A real-time approach to robust identification of tyre-road friction characteristics on mixed-μ roads

The interaction between the tyre and the road is crucial for understanding the dynamic behaviour of a vehicle. The road-tyre friction characteristics play a key role in the design of braking, traction and stability control systems. Thus, in order to have a good performance of vehicle dynamic stability control, real-time estimation of the tyre-road friction coefficient is required. This paper presents a new development of an on-line tyre-road friction parameters estimation methodology and its implementation using both LuGre and Burckhardt tyre-road friction models. The proposed method provides the capability to observe the tyre-road friction coefficient directly using measurable signals in real-time. In the first step of our approach, the recursive least squares is employed to identify the linear parameterisation form of the Burckhardt model. The identified parameters provide, through a T-S fuzzy system, the initial values for the LuGre model. Then, a new LuGre model-based nonlinear least squares parameter estimation algorithm using the proposed static form of the LuGre to obtain the parameters of LuGre model based on recursive nonlinear optimisation of the curve fitting errors is presented. The effectiveness and performance of the algorithm are demonstrated through the real-time model simulations with different longitudinal speeds and different kinds of tyres on various road surface conditions in both Matlab/Carsim environments as well as collected data from real experiments on a commercial trailer.