Wheelchair Lift System Redesign

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Date
2022-12-07
Authors
Desrochers, Kyle
Sanchez, Mika
Youssef, Maria
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Abstract

Move Mobility has tasked Team 23 with designing an original wheelchair lift system capable of safely on-boarding and off-boarding a wheelchair and its user. Reliability and maintenance issues with Move Mobility’s current products in cold weather and rough road conditions has prompted this project to come up with a reliable alternative. Move Mobility has also expressed their desire to introduce an industry-first product to market rather than attempt to eliminate the issues in their current products. The concept development phase was split up into two parts, concept generation and concept selection. To begin, the team first generated concepts by means of brainstorming and external research and client input. Functional decomposition was used to break down the concepts into key functions. The key functions identified were actuator type, storage method, and platform movement method. Weighted decision matrices derived from the client’s needs were then used to identify the winning concept from each function group. The concepts were then combined together to obtain the final concept. The design concept selected to proceed to the final phase consists of a lift platform integrated into the vehicle floor, scissor arms to raise and lower the lift platform, and an electrical motor to actuate the scissor arms. These features are compatible with each other and their selection was done considering the client needs and input. A design development stage followed, where the winning concepts were combined to serve the overall function of the design. The system consists of a platform that is lifted and lowered through a scissor arm lift mechanism. The scissor arms are actuated by an electric motor via a lead screw and nut. The nut is fixed to a rod that spans the platform and connects the scissor arms, creating the rising and lowering motion of the platform. The lead screw is attached to the motor with a flexible coupling and supported using pillow block mounted bearings. A hollow shaft encoder is mounted on the screw to monitor the position of the platform and the speed at which it moves. For the lift platform to clear the rear axle, linear rails were used to first move the platform outwards before lowering to the ground. Analytical calculations were primarily used to verify that the size and material of the components used are strong enough to hold a weight capacity of 1000 lbs. A bill of materials was completed outlining the necessary parts and materials to build this design. The cost of these materials is $4,359.79, excluding the costs of manufacturing and labor. This amount falls within the budget of $7,800. In conclusion, the final wheelchair lift system design is an innovative alternative to current products that is safe to use and requires less work to on-board and off-board a wheelchair and its passenger. Recommendations and future tasks include exploring the option of using two lead screws or a ballscrew, identifying the actuator for the linear bearing rails, and finally identifying the layout of electrical wiring throughout the vehicle.

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Mechanical Engineering
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