Vision-based determination of wheel camber angle and tire deflection

Accurate determination of vehicle’s lateral behavior is necessary in the domain of vehicle dynamics and more particularly in the context of improvement of vehicle safety. Thus, a cutting-edge knowledge of its interaction with the road surface is primordial. In consequence, the integration of a force model, representing the tire/ground interface, into the global vehicle model is needed. The validity of such a model directly depends on its nature and more particularly on the determination accuracy of its inputs and outputs. This paper focalizes on an input: the wheel/road camber angle. Studies in collaboration with a carmaker have shown a required measurement accuracy lower than ± 0.1◦ in order to identify the tire model parameters from real data with a high precision. Different existing solutions were studied and their accuracy was estimated. In parallel, a new method for direct camber determination was developed in the laboratory. Its vision-based principle’s major purpose is to give an accurate measurement: its precision is robust to the road unevenness and the vehicle’s velocity. The tire deflection is estimated in the same time. The method feasibility and its measurement precision were studied from real tests with the laboratory test car.