An attractor-based Whole-Body Motion Control (WBMC) system for humanoid robots

This paper presents a novel whole-body torque-control concept for humanoid walking robots. The presented Whole-Body Motion Control (WBMC) system combines several unique concepts. First, a computationally efficient gravity compensation algorithm for floating-base systems is derived. Second, a novel balancing approach is proposed, which exploits a set of fundamental physical principles from rigid multi-body dynamics, such as the overall linear and angular momentum, and a minimum effort formulation. Third, a set of attractors is used to implement both balance and movement features such as to avoid joint limits or to create end-effector movements. Superposing several of these attractors allows to generate complex whole-body movements to perform different tasks simultaneously. The modular structure of the proposed control system easily allows extensions. The presented concepts have been validated both in simulations, and on the 29-dofs compliant torque-controlled humanoid robot COMAN. The WBMC has proven robust to the unavoidable model errors.