Free gait for quadruped robots with posture control

A quadruped robot is able to walk on discontinuous irregular terrain as steps. The walking robot, furthermore, can change its posture during walking. This is valid for passing under overhead obstacles and through narrow passage with reducing lateral foot breadth. These abilities are more useful for motion in 3D complex environment than weeled robots or crawlers. On the contrary, the robot has some problems, that is, unstability and limited workspace. Although a lot gait patterns for quadruped robots have been proposed in order to improve these problems, most of them were generated by periodic swing pattern, called periodic gait. However, it is difficult for the gaits to achieve rapid trajectory change due to the problems. Recently, gaits with aperiodic swing patterns, called free gait, are proposed for high mobility and flexibility. However, these gait patterns control to keep level without the posture changing ability. Consequently, we propose a new free gait pattern, which adopts parallel processing of body and leg motion planning, in order to improve the robot problems and enhance the posture changing ability. Furthermore, the posture planing achieves autonomous body conditional compensation because the body motion can be planed without concern of legs condition. In this paper, we experiment the robot operation on unknown irregular terrain with automatic body posture compensation by the proposed gait.