Climbing obstacles with legged-wheels using foot mechanism

Small mobile robots with round wheels are not able to climb obstacles of which the height is greater than their wheel radius without extra propulsion mechanism. Legged-wheels have been suggested as an alternative to overcome this weakness of round wheels. A legged-wheel puts its leg on the upper side of an obstacle and rotates on contact with the surface. In this mechanism, the vertical reaction force at the point of contact plays a crucial role in stopping the leg from slipping. The magnitude of it, however, changes while the wheel is rotating. An insufficient vertical reaction force results in the leg slipping, which makes it impossible for the robot to climb the obstacle even when the leg is in contact with the uppermost surface. In this paper, we adopted the foot mechanism to gradually increase the vertical reaction force at the contact point even when the leg slips. The foot mechanism maximizes the advantages of a legged-wheel so that it can climb any obstacle as long as it can put one of its feet on the top of the obstacle.