Tyre-road friction estimation - a comparative study

This paper proposes a comparative study of three observers: a second-order sliding mode observer, a third-order sliding mode observer, and an adaptive observer. The observers are designed for tyre-road friction coefficient p estimation during a braking manoeuvre in an automotive vehicle. The second-order sliding mode observer and the third-order sliding mode observer reconstruct the friction coefficient p using equivalent output error injection ideas, while the adaptive observer uses explicit estimates of the road condition parameter as part of the scheme. The new second-order observer that is proposed in this paper is based on a quarter-vehicle representation and is independent of the model used to represent the tyre-road friction. The paper considers a dynamic LuGre friction model, a pseudostatic LuGre friction model, and a parameter-based friction model as a basis for a comparative study.