9165 - SIMULATION OF THE RELATIONSHIP BETWEEN THE DECREASED BEARING CAPACITY WHILE IMPARTING VIBRATION TO GROUND AND VIBRATION FREQUENCY IN THE DISCRETE ELEMENT METHOD

Paper presented at ISTVS 2025 | 55th Conference of the International Society for Terrain-Vehicle Systems https://doi.org/10.56884/JUY2WUYX

Authors: Tomohiro Watanabe, Dai Watanabe, Kojiro Iizuka

Keywords: Discrete element method; bearing capacity; planetary exploration; vibration

Abstract:

Recently, moving underground has been focused on as a method of planetary exploring robots' movement.　Exploration rovers have difficulty moving underground because the drag force from the ground restricts their movement, hindering underground exploration. A previous study developed a mechanism that moves underground by imparting vibration to the ground and decreasing the drag force. The experimental results demonstrate the superiority of the proposed method, as the movement distance achieved with vibration is considerably greater than without vibration. The optimal vibration should be selected to improve the proposed mechanism's underground mobility. When imparting vibration, the change of the bearing capacity, which is the resistance from the ground, depends on lift-off acceleration. Lift-off acceleration is the minimum vibration acceleration that causes the flow of the ground particles. The bearing capacity increases when the rod's movement is under lift-off acceleration. Conversely, it decreases when the rod's movement is over lift-off acceleration. If the simulation reproduces the change of the bearing capacity when imparting vibration and lift-off acceleration, the optimal vibration can be selected. This study conducted the experiment and the DEM simulation in which the rod is dragged while vibrating on the ground. These methods measured the bearing capacity that the rod received from the ground. In the experiment and simulation, the vibration frequency was changed. As the vibration frequency increases, the acceleration of the rod's movement caused by the vibration eventually exceeds the lift-off acceleration. The reproducibility of DEM simulations was evaluated by comparing the relationship between the bearing capacity and vibration frequency in each method.