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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

2. Background 1.6 – 2.2 million American wheelchair users 1 146.8% increase in wheelchair related injuries from 1991 to 2003 1 Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

6. How will it move? Use of pre-existing HiRoller Elevating Wheelchair ™ technology Roller-track movement technique Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

7. How is the movement controlled? Spring loaded to be biased in forward direction  Moves COG forward, in front of rear axle Rear wheel propulsion naturally resets COG to original position Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

8. 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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

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

10. How will it stay in place? Spring-loaded locking pins Two sets of pins to simplify user operation Each set designates different setting User controlled through lever placed on side of seat Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

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

12. Future Directions Get assistance with AutoCAD Build prototype Welding, Metalwork, Construction Test/Revise prototype Lossing, Mobley, Spiegel http://www.bme.vanderbilt.edu/srdesign/2009/group5/ D-COG Senior Design 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/

13. 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 2009-10http://www.bme.vanderbilt.edu/srdesign/2009/group5/