Checking out ArduCopter 2.6

king pretty good!  I went out with Andreas who had downloaded 2.6 onto his heavy lifter hex.

There's been a lot of discussion about Turnigy 9x failsafe.  The solution is simple, in both Andreas' and my opinion:  swap out the module for FrSky... cheap too, at $40 for the module and Rx.  I'll cover setting the failsafe in an upcoming post.

Idea: ArduPilot Differential GPS

Update


Fail... lots of people have thought of this idea and it won't work.


Executive Summary

• Hook a GPS to GCS.
• GCS calculates GPS difference.
• GCS transmits GPS correction over xbee MAVLINK connection
• ArduCopter Stabilize mode gets very fine resolution.

Background

I was just reading the ArduCopter 2.0 docs and saw this:

The quad should stay in a 4-5 meter diameter "circle" around the target position.

I recalled an old TV show where somebody used differential GPS (hereafter DGPS... is that a common name?) to track glacier movement... they had DGPS receivers planted across the ice, and a DGPS transmitter attached to rock.  I recall being impressed that they were able to get 1-inch resolution.

I googled around for DGPS products -- wouldn't it be neat if you could just buy something and have your ArduCopter hover with that kind of resolution! -- but found out a couple of things:

• DGPS seems pretty common in the GIS world.
• the definiton of "highly affordable" DGPS systems was about $15k.  Yikes!
• "portable" DPGS receivers were touted as being easy to carry around by a single person.
• DGPS seems to work by sending the sideband correctional signal over some kind of modem.
• "normal" GPS receivers won't benefit from a DGPS transmitter.

Idea

So, I had an idea for implementing DGPS in the ArduPilot/ArduCopter world.

• Hook up a GPS unit to your ground control station (GCS).  This could be any GPS unit... You could use a hand-held receiver with USB, make a custom arduino-based unit, etc.  The purpose of this unit is to be near the GCS and feed a love GPS signal of the GCS's current position.
• When setting up the GCS, allow an absolute current position to be entered.
• Add a MAVLINK message outbound from the GCS to the plane(s), broadcasting the difference in measured and specified absolute position and altitude.
• When in stable mode, the ArduPilot software takes the DGPS correction into account if it is available.
• Super Precision Stable Mode!

arr, it's the ardupirates!

Here are some links for the Ardupirates.  Arr! They've forked the arducopter code base and have some impressive demos regarding camera stabilization.  On their wiki they mention these features:

• Working Sparkfun Magnetometer
• GPS hold
• Altitude hold with Barometer and Sonar
• Automatic camera leveling plus an automatic camera trigger! 

Here's some links:

• Ardupirates RCG thread
• Google Codebase
• Ardupirates Wiki
• Ardupirates Configurator (supports multiple hardware platforms) 
• Ardupirates Installer

Setting up the Ardupilot software

The Ardupilot software uses the Arduino environment to compile and download to the Ardupilot board.  Here's how to set up your environment for that.

Download and install the Arduino Software

• The software is here: http://arduino.cc/en/Main/Software.  Get the latest version.  There are pre-compiled binaries for Mac, Windows, Linux-32 and Linux-64.
• I'm using a Mac.  It's a DMG with the Arduino software, ready to drag into your Applications folder.
• There's also an enhanced FTDI USB driver.  It's a package that installs using a password.

Set up a Working Environment

• This is a software project, and tidy housekeeping now will pay off handsomely in the end!
• I chose this as my base directory: $HOME/Dropbox/projects/ardupilot.  I'll call this $TOP below.
• Later we'll set up a SVN checkout.
• For now we'll just unzip the Ardupilot and Arducopter distributions here.  I'll save local copies of the zipfiles in $TOP/dist.

