Design of a hydraulic ankle-foot orthosis

This paper presents the design and simulation of an ankle-foot orthosis (AFO) to assist human walking. Design requirements were established based on a quantitative study of published data, simulations of human walking, and a model of intrinsic and reflex ankle joint stiffness. The design of an AFO that meets these requirements is then presented; it comprises a small linear, hydraulic actuator, a servo-valve, a hydraulic power supply, and an accumulator. Two methods of selecting the kinematic parameters of the AFO are introduced. One is based on force minimization and the other on compactness maximization. The performance expected of the AFO is demonstrated in a simulation study.