A Chattering Suppression of Proportional Sliding Mode Control with Composite Nonlinear Feedback Technique using Sigmoid Function for MacPherson Active Suspension System

Abstract

The chattering problem phenomenon occurred due to the high-frequency switching of a sliding mode controller exciting unmodelled dynamics in the closed loop. Unmodelled dynamics may be those of sensors and actuators neglected in the principal modelling process since they are generally significantly faster than the main system dynamics. In the MacPherson active suspension system, the phenomenon occurred due to unmodelled dynamics on tire in a quarter car model. The Proportional Integral Sliding Mode Control (PISMC) is combined with Composite Nonlinear Feedback (CNF) technique due to its characteristics on the transient response and fast settling time. The sigmoid function is used in PISMC-CNF control law to reduce chattering problem. The Evolution Strategy is used to find the best boundary layer thickness based on the road profiles applied to the MacPherson active suspension system. The results show the significant of the proposed solution in the mentioned application based on acceleration of spring mass.

Keywords

• boundary layer solution
• chattering problem
• sigmoid function
• unmodelled dynamics