An Innovative Upper Limb Rehabilitation Mechanism and Its Optimal Design

This paper presents a hybrid $\mathbf{3}+\mathbf{2}$ DOFs shoulder-elbow rehabilitation mechanism, with a primary focus on optimizing the dimensions of the 3-UPS/S parallel mechanism in the shoulder joint. An innovative hybrid mechanism configuration is established, and the screw theory is employed to analyze the motion characteristics of the 3-UPS/S shoulder parallel mechanism. To quantify its performance, three key indices are applied to measure the workspace volume, the global dynamic manipulability, and the global stiffness performance. Using such indices as objective functions, the SPEA2 multi-objective optimal algorithm is applied for dimensional optimization. Furthermore, the Analytic Hierarchy Process is also employed to identify optimal solutions to balance dynamic and static performance preferences.