Robust sliding mode control of 4WS vehicles for automatic path tracking

This paper investigates the use of four-wheel steering system (4WS) for the automatic vehicle control in the context of path tracking. The 4WS vehicle is assumed to be set up in a previously studied look-down reference system with sensors installed on the vehicle´s front and rear bumpers to measure its lateral displacements from the reference path. Past research in the path tracking control have showed the difficulties to design a controller that is robust against the intensive vehicle modeling uncertainties and disturbances. In this paper, noticed the new dynamic characteristics of 4WS vehicles, we firstly found a new robust sliding mode controller for a class of linear systems and then apply it to the path tracking problem of 4WS vehicles. Both theoretical analysis and simulations show that with the proposed controller, the system´s tracking accuracy, stability and robustness against the parameter variances and external disturbances, especially the changes of road friction condition, longitudinal velocity and crosswind forces, are identically guaranteed.