A study on the effect of road friction on driveline vibrations

The aim of this article is to assess the influence of the tyre/road contact interface on driveline vibrations. The mode shapes of a vehicle driveline are obtained and analysed, initially using three tyre models: a simple torsional spring, linear slip, and relaxation length-based models. Additionally, a fully transient load- and slip-dependent non-linear relaxation length model is incorporated into the driveline to determine the dynamic response on different surfaces. Simulations of pull-away manoeuvres on various surfaces are carried out. The halfshaft torque in each case is analysed and conclusions drawn on the effect of tyre dynamics on the frequency and intensity of driveline vibrations. In order to investigate the influence of higher-frequency tyre dynamics, a model incorporating tyre belt inertia is simulated for the same cases. It is found that the higher-order dynamics introduced by the tyre belt result in additional frequencies in the response, as well as differences in response amplitude. Using the non-linear relaxation length and belt inertia models it is observed that low-μ surfaces promote driveline vibrations at higher and more numerous frequencies compared with the typical shuffle response observed on a high-μ surface. It is shown that this frequency migration can be physically explained by considering the effect of decoupling between driveline and vehicle on low-μ surfaces. It is also shown that the observed frequencies can be predicted by appropriately modified linear models.