Conceptual Design of a Powered Ankle-foot Prosthesis for Walking with Inversion and Eversion

Human ankle is a series of joints that are highly integrated [1], , [2], where tolecular joint (permits dorsiflexion-planter flexion) and subtalar joint (permits inversion-eversion) play vital roles.A conceptual design of an ankle joint is presented here to facilitate the terrain adaptability maintaining natural gait patterns and stability for person with single limb transtibial amputation. The design consists of physiological ankle movements during walking on flat surface as well as uneven terrain. The ankle joint (spherical joint) permits planter flexion-dorsiflexion by the control of passive actuators (springs) and active actuator (motor). It further allows movement in the frontal plane inward/outward about an imaginary centre line of body in order to adapt the roughness of surface. The kinematic behavior of the prosthesis is analyzed. Foot portion of the ankle prosthesis are conceptualize as composite structure to minimize ground contact shock. A 3D prototype is created to represent the conceptual design, which successfully demonstrated the ankles rotational motion.