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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.

Legged robots are expected to walk on irregular terrain with their high ground adaptability. Working in irregular environments, the robot is required to keep safe, that is, it is necessary to consider the terrain. This ability is difficult to be installed to the robots due to not enough intelligence and experience. Here, we focus that human can guess and estimate the safety foot position with global environmental recognition and prediction. We propose leg selectable interface for walking robots on irregular terrain. This time, we introduced this system into a quadruped robot. Proposed interface employ four fixed cameras above each foot to show the ground condition of around foot. The operator selects the object (each leg or main body) with the touch panel, and operates its position with the joystick. Our interface displayed a lot of information as robot condition. Additionally, to improve the stability of the robot, we install the two kinds of corrections, one is correction by robot's center of gravity and another is correction by leg angle. We verify the effect of above compensation with an experiment by a real machine. As a result, it was possible to walk by avoiding the obstacle, the robot was able to be stabilized by the correction.

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