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.
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October 2018
Research-Article
Passive Prosthetic Foot Shape and Size Optimization Using Lower Leg Trajectory Error
Kathryn M. Olesnavage,
Kathryn M. Olesnavage
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: kolesnav@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: kolesnav@mit.edu
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Victor Prost,
Victor Prost
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: vprost@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: vprost@mit.edu
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William Brett Johnson,
William Brett Johnson
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: wbj@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: wbj@mit.edu
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Amos G. Winter, V
Amos G. Winter, V
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: awinter@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: awinter@mit.edu
Search for other works by this author on:
Kathryn M. Olesnavage
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: kolesnav@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: kolesnav@mit.edu
Victor Prost
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: vprost@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: vprost@mit.edu
William Brett Johnson
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: wbj@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: wbj@mit.edu
Amos G. Winter, V
Global Engineering and Research (GEAR)
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: awinter@mit.edu
Laboratory,
Department of Mechanical Engineering,
Massachusetts Institute of Technology,
Cambridge, MA 02139
e-mail: awinter@mit.edu
1Corresponding author.
Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received November 6, 2017; final manuscript received June 11, 2018; published online July 31, 2018. Assoc. Editor: Massimo Callegari.
J. Mech. Des. Oct 2018, 140(10): 102302 (11 pages)
Published Online: July 31, 2018
Article history
Received:
November 6, 2017
Revised:
June 11, 2018
Citation
Olesnavage, K. M., Prost, V., Johnson, W. B., and Winter, A. G., , V (July 31, 2018). "Passive Prosthetic Foot Shape and Size Optimization Using Lower Leg Trajectory Error." ASME. J. Mech. Des. October 2018; 140(10): 102302. https://doi.org/10.1115/1.4040779
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