Final Project

Inspiration

For my Week 1 Assignment, I described a project I was not entirely happy with. There were a few reasons for that. One major reason was that I wanted to make something big (which I don’t have a lot of experience with). After weeks of agonizing over what to make, I asked my wife what she thought, and withing 5 minutes she had the perfect idea.

The Luggage

Figure 1 | from https://wiki.lspace.org/File:Luggage.jpg. © Discworld Emporium

This is The Luggage from the late Sir Terry Pratchett’s Discworld series of books. The Luggage has many legs and can hold many things, but above all is a true companion.

Initial thoughts

I cannot make The Luggage, because it has too many legs and also because it is sentient. But I think I can make something similar to The Luggage.

My version of The Luggage will consist of a box, which will be just a box, and some number of legs. I don’t want to make each leg independently controlled because that will limit the number of legs I can make. Instead, I plan to build a few axles with legs attached. They could be similar to camshafts, or they can simply have the legs attached directly, and spin them around like bristles on a vacuum cleaner. The legs themselves can be injection-molded, but will probably have to have a solid core to support meaningful weight in the box. I want my luggage to be able to make turns, so I will include two sets of axles, and rely on slipping to make turns, like continuous track vehicles do. Each set of axles will turn together, so I can connect each set together with toothed belts, and have the whole system operate using only two (geared) motors. At this point, it’s probably evident to the reader that I am not a mechanical engineer, which is why I’m so excited about this project.

I feel much more confident about the electronics and software portions of the project. To enable easy testing of the mechanical components, I will initially put a radio onboard so that I can move the luggage around with a controller (like an RC car). If I can get to a point where that works well, I will attach a camera and train a very simple model to recognize silhouettes. When there is exactly one silhouette in view, I will create a control loop that tries to keep the silhouette centered and of a particular size. That way, my luggage should be able to follow me around.

Block diagram

Electronics Block Diagram

Figure 2

The block diagram for the electronics is given in Figure 2. The BLDCs will drive the legs through closed belts. The axles will be attached through bearings to a wooden or acrylic frame.

Plan of action

Before machine week, I prototyped the BLDCs and the casting and molding process. I will not work on the final project until machine week is complete. After that, I will focus on the mechanicals first, because I am confident in the electronics and software.

Plans Are Worthless, But Planning Is Everything

– Dwight D. Eisenhower, maybe?

Here’s my current plan of action:

  • 11/20 - 11/24: CAD (frame with bearings, axles, legs, boots for casting and molding)
  • 11/24 - 11/26: 3D printing, casting and molding, testing
  • 11/26 - 11/30: Thanksgiving (hoping mechanicals don’t bleed into it)
  • 12/01 - 12/02: Schematic and PCB design
  • 12/02 - 12/03: PCB Fabrication
  • 12/04 - 12/05: Firmware
  • 12/05 - 12/06: Software
  • 12/07: Break
  • 12/08 - 12/12: Integration
  • 12/13 - 12/14: Bonus Features (e.g. motion detection)
  • 12/15: project presentation