Next Generation Assistive Anti-tippers
Led a team of 3 in designing and building powered assistive anti-tippers to prevent long term muscle injuries in wheelchair users in collaboration with potential consumers of the products at Rancho Los Amigos Rehabilitation Cente. We presented our idea with a proof of concept during the Aging into Future Conference in LA during March and our final product at Rancho Los Amigos Rehabilitation Center during June.
PROBLEM STATEMENT
The act of propelling a manual wheelchair can be quite hard on the body. The simple act of hitting the handrim creates force against the shoulder. Up to 78% of manual wheelchair users suffer from upper extremity pain originated from the pushing motion that propel them forward.
To address this issue, we are developing a next-generation wheelchair power assist, which would allow wheelchair users to maintain the same level of mobility while decreasing the required physical exertion. We want to allow the chair to “glide” for longer, cutting the number of times a user would need to push drastically. We also want to implement a remote control system for our customers, allowing them to perform functions such as calling it back to them and parking it somewhere else after transfer. This power assist will essentially act as remotely controllable motorized anti-tippers, allowing the user to drive the wheelchair intuitively without loss of anti-tipper functionality.
OBJECTIVES
We aim to make our product adaptable, usable, and affordable. In terms of adaptability, the device will be able to attach to all kinds of wheelchairs and works in all kinds of environment and terrain. In terms of usability, the device will possess a user-friendly interface easily assessed by the user and sensitive to user input. In particular, the device will be able to brake rapidly and be convenient enough for everyday use maneuvering down a busy street. We envision it to be something that will be long term integrated to the wheelchair instead of a device people use once in a blue moon. Finally, in terms of affordability, we aim to make the produce easy to manufacture and able to be cheaply mass produced so that even people without insurance can take the product into consideration without backing out at the sight of the pricetag.
We believe that our product can not only help the manual wheelchair users but also the caregivers. These assistive antitippers will ease wheelchair transportation for them, especially on inclines.
OUR VISION
We envisioned two possible designs of this product. The first design consisted of rigid structure with the spring for suspension and anti-tipper functionality but in constant contact with the ground. This is the the design we followed for our initial proof of concept we demonstrated at the Aging into the Future Conference. The second design that we may further investigate in the future will allow the user to raise and lower bottom shaft of the device so that the device can be kept in contact with ground when needed but also be able to be lifted up to provide anti-tipper functionality. This is for a scenario where the spring that helps the wheel to stay in contact with the ground is too strong for the user to pop a wheelie.
We envisioned our final product to be sleek, lightweight (~10lbs), compact, and modern. We imagined a system with the transmission and motor tightly and efficiently packed near the wheel, and the battery and controller on the wheelchair shaft the anti-tippers are attached to.
OUR PROGRESS
Our first prototype was a 3D printed mock-up of the shaft system that reflects the second design that was previously mentioned. The shape of this product was designed so that the top shaft angled towards the back of the wheelchair would prevent the anti-tippers from protruding out significantly.
Our proof of concept model was created with a PVC pipe as the outer shaft and a dell ring as the inner shaft. The clamp was made from aluminum using manual milling and waterjet. The plastic surrounding the gearbox was 3D printed. The wheel is an omniwheel that allows it to slide sideways, and the spring will allow the user to pop a wheelie while having the device remain in contact with the ground at all times.
During the second term, we successfully programmed the controls and propelled an empty wheelchair forward with the assistive motorized anti-tippers we developed. With the springs, the user can pop a small wheelie as well. However, the motors we had were not strong enough and our gear ratio was too high so when the antitippers attempt to move people on the wheelchair, they do so extremely slowly and skip easily. There is still a lot of room for future development including making the controls more intuitive, making the design more compact, and improving on the mechanical strength of the propellers.
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MY ROLE IN THE TEAM
I functioned as both the team leader and the technical lead for this team of 3. I was in charge of designing the overall structure and CADing the gearbox/ wheel subassembly. Together, our team manufactured and assembled to realize our ideas through prototyping and worked our way towards a final product.
