A Portable Passive Ankle-Foot Orthosis for Walking Propulsion and Drop-Foot Prevention

Individuals with a drop-foot generally have issues of foot-slap and toe-drag, and ankle-foot orthoses (AFOs) have been developed for them to address the drop-foot gait. However, the currently available active AFOs usually have heavier mass, larger volume, and additional power sources, and almost all of the passive AFOs can achieve dorsiflexion assistance at the cost of making plantarflexion more difficult, which increases the wearer's metabolic cost of walking. This paper illustrates the development and validation of a passive AFO for walking propulsion and drop-foot prevention of individuals with a drop-foot gait. The AFO is primarily composed of a propulsion module, a drop-foot prevention module, and a support module. The propulsion module can detect the wearer's gait stages, and it can control the energy storage and release of an energy storage spring-A by switching the state of a clutch-A mechanism. The drop-foot prevention module is designed to correct the abnormal gait of individuals with a drop-foot gait during the swing phase. Experiments are conducted to evaluate the performance of the developed AFO. The experimental results demonstrate that during a gait cycle, reductions of 7.74%, 6.72%, and 16.36% of the average muscle activities of the gastrocnemius, soleus, and tibialis anterior are observed, respectively. The significance of this study is the development of a portable passive AFO that has the potential to provide plantarflexion assistance and dorsiflexion assistance for the wearers during the late stance phase and swing phase, respectively.