SOIL FLOW ANALYSIS FOR PLANETARY ROVERS BASED ON PARTICLE IMAGE VELOCIMETRY AND DISCRETE ELEMENT METHOD

Planetary rovers commonly have grouser wheels to improve locomotion performance on deformable terrains such as the surfaces of the Moon or Mars. The biggest difference between the wheel with grousers and without grousers is soil behavior underneath the wheel since the grousers shovel the sand. Hence, analyzing soil flow gives us beneficial information on wheel-soil interaction. The detailed investigation for micro-scale soil behavior and gravity effect, which are difficult to see in the laboratory test, contributes to further understanding of wheel-soil interaction mechanics. This paper presents a two-dimensional discrete element method (DEM) simulation to analyze soil flow beneath the grouser wheel. The soil flow in the simulation is validated by comparing it with that of the measurements, which is visualized by particle image velocimetry (PIV). The comparison results are discussed from four perspectives: 1) wheel slip ratio, 2) traces formed behind the wheel travels, 3) entrance and leaving angles of the grousers, 4) soil velocity field. The results indicate that DEM could describe the soil deformation. This work would contribute to further investigations of the state inside the soil by using developed DEM simulation.