design of a wheelchair-mounted transfer assist device

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

• Wheelchair Patients

• Have trouble transferring from chair

• Bed, toilet, sofa, etc.

• Must carry bulky transfer boards, benches

Background

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

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

• 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

• 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

• 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

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

Original Design

Final Design

Our Prototype

Our Prototype

Prototype Fabrication

•Human Engineering Research Laboratory

•Wire EDM

•Aluminum 6061 Alloy (prototype)

•Mass Production

•Plastic Injection Molding

•High-density polyethylene

Finite Element Analysis

Maximum displacement = .006 inches

Minimum factor of safety = 3.2

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

Experimental Testing

Experimental Results

FEA test Exp. test

.0007 .0011

.0024 .0097

.0015 .0031

**All units are inches

High-density Polyethylene

Maximum displacement = .37 inches

Minimum factor of safety = 1.4

Standard Transfer Board

Maximum displacement = 0.4 inches

Minimum factor of safety = 1.1

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

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

Competitive Analysis

Strengths

• Price• Comparable to current transfer boards

• Portability

• Minimal additional weight

Weaknesses

• Limited armrest adjustability

• One sliding mechanism

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

Manufacturability Considerations

• Simple Design

• Ease of injection molding

• Standard shapes

• Lack of small, irregular pieces

• Ease of mass production

Human Factors Considerations• Standard transfer material

• Patient can slide easily across board

• Cushioning consistent with standard armrests

• Handles in transfer board

• No sharp edges

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

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

Project Timeline

Future Considerations

• Human subject testing

• Additional sliding mechanism

• Armrest height adjustability

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

Thank You

• Questions?