The Research and Design of a Low Cost, Terrain, Mechanically Advantageous Wheelchair for ...

109 Pages·2012·12.67 MB·English

The Research and Design of a Low Cost, All
Terrain, Mechanically Advantageous Wheelchair
for Developed Markets
by
Benjamin Michael Judge
Submitted to the Department of Mechanical Engineering
in partial fulfillment of the requirements for the degree of
Bachelor of Science in Mechanical Engineering
at the ?
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
June 2011 ARCHIVES
© Benjamin Michael Judge, MMXI. All rights reserved.
The author hereby grants to MIT permission to reproduce and
distribute publicly paper and electronic copies of this thesis document
in whole or in part.
Author....................... .. ...........................
>,) t rtme offechanical Engineering
May 6, 2011
....... ..... ............
Certified by............ ......
Daniel D. Frey
Associate Professor ineering
-ThesiSupervisor
Accepted by ...........
o h ohn H. Lienhard V
Collins Professor of Mechanical Engineering
Chairman, Undergraduate Thesis Committee
2.
The Research and Design of a Low Cost, All Terrain,
Mechanically Advantageous Wheelchair for Developed
Markets
by
Benjamin Michael Judge
Submitted to the Department of Mechanical Engineering
on May 6, 2011, in partial fulfillment of the
requirements for the degree of
Bachelor of Science in Mechanical Engineering
Abstract
This thesis presents a case for a paradigm shift in the way mobility technology is
approached in the United States. Spawning from the research of developing world
wheelchair technology, a conceptual design for a capable wheelchair is proposed based
on the unique market elements of the United States. These factors include: user de-
sire for devices that enable functional independence over a wider range of terrain, a
user demographic that is among the most marginalized in the U.S. economy that can-
not afford the typically high cost of assistive devices, and a cumbersome government
reimbursement process that won't necessarily support more functional products, re-
tarding industry development. A path for development is outlined through industrial
design, solicitation of stakeholder input, and the exploration of both competitors and
analogous technology. Notably, bicycling componentry, which is both appropriately
engineered and ubiquitous, allows for drivetrain mechanism innovation within the
wheelchair space. This leads to a robust, low cost, and mechanically advantageous
wheelchair design for developed markets such as the United States.
Thesis Supervisor: Daniel D. Frey
Title: Associate Professor of Mechanical Engineering
4
Acknowledgments
I would like to thank my friends and family for the support and encouragement for
the journey that was my undergraduate career at MIT. Specifically, I would like to
thank the UROP office, Jake Childs, Jung Tak, and Professor Frey for allowing me
to explore my passions to become a more engaged and invested engineer. Finally,
I thank the entire Mobility Lab team, especially its fearless leaders and inspiring
adventurer-engineers, Amos Winter and Mario Bollini.
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Contents
1 Introduction
1.1 M otivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Wheelchair Design in Developing Countries . . . . . . . . . . .
1.2.1 Human Performance Data . . . . . . . . . . . . . . . .
1.3 The U.S. Leveraged Freedom Chair . . . . . . . . . . . . . . .
2 Developed Country Wheelchair Design: The United States
2.1 Wheelchair User Demographics... . . . . . .. . . . . . . .
2.1.1 C onditions . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 Incom e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.1.3 Education and Employment . . . . . . . . . . . . . . . . . . . 25
2.2 Acquiring Mobility Equipment . . . . . . . . . . . . . . . . . . . . . . 26
2.2.1 Centers for Medicare and Medicaid Services . . . . . . . . . . 26
2.2.2 U.S. Department of Veterans Affairs . . . . . . . . . . . . . . 28
2.3 Wheelchair Market Benchmarking . . . . . . . . . . . . . . . . . . . . 28
2.3.1 Depot Wheelchairs . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3.2 Lightweight Wheelchairs . . . . . . . . . . . . . . . . . . . . . 29
2.3.3 Ultralight Wheelchairs . . . . . . . . . . . . . . . . . . . . . . 29
2.3.4 Wheelchair Accessories . . . . . . . . . . . . . . . . . . . . . . 29
2.3.5 Market Opportunity . . . . . . . . . . . . . . . . . . . . . . . 30
3 Design Concept 35
3.1 Industrial design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 The model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.1 Functional requirements . . . . . . . . . . . . . . . . . . . . . 36
3.3 Engineering the model . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3.1 Parts list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.3.2 Structural frame . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.3.3 Norm al stresses for beams in bending . . . . . . . . . . . . . . 39
3.3.4 Curved beams in bending . . . . . . . . . . . . . . . . . . . . 44
3.3.5 Stress in other com ponents . . . . . . . . . . . . . . . . . . . . 47
3.4 Sourcing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.1 Bicycle parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.2 W heelchair parts . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.3 Other components and hardware . . . . . . . . . . . . . . . . 50
3.5 Part Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.1 Spine Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.6 M odel completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4 Functional LFC Design 57
4.1 W heelchair product engineering . . . . . . . . . . . . . . . . . . . . . 57
4.2 Understanding the market . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2.1 Competition analysis . . . . . . . . . . . . . . . . . . . . . . . 58
4.2.2 Bike industry . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.3 Need identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.1 User survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.2 User profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.3.3 Product Attributes . . . . . . . . . . . . . . . . . . . . . . . . 63
4.4 Solving key risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.4.1 Lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4.2 Lever coupling mechanism . . . . . . . . . . . . . . . . . . . . 66
4.4.3 Crank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4.4 Lever pivot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.4.5 Brake actuator . . . . . . . . . . . .
4.4.6 Transmission . . . . . . . . . . . . .
4.4.7 Brake system . . . . . . . . . . . . .
4.4.8 One-way clutch . . . . . . . . . . . .
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4.4.9 Wheel chair detachment mechanism
4.4.10 Wheel detachment mechanism . . . .
4.5 Most critical module conceptualization . . .
4.5.1 Standard parts . . . . . . . . . . . .
4.5.2 Bespoke components . . . . . . . . .
4.5.3 Future work . . . . . . . . . . . . . .
5 Conclusion
A Guatemala LFC Trial Data Processing
A. 1 Overview of system . . . . . . . . . . . . . . . . . . . . . . . . . . . .
/
A.2 Speed distance data . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.3 Accelerom eter data . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.4 Mechanical power output . . . . . . . . . . . . . . . . . . . . . . . . .
A.5 V0 , oxygen consumption, heart rate, and conclusions . . . . . . . .
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B Certificate of Medical Necessity 97
C Wheelchair Product Benchmarking 101
D LFC Concept Model Development 105
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