Passivity-based full-body force control for humanoids and application to dynamic balancing and locomotion

This paper proposes a passivity-based hierarchical full-body motion controller for force-controllable multi-DOF humanoid robots. The task-space forces are treated in a uniform manner for a variety of position/force tracking and force/moment compensation. The contact force closure is optimally solved and transformed directly into the joint torques in real-time without any joint trajectory planning. With this framework, we introduce gravity compensation at the lowest layer of the controller that makes the closed-loop system passive with respect to additional inputs as well as external forces. Furthermore, we propose two upper-layers: one layer controls the ground reaction forces, which enables the robot keep the dynamic balance. The other layer is the another passification control, which constructs an invariant manifold that prevents the robot from falling during walking. Four realistic dynamic simulations: balanced squatting, reaching, externally driven, or speed-controlled walking with disturbances demonstrate the effectiveness of the proposed methods.