The Control of a Bipedal Running Robot based on Output Zeroing considered Rotation of the Ankle Joint

For the bipedal robot, this paper investigates natural running motion like human running, without performing tracking control to the optimal trajectory of such a motion. The bipedal robot considered in this paper is planar and has revolute joints which actuate ankle, knee and hip. The running motion is assumed to consist of two successive phases which are composed of a flight phase and a stance phase: the flight phase where the bipedal robot floats, the stance phase where either a heel or a toe keeps contact with the ground. In order to realize the natural motion of the human, an output function which is easily understood in the physical aspect is designed on the basis of the human actual motion. Running motion of bipedal robot is generated autonomously by zero dynamics which appears by zeroing output function. Some parameters of this output function are re-configured online in order to suppress disturbance caused by unstable zero dynamics. Through a numerical simulation it is confirmed that running motion becomes stable