Adaptive Gait for Large Rough Terrain of a Leg-Wheel Robot (Third Report: Step-Down Gait)

A leg-wheel robot with four mechanically separated legs and two wheels is highly mobile and stable on rough terrain. We discuss the strategy for the robot movement over large rough terrain, classifying topographical features into 13 patterns of combined terrain surface. To traverse all classified terrain, we propose three adaptive gaits: (1) Step-up gait in which frontfoot landing is higher than contact with the wheel ground, and the robot raises itself toward frontfoot landing; (2) Step-down gait in which frontfoot landing is lower than contact with the wheel ground, and the robot lowers itself toward frontfoot landing; and (3) Step-over gait in which frontfoot landing is no higher than contact with the wheel ground, but the robot raises itself as high as possible.1