Kinematic design of a humanoid robotic shoulder complex

We present a mechanical design for a humanoid robotic shoulder complex. The aim of the mechanism is to support the load of the arm and to copy four principal motions of the human shoulder in order to furnish the desired arm mobility and reachability. We utilize a fully parallel mechanism with four driven legs that provide to the movable platform (on which the arm is to be attached) three rotations and one translation. These three rotations represent the shoulder's flexion-extension (about the vertical axis), the shoulder's abduction-adduction (about the anterior-posterior axis), and the shoulder's rotation (about the medial-lateral axis). The fourth degree of freedom is controlled depending on the angles of the first two rotations and represents the shoulder contraction and enlargement along the medial-lateral axis.