Higher-Order Sliding-Mode Observer Based Robust Controller Design for Four-Tank Coupled System

This paper presents the design of a robust observer based controller for four-tank coupled system (FTCS) using higher-order sliding-mode control scheme. The FTCS is considered as a multiple-input and multiple-output (MIMO) nonlinear system having significant coupled dynamics. The problem of liquid level control for FTCS is considered to achieve the desired set point. First, a sliding mode observer of higher order has been designed so that the estimated states achieve convergence to the plant states. Based on this observer, a robust controller using super-twisting algorithm has been proposed which can improve the performance of the FTCS. The applicability of this proposed robust controller for FTCS has been illustrated through simulation studies. Finally, a comparison has been made with the existing controller for FTCS to show the efficacy of proposed control scheme.