Push Recovery by Angular Momentum Control during 3D Bipedal Walking based on Virtual-mass-ellipsoid Inverted Pendulum Model

During walking, humanoid robots may encounter many exogenous disturbances under unknown environments. Enabling humanoid robots to have applicability to resisting such disturbances is very important. Therefore, push recovery is an interesting issue attracting many humanoid robot researchers. Previous works based on Linear Inverted Pendulum (LIP) model have limitations because of the limitations of the LIP models. In this paper, we extend the usage of the Virtual-mass-ellipsoid Inverted Pendulum (VIP) model proposed in our previous work to recover orientational push by angular momentum control. Our proposed methods have three main characteristics. Can recover push during walking (not just during standing); Be suitable to 3D uneven terrains; Most significantly, completely remove the constant center of mass (CoM) height (or height on a constant slope) limitation and the constant centroidal angular momentum (CAM) limitation. Simulations using HRP4 have validated the effectiveness of our proposed methods.