Abstract
Vehicles operating in the terrain have to meet quite special requirements due to the uneven and deformable ground. Thereon particular processes, which do not exist for operations on the rigid road, are important. Regarding ride dynamics, the roughness of the terrain is inducing high dynamic wheel loads, which deform the waves of the ground; therefore the dynamic wheel loads and the deformation of the unevenness influence mutually. Regarding mobility, there are many interacting factors, which are responsible for the traction and the motion resistance:
The different processes, such as sinkage, multipass, slip, slip-sinkage, etc., have been explored separately in many experimental and theoretical investigations. Models to describe these processes analytically, correlating the vehicle characteristics and soil data and the relevant mobility factors, are available. However, the different processes of wheel-soil interaction, superposing each other, make conclusions for the vehicle design and layout on base of these separate models difficult. In addition, the different load on each one of the vehicle wheels and the varying soil conditions under the wheels extend the problem, so that there is the need of simulation of the over-all-system.
A most sophisticated simulation program of vehicle operation in the terrain is ORIS (Off Road Interactive Simulation), developed at the Institute of Automotive Engineering of the University of German Forces, Hamburg. Its development is progressing steadily by considering additional factors. The latest state of development of ORIS, its structure, the involved processes, the input vehicle design parameters and characteristics, as well as the stochastic terrain data, given in a digital map, will be explained in the paper. Attention will be drawn to the manifolded possibilities of application of ORIS as tool for vehicle layout, optimal adaption of components, hardware in the loop integration in combination with teststands, evaluation of competing vehicles, and mission planning.
The examples discussed will especially concern with tire inflation pressure control, multi axle drive concepts, propulsion torque distribution, differential locking control, multi axle steering. Those measures, improving the off road mobility, have become realisable for terrain vehicles due to electronics and on-board computers.