An Analytical Tire Model for Vehicle Simulation in Normal Driving Conditions 2000-01-0356
In the simulation of the dynamic response of a vehicle, the accuracy of the predictions strongly depends on the tire properties. Since the physics of tire force generation is highly nonlinear and complex, semi-empirical models are used, which are mathematically curve fitted to experimental data. Although this approach yields realistic tire behavior, it requires many experimental coefficients.
Even though tire forces generated by a real tire are nonlinear, there is a linear region where the slip and slip angle are low. Most normal driving is done in this region. This paper will present a new analytical tire model capable of simulating pure cornering, pure braking, and combined braking/cornering in this region. The dynamic properties of the tire are analytically derived as functions of the slip, slip angle, normal force, and road friction coefficient. For the combined braking/cornering condition the unique function which effectively determines the tradeoff between longitudinal force and cornering force is derived. The longitudinal and cornering forces in the proposed tire model well match those of empirical models in the normal driving range. The proposed tire model can be analytically linearized about a given operating point, thus it can be very useful for designing controllers and observers for use in vehicle dynamic control systems. This paper develops this tire model and compares it with an empirical model.