Off Road Vehicles in a Dynamic Three-Dimensional Realtime Simulation

The simulation of off-road driving is a scientific field with special problems that are only dealt with by a few institutions in the world. Up to now, there was no commercial tool that was capable of reproducing the complex interactions between vehicle and terrain. At former conferences of the ISTVS, the simulation program ORSIS (Off Road Systems Interactive Simulation) was introduced. It was developed at the Institut fur Kraftfahrwesen und Kolbenmaschinen (IKK) and is still advanced. In the latest version, the vehicle model is calculated by means of a dynamic multi-body system. This allows one to simulate the vehicle dynamics in all three dimensions (longitudinal, vertical and lateral). Moreover, the wheel-soil model was completely reenginered so that it is possible to calculate the lateral forces on soft soils. The shear-stress in the contact area is calculated on the basis of the local pressure and the local shear displacement. Another important improvement in the tire-soil-model is the consideration of the elastic soil properties. This allows a more realistic description of the pressure distribution under the elastic wheel and brings some advantages in the calculation of the multi-pass effect. In this paper, a short overview concerning the further developments of ORSIS will be given. This refers to the new simulation structure including the multi-body vehicle model, the driveline model, the steering model, tire-soil model and the terrain model. The single submodels will be presented and the further developments will be discussed. In the second part of the paper, some examples of simulation results will be presented. The focus will be on the effects of the lateral dynamics. The influences of different driveline concepts as well as the impact of differential locks while cornering will be shown. The paper will be finished with a short discussion of the field of applications of the simulation program ORSIS.