Wheel-Slip Regulation Based on Sliding Mode Approach

This paper presents a nonlinear observer and controller based on passivity and sliding mode approach for vehicle traction control. The main contribution is the on-line estimation of the tire force which is needed for control. The concept of relaxation length describes the wheel-slip variation as a first order model. From this concept a differential equation of tire force is proposed to design a controller based on nonlinear observer. Only longitudinal dynamics are considered in this study. Stability analysis in closed-loop is proved by Lyapunov's method. Sufficient conditions for applying sliding mode based control are derived. The proposed control is verified through one-wheel simulation using “Magic formula” tire model. The robustness of control is tested by including errors in the parameters and by changing value of tire adhesion. A comparison of the proposed approach of control with PD control is given.