Mechanical system and stable gait transformation of a leg-wheel hybrid transformable robot

This paper proposes a novel and mechanically decoupled leg and wheel hybrid transformable robot called HyTRo-I that combines the fast speed of wheeled vehicles on a flat ground and the high degree of flexibility of legged robots over irregular terrains. According to different terrain conditions, HyTRo-I can choose from three motion modes: wheeled rolling, quadrupedal walking mode and leg-wheel hybrid mode. By shifting among these moving patterns, the mobility of HyTRo-I over various surface conditions can be fully realized. While the control technology of actuating the wheeled vehicles is mature and simple, the control of quadruped walking is an area of active research. Therefore, we develop a statically stable gait controller for our robot. In addition, we study the locomotion mechanism of transformation that concerns the feasibility of three moving methods of HyTRo-I. By the mutual transformation gaits illustrated in details, HyTRo-I can be smoothly and reciprocally transformed between wheeled rolling mode and quadrupedal walking mode. Finally, we experimentally test the mode transformations of HyTRo-I.