Design and characterization of a quasi-passive pneumatic foot-ankle prosthesis

Jeffrey D. Lee, Luke M. Mooney, Elliott J. Rouse*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The majority of commercially available passive prosthetic feet are not capable of providing joint mechanics that match that of the intact human ankle. Due to their cantilever design, their stiffness characteristics contrast with what has been observed in the biological ankle, namely, an increase in stiffness during the stance phase of walking. In this paper, we introduce the design and control of a pneumatic foot-ankle prosthesis that attempts to provide biomimetic mechanics. The prosthesis is comprised of a pneumatic cylinder in series with a fiberglass leaf spring, and a solenoid valve to control the flow of air between the two sides of the cylinder. The solenoid valve acts as a mechanical clutch, enabling resetting of the ankle's equilibrium position. By adjusting the pressure inside the cylinder, the prosthesis can be customized to provide a range of ankle mechanics. A mechanical testing machine is used to compare the torque-angle curve of the pneumatic prosthesis with a low-profile passive prosthetic foot. Finally, data are presented of one transtibial amputee walking with the prosthesis at 1.2 m/s. The testing shows that the pneumatic prosthesis is capable of providing an appropriate range of motion as well a maximum torque of 94 Nm, while returning approximately 11.5 J of energy.

Original languageEnglish (US)
Article number7914781
Pages (from-to)823-831
Number of pages9
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number7
StatePublished - Jul 2017


  • Amputation
  • Ankle prosthesis
  • Prosthetic feet
  • Quasi-stiffness
  • Transtibial amputee

ASJC Scopus subject areas

  • Rehabilitation
  • General Neuroscience
  • Internal Medicine
  • Biomedical Engineering


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