[ros-users] ROS Interface for AR.Drone Quadrotor

[Eric Perko]

Hi Nate,

Sweet! I was looking at the AR.Drone and wondering how easy it would be to
get it to support ROS. Much easier now thanks to your work :). I do have a
few comments/questions below.

On Fri, Oct 15, 2010 at 4:24 PM, Nate Roney <roney.nate at gmail.com> wrote:

> Greetings everyone,
>
> I'd like to share a project I've been working on with the ROS community.
>
> Some may be familiar with the Parrot AR.Drone: an inexpensive quadrotor
> helicopter that came out in September. My lab got one, but I was pretty
> disappointed that it didn't have ROS support out of the box. It does have
> potential, though, with 2 cameras and a full IMU, so it seemed like a
> worthwhile endeavor to create a ROS interface for it.
>

> So, I would like to announce the first public release of the ROS interface
> for the AR.Drone. Currently, it allows control of the AR.Drone using a
> geometry_msgs/Twist message, and I'm working on getting the video feed, IMU
> data and other relevant state information published as well. Unfortunately,
> the documentation on how the Drone transmits it's state information is a bit
> sparse, so getting at the video (anyone with experience converting H.263 to
> a sensor_msgs/Image, get in touch!) and IMU data are taking more time than
> I'd hoped, but it's coming along. Keep an eye on the ardrone stack, it will
> be updated as new features are added.
>

Can you access the H.263 stream using GStreamer? If so, you ought to be able
to use the gscam node (http://www.ros.org/wiki/gscam) to go from GStreamer
to ROS images. Sadly, pointing you to the node is about the extent of my
experience with gscam, but others might be able to help further if you can
verify that GStreamer by itself can read in the video streams.


>
> For now, anyone hoping to control their AR.Drone using ROS, this is the
> package for you! Either send a Twist from your own code, or use the included
> ardrone_teleop package for manual control.
>

I was looking at your driver docs and noticed a bit of nonstandard
coordinate frames going on. First, see
http://www.ros.org/reps/rep-0103.html for
an overview of how coordinate systems are defined in ROS. Body frames are
generally defined as +X forward, +Y left and +Z up. In that case, what you
do with the Twist is a bit non-standard; linear.x should be forward/back,
linear.y would be left/right and linear.z would be up/down, with angular.z
as yaw if the AR.Drone's body frame was following the standard ROS
convention for coordinate systems. Any reason why you went with the Twist
interpretation as documented on the wiki at
http://www.ros.org/wiki/ardrone_driver as opposed to a more standard
interpretation?

Also, what sort of units are on those components? meters/s for the linear
ones and rad/s for the angular?

- Eric


>
> You can find the ardrone_driver and ardrone_teleop packages on the
> experimental-ardrone branch of siue-ros-pkg, which itself never had a proper
> public release. This repository represents the Mobile Robotics Lab at SIUE,
> and contains a few utility nodes I have developed for some of our past
> projects, with more packages staged for addition to the repository once we
> have time to document them properly for a formal release.
>
> http://github.com/siue-cs/siue-ros-pkg
>
> http://github.com/siue-cs/siue-ros-pkg/tree/experimental-ardrone
>
> I'm hopeful that someone will find some of this useful. Feel free to
> contact me with any questions!
>
> Cheers,
> Nate Roney
>
>
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