Title: Identifying the stabilising regions of PI controller based on frequency specifications for a lab scale distillation column
Authors: R. Janani; Vinayambika S. Bhat; Indiran Thirunavukkarasu; V.I. George
Addresses: Department of Electronics and Instrumentation Engineering, Sri Chandrasekharendra Saraswathi Viswa Mahavidyalaya, Enathur, Kanchipuram-631561, Tamilnadu, India ' Department of Electronics and Communication Engineering, Mangalore Institute of Technology and Engineering, Moodabidri-574225, Karnataka, India ' Department of Instrumentation and Control Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal-576104, Karnataka, India ' Department of Instrumentation and Control Engineering, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal-576104, Karnataka, India
Abstract: The aim of the study is to design and implement decentralised PI controller for a lab scale distillation column based on the frequency specifications. Designing an effective PI controller for an MIMO process is a challenging task because of the loop interaction and system with dead time. In order to eliminate these interactions between the control loops, an ideal decoupling technique is implemented and first order plus dead time model is obtained for each decoupled subsystems. By plotting the boundary locus for each subsystems based on the desired gain and phase margin in (kp, ki) plane a wide range of PI values are obtained. Also, the performance measurement calculations were compared and tabulated for various values of kp and ki with the boundary locus. In this present research the pressure and temperature near the bottom of the column is considered. It is also shown that the system become unstable when the value of PI controller is selected outside the boundary locus.
Keywords: boundary locus; decentralised controller; gain margin; phase margin.
International Journal of Digital Signals and Smart Systems, 2020 Vol.4 No.1/2/3, pp.1 - 16
Received: 07 Mar 2019
Accepted: 24 May 2019
Published online: 19 Mar 2020 *