Research Papers

Design of an Active Ankle-Foot Prosthesis Utilizing a Four-Bar Mechanism

[+] Author and Article Information
Bryan J. Bergelin

Department of Mechanical Engineering,  Marquette University, Milwaukee, WI 53233bryan.bergelin@nasa.gov

Philip A. Voglewede

Department of Mechanical Engineering,  Marquette University, Milwaukee, WI 53233philip.voglewede@marquette.edu

J. Mech. Des 134(6), 061004 (May 02, 2012) (7 pages) doi:10.1115/1.4006436 History: Received August 25, 2010; Revised March 08, 2012; Published April 30, 2012; Online May 02, 2012

This article discusses the design and testing of a powered ankle prosthesis. This new prosthesis mimics nonamputee (normal) ankle moments during the stance phase of gait through the use of an optimized spring loaded four-bar mechanism. A prototype prosthesis based on the optimization was designed, fabricated, and tested. The experimental results achieved 93.3% of the simulated theoretical ankle moment giving substantial evidence that this approach is a viable in designing powered ankle prostheses.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Moment versus gait cycle with ±1 standard deviation through consecutive heel strikes of the same foot. Raw data are from Ref. [4].

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Figure 2

Model of the four-bar prosthesis configuration, where C is the location of the spring/motor and l0 through l3 are links of the four-bar mechanism

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Figure 3

Normal ankle stiffness plotted with the latest four-bar optimum for stance phase of gait. Raw data are from Ref. [4].

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Figure 4

Motion simulation model with motor inertia disk not shown

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Figure 5

Link 2 FEA modification. Units are in Pascals. Although the scales are the same in color, the values associated with each are lower for the modified link.

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Figure 6

The prosthesis fully assembled mounted to the bench testing foot plate and testing pylon

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Figure 7

Reaction force comparison for the new prosthesis (spring only/motor turned off) prosthesis reaction force data fit with a polynomial of order 10



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