Analysis of Wheel-Soil Interaction under Combined Slip Condition 2008-01-0779

The understanding of wheel-soil interaction under longitudinal and lateral slip conditions is very important for off-road vehicle dynamics. However, understanding the physics of wheel-soil interaction is not easy, especially with uncertain operational environment and with the limitation of current measuring technique and hardware. This paper explores important aspects of off-road vehicle mobility using as a case study a 7 degree of freedom (DOF) vehicle model under steady-state cornering. In the evaluation of the vehicle response over a two-dimensional (2-D) terrain profile the load transfer due to cornering was taken into account. The tractive and the cornering vehicle capabilities were predicted using an algorithm that chooses the appropriate tire model (rigid or flexible) and finds the optimal geometry of the contact patch. The parameters of the wheel-soil interaction, such as the sinkage, the entry and exit angles, the relaxation length, the slip angle, the normal pressure, the longitudinal shear stress and displacement, and the lateral shear stress and displacement, were determined.

In this study, all simulations were done under deterministic and stochastic scenarios. The vehicle model and the terrain profile used were developed in a deterministic framework. In addition to the average ground pressure and the slip ratio, key soil parameters were considered uncertain in the prediction of tractive and cornering capabilities. A polynomial chaos approach was used to quantify and propagate these uncertainties through the model.