Upper limb exoskeleton supporting exercise for improving range of motion of human joints

Abstract

Individuals with strokes or musculoskeletal conditions often experience a restricted shoulder range of motion, necessitating rehabilitation that is generally time-consuming, and due to high therapist workloads, patients often need to perform the exercises independently to complete their program. To address this, robotic exoskeletons offer a promising solution by guiding and supporting patients, ensuring accurate exercise execution, and potentially accelerating recovery. This research aimed to design and build an upper-limb exoskeleton prototype with two active revolute joints at the shoulder and elbow, and passive link length adjustments, characterize its system parameters, and develop a control system to support range of motion exercises. Furthermore, the study explored the influence of external joint torque on human muscle activity and evaluated the exoskeleton's assistive performance on healthy volunteers during active assistive exercises. A lightweight exoskeleton prototype was successfully developed, and a five-bar mechanism was adopted to minimize inertia. System characteristics were determined, and two operational modes, which are constant torque and gravity compensation, were implemented. Human-robot interaction experiments with healthy participants showed consistent muscle activity trends relative to joint angle and revealed the effectiveness of gravity compensation in reducing muscle activity in most motion.