Impact of Tire Compliance Behavior to Vehicle Longitudinal Dynamics and Control

Empirical tire models, generally obtained through lab tests, are commonly used in vehicle dynamics and control analysis. Most of the empirical tire models describe the linear (or nonlinear) static tire behavior and overlook the tire compliance with one exception: the relaxation length tire (RLT) model inserts first order tire dynamics. However, the RLT model creates an undamped oscillation when describing the low-speed tire dynamics. This paper presents an improved longitudinal tire model that describes the tire compliance without exhibiting the undamped vibrations. By incorporating this improved tire model into a vehicle longitudinal model, the dominant flexible modes of the vehicle can be easily captured. The predictions from the improved vehicle model show that the often-ignored tire compliance can impact longitudinal ride comfort and vehicle control designs. Experiments were conducted on a passenger car as an example and the experimental data verified the model predictions.