A Soft Wearable Robotic Ankle-Foot-Orthosis for Post-Stroke Patients

Abstract

We propose a soft robotic ankle-foot-orthosis for poststroke patients, which is inexpensive, lightweight, easy to wear, and capable of gait assistance for rehabilitation not only in the clinic but also in daily life. The device includes a 3D-printed flexible brace and an ankle support that allows natural flexion and extension of the ankle but provides support in the vertical direction preventing the structure from buckling. A bi-directional tendon-driven actuator was used for assisting both dorsiflexion and plantarflexion. The device also contains a wearable gait sensing module for measuring the leg trajectory and the foot pressures in real time for feedback control. Since the device is powered by a rechargeable battery and communicates with the main controller wirelessly, it is fully untethered, making it mobile and comfortable. Using the measured sensor data and the biomechanics of the legs, the realtime gait phase is detected, and then a gait assistance algorithm for both dorsiflexion and plantarflexion provides an accurate prediction of a control phase and timing although there are variations in the gait trajectories among individuals. As a feasibility test, the walking experiment was conducted with a post-stroke patient. The result showed improvement in both gait propulsion and foot-drop prevention.