Design and Swing Control of a Power-Assisted Hip Disarticulation Prosthesis

Hip disarticulation prostheses (HDPs) are developed to restore walking ability in individuals with the most severe lower limb amputations. Although existing powered HDPs aim to replicate hip kinematics by providing positive work, they are often bulky, energy-inefficient, and hampered by poorly adapted control algorithms, rendering them impractical for amputees’ daily activities. This article presents an innovative power-assisted HDP (PA-HDP) that provides lower weight, better compliance, and intuitive adaptive control properties than existing powered HDPs. First, the prosthetic hip is designed with a remote center of motion mechanism that restores the center of rotation of the hip. The prosthetic actuator utilizes a quasi-direct-drive motor with low impedance to provide assistance and is combined in series with a variable stiffness actuator based on dual torsion springs to provide compliant assistance to the user. A swing-assist controller was developed, utilizing amputee-driven stance characteristics as inputs to generate swing phase assist torque matched to both temporal and spatial parameters of speed and stride length. This approach helps hip disarticulation amputees (HDAs) who lack available residual limb control signals to intuitively adjust the assist torque of the prosthesis to accommodate different speeds/step lengths. Experimental evaluation involving two HDAs demonstrated the PA-HDP’s capability to provide adaptive assist torque across different walking speeds (1.2, 1.6, and 2.0 km/h) and stride lengths (small stride, preferred stride, and large stride), with peak power consumption remaining below 35 W. These findings underscore the PA-HDP’s potential to significantly improve walking efficiency and mobility through its power-assisted design.