A biologically-inspired anthropocentric shoulder joint rehabilitator: workspace analysis & optimization

This paper presents the design of a biologically-inspired anthropocentric 7-DOF wearable robotic arm for the purpose of stroke rehabilitation. The proposed arm rehabilitator utilizes the human arm structure to combine with underdeterministic cable driven parallel mechanisms so as to form completely deterministic structures. It adopts an anthropocentric design concept, thereby offering the advantages of being lightweight, having high dexterity and conforming to the human anatomical structure. This paper mainly focuses on the workspace analysis of the 3-DOF shoulder module, with respect to the shoulder joint motion range. Workspace parameterization is based on a modified Z-Y-Z Euler angles approach and utilizing cylindrical coordinates to determine the workspace volume, while workspace evaluation is carried out based on the shoulder joint motion limits and the cable tension analysis. An effective cable tension analysis method is also proposed based on the duality between force closed multifingered grasping and cable driven mechanisms. Finally, the workspace of the mechanism is optimized to match with that of the human shoulder and to obtain a set of dimensions for the shoulder module prototype development.