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Design of a Wheelchair-Mounted Transfer Assist Device
University of PittsburghSenior Design – BioE 1160/1161
Michael AndersonAndrew Feola
Jill MarionBryan Shelly
April 18, 2006
Mentors: Alicia Koontz, PhD, RET Jeremy Puhlman, BSE
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• Wheelchair Patients
• Have trouble transferring from chair
• Bed, toilet, sofa, etc.
• Must carry bulky transfer boards, benches
Background
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Current Solutions
•Transfer boards, benches•Wall and ceiling-mounted devices
•Portability Issues!
•Our goal•To design a modified wheelchair armrest such that a transfer assist device is contained within the armrest
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Market Analysis- Frost and Sullivan
• North American Mobility Aids Market• Manual Wheelchairs
• 313,000 units in 2001(standard)• 77,000 units in 2001 (lightweight)• 313,000 units + 77,000 units = 390,000
units * $60 /unit=
$23,400,000 market for our product to be used on manual wheelchairs
Frost and Sullivan, 2001
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• Lightweight manual wheelchairs• $102 million/ 77,000 units in 2001
• $130 million in 2008• Sunrise Medical Quickie II 30% of market
• 0.3 * 77,000 = 23,100 units
23,100 units * $60/unit = $1,386,000
$1,386,000 market for our product to be used on the Quickie II model
Market Analysis- Frost and Sullivan
Frost and Sullivan, 2001
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• Home Healthcare Market (US)
• $2.03 billion-devices in homecare (2001)
• $1.23 billion- home durable medical equipment (1999)
Market Analysis- Frost and Sullivan
Frost and Sullivan, 1999, 2001
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• Growth rate of home healthcare market- 14% due to:• Increasing number of elderly (baby
boomers)• Medicare moving toward covering at
home treatments/devices more than in hospital
• Improvements in technology• Allows greater number of medical
procedures/monitoring to be done at home
Frost and Sullivan, 2001
Market Analysis- Frost and Sullivan
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Design Requirements
•Armrest converts into a transfer board
•Fit in space occupied by standard armrest
•Weight < 10 pounds
•Provides same comfort as standard armrest
•Able to support up to 250 pounds
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Original Design
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Final Design
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Our Prototype
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Our Prototype
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Prototype Fabrication
•Human Engineering Research Laboratory
•Wire EDM
•Aluminum 6061 Alloy (prototype)
•Mass Production
•Plastic Injection Molding
•High-density polyethylene
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Finite Element Analysis
Maximum displacement = .006 inches
Minimum factor of safety = 3.2
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Experimental Methods
• Validate FEA results
• Protocol – both ends supported
• Digitize a point (no load applied)
• Apply load
• Digitize same point (with load applied)
• Compute displacement
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Experimental Testing
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Experimental Results
FEA test Exp. test
.0007 .0011
.0024 .0097
.0015 .0031
**All units are inches
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High-density Polyethylene
Maximum displacement = .37 inches
Minimum factor of safety = 1.4
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Standard Transfer Board
Maximum displacement = 0.4 inches
Minimum factor of safety = 1.1
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Survey Results
•Eight (8) volunteers
•7 use transfer boards
•3.9 / 5 difficulty rating of current boards
•4.75 / 5 aesthetic rating of our product
•All 7 would prefer a transfer board that does not need to be carried
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Competitive AnalysisTransfer bench
• Invacare transfer bench• $120
• Carex transfer bench• $300
Standard transfer board• Allegro Medical wooden board
• ~ $37 per unit
• Therafin Theraslide transfer board• $100 per unit
Our device• Plastic Injection Molding
• $50-60
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Competitive Analysis
Strengths
• Price• Comparable to current transfer boards
• Portability
• Minimal additional weight
Weaknesses
• Limited armrest adjustability
• One sliding mechanism
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Constraints—Testing Human factors
• Lack of human subject testing• Falls, etc.
Production• Material availability
• Testing done on aluminum, not plastic
Economic• Cost of prototyping
• Only one prototype
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Manufacturability Considerations
• Simple Design
• Ease of injection molding
• Standard shapes
• Lack of small, irregular pieces
• Ease of mass production
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Human Factors Considerations• Standard transfer material
• Patient can slide easily across board
• Cushioning consistent with standard armrests
• Handles in transfer board
• No sharp edges
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FDA Regulation
• CDRH website
• Sec. 890.3910 Wheelchair accessories
• Includes armrests, transfer boards
• Class I device
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPCD/classification.cfm
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Individual Project Work
• Jill Marion• Contact companies and
patients
• Market Analysis
• Prototype testing
• DHF, SBIR
• Mike Anderson• SolidWorks design
• Prototype testing
• COSMOSWorks analysis
• DHF, SBIR
• Andrew Feola• SolidWorks design
• COSMOSWorks analysis
• Prototype testing
• DHF, SBIR
• Bryan Shelly• Material selection
• DHF, SBIR
• Manufacturing
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Project Timeline
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Future Considerations
• Human subject testing
• Additional sliding mechanism
• Armrest height adjustability
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AcknowledgementsAlicia Koontz, PhD, RET
Jeremy Puhlman, BSE
Alexis Wickwire, BS
Human Engineering Research Labs
Pittsburgh Life Sciences Greenhouse
University of Pittsburgh BioE Dept.
A generous gift from Dr. Hal Wrigley and Dr. Linda Baker
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Thank You
• Questions?