A Hydraulic Powered Ankle-Foot Prosthesis with Adjustable Nonlinear Stiffness

We propose a powered ankle-foot prosthesis design based on the drive concept of Series Elastic Actuation (SEA). Unlike most existing SEA prostheses, our design is built upon an Electro-Hydrostatic Actuation (EHA) system. By integrating the nonlinear characteristics of the hydraulic accumulator into the SEA, we achieve nonlinear and variable stiffness, enabling the prosthesis to accommodate different locomotion modes. Additionally, we employed metal additive manufacturing to design a compact hydraulic valve block and selected a frameless motor as the power source, enhancing the overall system integration and compactness, particularly in terms of space and component arrangement.