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 …
Read the rest... >>

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 …
Read the rest... >>

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 …
Read the rest... >>

Hacking the APM2 Part #2: Fun with Baud Rates

The autopilot architecture I am building involves and APM2 collecting all the sensor data and sending it over a serial connection to a Gumstix Overo running Linux, and then in return the Overo sends servo commands back to the APM2.  As you can guess, this turns out to be quite a bit of data being sent at a high rate.  If all the processing, filtering, and computation is being done on the Overo it is important to have a high update rate, low latency, reliable communication, and no major pauses in processing at either end.

In this architecture, the APM2 …
Read the rest... >>

Hacking the APM2 Part #1: Introduction


I would like to start off my first post in this series by briefly describing where I’ve been and where I’m going.  Hopefully this will give a bit of context to help understand subsequent posts and hopefully will help put my engineering decisions in some context.

History of the World, Part 1

Somewhere around 2005 I became very interested in aerial robotics.  I have always been an aviation enthusiast, I’ve built model airplanes since I was a kid, and I have been flying RC airplanes since high school.  At the time I was working for the Univ. of Minnesota …
Read the rest... >>