract

Internal model controllers (IMCs) are popular strategies for controlling stable systems with dead time. The relocated IMC (RIMC) design reportedly achieves the expected performance-robustness tradeoff for stable processes. Hence, an attempt has been made in this work to modify the RIMC (as a bi-loop RIMC proportional-derivative (RIMC-PD)) strategy to make it applicable to a class of unstable and integrating systems involving dead time. The secondary-loop stabilisation is achieved with a PD controller constructed by Routh stability constraints. The primary loop contains a RIMC controller for reference following. Both primary, as well as secondary-loop controller parameters, are optimally tuned in the search space using the equilibrium optimiser subjected to minimal integral square error. The RIMC-PD control strategy delivers reasonable enhancement in performance measures when compared with some of the recently reported strategies. A robust stability investigation is also carried out. Finally, experimental verification of the RIMC-PD strategy is carried out using a magnetic levitation laboratory setup.

KEYWORDS:

• Bi-loop control
• re-located internal model control
• integrating and unstable processes
• time delay
• equilibrium optimiser
• integral squared error

Acknowledgements

The authors would like to acknowledge Dr. Ahmad Ali and Mr. Kumar Swapnil for allowing to use the research facility of the control and instrumentation lab, Indian Institute of Technology (IIT) Patna, India for performing the MAGLEV experiment. This work has also received support from the Catalan Government under Project 2021  SGR 00197 and also by the Spanish Government under MICINN project PID2019-105434RBC33 co-funded with the European Union ERDF funds.

Disclosure statement

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

Data availability statement

The authors confirm that data and materials that support the results or analyses presented in this paper are freely available upon request.

Additional information

Notes on contributors

Pulakraj Aryan

Pulakraj Aryan (Graduate Student Member, IEEE) received the bachelor's degree in electrical and electronics engineering from Birla Institute of Technology, Mesra, Ranchi, India in 2016 and Master's degree from National Institute of Technology, Patna, India in 2020. He is currently working towards the Ph.D. degree in control systems with the National Institute of Technology Patna, India. His current research focuses on optimal control strategies for industrial processes. He has authored several book chapters and has more than 15 publications in peer-reviewed international conference proceedings and reputed journals.

G. Lloyds Raja

G. Lloyds Raja (Member, IEEE and IFAC-ACDOS) received his Bachelors (in Electronics and Communication Engineering) and Master's (in Embedded System Technologies) degrees from Anna University in 2009 and 2011, respectively. He was awarded Ph.D. from the Electrical Engineering Department of Indian Institute of Technology Patna in 2018. While serving as an Assistant Professor at Kalinga Institute of Industrial Technology (between 2017 and 2020), he visited the department of Automation at Shanghai Jiao Tong University (China) for a short duration as a postdoctoral researcher. Since 2020, he is with the Electrical Engineering Department of National Institute of Technology Patna where he serves as an Assistant Professor. His current research interests include chemical process control, advanced load frequency control strategies, adaptive control and applications of meta-heuristic optimization techniques for controller tuning. He has edited two books on control engineering, authored several book chapters and has more than 35 publications in peer-reviewed international conference proceedings and reputed journals.

Ramon Vilanova

Ramon Vilanova (Member, IEEE) graduated in the Universitat Autònoma de Barcelona in 1991. He received the Ph.D. degree from Universitat Autònoma de Barcelona in 1996. He is currently a Full Professor of ‘Automatic Control and Systems Engineering’ with the School of Engineering, Universitat Autònoma de Barcelona where he teaches subjects like signals and systems, automatic control and technology of automated systems. His research interests include methods of tuning of PID regulators, systems with uncertainty, analysis of control systems with several degrees of freedom, application to environmental systems and development of methodologies for design of machine-man interfaces. He is author of several book chapters and has more than 100 publications in international congresses/journals. He is a member of IFAC and IEEE-IES.