A Lightweight Robotic Lower-Limb Prosthesis With Unified Knee and Ankle Actuators

Abstract Recent advancements in robotic (powered) lower-limb prostheses have significantly improved joint function for amputees, enabling them to perform a range of energetically demanding daily activities that exceed the capabilities of passive prostheses. While robotic knee and ankle prostheses share the common goal of restoring joint function, they are typically treated as standalone devices with little commonality. This paper presents a unified design framework for both the prosthetic knee and ankle actuators, namely, Common Core Components Knee–Ankle Prosthesis (C3KAP). While enabling the use of a common set of core components and device structure, the C3KAP also incorporates sufficient flexibility in the transmission design for joint-specific customization. Through its lightweight design, the C3KAP prototype is only about 1.4 kg in weight but provides a peak torque of 80 N·m to support user locomotion. Through benchtop testing, the prototype has shown high back-drivability (back drive torque of 2.27 N·m) and large control bandwidth (20.7 Hz in 10 deg sinusoidal tracking). Human testing further validated the effectiveness and functionality of the C3KAP, demonstrated by the participant's natural walking gait, the prosthesis's well-coordinated movement with the sound leg, as well as the prosthesis motion's close match to the able-bodied (AB) biomechanics.