Wheel slip estimation based on real-time identification of tire-road friction conditions

This paper is to develop efficient nonlinear observers for wheel slip with real-time friction parameter estimation only using wheel angular velocity. The model-based wheel slip control approach is adopted, which models the friction forces between the tires of the vehicle and the road surface, and an adaptive algorithm is designed for each wheel. It is shown that the adaptive observer is uniformly globally asymptotically stable under the condition of uniform δ-persistency of excitation. In addition, a stronger local stability result is obtained, where uniform local exponential stability is proven. Simulation results are provided to demonstrate the performance of the adaptive observer, even on the low friction road surface.