Analyzing bearing capacity changes due to vibration in discrete element method simulations

Recently, legged robots have gained significant attention as highly mobile platforms for planetary exploration. However, the surfaces of celestial bodies such as the Moon are mainly composed of loose materials, leading to slippage due to the deformation of the surface under the movements of the rover's legs. To address this issue, we proposed a walking method designed to minimize slippage. Our previous research demonstrated that applying vibrations can increase both the shear strength of the ground and the amount of the rover's leg subsidence, thereby enhancing the ground's bearing capacity, which is related to the counterforce provided by the ground against the legs of the rover. For the robot to perform optimally, it is essential to accurately estimate this bearing capacity to select efficient vibration settings. In this study, we utilized the discrete element method (DEM) to simulate the ground's bearing capacity under various vibrational influences changing both the sinkage depth of a leg and the vibration frequency. Our simulations successfully mirrored the real-world effects of vibrations on bearing capacity, providing insightful perspectives on how vibration can be used to enhance ground support for these robotic explorers.