BME.17 – ExoNET Lower Extremity Model

• Maria Gamez
• Brenden Holmes
• Matthew Kennedy
• Daniel Park
• Lizzie Zeller

The ExoNET (Exoskeletal System for Elastic Torque) is a proprietary gait assistance technology developed by the Shirley Ryan AbilityLab. The ExoNET system is a network made of diagonal tension elements that simulate the torques created by the muscles about joints. The system can be worn on the upper or lower extremities, with elastic bungee cords connecting the joints of the user via moment arms. For example, if the system were worn on the leg, there would be bungee cords attached from the hip to the knee, the hip to the ankle, and the knee to the ankle of the user. This is done in order to assist the gait of the user, as simple spring assisted gait has been found to reduce the amount of energy exerted by the user. While this technology is still in development, the engineers lack a physical model as well as a proof of concept of the lower extremity ExoNET. This physical model can be used for further development as well as demonstrate the technology to lab visitors. This project approximates the effect of ExoNET at the lower extremity on a mannequin leg simulating the gait cycle. Our model consists of a lower extremity mannequin with ExoNET components (moment arms/cables) and motors at the hip and knee. Inelastic cables were used to connect the joints to the moment arms of our model, which allow the motors to generate torque about the moment arms resulting in movement of the leg. Our verification testing plans include ensuring our model can achieve 1 gait cycle/second (1 Hz) and can operate continuously for 2 hours without intervention in a lab setting. This project has the potential to help gait impaired people by providing a workable base for the lab to further develop and demonstrate the ExoNET system.