Tyres

Chapter 3 focuses on modern tyre modelling. While classical two-dimensional nonholonomic- constraint models work reasonably well at very low speeds, these models are not acceptable in realistic applications. This chapter aims to explain the mechanisms and modelling issues related to the generation of tyre forces and moments. Physical models such as the brush and string models are used to clarify the basic concepts. Building upon these findings, the empirical models widespread in vehicle dynamics analyses are discussed. An overview of some of the advanced models currently used in the industry is also given.

A comprehensive active-steering control method for improvement of vehicle handling performance

Non-linear system control has always been a difficult point for vehicle stabilization. To improve the vehicle handling performance, a comprehensive active-steering control method is proposed and derived. Different from traditional strategy, this new controller is based on a piecewise tyre modelling ideology combined with feedback linearization controlling method. In the linear region of wheel–terrain contact, vehicle dynamic system turns to be a linear system, an optimal control is designed for the sake of rapid response in tracking desired values. In the non-linear region, where the controlling difficulty always lies in, the tyre lateral force is described by a new polynomial formula model, which is simpler than magic formula model and more accurate than linear model. This new tyre modelling ideology ensures the feasibility of feedback linearization method in non-linear system control. To verify the proposed controller, a numerical seven-degrees-of-freedom vehicle model is built and validated by standard input simulation. Then, simulation under limit conditions, including high friction case and low friction case, are conducted and results are presented and discussed. Compared with optimal controller and free-control method, comprehensive controller has a much more desirable applicability in both cases and greatly improves the vehicle handling performance.