A Novel Transformable Leg-Wheel Mechanism

In this paper, a novel transformable leg-wheel mechanism is proposed. It has three active joints, among which the hip roll joint is directly driven, the hip pitch joint is driven by gear transmission, and the knee joint is driven by synchronous belt transmission. All the actuators are mounted on the body to reduce the weight of the leg-wheel mechanism as possible, so that the motion of the leg-wheel mechanism will be slightly affected by the inertia. The proposed mechanism has two characteristics, the big wheel radius and the reduced actuator. The design and kinematics modeling methods of the leg-wheel mechanism are described. A half-a-heart shape trajectory is proposed to plan the foot motion of the leg-wheel mechanism in the legged locomotion. To make the locomotion mode transition smooth, the transition strategy is designed. Simulation and experimental results verify the feasibility of the proposed leg-wheel mechanism.