Going uphill is difficult for manual wheelchair users. The user must rapidly make short strokes to propel themselves uphill without allowing the wheelchair to roll backwards. This is exhausting and puts significant strain on wheelchair users' shoulders.
Stopping on hills with traditional grade aids can be dangerous. Traditional grade aids do not automatically disengage, so leaning back to relax can be disastrous.
Disadvantages of the traditional grade aid:
- Sharp teeth can destroy wheelchair tires
- Users can forget to engage and disengage the device.
- Device poses a tipping hazard.
We set out to design a grade aid which would fulfill the following key requirements:
- Limits backwards motion on an incline
- Automatically engages and disengages, includes a safety override
- Allows the user to perform a wheelie
- Allows the chair to roll backwards on flat ground
- Lightweight
- Does not damage wheelchair tires
- If battery powered has sufficient charge for extended use
Slides Outlining the Project and My Individual Contributions:
Iterative Design Process
First CAD mockup
Actuator implementation
Tooth disc
CAD model used for first prototype
Hub inserts
Inset tooth disc to save space
Huh insert profile
Closeup of actuator-disc interface
First prototype on the chair
First prototype closeup
Final CAD model (colored for visibility)
Dual actuator inset tooth disc with threaded guide rod holes
Closeup of hub and hub inserts
Final design on the chair
Final design mounted on the wheelchair.
Software logic which I implemented.
Demonstration of logic in early prototyping stage.
Public design show video.
