Standing Posture Control in Constant Force Field Based on Ground Reaction Force

In this paper, we consider standing posture control of biped system. When standing on a slope, a human adjusts his posture, i.e., ankle joint angles adjust to the gradient of the slope. In this case, the resultant stationary posture is not determined until the slope angle is given to the system. To solve this problem, we propose a new posture control law, where the standing posture is adjusted based on the ground reaction forces in such a way that the entire weight is placed evenly on the feet. This control law consists of PD control and force feedback control, whose stationary posture possesses local stability in adequate feedback gain. By applying this control law to a simple robot system, we examine its e±ciency. In this experiment, we show the robot behavior is adaptive to the slope angle or external force generated by wind.