Torque amplification using a cable driven multi-pulley mechanism for ankle foot orthosis

Neuromuscular diseases, such as stroke, often causes ankle joint impairment making daily life activities difficult. The inability to create plantar flexion and dorsiflexion at the ankle joint results in an abnormal gait. To support ankle joint movements during gait, different types of an ankle-foot orthosis (AFO) are extensively used in rehabilitation programs. In the present article, a powered cable-driven AFO utilizing multiple pulley arrangements is presented. The novelty of the presented AFO design is the inclusion of a multi-pulley mechanism (MPM) that can be used for torque amplification at the ankle joint allowing the stakeholders to use low-power BLDC motors for actuation. The presented design also allows for bidirectional joint actuation, reducing the number of motor units required to actuate the ankle-foot orthosis. The current article discusses the design of MPM AFO. Further, a benchtop experiment is presented to test the dynamic and step response of the MPM AFO.