Contact phase invariant control for humanoid robot based on variable impedant inverted pendulum model

Being expected as the utilities in the future, humanoid robots should be given much higher mobility. A seamless transition between contact and aerial phase is essential to behave robustly against disturbance in the real environment, and to expand the range of their activities and perform a variety of motion. Manipulation of both the contact condition and the external force is the key issue to enhance the mobility of humanoids since they are driven by the external force converted from the inner force through the interaction with the environment. The difficulty lies on the complexity of their dynamics so that they consist of number of degrees of freedom and their structures vary in accordance with contact phase transition. We propose variable impedant inverted pendulum (VIIP) model control, which allows one to handle the external force rather easily. The advantage of the proposed is that it is invariant on contact phase so that both cases in contact and in aerial are treated in the unified way. It also reduces the amount of computation. Thus, quick responsive motion of the robot can be practically achieved. We verified the effect of the controller in computer simulation, using a small humanoid robot model.