Anti-Rollback & Brake Assist Device for Manual Wheelchair Problem Statement When users of manual wheelchairs are required to traverse an incline, the wheelchair tends to roll backwards as they adjust their grip on the wheels, thus impeding forward motion. Similarly, when traversing a decline, users do not have the ability to steer or slow their speed without endangering their hands. In both scenarios, users that may otherwise be independently mobile would require an aid. System Diagram Rotor Ratchet Wheel lock Shaft Bearing Blocks Rotor Mount Pawls (3) Engineering Requirements Tooth Analysis Load set: Ratchet Stress von Mises (WCS) (psi) Above illustrates the maximum loading scenario (41.4 lbf) applied to the face of the tooth. Assuming only 1 pawl is engaged, the system will not fail nor yield. Importance Function Engineering Requirements Status 9 Movement Force exerted by user to hold position on incline Pass Grip force exerted by user to brake on decline Wheelchair will rollback <= 0.5" when engaged Fail 1 Independent braking inputs 3 Portability Increase of wheelchair width when in use Component interference when wheelchair is folded Total system weight Maintainability Designed test life COTS components Total system cost Number of models that system can interface Maximum static user weight Time to revert to original configuration Shaft Analysis Testing The test fixture to the left was used to evaluate wear patterns of the pawls as the ratchet rotates past them. This simulates an engaged system on an actual wheelchair. Rotations were counted using an encoder disc and IR sensor mounted to a plate on the motor. A LabView VI recorded the data from the sensor. The Design Chart to the left displays potential shaft materials and their respective factor of safety as a function of shaft diameter. The chosen material, 4140PH in blue with associated trend line has a factor of safety greater than the desired 1.3 bold line for all diameters above 0.44 in. Alpha Prototype Beta Prototype Team 15007 ~7 lbs Weight reduction Adaptable Fully revertible 3 pawl design Team 14007 ~22 lbs Maintain quick-release functionality by adding a pin in shaft Review design to reduce variation in size and length of fasteners Weight reduction through component design Material selection Alert system to ensure client is aware of system reaching end of life Future Recommendations Senior Design Team P15007 Members: Jessica Jeffrey (ISE) Jacob McCarthy (ME) Warren Roser (ME) John Sweet (ME) Faculty Guide: Edward Hanzlik Customer: Dr. Elizabeth DeBartolo, Jack Cholette Acknowledgements: Jan Maneti, John Bonzo, Rob Kraynik