Biologically Inspired Design and Development of a Variable Stiffness Powered Ankle-foot Prosthesis

Research output: Contribution to journalArticle

  • Authors:
  • Alexander A. Dobson
  • Guowu Wei
  • Lei Ren


Recent advancements in powered lower limb prostheses have appeased several difficulties faced by lower limb amputees by using a Series-Elastic Actuator (SEA) to provide powered sagittal plane flexion. Unfortunately, these devices are currently unable to provide both powered sagittal plane flexion and 2-DOF at the ankle, removing the ankles capacity to invert/evert, thus severely limiting terrain adaption capabilities and user comfort. The developed 2-DOF ankle system in this paper allows both powered flexion in the sagittal plane and passive rotation in the frontal plane; a SEA emulates the biomechanics of the gastrocnemius and Achilles tendon for flexion, while a novel universal-joint system provides the 2-DOF. Several studies were undertaken to thoroughly characterize the capabilities of the device. Under both level and sloped-ground conditions, ankle torque and kinematic data was obtained by using force-plates and a motion capture system. The device was found to be fully capable of providing powered sagittal plane motion and torque very close to that of a biological ankle, while simultaneously being able to adapt to sloped terrain by undergoing frontal plane motion, thus providing 2-DOF at the ankle. These findings demonstrate that the device presented in this paper poses radical improvements to powered PAFD design.

Bibliographical metadata

Original languageEnglish
JournalJournal of Mechanisms and Robotics
Publication statusAccepted/In press - 13 Apr 2019