Design of a novel variable stiffness active ankle foot orthosis using permanent magnets for drop foot assistance

In this paper, we present the design of a novel variable stiffness ankle-foot orthosis for correcting the drop-foot condition. The proposed mechanism controls the position of permanent magnets to provide torque and stiffness assistance to the patients suffering from drop foot. A publicly available gait dataset of 20 healthy individuals is used to extract the stiffness and torque requirements of a gait cycle and the information is used to evaluate the foot orthosis. It is shown that the proposed foot orthosis can provide appropriate torque and stiffness assistance to the ankle joint during the swing and the stance phase respectively. Moreover, the spring-like nature of the repelling magnets reduces the impact forces on the patient’s joints.