Passive Gripping Foot for a Legged Robot to Move Over Rough Terrain

Abstract

This paper proposes a passively driven gripping foot that can be attached to any mobile legged robot without intervening in the robot’s controller. In rough terrains with uneven slope surfaces, it is often difficult to move by a legged robot having normal flat foot. One idea is to give a gripping functionality onto foot and grasp ground to establish firm contact. However, grasping at appropriate timing to contact to the ground usually needs coordinated control with the robot’s gait and externally powered open/close movement of the gripper. This prohibits easy installation of this type of gripping foot onto existing legged robot. To this problem, we propose a gripping foot that automatically grasps ground by the robot’s weight when the robot put its foot onto ground and opens when the robot raises its foot. By this, any legged robot will be able to attach this foot as a shoe, and the robot has an ability to walk under rough terrains. The mechanism of the grasping foot uses a simple linkage to transfer the gravitational force into appropriate side gripping force. By the experiments conducted on a slope with sand and small rocks by a six-legged robot attached with this foot, it was shown that the proposed mechanism could achieve forward climbing movement while the robot with a bare flat foot could not move forward.