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Wheelchair Dynamic Center of Gravity (D-COG)

Wheelchair Dynamic Center of Gravity (D-COG). Kyle Mobley, BME Garrett Spiegel, BME Andrew Lossing , ChBE Advisor: Dr. Mark Richter, President. Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10. Background.

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Wheelchair Dynamic Center of Gravity (D-COG)

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  1. Wheelchair Dynamic Center of Gravity (D-COG) Kyle Mobley, BME Garrett Spiegel, BME Andrew Lossing, ChBE Advisor: Dr. Mark Richter, President Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  2. Background • 1.6 – 2.2 million wheelchair users in United States alone1 • 146.8% increase in wheelchair related injuries in U.S. from 1991 to 20031 Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  3. Background (cont’d) • Most users cannot climb hills greater than 8% grade for more than 30 feet [2] • Necessitates user folding to maintain stability. Leads to discomfort and greatly increased effort. Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  4. Basic Design Questions Seat or Axle movement? How will it move? How is the movement controlled? How far does it need to move? How will it stay in place? How is it designed? Feasibility - upgrade possibility Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  5. Seat or Axle Movement? • Axle Movement necessitates overcoming weight at wheels’ point of contact • Seat Movement is much more feasible • Similar to movement of driver or passenger seat in a car Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  6. How will it move? • Seat will move in relation to base Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  7. How will it move? • Use of concave wheels between two bars Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  8. How is the movement controlled? • 8° decline biases seat in forward direction • Releasing seat results in forward motion • User can further facilitate motion by braking • Rear wheel propulsion naturally resets COG to original position Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  9. How far does it need to move? • Choosing tippiness is a “compromise between risk of rearward instability and the ability to propel and maneuver easily”.3 • Shorter wheelbase = more tippy = COG backwards • Longer wheelbase = less tippy = COG forwards Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  10. How far does it need to move? (cont’d) Determinations: 20% COG change necessary for desired effect 4 inches of axle (or seat) movement Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  11. How will it stay in place? • User controlled clamping brake pads • When brake released, seat is free to move • Clamping brake/guard holds seat in desired position, keeps seat on track Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  12. How is it designed? • Altering pre-existing base design to conform to our specifications • Dimensional constraints • Brake/Stopper placement • Roller placement Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  13. Future Directions • Complete design with SolidWorks • Build prototype • Have parts manufactured • Metalwork/Construction • Test/Revise prototype Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

  14. References 1. H Xiang, A-M Chany, G A Smith. 2006. “Wheelchair related injuries treated in US emergency departments”. Injury Prevention. 12:8–11. 2. “ADA Wheelchair Ramp Specifications”.Mobility Advisor. http://www.mobility-advisor.com/wheelchair-ramp-specs.html 3. “Guidance on the Stability of Wheelchairs”. March, 2004. MHRA. DB2004(02). Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10

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