In order to evaluate our idea/prototype our team proposed a few different tests. These tests are outlined in the proposal linked here: https://docs.google.com/document/d/1RR0XJ0lT5SbrkakTXGXjWu0pHOj4gL7n4tHE2Zjfsv0/edit?usp=sharing. To overview them the team wished to perform usability tests with older adults/any users to see how users interact with the prototype and gather information on how they use the product. The team also wished to perform fit tests and measure how the device fit in different vehicles to gain insight on if the product fit in a wide variety of vehicles. The team lastly performed FEM analysis on various components like the handles and base to see what force these components could take before failure.
User Testing:
Users were asked to perform a variety of tasks such as sitting in the seat, rotating in the seat, buckling, adjusting handles, etc. As the user performed these tasks the following survey was filled out and feedback was asked for at the end: https://docs.google.com/forms/d/e/1FAIpQLSd_3o9laetFrBsyqnp5vCBwcvCFWgmMUUoZ9Jc3ST3pe2JL-A/viewform?usp=sf_link
Users ranged from age 22-84 and used vehicles such as cars, SUVs, and minivans. The results of these surveys are shown below. Overall, people liked the seat rotation and did not struggle to buckle it. Some people had complaints about comfort but everyone felt like they fit in the seat.
During one of the user tests, the seat handle broke as illustrated below. This showcased a point of failure in our product to be focused on if the idea were to continue with development. Overall, most users had a positive experience with the product. User’s feedback for improvements included moving the locking mechanism position to the side, adding rubber to the bottom pad to prevent slippage, possibly looking at a new cushion design.
Vehicle Measurements:
Measurements were taken with the seat in a wide variety of cars to better understand its fit. A spreadsheet with this data can be found here: https://docs.google.com/spreadsheets/d/1Fzu5ki6l7Eub5tyXiY4yljmx64KMVm15ZoV48BP2PCY/edit?usp=sharing
The measurements were taken at the locations shown below in the picture:
From this data it was found:
- The average height from ceiling to cushion was 33.3 inches, which is below the male average sitting height of 37.1 and female height of 33.4
- Potential fix: person could lower their seat
- Handles hit steering wheel on driver side
- Product works with just one handle in place
- Product fits best in larger vehicles
- No space lost in horizontal direction of testing
Finite Element Method Testing:
FEM analysis was performed on the bottom seat plate and seat handle to understand their force limits. Images of these are shown below.
From these handle FOS was 4, and the seat top was found to have large deflection but stress well below yield. Stress concentration would be at flange of product.
Future Steps:
- Use thrust bearing with a bigger OD to prevent deflection between 2 sliding pieces
- Replace 3D printed PLA components with metal, especially for load bearing components such as handles and locking mechanism
- Material and ergonomics of the cushion could be improved, more cushion/better cushion material and the shape of the cushion should hold the user in the seat better
- Keeping the prototype stable on the existing car seat (rubber)?
Original specifications:
- Product fits in vehicles without restricting driver usage
- Product is easy to use/operate by one older adult
- Product provides surfaces to push off of without breaking
Specifications met?
- User tests showed product could be used in vehicles, measurement tests showed that product doesn’t fit well in all vehicles without restricting usage
- User testing showed product operable by one adults
- User testing and FEM showed that there was an additional surface to push off of, but not a reliable and stable surface; specification not fully met
Seat Improvements:
- The seat could definitely be improved to be stronger, such as using a metal seat top or using a thrust bearing to increase support.
- Improve handle stability on base with stronger materials
- In manufacturing settings parts would be made in molds which might improve strength since all one component
- In full production would want to make customized bottom cushions to fit in different car’s bucket seats better
- Could reduce down to one handle maybe?
What we learned:
- Learned a lot about the process of product development, both with research and designing a product that solves a problem efficiently.
- Iterative prototypes are extremely helpful to test new ideas and improvements.
- How to go about working with users and progressing ideas with users in mind
- Value of feedback from others beyond just your team; fresh set of eyes