Discrete Element Modeling of a Rover Wheel in Granular Material Under the Influence of Earth, Mars, and Lunar Gravity

A three-dimensional computer model of the Mars Exploration Rover wheel interaction with soil has been developed using the discrete element method. This simulation incorporates the important geometric aspects of the rover wheel and has the ability to perform specific soil tests such as compaction and excavation of layered soil and to vary soil properties such as grain size and shape, particle cohesion and friction. In addition, in simulations the effects of reduced Martian and lunar gravity can be explored. The rover wheel has a rather intricate non-uniform geometry because of a cavity used to attach the rover to the lander that is captured in the model. We investigate the effect of reduced gravity, the effect of the presence and absence of the attachment point, and qualitative variations in the model soil used in the simulations. Finally, we compare the simulated rates of excavation and torque to experimental results.