A CONTACT MODEL BETWEEN TYRE AND PAVEMENT AT LOW SPEED FOR PERIODIC MOTOR VEHICLE INSPECTION

摘要

The behaviour of the tyre plays an important role in the vehicle handling. Thus for the analysis of vehicles and road safety it is necessary to take into account the forces and moments generated at contact patch. An accurate tyre model that estimates these forces and moments is highly essential for the studies of vehicle dynamics and control. Most of the tyre models have been developed for high speed, combined forces, etc. But, usually, automobile vehicles run at low speeds during an important part of their operating life (less than 60 km/h) and in steady state conditions. Furthermore, during vehicle inspection and maintenance of the steering and brake system, by means of sideslip tester and roller brake tester respectively, the forces transmitted by the tyres are measured, all of these inspections are carried out at low speeds. Therefore, it is particularly interesting to develop a model of the contact patch tyre-pavement for low speeds without the complexity of models that cover a wide speed range but with a bigger precision at low speeds. The dynamometer plate has proved to be an appropriate test equipment to characterise the tyre-pavement contact at low speed and the steering geometry and wheel alignment. It has the feature of being able to carry out tests for any type of tyre allowing to test with a great flexibility and operating speed. For this reason, the dynamometer plate has been chosen as test equipment. The main aim of this research is to set up a contact model between tyre and pavement at low speed, based on the measurement of longitudinal and lateral forces. The experimental tests carried out by means of the dynamometer plate have allowed to establish a relationship between influence variables and the longitudinal and lateral forces in the contact patch for steady state low speeds. A sensibility study has shown that the most influential variables in the forces of the contact patch are the pressure, the vertical force and the toe angle. However, the influence of temperature and camber angle is lower for the defined model conditions. A test methodology that allows carrying out the experimental tests in a systematic and controlled way in the dynamometer plate has also been developed.