A Compact, Lightweight and Singularity-Free Wrist Joint Mechanism for Humanoid Robots

Building humanoid robots with properties similar to those of humans in terms of strength and agility is a great and unsolved challenge. This work introduces a compact and lightweight wrist joint mechanism that is singularity-free and has large range of motion. The mechanism provides two degrees of freedom (DoF) and was developed for integration into a human scale humanoid robot arm. It is based on a parallel mechanism with rolling contact joint behaviour and remote actuation that facilitates a compact design with low mass and inertia. The mechanism's kinematics along with a solution of the inverse kinematics problem for the specific design, and the manipulability analysis are presented. The first prototype of the proposed mechanism shows the possible integration of actuation, sensing and electronics in small and narrow space. Experimental evaluations shows that the design feature unique performance regarding weight, speed, payload and accuracy.