An ergonomic shoulder for robot-aided rehabilitation with hybrid control

Over the past years, robot-aided rehabilitation has gained traction to regain lost mobility in upper limb due to stroke. In most cases, rehabilitative robotic devices have not considered movement of shoulder joint center (center of glenohumeral joint); however, this movement leads to misalignment of human joints with robot joints, which is undesirable in any circumstances. In this research, a 2 degrees of freedom (DOF) ergonomic robotic shoulder, namely RDS-2, was developed to realize full range of motion (ROM) for abduction/adduction and vertical flexion/extension. Two mechanisms, which were designed in our previous research, have been included to realize shoulder elevation/depression and shoulder protraction/retraction during shoulder movement. To control the exoskeleton, a simple hybrid non-liner control approach based on model robot’s dynamic model and its tracking error was developed. The stability of the controller was proved by Lyapunov stability. Experiments were done with slow, medium and fast pre-determined trajectories to see the efficacy of the used controller. The results show stability and robustness of used control approach for developed ergonomic shoulder.