A Compact Elbow Exosuit Driven by Pneumatic Artificial Muscles

This letter presents a pneumatic artificial muscle-based elbow exosuit designed for driving and assisting the elbow joint. By combining the bionic attachment method inspired by the brachioradialis muscle and the pennation architecture of the artificial muscle, the elbow exosuit achieves high output torque while maintaining a slim profile of only 10 mm thickness. To guide the design process, the letter utilizes the force balance condition of infinitesimal parts of the artificial muscle fiber and the virtual work principle to calculate the path change of the muscle wrapped around the arm surface. This approach helps determine key parameters and obtain the theoretical assisting torque. To validate the model, a test bench is constructed to measure the relationship between assisting torque and flexion angle, demonstrating the accuracy of the theoretical calculations. Furthermore, a bionic elbow joint is built to verify the driving ability of the exosuit. Preliminary human feasibility test is conducted, and users report no discomfort. The results indicate a 37.5% decrease in muscle effort in the bicep brachii when lifting a 4 kg weight and a 30.5% decrease during the holding task. A stroke survivor successfully bends the arm and raises his hand to the mouth while wearing the exosuit. These findings demonstrate the feasibility in driving and providing assistance to the user and significant potential for assisting individuals in their daily lives.