What is Prototyping?

In this section we will step through an example of how to iteratively prototype towards a solution.

prototype: a model that a design team builds of a solution to test and validate ideas quickly

To do this we will be going back to the example of the arm holder for Kenzie, the child with cerebral palsy. In this scenario, Kenzie and her mom are the co-designers and you (and the AT course staff) are the design team creating this device.

Through the activities in this module, you will work through the design process and learn how to make decisions during prototyping quickly and cheaply towards the best solution.

Mission Statement

You are a part of a team that has this mission statement:

"To design and build a mobile arm support for children and adults with cerebral palsy that will aid in arm mobilization when working on everyday movements in therapy; specifically eating and writing."

Benchmarking

The team did some benchmarking during the concept generation phase. Some of those results are here.

The first system researched was the Medifab Dynamic Arm Support. The team discussed the pros of this product including its advantages of user-friendly clamp, flexibility in movement, and the simple height adjustment. The major disadvantages include its unwieldy size as well as a lack of tension adjustment. Lastly, it is expensive and difficult to purchase.

The second system researched was the Armon Edero which has key elements required by the co-designer, including a clamping mechanism compatible with table and chairs, portability, and all the required axes of rotation with adjustable tension at the joints. The pitfalls of this product include its expense, appearance, and overall safety of moving joints for young users.

Lead User and Experts Survey

The team did a survey with therapists and parents of potential patients who may be interested in the project to gain a better understanding of how the product will be used in the future.

The team learned these things from the surveys:

  1. Safety is the most important.
  2. The device needs to be easy to clean and maintain.
  3. The device needs to be comfortable.
  4. The device needs to be light and easy to transport.
  5. The arm support should have more functionality than the movements described (writing and eating)
  6. The movement required to eat is the most important function for this device.
  7. Users will use this device between 1 and 4 hours at a time.
  8. More than 60% of the participants would not pay over $500 for this device.

More extensive interviewing and testing was also done until all customer needs were understood by the design team. The next step is to turn these needs into requirements.

Requirements

These requirements are written in technical engineering terms. The terminology may be unfamiliar, but the point of sharing these is to give an example of what real requirements would look like.

Here are some of the requirements the team defines for the product:

  1. Physical Requirements
    • The product shall weigh under 25 lbs.
    • The product shall fit within a 1.5 ft. cube.
  2. Functional Requirements
    • The product shall provide 2 degrees of freedom (more information here).
    • The product should provide 5 degrees of freedom with a z-direction (height) adjustability.
    • The product shall have a common interface for the various arm molds provided by the user.
    • The product shall attach to desk and chair surfaces.
  3. Performance Requirements
    • The product shall support load imposed by individuals between the ages of 8 and 40 years old.
    • The product shall attach to a surface between 0.5" and 3" in thickness.
    • The product shall attach to a surface with at least a depth of 1" using a clamp.
    • The product will rotate 180 degrees about the z-axis and 30 degrees about the y-axes.
  4. Operational Requirements
    • Facilities, transportation storage: The product shall be able to be transported easily by one person.
    • Reliability: The product shall function for maximum usage multiple times a day, five days a week, for up to 5 years.
    • Installation and Removal: The product shall be clamped to a surface.
    • Safety: The product shall be free of pinch points, sharp edges, loud noises, splinters and burrs, and extreme temperatures.

Device Concept

Given the requirements made from customer (or co-designer) needs and a rigorous selection process, the concept selected was a ball joint based system with a product breakdown shown here. This shows the components of the system and how they are connected. Level 1 is the entire system. Level 2 and 3 break the system down into the individual components.