Toward A Soft Robotic Ankle-Foot Orthosis (SR-AFO) Exosuit for Human Locomotion: Preliminary Results in Late Stance Plantarflexion Assistance

Abstract

This paper presents the design of a soft robotic ankle-foot orthosis (SR-AFO) exosuit to aid in plantarflexion for gait rehabilitation in individuals who suffer from irregular gaits due to stroke or other injuries. The SR-AFO exosuit is a sock-like garment fabricated from compliant fabrics. The SR-AFO exosuit aids in late stance of the walking gait in plantarflexion by contracting the actuator to pull the posterior end of the foot upward. This helps to reduce the muscle effort of the user during plantarflexion. The addition of a second actuator shows a 45.3% increase to 13.51 ± 0.31 kg payload capacity. The actuators are oriented at an optimal angle of 5° to produce the highest pulling force. Three healthy participants are evaluated during walking trials with and without SR-AFO exosuit assistance while ankle angle and muscle activity are monitored. The gastrocnemius (GA) and soleus (SOL) muscle activity during late stance is reduced by 13.4% and 16.6% respectively. Tibialis anterior (TA) increases slightly during swing most likely due to the hysteresis in the system deflating during that window. The ankle range of motion remains within natural walking limitations and plantarflexion angle increases when the SR-AFO exosuit is active.