Discrete element method simulations of Mars Exploration Rover wheel performance

Abstract

Mars Exploration Rovers (MERs) experienced mobility problems during traverses. Three-dimensional discrete element method (DEM) simulations of MER wheel mobility tests for wheel slips of i = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 0.99 were done to examine high wheel slip mobility to improve the ARTEMIS MER traverse planning tool. Simulations of wheel drawbar pull and sinkage MIT data for i 6 0.5 were used to determine DEM particle packing density (0.62) and contact friction (0.8) to represent the simulant used in mobility tests. The DEM simulations are in good agreement with MIT data for i = 0.5 and 0.7, with reasonable but less agreement at lower wheel slip. Three mobility stages include low slip (i < 0.3) controlled by soil strength, intermediate slip (i $ 0.3-0.6) controlled by residual soil strength, and high slip (i > 0.6) controlled by residual soil strength and wheel sinkage depth. Equilibrium sinkage occurred for i < 0.9, but continuously increased for i = 0.99. Improved DEM simulation accuracy of low-slip mobility can be achieved using polyhedral particles, rather than tri-sphere particles, to represent soil. The DEM simulations of MER wheel mobility can improve ARTEMIS accuracy.

Mars Science Laboratory Curiosity Rover Megaripple Crossings up to Sol 710 in Gale Crater

“…It remains to be seen how the rover will respond during these crossings. To prepare Artemis for more realistic high slip simulations of any future megaripple and dune crossings, the classical terramechanics model for wheel‐sand interactions are being updated with more realistic discrete element method approaches (Johnson et al., ).…”

Earth and Space 2014

“…MER wheel mobility measurements of DP and sinkage were performed in the MIT RMG's multipurpose terramechanics test bed (Iagnemma et al, 2005;Johnson et al, 2014). Tests were conducted using a MER spare flight aluminum wheel with an approximate radius of 0.…”

“…Wheel sinkage for MIT tests increases with a relatively constant slope until a wheel slip of about 0.6 when the slope of the sinkage/ wheel slip curve increases (the significance of the slope increase is somewhat suppressed due to the large values of DEM calculated wheel sinkage at 0.99 slip.). Johnson et al (2014) attributed the three-stage development of MER wheel mobility to: (1) A range of slips that produce soil deformations up to those associated with the peak soil strength with minimal sinkage (low wheel slips of between 0 and 0.3) amount of sinkage produces a large wheel contact area with soil that results in a high DP even though the soil retains only its residual strength.…”

A multi‐core ready discrete element method with triangles using dynamically adaptive multiscale grids

“…They tailor the forces to make them comprise both first‐principle collision terms (“real collisions”) and terms that imitate non‐spherical behaviour. Many friction or rotation effects, eg, do not arise for real spheres, but can manually be added to a force term and thus make a sphere behave non‐spherical/analytical . With these modelling decisions, assemblies of (almost) uniform analytical shapes start to realistically model larger structures.…”