Analysis of Soil Deformation and Wheel Traction on Loose Terrain Using PIV

A planetary rover experiences mobility problems, such as excessive slippage and entrapment, on loose terrain known as regolith. To prevent such situations, understanding wheel-soil interaction mechanics is necessary. Thus, this study focuses on the soil deformation beneath a grouser wheel and the wheel traction performance. The soil deformation is analyzed by using particle image velocimetry (PIV) technique, and the wheel traction is measured by a force-torque (FT) sensor. The experimental results present that the soil around a grouser moves to the directions on the front and rear of the wheel when the grouser enters into the soil. After that, the soil flow describes an arc-shaped flow from the front of the wheel towards the rear-end of the wheel caused by the grouser. These results indicate that the grouser wheel causes a different flow of soil than a wheel without grousers. Therefore, a model for the grouser wheel that takes into account the soil deformation must be developed in the future. We also investigate the effects of the normal load of the wheel on the soil deformation. The normal load of the wheel affects the thickness of the soil deformation area rather than the shape of the boundary line of the soil deformation area. In addition, the maximum thickness of the soil deformation area and the velocity of the soil particles increase with an increase of the normal load of the wheel. As for the wheel performance, the increase of the normal load causes an increase of wheel sinkage and traveling traction. From these results, it can be deduced that an increase in the thickness of the soil deformation area leads to an increase in the traction performance of the grouser wheel. In conclusion, this work contributes further to the understanding of wheel-soil interaction and the relationship between wheel performance and soil deformation.