Design and analysis of shoulder joint exoskeleton rehabilitation mechanism based on gear and rack transmission

Due to insufficient muscle strength, a novel rehabilitation mechanism of the shoulder joint exoskeleton is proposed and analyzed based on gear and rack transmission, which solves the problem that stroke patients need repetitive exercise rehabilitation training. First, the range of motion angle of the shoulder joint is determined, and the mechanical structure of shoulder joint rehabilitation is designed. The arc rack is engaged with the output shaft gear of the reducer, and the servo motor is utilized as the driving force to realize the internal/external rotation movement of the shoulder joint. The motor connects the horizontal connecting rod and the rotating rod through the cross roller bearing to realize the abduction/adduction and flexion/extension movement of the shoulder joint. Second, the kinematics and dynamics of the shoulder joint exoskeleton are analyzed, investigated, and verified for the rehabilitation mechanism. The simulation analysis of the mechanism is completed in the virtual prototype. The changes in the joint angle and end trajectory and joint moment with time and angular velocity under the given working conditions are obtained, which directly reflect the movement of each joint of the rehabilitation mechanism. Finally, aiming at the nonlinear disturbance in the trajectory tracking control of the rehabilitation mechanism of the shoulder joint exoskeleton, the trajectory tracking approach of the mechanism is achieved aided with the closed-loop PD iterative learning control method. The results demonstrate that the actual trajectories are in good agreement with the desired trajectories, which can achieve effective tracking and improve the control quality of the system.