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Critical Function Prototype (CFP)

Each group will choose a CFP. A CFP could take many forms. In the broadest sense, a CFP is a prototype that will allow your team to learn about some important aspect of your project. Topics that are good to learn about when designing products tend to be aspects that are not well understood, have risk associated with them, or have no obvious answer (and are important enough to want to answer).

In order to choose a CFP, your team should first have a good understanding of what your project is about and where some of the challenges will arise.

You will document your choice (or possible choices if unsure) of a CFP in a memo (see CFP & Analysis Memo. In this memo you will include the motivation behind choosing this CFP

For additional information and considerations on choosing a CFP, refer to the “Prototyping” chapter in Ulrich and Eppinger’s textbook. They lay out 4 steps for choosing a prototype.

Good Critical Function Prototype (CFP) examples

In each of these presentations of CFPs from privious years, they:

1. provide a concise description of their project and project goals
2. briefly discuss budget and schedule
3. then discuss their CFP
   1. They provide the motivation behind their CFP and what they hope to learn
   2. They perhaps discuss different design options and how they will evaluate their CFP
   3. They present their CFP and features (typically taking pictures and putting them in the presentation is better than pointing to a small prototype, though please do bring your prototype).
   4. They discuss lessons learned
   5. They make recommendations to use the design, how to improve it, or plans for an alternative design

• ESK8 CFP (electric skateboard)
  • They put all of the working parts together for their electronics
    since no one on the team had much electronics experience, this was a great learning experience for the team)

• Wind Turbine CFP presentation
  • Great example of a software/simulation CFP done in Matlab
    great tool that they used in the rest of their project and continued to build on throughout the project.

• Emergency Snowboard binding CFP presentation
  • They were exploring learning about SMA actuators as an actuator for their release mechanism
    (good idea, but this group should have taken their prototype testing further and been more quantitative with their results and/or do some basic statics calcuations)

• Electronic Valve Control CFP presentation (link to page)
  • This team was investigating to see if a loudspeaker voice coil would have enough stroke and bandwidth to act as an injection valve on their engine and engine controller.
    this was a good CFP and presentation. I wish they had been a little more quantitative, but otherwise it was quite good.

• Lower Limb Modeling CFP presentation
  • This team knew that they would need to prototype a linkage with a series of joints and measure the angle of these joints. Therefore, they prototyped one of the joint types, installed an encoder and hooked this prototype to a computer interface to acquire the position from the encoder (angle sensor).
  this is a good CFP. While the prototype is not very pretty, they learned a bit about making the mechanical assembly and figured out how to do data acquisition with the computer.

• Downhill Wheelchair CFP presentation
  • This group produced their entire chassis and for their CFP they investigated using a cable driven steering linkage. The key advantage to using the cable driven mechanism is that it could be routed around the perimeter of the chassis.
    This group put together their prototype, however they came to the wrong conclusion because it was not put together with care. This led to the conclusion that it took too much force to actuate the system. Later they took greater care with their prototype and corrected this issue.

• Moonbuggy CFP presentation
  • This group investigated their suspension design and steering to ensure they didn’t get bump steer
  • Pictures of their CFP
    This is quite possibly the best CFP I’ve seen. It’s quite a nice prototype and the students did their design using available software design tools.

• Robot Hand Mechanics CFP
  • This team investigated how to make a custom fluid boot, how the geometry of the cams in their finger prototype should be modified, and how to do their mechanical and liquid connections.
    this was a very strong CFP presentation with many prototypes and many lessons learned