A Sagittal Planar Ankle–Foot Prosthesis With Powered Plantarflexion and Socket Alignment

Powered ankle–foot prostheses can often reduce the energy cost of walking by assisting with push-off. However, focus on providing mechanical work may lead to exacerbating common issues with chronic pain in persons with amputation. This article presents the design and validation of a novel ankle–foot prosthesis informed by predictive simulations of gait which minimize muscle effort and socket loading. The device was designed with an anterior– posterior translation degree of freedom to control the alignment of the prosthetic foot with the residual limb. The system is both mobile and tethered, with batteries, actuators, and electronics located in a small backpack. We measured torque and force sensing accuracy, open-loop actuator performance, closed-loop control bandwidth, and tracking error during walking. The system can produce up to 160 N·m of plantarflexion torque and 394 N of AP translation force with a closed-loop control bandwidth of about 7 Hz in both degrees of freedom. Torque tracking during walking was accurate within about 10 N·m but position tracking was affected by phase lag, possibly due to cable slack. The prototype replicated simulated prosthesis dynamics during gait and offers insights into the practical considerations of using predictive biomechanical simulation as a design tool for wearable robots.