On Design of an Ankle Prosthesis with a Series and Parallel Elastic Actuator for Sagittal Movement and a Passive Inversion-Eversion Joint

Series and Parallel Elastic Actuators (SPEA) provide manyadvantages in torque control of the prosthesis and reducingthe peak power and energy requirements. In this paper, wedesign the ankle prosthesis with one passive joint for ankleinversion and eversion movement and one active joint fordorsiflexion and plantarflexion of the ankle by employingthe SPEA. Design parameters such as length of the linksand stiffness of springs are selected optimally to minimizethe error between the human intact leg and designedprosthesis torque-angle curve of the ankle joint. Thistorque-ankle curve causes the same stiffness of theprosthesis to the human body and subsequently the samewalking gait properties.