Preprint Article Version 2 Preserved in Portico This version is not peer-reviewed

Design, Characterization, and Preliminary Assessment of a Two-Degree-of-Freedom Powered Ankle-Foot Prosthesis

Tsung-Han Hsieh
ORCID logo ,
Hyungeun Song
,
Tony Shu
,
Junqing Qiao
,
Seong Ho Yeon
,
Matthew Carney
,
Luke Mooney
,
Jean-François Duval
,
Hugh Herr
*
Version 1 : Received: 31 December 2023 / Approved: 2 January 2024 / Online: 2 January 2024 (09:34:30 CET)
Version 2 : Received: 22 January 2024 / Approved: 23 January 2024 / Online: 23 January 2024 (15:18:30 CET)

A peer-reviewed article of this Preprint also exists.

Hsieh, T.-H.; Song, H.; Shu, T.; Qiao, J.; Yeon, S.H.; Carney, M.; Mooney, L.; Duval, J.-F.; Herr, H. Design, Characterization, and Preliminary Assessment of a Two-Degree-of-Freedom Powered Ankle–Foot Prosthesis. Biomimetics 2024, 9, 76. Hsieh, T.-H.; Song, H.; Shu, T.; Qiao, J.; Yeon, S.H.; Carney, M.; Mooney, L.; Duval, J.-F.; Herr, H. Design, Characterization, and Preliminary Assessment of a Two-Degree-of-Freedom Powered Ankle–Foot Prosthesis. Biomimetics 2024, 9, 76.

Abstract

Powered ankle prostheses have been proven to improve the walking economy of people with transtibial amputation. All commercial powered ankle prostheses that are currently available can only perform one-degree-of-freedom motion in a limited range. However, studies have shown that the frontal plane motion during ambulation is associated with balancing. In addition, as more advanced neural interfaces have become available for people with amputation, it is possible to fully recover ankle function by combining neural signals and a robotic ankle. Accordingly, there is a need for a powered ankle prosthesis that can have active control on not only plantarflexion and dorsiflexion but also eversion and inversion. We designed, built, and evaluated a two-degree-of-freedom (2-DoF) powered ankle-foot prosthesis that is untethered and can support level-ground walking. Benchtop tests were conducted to characterize the dynamics of the system. Walking trials were performed with a 77 kg subject that has unilateral transtibial amputation to evaluate system performance under realistic conditions. Benchtop tests demonstrated a step response rise time of less than 50 milliseconds for a torque of 40 N·m on each actuator. The closed-loop torque bandwidth of the actuator is 9.74 Hz. Walking trials demonstrated torque tracking errors (root mean square) of less than 7 N·m. These results suggested that the device can perform adequate torque control and support level-ground walking. This prosthesis can serve as a platform for studying biomechanics related to balance and has the possibility of further recovering the biological function of the ankle-subtalar-foot complex beyond the existing powered ankles.

Keywords

Powered Ankle Prostheses; Two-Degree-of-Freedom; Subtalar joint; Transtibial Amputation; Eversion and Inversion; Level-Ground Walking; Frontal Plane Motion; Torque Control

Subject

Engineering, Mechanical Engineering

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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