Home » Drone, Issues, Programming » Controlling the drone with our own built program – roundels recognition

Controlling the drone with our own built program – roundels recognition

So far, what has been shown here about the drone was mostly made possible thanks to third-party applications, that we managed in some way to have working with our devices (PC or smartphone). This was good as an introduction, but here you will read how we had it controlled thanks to programs we could compile by ourselves.

First of all, we are using the AR.Drone SDK 1.6, with the last firmware to this day running on the drone, that is version 1.5.1. Lots of issues have been encountered with the latter by the developing community, among them:

  • Updating the firmware from version 1.3.3 directly to 1.5.1 while skipping 1.4 results in bricking the quadricopter. Parrot is currently working on a solution affordable to everybody12.
  • Using the Windows SDK 1.6 with the newest firmware implies losing the video stream, on top of many timeout issues and not working controls (well, not sure is this last one is directly linked to that combination).

So we tried the examples provided in the SDK, that enable basic control of the drone. However, before running them, one needs to compile and build the source code, making sure that all the libraries are correctly installed.

Windows SDK example

To basically enjoy a good experiment with the Windows SDK 1.6, it is recommended to stay to a firmware version no more recent than the 1.4.7. This way, it is possible to display the camera feeds on the computer screen. The setup is completely tedious since nothing is working straight out of the zip archive. One would have to follow instructions made by other developers3, on top of looking for help in the official API forums. It looks as though this Windows part of the SDK was not tested before its release.

We eventually has it working on our Windows 7 laptop. It was possible to move the UAV using the keyboard, but the program was really high processor consuming, which often resulted in laggy controls, timeout issues and unresponsive drone. Yet commands were better once the video shut down.

We then took the opportunity to play a little with the source code and do our own stuff, like launching LED animations, but its was overall not satisfying because of the bad response time.

 

Observe the frequent timeout issues resulting in unwanted moves. It was still nice to run this Windows example to get a first glance of the raw navigation data in real time directly in our Windows terminal. Keyboard controls give a good feeling of the drone piloting. Note how CPU demanding this program is.

 

Linux SDK example

So we had to move on to another platform, that is better supported and knows less issues. Linux with Ubuntu 10.10 proved its magic in this matter, and the instructions to follow in the official developer where quite comprehensive and sufficient to have a running project after a few command lines.

The icing on the cake is that the navigation example gets on improved GUI that displays tons of navigation data in real-time. It is also CPU friendly, is efficient with the video while using the latest firmware, and works well with a game controller.

Excerpt of the Linux navigation screen. The yellow section shows that an oriented roundel has been found on the ground, and provides its orientation, its coordinates (xc, yc) in the camera view, its width, its distance from the drone.

The other good news is that the code is more readable, and it was not a pain in the neck to manage to display some data about tag tracking. We indeed fulfill this goal by calling some of the drone embedded functions that enable roundels tracking on the ground or in the air.

Basically, we can now recognize one or more -up to five, actually, according to the documentation- ground robots carrying the same kind of roundels on their back, and report their coordinates with their orientation as well (coordinates represented in the system of the video capture – we still have to investigate its specifications). We did not fulfill following one specific robot by hovering over a roundel, since the pre-implemented function does not seem to work anymore (we are waiting for an answer from the developers on their forum). We guess then that we will have to do it by ourselves, which is now our next objective.

As an aside, we discovered the resolution of the vertical camera: it is a QCIF resolution of 176×144 pixels4.
  
References

  1. Have a look at the official and public forums to be kept up to date: http://forum.parrot.com/ardrone/en/viewforum.php?id=7 []
  2. http://www.ardrone-flyers.com/ is a great website to get answers on how to save your drone by yourself. Previous firmware versions can also be found in its wiki section. []
  3. Very clear instructions can be followed on this website to achieve that: http://www.sparticusthegrand.com/ardrone/ardrone-compile-windows-sdk-1-5-in-visual-studios-2010/ (it is about SDK 1.5, but still necessary for 1.6) []
  4. Wikipedia explanations on the CIF conventions []

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