Safe 3D Bipedal Walking through Linear MPC with 3D Capturability

Adrien Pajon (1) , Pierre-Brice Wieber (1)

1 Inria Grenoble - Rhône-Alpes

We propose a linear MPC scheme for online computation of reactive walking motions, necessary for fast interactions such as physical collaboration with humans or collision avoidance in crowds. Unlike other existing schemes, it provides fully adaptable height, adaptable step placement and complete kinematic and dynamic feasibility guarantees, making it possible to walk perfectly safely on a piecewise horizontal ground such as stairs. A linear formulation is proposed, based on efficiently bounding the nonlinear term introduced by vertical motion, considering two linear constraints instead of one nonlinear constraint. Balance and Passive Safety guarantees are secured by enforcing a 3D capturability constraint. Based on a comparison between CoM and CoP trajectories involving exponentials instead of polynomials, this capturability constraint involves a CoM motion stopping along a segment of line, always maintaining complete kinematic and dynamic feasibility.

Domaines: Robotique [cs.RO]; Automatique / Robotique; Systèmes et contrôle [cs.SY]; Optimisation et contrôle [math.OC]

Adrien Pajon, Pierre-Brice Wieber. Safe 3D Bipedal Walking through Linear MPC with 3D Capturability. ICRA 2019 - International Conference on Robotics and Automation, May 2019, Montréal, Canada. pp.1404-1409, ⟨10.1109/ICRA.2019.8794117⟩. ⟨hal-02177530⟩