Design, simulation and experimental evaluation of a shoulder abduction/adduction exoskeleton for rehabilitation and partial assistance in older adults

Purpose The purpose of this study is to develop an affordable, lightweight, portable and fully wearable exoskeleton for individuals with shoulder impairments, particularly for older adults. The objective is to restore muscle strength and coordination, increasing users’ independence in daily activities and rehabilitation exercises. Design/methodology/approach The shoulder complex abduction/adduction (A/A) exoskeleton is designed for rehabilitation and support in partial assistance. The exoskeleton features five degrees of freedom (DoFs), including one active DoF for A/A and four passive DoFs, enabling natural joint movement and comfortable adaptation to the user’s anatomy. The shoulder glenohumeral joint mechanism is constructed using arc-type linkages forming a common remote center of rotation. A bidirectional cable-driven mechanism facilitates shoulder A/A, with experimental and simulation-based analyses for kinematics and dynamics. The design emphasizes ease of use, portability and wearability, making it suitable for home and outdoor rehabilitation environments without the continuous supervision of a professional. The device is evaluated for range of motion, torque and overall performance. Findings The shoulder exoskeleton achieves 90% ROM required for A/A in daily living activities and demonstrates an accuracy error of less than 4.2 degrees. It provides A/A support with a peak torque of 10 Nm and velocity of 24 deg/sec. Experimental results show the exoskeleton can partially assist shoulder A/A movements, providing approximately 50% assistance, and fully supports the arm within a 40-degree abduction angle. The lightweight design (1.4 kg, excluding the harness and battery) enhances its useability in rehabilitation settings. Originality/value This research introduces an affordable, lightweight and fully wearable shoulder device, combining active A/A assistance with a portable design, addressing the rehabilitation needs of individuals with shoulder impairments.