Revisiting Basics of Sliding Mode Control to Achieve a Controller Design without Undesired Dynamics inducing Chattering

Abstract

Sliding Mode Control is an effective robust control approach based on the induction of an exponential attractive condition by switching between control structures. However, high frequency oscillations on the closed-loop dynamics, inherent to the switching, impose the major drawback to this approach of being accepted as a common design tool in industry. In this paper, to better understand the induction of parasitic dynamics by the conventional sliding controller and to improve its design to suppress them, the author analyzes the dynamic excited by the switching transitions and the ambiguous definition of the dynamic flow on the thick-less switching surface, to proposes as design improvements the introduction of the Sliding Surface with its equivalent control as an intermediate dynamic structure, integrated to the other structures into a unique soft and continuous controller by a Fuzzy like algorithm, and presents a continuous version of the simplest Sliding Mode controller, briefly described on this paper but detailed and analyzed in a companion paper also submitted to this conference. Discussions and simulation analysis are based on a second order linear system as a generic plant with the basic dynamics of inertia, dissipation and restitution forces. Simulation results show the smoothness of the closed-loop response with a reduced gain keeping the properties of the Sliding Mode Control without chattering.