Non-Linear System Controller Design Using Sliding Mode Control

Abstract

Throughout the years, many researchers have problems in stabilizing non-linear, uncertain system.
One of the methods used to design a robust state feedback controller for an uncertain system is variable structure
control (VSC). VSC systems are designed to drive the system states to a sliding surface in the state space in sliding
mode control. By using a feasible high-speed switching feedback control to achieve the desired plant behaviour
or reaction, the controller structure around the plant is deliberately modified. The problem of developing a VSC
law for uncertain system, Electrohydraulic control system is considered in this paper. An alternative design
method of a linear sliding surface that is linear to the state is generated using the LMI technique. A proper
condition is given for the linear sliding surface to exist. In addition, an explicit linear sliding surface formula to
ensure quadratic stability is derived from the reduced-order equivalent system dynamics, constrained to the sliding
surfaces. Then, an Electrohydraulic servo system is applied to the sliding mode controller. MATLAB/SIMULINK
software was used to carry out the simulation work. Comparison of the controller design, using LMI approach
method with and without the sliding mode control shows that LMI approach with a sliding mode control method
produces a better performance response.