Free gaits for quadruped robots over irregular terrain

Although walking machines exhibit many advantages over wheeled or tracked vehicles, legged vehicles have yet to be introduced in real applications because of the primitive development of specific techniques such as gait generation. This article addresses the design, implementation and experimentation of gaits to negotiate uneven terrain with a real machine. The gaits presented are a mixture of free and discontinuous gaits. Discontinuous gaits were selected because of their ground adaptability features and ease of implementation, while free gaits were chosen because they facilitate path tracking. The fusion of these two main gaits plus the addition of extra constraints to avoid leg-transfer deadlocking produced a new free-crab gait, a free-spinning gait and a free-turning gait. Some experiments have been conducted to illustrate the features of these gaits on a real machine.