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 online 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.