Passive Prosthetic Foot Shape and Size Optimization Using Lower Leg Trajectory Error
Name
md_140_10_102302.pdf
Description
Published version
Size
2.62 MB
Format
Adobe PDF
Checksum (MD5)
3267d8b3cd24917467bb97078c7ae119
Author(s)
Olesnavage, Kathryn M
Prost, Victor
Johnson, William Brett
Winter, Amos G
Date Issued
2018
Journal
Journal of Mechanical Design
Publisher
ASME International
Version
Final published version
Abstract
Copyright © 2018 by ASME. A method is presented to optimize the shape and size of a passive, energy-storing prosthetic foot using the lower leg trajectory error (LLTE) as the design objective. The LLTE is defined as the root-mean-square error between the lower leg trajectory calculated for a given prosthetic foot's deformed shape under typical ground reaction forces (GRFs), and a target physiological lower leg trajectory obtained from published gait data for able-bodied walking. Using the LLTE as a design objective creates a quantitative connection between the mechanical design of a prosthetic foot (stiffness and geometry) and its anticipated biomechanical performance. The authors' prior work has shown that feet with optimized, low LLTE values can accurately replicate physiological kinematics and kinetics. The size and shape of a single-part compliant prosthetic foot made out of nylon 6/6 were optimized for minimum LLTE using a wide Bezier curve to describe its geometry, with constraints to produce only shapes that could fit within a physiological foot's geometric envelope. Given its single part architecture, the foot could be cost effectively manufactured with injection molding, extrusion, or three-dimensional printing. Load testing of the foot showed that its maximum deflection was within 0.3 cm (9%) of finite element analysis (FEA) predictions, ensuring the constitutive behavior was accurately characterized. Prototypes were tested on six below-knee amputees in India-the target users for this technology-to obtain qualitative feedback, which was overall positive and confirmed the foot is ready for extended field trials.
MIT Department
Massachusetts Institute of Technology. Global Engineering and Research Laboratory
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1115/1.4040779
