Parametric Excitation of a Biped Robot as an Inverted Pendulum

For stable gait generation on the level floor, restoring mechanical energy lost by heel-strike collision at the ground is necessary. Parametric excitation principle is one of the solutions. Harata et al. applied this principle to a knee actuated robot to achieve parametric excitation by bending and extending the knee, and succeeded in generating a sustainable biped gait by computer simulation. Although only the dynamics of the swing-leg was considered in the method, the stance-leg's dynamics also affects the swing-leg's dynamics. Therefore we considered the whole dynamics of the robot in this paper. Therefore, we dealt with the robot's center of mass as an inverted pendulum and achieved stable gait generation by parametric excitation of the inverted pendulum. The resultant energy efficiency was increased significantly.