Embedded Files
The final design of the armbar, with a 3D printed part that holds the camera and the dampers needed.
From left to right: 1. A picture of the final assembly on the wheelchair; 2. The view from the wheelchair user's perspective; 3. The underside of the camera mount, showing how the camera is held up and the set screws; 4. The final CAD of the armbar and its attachments.
Components
Ninjaflex damper (teal and green): 3D printed with a thermoplastic polyurethane called Ninjaflex that remains elastic after printing. Two sets of holes are provided for the zip ties to pass through to secure it to the camera mount. This material could be printed in a variety of configurations and sizes, allowing for custom spring and damping coefficients. Ultimately, a chart could be provided that allows users to choose the correct configuration for their weight range.
Camera mount (red and gray): 3D printed with regular PLA, it holds the depth camera needed for the wheelchair to "see" where it's going as well as the latch needed to hold the armbars closed. The dampers are attached to the back of it with zip ties. Set screws scattered throughout the underside of the mount prevent it from rotating about the arm bars. 3D printing the mount is a cheap and quick way to create this piece, and allows the team to easily change the design if they decide to use a different camera.
Latch (yellow): A simple sliding latch used in doors mounted sideways. The sliding bolt is mounted over the camera, and the corresponding lock is mounted on the right armbar.
Arm bars (brown): Threaded steel pipes and a 45 angle pipe fitting from Home Depot. At the location we went to, they offer to cut the pipes in-store.
Hinges (gray, at the edges): Ordered from the wheelchair manufacturer - they were originally used to raise and lower the side armrests, but work well in acting as the pivot point for the front arm bars.
Video Demonstration of the Smart Wheelchair Armbar
Future Improvements
The honeycomb is only one of many possible geometries, and other shapes and configurations will have different interesting and useful properties. As an alternative safety restraint system, the use of a seat belt can be further explored. Although a seat belt was avoided in this project partially due to the injuries it sometimes causes, there are ways to make seat belts safer, such as with a ratcheting system or a load limiter. The current design could also be improved in regards to making the wheelchair water resistant, as users have expressed concerns about driving their wheelchairs into the restroom.
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