Spiraling Under Control

One of the staples of fixed wing autopilots is the circle hold.  A circle hold is the closest thing you can get to a pause button with a vehicle that must be in constant forward motion to stay aloft.  There are a few hidden challenges in the task, including wind compensation and some unexpected coupling that can lead to weird looking oscillations if not handled well.  People have been doing circle holds with UAV’s for a long long time, so I don’t bring anything new to the table, but it is always fun to play, err I mean experiment.

Circles


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RC Aircraft Precision Balancer and Work Stand

This morning I whipped together a “precision aircraft balancer” (like the Great Planes “C.G. Machine”.)  I built it out of $5.57 worth of PVC pipe and connectors from Fleet Farm and it probably took me an hour at the most.

The Plan

Here is my concept drawing:

IMG_20130625_083257

Shopping List

Here you are looking at $5.57 worth of PVC parts purchased locally.  The one flaw in the original design is that no one locally sold those 3-way corner connectors.  Maybe they don’t even exist?  So I made an on the fly design change while I was shopping.  The new design uses …
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“fedup” with Fedora!

Fedora 18 “Spherical Cow”

f18release

I think everyone has a bit of a love/hate relationship with their technology.  We hate it when it doesn’t work, or we can’t figure something out, or something breaks or doesn’t make sense.  But we love the new upgrade, the fancy new desktop background, animated menus, or what have you.  Fedora 18 was just recently released so of course I had to jump on that and get all the new stuff here as quickly as possible.  Is it great?!?  Was it worth the wait?  Is it a waste of time?  Do I love it?  Do I …
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Python Airfoil Manipulation Library

For lack of a better title …

I am creating a set of python libraries for designing and modeling aircraft.  Rather than spend a couple months learning a complicated and expensive CAD tool, why not spend that time learning python?  It makes perfect sense to me. 🙂

Scripted modeling (versus interactive point and click modeling) is a different mind set, but the advantage is you can make a change to the script and rerun it and that change cascades through all the parts and drawings and layout sheets.  In a gui based CAD system if you need to change the …
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I’m Thankful for my Senior Telemaster

This Thanksgiving day I’m thankful for many blessings: family, friends, neighbors, shelter, food, our siberian husky who lived 16 years, and many other things.  The weather was nice Thanksgiving morning so I was thankful to have an hour to run out to the field first thing to do some flying.

On Thursday, November 22 (Thanksgiving day) my Senior Telemaster past an interesting milestone: 12 cumulative hours of fully autonomous flight. This may not sound like a whole lot, but it represents 58 separate flights over the span of 3 years. In every flight it has performed beautifully and majestically and …
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Setting up “autologin” on a gumstix running the 3.5 kernel (yocto, poky, et. al.)

The gumstix.org wiki has a page on how to configure your gumstix to auto-login on boot.  This can be very nice for “production” systems where the intention is to power on and run some specific firmware/code every time.

However, with the new Yocto/Poky images based on the 3.5 kernel, things have changed and the old instructions no longer work.  Here is a quick recipe to get autologin running again on the newer systems.  First of all credit to http://fedoraproject.org/wiki/Systemd for their section on setting up autologin on a virtual terminal with the new systemd architecture.

Step #1:

Compile this “autologin.c” …
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Hacking the APM2 Part #5: Flight Testing

This is the payoff video showing the hybrid autopilot system in action in the Resolution 3 airframe. (By the way, this is HD video so watch it full screen if you can!)

I am skipping many details between integrating the hardware and flying, but just as a quick overview:

We first integrated the system into a Senior Telemaster.  After 4 trips to the field over the span of 2 days, numerous flights, and a bunch of work in the evenings, we felt like the system was coming together and working every bit as well as it was supposed to.  There …
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Hacking the APM2 Part #4: Laying out a “hybrid” system

Imagine for one second that you are a UAV developer. The DIYdrones ArduPilot is an awesome piece of hardware; you love all the great sensors that are attached; you love the all-in-one design and the small/light size.  But you are also feeling the limits of it’s ATMega 2560 processor and the limits of it’s 256Kb of RAM.  And maybe, you enjoy developing code within a full blown Linux developers environment with all the supporting libraries and device drivers that Linux has to offer.

Hardware Layout

Here is a picture of a protype “hybrid” autopilot system for small UAV’s.  What you …
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Hacking the APM2 Part #3: Servos

Here are a few random notes on the APM2 and servos.

As we all know, the servos are controlled by sending a digital pulse on the signal line to the servo.  The length (time) of the pulse maps to the position of the servo.  A 1500us pulse is roughly the center point.  900us is roughly one extreme and 2100us is roughly the other extreme.  Different systems will use slightly different numbers and ranges, but these are good numbers to start with.  Historically, RC systems stacked the pulses for multiple channels on a single radio signal — affectionately called the “pulse …
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