Linearisation of three phase horizontal gravity separator
by S. Janakiraman; Rajagopalan Devanathan
International Journal of Automation and Control (IJAAC), Vol. 15, No. 6, 2021

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.

Online publication date: Thu, 28-Oct-2021

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