Tyre–road friction μ -estimation based on braking force distribution

In this work, we develop a rules-based µ-estimation algorithm which is independent of any tyre model and may be employed independently by brake control systems of the vehicle. The algorithm proposed herein aims at estimating the tyre/road friction coefficient during braking, in particular when one or more of the tyres approach the limit of adhesion. The proposed algorithm avoids the use of any particular tyre model and the need to identify several parameters of such models. It uses measurements of variables that are typically available in modern vehicles, namely, vehicle demanded and actual deceleration and wheel angular velocity, as well as the brake force distribution applied by the brake system. The algorithm is validated through implementation in high-fidelity vehicle dynamics simulation and by experimental data collected during experiments with a brake-by-wire electric vehicle.