Modelling of longitudinal vehicle motion during low-speed driving

Abstract

The phenomenon of sudden jolts when riding in a vehicle is a well-known phenomenon which is caused by friction forces between the ground, tyres, disc-brake systems and suspensions. It is caused by two significant nonlinear singularities, which arise from friction forces between the ground and the tyres as well as within the disc-brake system. The jerk phenomenon occurs due to the frictional forces between two surfaces when there is a change in the direction of their relative velocity. In this thesis, some of the most common friction models will be investigated. Simulations are performed to evaluate the limits and the performances of the different models applied to a brake disc. Additionally, a novel tyre model based on the LuGre friction model is implemented to address singularities at low speeds. A comparison is made between this new model and the widely recognized Pacejka tyre model to highlight the differences and the limits of each. Furthermore, a complete longitudinal vehicle model featuring these tyre and brake models is developed. Different complexities of the model are considered, ranging from a complete rigid vehicle model to models featuring suspensions and compliances. This will allow us to gain knowledge of where the jerk phenomenon arises. To validate the model, the mathematical results are compared with experimental data obtained from actual vehicle manoeuvres.