Harnessing Energy of a Treadmill for Push-Off Assistance During Walking: a Proof of Concept study

Various approaches in ankle exoskeleton design and control have recently been proposed and implemented, but few have been able to produce devices suitable for rehabilitation in clinical environment. In a recent in-silico study, we proposed a novel device: Ankle Exoskeleton using Treadmill Actuation for Push-off assistance (AN-EXTRA-Push). Using a brake and an elastic tendon, it harnesses energy of a moving treadmill during stance phase, then releases it during push-off to aid with plantarflexion torque generation. Simulation studies suggest inherent synchrony between the body's own efforts and ANEXTRA-Push assistance, allowing for intuitive use and simple control of the device. In this contribution we describe a mock-up device and the findings of a proof of concept study. Kinematics, ground reaction forces, interaction forces and EMG signals were measured for one subject walking with AN-EXTRA-Push with different levels of assistance. Using AN-EXTRA-Push did not result in substantial changes in the subject's kinematics and the activity of ankle plantarflexor muscles was successfully reduced. Preliminary results suggest that the concept is promising and appear to confirm the conclusions drawn from our previous simulation study.