Experimental Investigation of Relationship between Inner Ground Resistance Force and Vibration Kinds for Underground Moving Robots

In recent years, there have been many missions where the rovers land and explore the surface of planets or other extraterrestrial bodies. The purpose of these missions is to return the samples of extraterrestrial ground. These samples can solve the planets' origins and their sources of life. They have not only scientific value but also engineering value. Information on ground characteristics is helpful when building the base. The underground samples are especially valuable because they are not affected by space weathering and keep good conditions. In this background, the rovers, which move underground, have received attention as the method to obtain underground samples. In our previous study, the moving mechanism, which moves underground using vibrations, was proposed. The internal ground resistance decreases when imparting vibrations because the ground particles move and behave like a fluid. On the other hand, the inner ground resistance increases after imparting vibrations because the ground was compacted. The proposed mechanism moves underground while changing the ground condition. This study investigated the relationship between internal ground resistance force and vibration kinds because this relationship helps move underground. In the experiment, inner ground resistance force was measured when an object vibrating was dragged on the ground. In the results, the inner ground resistance force is increased by the vibration whose vibratory force is low. On the other hand, it is decreased by the vibration whose vibratory force is high. This knowledge is valuable for designing the rover's underground movement using vibrations.