Simulation of Rover Locomotion on Sandy Terrain – Modeling Verification and Validation

In this paper a modeling technique called SCM (Soil Contact Model) for simulating the physical interaction between a rover mobility system (wheel, legs, tracks etc.) and a planetary soil surface will be presented. SCM computes the contact forces between the soil and the contact objects based on Bekker’s empirical terramechanics formulae. Within SCM the soil geometry is described as digital elevation model (DEM) while the contact objects are described as general polygonal surface mesh grids. Based on this method SCM is able to deal with arbitrarily shaped contact objects without any restrictions in terms of application cases. Moreover, SCM provides a module for plastic soil deformation in order to take typical terramechanics phenomena like sinkage, bulldozing and multi-pass effects into account, which strongly affect the entire contact dynamics. The preferred simulation engine for SCM is SIMPACK, a 3D multi-body simulation package. In the verification process the correctness of the model has been demonstrated by bevameter tests proposed by Bekker. A first step in the validation process was made by applying SCM for simulations of ExoMars rover drawbar pull tests. It has been demonstrated that SCM creates simulation results with partly good correlation with real test measurements. Additional investigations are required for low contact velocities.