Title: Linearisation of three phase horizontal gravity separator

Authors: S. Janakiraman; Rajagopalan Devanathan

Addresses: Centre for Automation and Robotics, Hindustan Institute of Technology and Science, Chennai, Tamil Nadu, India ' Department of Electrical and Electronics Engineering, Hindustan Institute of Technology and Science, Chennai, Tamil Nadu, India

Abstract: Control of nonlinear systems through linearisation has a wide application in process operations. The idea is that once linearised at an operating point, linear theory can be applied for control. Three phase horizontal gravity separator (TPHGS) system with its nonlinear characteristics can be a candidate for linearisation. Approximate linearisation approach due to Kang and Krener is utilised to linearise the dynamic model of the separator. Approximate linearisation avoids the zero dynamics problems that might arise in exact feedback linearisation. Starting with a differential equation model of TPHGS, a state space model of TPHGS is obtained through a special transformation. Considering deviation around an operating point, a control affine model is obtained. Quadratic linearisation is then applied to the control affine model, using coordinate change and input transformations. Quadratic linearisation leads to a linearised system with only third and higher order nonlinearities in deviations present which can be considered negligible. A numerical example together with a MATLAB simulation shows the effectiveness of proposed linearisation.

Keywords: three phase horizontal gravity separator; TPHGS; state space analysis; nonlinear systems; approximate linearisation; quadratic linearisation.

DOI: 10.1504/IJAAC.2021.118530

International Journal of Automation and Control, 2021 Vol.15 No.6, pp.744 - 773

Received: 03 Oct 2019
Accepted: 13 Mar 2020
Published online: 28 Oct 2021 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article