Customers
Thomas Quiter, Founder and President of the Mobility Independence Foundation
Matthew Lacey, Vice President of the Mobility Independence Foundation
Authors
Ila Benciolini, Anna Hinchcliffe, Jayden Collins, Ivy Chang, Gavin Wong (Left to Right)
Problem Statement
Individuals with mobility impairments face significant barriers to accessing affordable and functional power wheelchairs. This project addresses this issue by developing an open-source, modular seating system with motorized tilt and recline, and an expandable seat pan, prioritizing an accessible design for anyone to recreate with the help of their community.
Customer Identification and Scenario
This modular seating system is designed for people with mobility impairments who spend most of their time on a power wheelchair. This device is an alternative option to those seeking wheelchairs due to high costs or inadequate insurance coverage. This design can also serve as a replacement for commercial wheelchairs that are prone to damage and have slow repair times. Customers will access the open-source design through the Mobility Independence Foundation and be able to contact a local mechanic or manufacturer to assist in creation of parts and assembly. Smaller repairs to the device should be repairable by the user, due to the simplicity in the design. The wheelchair will provide free movement with tilt, recline, and leg rest adjustments, allowing users to perform daily tasks. The design prioritizes durability, and when repairs are needed, the user can get them without reliance on healthcare providers or insurance companies.
Design Concept
Our seating system consists of a back rest, legs rests, expandable seat pan, and a control system to allow for actuation, and is built onto a chassis provided to us by the MIF. The system is currently capable of tilting 30°, with the hope of reaching a full 90° with the final steel prototype. The legs and the backrests can reach a full tilt of 90°. For the development of the product, the overall system was broken into subsystems; the frame, actuation system, electrical and control system, and the user interface. The frame and actuation system was modeled using CAD, and the prototype was developed primarily using wood, 3D printed connections, linear actuators, and metal sliders.
Tilt and Recline Features
Below are examples of possible configurations of the wheelchair. Given that potential users might be restricted to the confines of the wheelchair for most of their lives, we want to provide as much freedom and mobility as possible. The primary advantage of these movement is the ability to redistribute loads and relieve pressure sores, preventing injuries.
Expandable Seat Design
The seat expansion mechanism was designed to expand from a 16 inch to a 24 inch width. The first two iterations of the design can be seen below, both of which incorporate a telescoping mechanism. The one on the left utilizes placeable rods to lock the width of the seat while the one on the right uses quick-release pins. These were designed using OnShape and Solidworks, respectively, and were planned to be made of aluminum. This was difficult to translate into a user friendly design, because of the lack of accessibility of aluminum telescoping rods and the machining required. The final design of the expandable seat pan was inspired by expandable dining room tables, whose width can be adjusted according to user needs. In the final prototype, drawer sliders are connected to two main parts of the seat pan, and can be slid open to either 20, or 24 inches and locked into place using a U-bolt. This final mechanism is more user-friendly and easily adjustable , which better aligns with our customers’ desire for this product.
Control System
The control system was designed to be a cost-effective solution for controlling the six linear actuators required to achieve motorized tilt, recline, and leg rest actuation. To achieve this, we utilized an Arduino UNO R3 board, three sets of 8-relays, and two simple 2-pin switches. Prioritizing modularity, we ensured that each part could be adjusted individually. The user interface comprises a 7-segment display and the switches. One of the switches enables the user to cycle through the functions, allowing them to select the part to actuate. The other switch triggers the actuators to control the recline, tilt, or leg rest angle, reversing the direction of movement with each click.
Prototyping Process/Approach
The prototyping process was primarily done using CAD. The frame, seat pan, and actuation systems were developed using OnShape and the design iterations were continuously updated until the final model was ready to be physically built. Currently the prototype is made mainly out of wood, 3D printed connections, linear actuators, and metal sliders. The next iteration of the prototype will be a steel model that can be tested for safety, strength, and durability.
Device Testing and Future Directions
Critical areas of failure were identified through static analysis and the prototype building process. Finite element analysis via Solidworks Simulation was conducted on these key areas to ensure that they would not fail under the anticipated stresses and strains specified by our customer. These results were then translated and scaled down into our physical prototype, which uses different materials than the ideal model.
Acknowledgements
We would like to thank our customers (Thomas and Matt from the MIF), our supervisor (Dr. Mark Buckley), our course instructor (Dr. Scott Seidman), our project management liaison (Ahmet Gurcan), and our senior lab engineer (Marty Gira). Your help has been invaluable throughout our project, and we couldn’t have done it without you!