DEVELOPMENT OF AN EXOSUIT FOR REHABILITATIVE USE AND UPPER ARM FORCE AMPLIFICATION

Introduction: In recent years, amplifying and rehabilitating arm performance with the use of an exosuit to provide lifting ability has been achieved through traditional robotics, though they lack the ability to remain compact and maneuverable while in use. Despite these advancements, traditional robotics has led to increased weight, immobility, and power consumption, thus decreasing usability. In response, our research addresses the issue using soft robotics by implementing passive aid through providing gravity assist to the arm. In an effort to test the effectiveness of a soft robotic exosuit, we have investigated its use in shoulder rehabilitation as well as arm strength amplification by testing the weighted range of motion in relation to muscle fatigue and strain. Methodology: The main focal points for the testing methods include the shoulder and bicep muscles as well as the overall fatigue and strain of the user. Our method of gravity assist, designated Passive Exosuit, provides mitigation of force away from the shoulder or bicep by use of polymer networks integrated into fabric that allows for weightless shoulder and bicep flexion by the user, leading to greater arm mobility without pain. In order to test this gravity assist force mitigation, we developed a test that allows for frequent use of the arm under lifting conditions of 5 to 25 lbs through a range of 60 to 90 degree movements from resting state to lifting state. The stopping point of lifting was designated by comparison of the apparent effort that was exerted by the user, as asserted through electromyographic (EMG) sensors, in relation to user reported effort. These EMG sensors read the potential difference across a given muscle and are monotonic with the flexion that the muscle is undergoing. Through the use of EMG sensors and user reported effort, a relation of fatigue and muscle strain can be accomplished that demonstrated user ability to lift approximately 15 lbs excess through the 60 degree range of motion with little to no fatigue or strain. Results: Similar to a fitted jacket, the soft robotic Passive Exosuit was found to assist users by providing a 35–60 degree increase in shoulder flexion range of motion under loads up to 15lbs, with negligible user effort exerted and including the suit weight of ~5lbs. These values of lifting capability exceed current modes of shoulder and bicep rehabilitation as well as upper arm force amplification among models of comparable weight. Conclusion: The Passive Exosuit, as a usable method of upper arm rehabilitation, decreases the size and mobility that other rehabilitation efforts have sought to accomplish while still maintaining a reasonable range of lifting aid that is capable of reducing pain during arm rehabilitation. Practical application for the device can be utilized in rehabilitation, where gravity assist can be conducted without large power or space requirements, or military use, where high mobility is vital to survival.