Friday, October 01, 2010


To make a long story short and close this chapter, the project was a success!

All the goals and conditions were met (with the exception of spontaneous combustion and/or disappearance trough a hole in space/time), and this is how it all went:

AVI@TOR MK3 was build, incorporating all of the knowledge gained so far.

This included two tone florescent paint job (orange for visibility in high brightness, yellow for low light), to avoid getting lost in the snow, clouds and twilight conditions.

Complete with reinforced wings (no more broken off wings during flight due to overweighted airframe), all the extra components packed in to the canopy, smaller cuts for a smaller phone resulting in weight reduction from previous model and so on.

And it flew on it's own, controlled only by an Android phone (HTC Legend), using only it's on-board sensors (accelerometer, magnetometer and GPS; NO gyroscope).

Battling winds (between autopilot sessions there is a moment when the plane is standing still in the sky), overweighted airframe (not easy keeping it steady) and slow sensors (accelerometer may be accurate but it's slow compared to a gyroscope). But even so it manages to fly in to the general direction where it was pointed, steadying itself and correcting course.

Unfortunately human pilot error (many like shown above) and flying home made electronic in sub 0°C weather (which has caused solder connection to break) has shortened the useful academic life of the plane.

But not before some more fun has been had with it!

Aerial video of the prowling grounds, this time on a phone with a decent camera.

Aerial video with a "fish eye" lens (an attachment, which was later found out to mess with the internal sensors of the phone enough to cause some autopilot crashes).

Not to dwell too much on the autopilot, some time went in to enhancing the distortion caused by the lens. First attempt, a brute force implementation of the Barrel algorithm (which took 7 hours to render the clip above).

Second implementation, using openCV and it's build in features (which took only 15 minutes to render, 2 minutes of that time used by a script to generate a command with over 8000 parameters (picture names)).

Despite all the mentioned adventures, experiments and much more, the plane still flies. But no more for science (too much glue to fly straight any more), only for fun and experience. A fitting retirement for a successful project!

Saturday, September 25, 2010

Testing out War Paint

In the preparations to rebuild the plane, this time a painting test:

Aimed for maximal visibility, the winning combination seems to be: florescent "lemon yellow" with no primer on the hull and florescent "signal red" with primer on the wings.

Regardless of the primer, the paint sticks the same and can be peeled off with duct tape.

Equipment Testing - Controller v2

Time to test the controller board:

Interestingly enough, the frequency at which the beeper operates, is not exactly audible to a mobile phone microphone.

Thursday, September 23, 2010

The Controller Reborn

And now it's time to show off the finished controller board v2:

A few correction of beginners mistakes later (it was literally designed to small for a few connections to function correctly), completed with a weight of 12.88 g. That's 3.5 times lighter and includes upgrades, such as, a beeper to signal who is control and a dip switch for manual overriding of control channels for testing.

Wednesday, September 22, 2010

Equipment Testing - Demodulator v2

After hacking an USB to COM converter cable, so it interfaces to the new demodulator board:

It was time to test it out:

Trusty FlightGear to help us out with this task and the setup works quite nicely.

Friday, September 10, 2010

The Demodulator Reborn

First one of the boards completed:

Stacked against the old one for size (no, the two part "construction" is not by design). The new one weighing exactly 5.43 g is 9 times lighter and way way smaller, which will hopefully bring stabler flights in the future.

Ceremonial Cutting of the Board

So, the big slab of integrated circuits from China have been cut:

To show them up against the previous version for size:

The weight savings on the boards alone is worth the trouble.

Monday, September 06, 2010

It's Over 9000

As the title conveniently trough a pop culture reference* suggest, we'll be talking about power.

Engine power that is. The question was, how much power does the used EMAX BL2210/25 engine consume. So a measuring contraption was built:

And after much fun fiddling with it, this is the result:

As expected, almost linear ratio between output power and consumption. Almost linear because the measurements themselves weren't perfect, since they needed to be interupted for the engine to cool off (no flight, no airflow).

* look up Dragon Ball Z.

Thursday, September 02, 2010

The Future has Arrived

And it has done so all the way from China:

This package contained nothing less than the redesigned boards, professional made to order:

Dual layer printed circuit boards, 0.6mm thick, with black coating and red silkscreen (which is visible under the sun, but not so much indoors). Obviously we ordered some excess boards for redundancy and cost savings.