Dowload and unzip the Ardupilot Software

• From here: http://code.google.com/p/ardupilot-mega/downloads/list.
• The following is what I did from the mac command line... Adust to your favorite workflow.
• cd $TOP/dist
  wget http://ardupilot-mega.googlecode.com/files/ArduPilotMega1.02.zip
  cd ..
  unzip dist/ArduPilotMega1.02.zip

Download and unzip the Arducopter Software

• From here: http://code.google.com/p/arducopter/downloads/list.  I grabbed Arductopter RC2.zip.
• Download and unzip as per above notes.

Set up the Libraries

• The most painful step in getting things set up is getting the libraries installed.
• Here's the biggest pain in the whole software setup.  There might be a better way, but this is an area where the Arduino software could stand improving.
• Find your Sketchbook path.
• On mac:
  grep sketchbook.path ~/Library/Arduino/preferences.txt
  sketchbook.path=/Users/mh/Documents/Arduino
• Go to the sketchbook path just discovered.
• mkdir libraries, if it does not already exist
• cd to the libraries directory.
• copy all the folders in the ArduPilot project libraries directory here.
  $ cp -rp ~/Dropbox/projects/ardupilot/1.0-BETA/libraries/* .
• restart the Arduino program.  These libraries should now be available during compiliation.

Test your installation

• Start the Arduino program
• From the top menu, File/Sketchbook/libraries should show you the libraries you just copied, something like the screenshot below.
• Open the standard "blink" Arduino Demo: Menu: File / Examples/ 1.Basics / Blink
• Compile by pressing the "Verify" button.
• If that works, add the line
  #include
  to the beginning of the file
• Compile again.  If this works, your libraries have been installed.
• If it doesn't work, get ready to pull out lots of hair and gnash your teeth.

Build the Ardupilot Software

• start the Arduino system
• asdf
• File/Load the main ArduPilot program, ArduPilotMega/ArduPilotMega.pde
• When you compile, you will get an error like this:
  config.h:58:3: error: #error XXX You must define GPS_PROTOCOL in APM_Config.h
  (ignore the Aduino environment highlighting, and scroll back in the error window to the beginning of the error messages.  this is another area where the Aduino system could use some work.)
• Look in APM_Config.  See where is says "READ THIS. REALLY! READ THIS."?  Take that advice.
• 
  

Build the Arducopter Software

A Closer Look at the ArduPilot Mega

We received the ArduPilot board last week, and now we're getting ready to start getting going with it.  We bought the assembled and tested system from uDrones.  They're providing a great service by providing assembled and tested boards, as well as selling RTF quadcopters as well.  There's a nice writeup on what they're doing on diydrones. 

Here is what we ordered from uDrones.  The assembled and tested price includes the Ardupilot, IMU, and MediaTek GPS.  There's an optional GPS upgrade from MediaTek to U-blox.  The magnetometer is optional; you'll need it for any copter configuration.

• Ardupilot Mega 1.4.  This is the red board.  It's a custom Arduino-based board.  A separate coprocessor handles PPM (radio control) decoding.
• IMU/Oilpan Board.  This is the blue board.  It came from uDrones attached to the Ardupilot. It holds the gyros, accelerometers, pressure sensor, magnetometer input, etc.
• MediaTek MT3329 GPS: 10Hz + Adapter Basic.  This is the cheaper GPS option when buying from uDrones.  It's the recommended standard unit.
• HMC584 Triple Axis Magnetometer: Rev 1.1.  This is most important for multicopters. 

Weights for each of the units are as follows:

• ArduPilot + IMU/Oilpan: 395 grams
• MediaTech GPS: 74 grams
• HMC584 Magnetometer: 22 grams

We received the unit pre-flashed for the X-quadcopter but we'll be downloading our own builds.

Lots more details to come as we start assembling and testing the quad and fixed wing versions.

jDrones, "making UAV's and aerial robotics easy and affordable"

jDrones

"Welcome to our store, we are the official manufacturer for ArduCopter kits. Our
we have a wide knowledge on GPS devices, Micro controllers, electronic design, aviation and open source projects."

Frames, boards, arms, lots-o-stuff!