Design and Kinematic Analysis of Co-Exoskeleton with Passive Translational Joints for Upper-Limb Rehabilitation

Abstract

A key approach for reducing motor impairment and regaining independence after spinal cord injuries or strokes is frequent and repetitive functional training. A compatible exoskeleton (Co-Exoskeleton) with four passive translational joints is proposed for the upper-limb rehabilitation. There are only three passive translational joints to track and assist movements of the glenohumeral joint (GH), where two joints are installed horizontally at the front section and another one at the connecting interface of the upper arm. This type of configuration can lower the influences of gravities of the exoskeleton device and upper extremity. The kinematic models of GH and the corresponding human–machine system are established using the analytical method. A numerical simulation of the kinematic models is implemented with MATLAB to emphatically analyze the kinematic characteristics of passive joints and the center of Co-Exoskeleton. The translational displacements of passive joints in four elevation planes are obtained during the elevating process. The results of the kinematic analysis show that the passive joints have similar motion characteristics under different elevation planes. Additionally, the position changes of GH in three directions can be tracked and compensated approximately. Co-Exoskeleton has an especially good compensation effect for the vertical movement of GH. The compensation effect and kinematic models are verified by using the elevating experiments. This research provides theoretical and methodological guidance for the ergonomic design and kinematic analysis of the rehabilitation exoskeleton.