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Final: An X-Bee Controlled Airship

July 2, 2009

Amongst other technical problems, we encountered massive power-to-weight issues here, but we did successfully get the Glove-Controller communicating with the Airship via X-Bees, doing a complete end-run around all the original electronics that came out of the box:

MVI_8120

We had optimistically planned to get all of this into the Gondola:

IMG_8112

You’re looking at an X-Bee on a breakout board, two H-bridges, and LED power indicator, and the world’s largest hacked heat sink attached to a 3.3v voltage regulator.  I literally hack-sawed the heat sink out of a CPU power supply.  We had been developing a really hot regulator and battery, and were worried about a Hindenburg redux, but ultimately concluded it was actually due to a last-minute short circuit.

Due mainly to gondola space constraints, we stripped the bread board of all but the bare essentials to get it down to this, sans battery:

IMG_8139

Tearing out the original radio controller would have likely meant the ultimate destruction of the gondola itself.

For X-Bee Controlled Airship v. 2.0, we’re definitely going to a soldered circuit board.  Breadboard’s unnecessary weight, and we’ll continue to throw as much overboard as possible.  I think we’re also ready to move beyond the original gondola to a more flexible framework.  It’s aerodynamic design is clearly not that critical.  With a rough back-of-the-envelope calculation, I don’t think the 30″ mylar helium-filled balloon can support more than 5.5 ounces.  The florist who filled it up skimped a little, and we really loaded the gondola up with junk, but we did succeed!  All Rube Goldberg comparisons aside.

A few other observations. The balloon was very sensitive to buoyancy.  A paperclip made the difference between it rocketing to the ceiling, or sinking to the floor.  Also, rigging it at one location and demonstrating it in another led to other practical frustrations.  Being in a near-perfect state of buoyancy, the balloon was very sensitive to changes in temperature and air currents, especially from air conditioners, fans and open windows.  Intro to PComp was held in a room affectionately known as “The Freezer”, while the lab was more forgiving, so these were factors for which we could have been better prepared.  I need to explore this further, and wonder if a larger gasbag would allow for a larger “buoyancy bandwidth”.  I cannot imagine, for example, a manned air balloon being this sensitive to changes in weight.  On the other hand, I could imagine it being sensitive to air currents and changes in temperature, and that would go a long way to explaining the success of fixed-wing aircraft, despite the lifting power of lighter-than-air craft.

We want to introduce object/collision detection with infra-red or ultra-sonic sensors, and a simple “follow-me” feature in which the airship behaves more like a pet, passively following the user about.

Subsequent to our presentation, Rory showed me this Arduino-controlled blimp from the Maker Faire–clearly we were onto something, and this is pretty impressive:

http://blog.makezine.com/archive/2009/06/blimpduino_and_uav_at_maker_faire.html

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