Adaptive Traction Control for Non-Rigid Tire-Wheel Systems

The designs of commercial Anti-Lock Braking Systems often rely on assumptions of a torsionally rigid tire-wheel system. However, variations in tire/wheel technologies have resulted in lower torsional stiffnesses that cannot be captured well using these rigid wheel assumptions. This paper presents an adaptive nonlinear controller based on a model that incorporates sidewall flexibility, and transient & hysteretic tread-ground friction effects. The sidewall stiffness and damping and as well as tread parameters are assumed to be unknown and subsequently estimated through a set of gradient-based adaptation laws. A virtual damper is introduced via a backstepping controller design to address difficulties associated with tires with low torsional damping.