An Ankle Foot Orthosis (AFO) with Energy Recycling Mechanism to Prevent Foot Drop

Ankle foot orthoses (AFOs) can accommodate people to prevent foot drops, a typical sequela of nervous system damage. Unpowered AFOs and powered AFOs could be considered two categories of existing AFOs. Compared with unpowered AFOs, powered AFOs can provide auxiliary ankle torque using electrical motors or fluid-driven actuators. Although they could help affected people relearn the ankle function to walk better, a fast reaction rate and high instantaneous power at the toe-off state are required, resulting in heavy weight and low efficiency. In this paper, we present a novel lightweight unpowered AFO that can recycle the work done by gravity and burst torque in dorsiflexion motion at toe-off to achieve foot clearance. The energy recycling efficiency was calculated and compared among different energy recycling pad designs. The results show that the energy recycling efficiency of our system could be up to 39.46%. The total weight of the AFO is 349 grams. We believe that our device has the potential to apply to people affected by foot drops and help them to rebuild motor functions.