This is the second tutorial in the Up and flying with the AR.Drone and ROS series. In this tutorial we will: In the next tutorials, we will: To complete this tutorial you will need: I also assume that you’ve completed the previous tutorial, which details how to setup the software, connect to the drone, etc. In this tutorial, we will be flying the AR.Flying inside can be dangerous. When flying inside, you should always use the propellor-guard and fly in the largest possible area, making sure to stay away from walls and delicate objects. Even when hovering, the drone tends to drift, so always land the drone if not being flown. I accept no responsibility for damages or injuries that result from flying the drone. It has been three weeks since the launch of the first tutorial and I am very happy with the response so far. The tutorial has been viewed over 720 times and ARDroneUbuntu downloaded over 50 times. I was also given the honor of partaking in RobotGarden’s very first Quadrocoptor Workshop, where we worked through the tutorial (and ironed out the bugs) together.

This response has taught me a few things about how to structure a tutorial series, and how to release a virtual machine. Based on what I have learned, I will be restructuring the source-code for the following tutorials. I will also be updating the virtual machine to reflect these changes. When writing the first tutorial, I thought it would be better to have a separate repository for each tutorial to keep everything atomic and isolated to ensure the addition of a new tutorial would not affect anything in the past – However having learned from the video-hangout with RobotGarden, I realize this could cause an update nightmare down the track. parrot ar drone indoor hull repairFor this reason, I have decided to operate from a single repository and will maintain a stable branch for each tutorial, with the master branch always synchronized with the stable version of the latest tutorial. parrot ar drone hotline

The source-code for each tutorial will also contain all source-code required to run the previous tutorials. Sorry for any hassle caused by the above, I hope this new structure will allow me to more easily deliver the next tutorials! Connect to the AR.Drone as detailed in the first tutorial (remembering to disconnect other network adaptors if they use the 192.168.1.x address range) From within your Linux installation, launch two terminal windows (ARDroneUbuntu users, refer to the first tutorial if you’re not sure what I mean)ar drone parrot fiyat In the first window, launch the KeyboardController from the first tutorial, using the command:read maine police buy $300 'toy' drone that's illegal to use Wait for everything to load and the video display to become active, then in the second terminal window enter the command:grendel drone commander schematic

This command lists all active “topics”, the communication channels through which ROS programs (called “nodes”) communicate. To view the currently running ROS Nodes, type: The window that appears will show a network of nodes, and how they are connected through the topics that we saw in the previous step. When you’re ready, close this window. We’re now going to have a look at the messages that are being sent between nodes. parrot ar drone vancouverAt the terminal, type: The navdata message is published by the AR.Drone driver at a rate of 50Hz. Press Ctrl-C to stop echoing the navdata message then switch to the other terminal window and press Ctrl-C again, to stop the roscore program After that whirlwind tour of the ROS communication hierarchy, lets take a look at what we’ll be building today: As shown above, today we’ll be setting up the joy_node (a standard ROS package) to listen for input from a joystick or control-pad.

This input will be converted into a ROS message, then sent to our controller over the joy topic. Our controller subscribes to the joy topic and reacts to the received messages by translating joystick movement into drone movement commands, which are then published to the cmd_vel topic; and button presses to takeoff, land, or emergency commands, which are each published to a respective channel. The ardrone_driver receives these various commands and then sends them via the wireless network to the physical drone, which in turn sends back a video stream. This video stream is published by the ardrone_driver onto the /ardrone/image_raw topic, from where it is received and subsequently displayed by our controller. Firstly, we need to connect the joystick and set it up to work with ROS. Now that we have the joystick installed, let’s check to make sure everything is working. Type the following at a terminal, substituting jsX for the joystick device you previously identified:

If you are greeted with a “jstest: Permission denied” error, type: Which enables all users to read the joystick device (ARDroneUbuntu users, the password is: ardrone). After running jstest, moving the joystick should cause the numbers on the screen to update, if not, try running jstest for the other jsX devices. Congratulations, your joystick device is working! Press Ctrl-C to exit. Now we’re ready to integrate the joystick device with the ROS ecosystem using ROS’s “Joy” package. We now have the task of identifying the various axis and buttons used to fly the drone. All in all, you will need to identify axes to control the AR.Drone’s roll, pitch, yaw-velocity and z-velocity; and buttons to trigger an emergency, command a takeoff, and command a landing. To identify the emergency button for example, press the button you would like to trigger an emergency, and watch the terminal to see which button is enabled. In my case, I use the joystick’s trigger button for emergency (being able to react quickly to an emergency is very important).

With the button pressed, the following is printed in the terminal window: From this I can identify that: Emergency = Button 0 (note that indexing starts from zero). The process follows similarly for identifying an axis: From this I identify that the Roll Axis = 0 and Roll Scale = 1. After you have identified all axes and buttons, press Ctrl-C in all terminal windows to stop the processes. In ROS, a “Launch File” is used to configure and launch a set of nodes. We’ve already seen this in the first tutorial (and at the beginning of this one), where we typed: In this command, keyboard_controller.launch configures the ARDrone driver for indoor flight, then launches both the driver and keyboard controller. Similarly in this tutorial, we will be launching the joystick controller (and related nodes) using a launch file. Go ahead and open a terminal window, then type: This will open the joystick_controller.launch file in the text editor (non ARDroneUbuntu users can use a text editor of choice).

You will need to customize this file for your setup. Feel free to have a look at some of the parameters used on the drone. The drone’s control parameters can potentially be increased to allow for more aggressive flight. Once you’re happy with the settings, save this file as joystick_controller.launch, then close the geany application. So, after that rather long endeavor (which you should only need to do once), lets fly! Connect to the drone, disconnect other network devices, then open a terminal and type: This will launch the nodes as you configured in launch file. If all goes well, you should now be able to fly the drone using your joystick. Before commanding the drone to take-off, you should first check that your emergency button works. With the drone still landed, press the emergency button once. All onboard LEDs should turn red. Pushing the button again will reset the drone, and the LEDs will once again turn green. In addition to this, whenever a (mapped) button is pressed, the joystick_controller will print a message to the terminal, such as “Emergency Button Pressed”.