But from idea to a delivered product in less then two weeks (would be way less if some beginner mistakes were avoided), ordered from PCBCORE and totally worth it.

Wednesday, September 01, 2010

Adjusting the View

One annoyance with using the camera on the mobile phone to take pictures from the plane was lack of perspective due to narrow angle of the lens.

Arriving today, a fix for that:

A 180° wide angle "fish eye" lens for mobile phones.

First impressions:

A proper mount and some zoom magic and the end result should be respectable or at least interesting.

Monday, August 30, 2010

Testing Safe Positions

Some "postmortem" tests on the crashed airframe before it gets scrapped for parts.

A homemade wind tunnel like device constructed from a air compressor gun, outfitted with a string of yarn to show path the air flow. Plus a straight carbon fiber stick to show deflection.

Test on the wing (obviously)

Test on the tail (obviously)

Noted, this measurements are far from being perfectly accurate (though they were fun to produce), but they will serve as a base to tweak the model of desired plane's attitude compared to the angle of attack.

Thursday, August 26, 2010

Designing Upgraded Electronics

With achieved milestone of (short) autonomous flight it's time to rebuild and improve the plane.

To optimize the build of new boards, my little brother had lend his talent and designed these:

New and shrunk demodulator board.

New and improved control board, now with a beeper for signaling states and hardware switches for continuous manual override on each channel.

Next step/experiment is having them professionally made from somewhere in China.

Sunday, August 08, 2010

Tools for All

Until the plane is rebuild, hardware side will have to wait. Which leaves just enough time to work on the software a little.

Now on the market, straight from this project: rrTimeLapse

For all your time lapsing photography needs. As of now it supports resolution selection, start/stop timer or continuous shooting, amount of lapse time and auto focus selection. And it can do all that in the background, enabling use of other applications simultaneously.

Posted as Open Source, you can find it here:

Or on the Android Market here:

P.S. If you find it useful, let me know!

Wednesday, August 04, 2010

Rooting HTC Legend


The PPTP VPN connection, used to connect to the phone over mobile Internet was not in a working state on this phone. As it turns out, there is a bug in Android 2.1, causing some mischief.

So, to fix this problem, the phone was "rooted", with the intent of flashing a software image with added appropriate tunneling drivers:

Thanks to the modding community, not such a daunting task, but some time was spent finding the right rom with the issue resolved.

The winning combination can be found here:

Thursday, July 15, 2010

Flying Lessons - How Not to Fly MK2

Just a quick recap what has been learned in the memory of the AVI@TOR 02 airframe.

Quit while you're ahead. Having the wing broke and fall of mid flight due to material fatigue is only amusing for so long. Once you know what kind of stress the airframe is going to be subjected to, reinforce it.

Also, physics works. Using ailerons as flaps changes the behavior of the plane. Don't forget to use the elevator to compensate for the shift in plane's Center of gravity.

That and the field test are fun! Hope for many more.

Tuesday, July 13, 2010

And so it Flies

A complete success. The plane flew on it's own and spectacularly crashed on it's own.

First the good news, two successful autonomous "straight" flights (without plotted course):

First flight lasted about 5 seconds, before it got knocked from the path by wind and it had to be landed down manually.

Second flight lasted about 8 seconds, before it got knocked from the path again by wind. Only this time the plane managed to stabilize itself, causing it to loose altitude, managed again to correct itself and fly upwards, but the maneuver was too steep and the worn out airframe failed and crashed.

For some reason the GPS resolution was poor on the second flight.

Now the bad news, the crash destroyed the airframe and broke the demodulator board. No more flying until the plane is rebuild and electronics are replaced.

As for the crash, the "official report" is this:

The plane flew stable, maintaining heading and altitude until it got hit off the path by wind. Even with stabilization it veered right both times, probably on the account of a worn out, slower and imprecise servo (it has seen a lot of crashes). The second time it managed to stabilize itself which resulted in the nose of the plane pointing downwards and loosing altitude. When attempting to achieve neutral pitch from previous maneuver it turned upwards too sharply, resulting in increased stress on the airframe, which due to materials being worn out (again, it has seen a lot of crashes), the wings bent out of shape, pulling out the link between the servo ans one of the ailerons, causing it to destabilize and crash in a spiral.