Up-Care: an Upper Limb Portable Cable Assistive Recovery Exoskeleton for Elbow Movement Assistance

Each year, many stroke survivors experience upper limb paralysis, negatively affecting their ability to perform activities of daily living. Powered assistive exoskeletons can help restore these abilities, promoting independence and improving their quality of life. While upper limb assistive devices show promise, challenges still remain in developing a lightweight and portable system for broad patient use. This paper presents the Upper limb Portable Cable Assistive Recovery Exoskeleton (UPCARE) a lightweight, portable robotic exoskeleton designed to assist elbow movement. UP-CARE features a brushless DC motor whose torque is amplified through a two stage planetary gearbox and dual-pulley cable system made with high strength additive manufacturing materials. By leveraging 3D printing, the actuator design achieved a 52 % weight reduction as compared to conventional off-the-shelf gear transmissions, while promoting design modularity and an increase in accessibility. UP-CARE has a total mass of 4.75 kg, with only 0.62 kg resting directly on the user's arm. Its high torque to weight ratio makes it suitable for portable assistive rehabilitation. Preliminary subject testing demonstrated accurate elbow position tracking up to 90°, while producing an average elbow joint torque of 18.9 Nm. The performance indicate that UP-CARE can support the assistive needs of elbow flexion/extension, helping stroke survivors regain independent living.