This article is part of a series on Robotic Lower Limb Exoskeletons, edited by Dr Ferris.

Research

A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop

Robin Chin¹ , Elizabeth T Hsiao-Wecksler¹ , Eric Loth² , Géza Kogler³ , Scott D Manwaring¹ , Serena N Tyson¹ , K Alex Shorter¹ and Joel N Gilmer¹

¹  Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA

²  Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, Illinois 61801, USA

³  Clinical Biomechanics Laboratory, School of Applied Physiology, Georgia Institute of Technology, 281 Ferst Drive, Atlanta, Georgia 30332, USA

author email corresponding author email

Journal of NeuroEngineering and Rehabilitation 2009, 6:19doi:10.1186/1743-0003-6-19

Published:	16 June 2009

Abstract

Background

A self-contained, self-controlled, pneumatic power harvesting ankle-foot orthosis (PhAFO) to manage foot-drop was developed and tested. Foot-drop is due to a disruption of the motor control pathway and may occur in numerous pathologies such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The objectives for the prototype PhAFO are to provide toe clearance during swing, permit free ankle motion during stance, and harvest the needed power with an underfoot bellow pump pressurized during the stance phase of walking.

Methods

The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.

Results

Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.

Conclusion

This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.