Design of the Fixation Mechanism for a Cable-driven Upper-limbExoskeleton Rehabilitation Robot

In order to reduce the kinematic modeling error caused by the structural instability of the cable-driven parallel exoskeleton, improve the adaptability of the exoskeleton to different subjects, and increase the comfortability of the exoskeleton, a new design of fixation mechanism is proposed and applied to the CURE-7 (cable-driven upper-limb rehabilitation exoskeleton with 7-degrees-of-freedom). Firstly, a cable-driven exoskeleton rehabilitation robot with a new fixation mechanism is introduced, which has the advantages of both cable-driven device and parallel mechanism. Then the underactuated fixation module and flexible elbow joint of the fixation mechanism are designed, a kinematic model is developed for the exoskeleton, and the influences of the key parameters are studied. Finally, a prototype of the fixation mechanism is developed and installed on the exoskeleton, with which the trajectory tracking experiment and the fixation stress experiment on healthy subjects are carried out to prove the effectiveness of the fixation mechanism. Experimental results show that the average standard error of the elbow joint flexion trajectory tracking decreases by about 41%, the average standard error of shoulder joint abductor trajectory tracking decreases by about 30%, the maximum fixation stress decreases by about 23%, and the variances of stress in different positions are also greatly reduced, by using the new fixation mechanism.