The Influence of Internal Tyre Pressure on Road Friction

Road safety is a very important topic for research and development divisions in the automotive industry. As the tyre is the only link between road surface and vehicle, it plays a very significant role in accident mitigation and prevention.

This thesis investigates the influence of internal tyre pressure on the brake distance both experimentally and theoretically. Brake tests were performed using a robotic system and a winch was used to pull a car with locked wheels. For both experiments, the tyre pressures were changed.
A rubber friction law is presented which can be used for tyre and vehicle dynamics calculations. The friction law was tested by comparing numerical results to the full rubber friction theory of Persson and to experimental data. A two-dimensional (2D) tyre model is introduced that combines the rubber friction law with a simple mass-spring description of the tyre body. The tyre model is very flexible and can be applied to different manoeuvres. It can be used to calculate μ-slip curves, self aligning-torque, braking, and cornering, or combined motion (e.g. braking during cornering). The theoretical predictions have been compared to measured data from indoor tyre testing on sandpaper substrate. Additionally simulations of anti-lock braking system (ABS) using two different control algorithms are presented.

In addition a method for rapidly changing the tyre inflation pressure while a vehicle is in motion is presented. This method can be used for novel safety system approaches.