Robust Pseudo Virtual Passive Dynamic Walking with Quasi-constraint on Impact Posture

This paper proposes a simplified method of underactuated virtual passive dynamic walking without having any singularities, which is termed as the pseudo virtual passive dynamic walking, and analyzes its properties considering quasi-constraint on the impact posture. First, we introduce a planar underactuated biped model with an upper body and formulate the simplified method based on the concept of pseudo center of mass. Second, we numerically investigate the effect of quasi-constraint on the gait stability. The simulation results show that falling down as a one-link rigid body dramatically increases the stable domain even though the hip angle at impact is not precisely kept constant. Finally, we discuss the mechanism from the energy-loss coefficient point of view.