Flock

Flock is a ROS driver for DJI Tello drones.

Packages

• flock meta-package glue
• flock_description robot description files (TODO)
• flock_driver interface between the Tello hardware and ROS, not required for simulation
• flock_base base nodes
• flock_rviz extensions to rviz (TODO)
• flock_gazebo extensions to Gazebo (TODO)

Nodes

flock_driver

Provides a ROS wrapper around TelloPy. Not required for simulation.

Subscribed topics

• ~cmd_vel geometry_msgs/Twist
• ~takeoff std_msgs/Empty
• ~land std_msgs/Empty
• ~flip flock_msgs/Flip

flock_base

Provides teleop and (eventually) autonomous control.

Subscribed topics

• ~joy sensor_msgs/Joy

Published topics

• ~cmd_vel geometry_msgs/Twist
• ~takeoff std_msgs/Empty
• ~land std_msgs/Empty
• ~flip flock_msgs/Flip

Installation

1. Set up your Linux environment

Set up a Ubuntu 18.04 box or VM. This should include ffmpeg 3.4.4.

ffmpeg -version

2. Set up your Python environment

Use your favorite Python package manager to set up Python 2.7 and the following packages:

• numpy 1.15.2
• av 0.5.2
• opencv-python 3.4.3.18
• opencv-contrib-python 3.4.3.18
• tellopy 0.5.0

3. Install ROS

Install ROS Melodic with the ros-melodic-desktop-full option. This will install Gazebo 9 and OpenCV 3.2, among other things.

Install these additional packages:

sudo apt install ros-melodic-joystick-drivers

4. Get Flock

Create a catkin workspace:

source /opt/ros/melodic/setup.bash
mkdir -p ~/flock_catkin_ws/src
cd ~/flock_catkin_ws/
catkin_make
source devel/setup.bash

Download and compile flock:

cd ~/flock_catkin_ws/src
git clone https://github.com/clydemcqueen/flock.git
cd ..
catkin_make

Running Flock

Test the environment

This script will connect to the drone and display a video feed in an OpenCV window. It will also look for ArUco 6x6 markers and highlight them in green. It does not require ROS.

Turn on the drone, connect to TELLO-XXXXX via wi-fi, and run this script:

python ~/flock_catkin_ws/src/flock/flock_driver/scripts/environment_test.py

Teleop

This ROS launch file will allow you to fly the drone using a wired XBox One gamepad.

Turn on the drone, connect to TELLO-XXXXX via wi-fi, and launch ROS:

roslaunch flock_base teleop.launch

For left-handed operation:

roslaunch flock_base teleop.launch left_handed:=true

Controls:

• The left stick controls forward motion and yaw
• The right stick controls altitude and allows for strafing
• The small menu button takes off
• The small view button lands
• The 4 buttons Y, X, B and A will flip forward, left, right and back, respectively. The Tello won't flip if the platform is unstable, so you may have a wait a second or two between flips.

An OpenCV window will pop up to show any 6x6 ArUco markers.

You can modify teleop.launch and/or flock_base.py to support other gamepads.

WARNING: the flock_driver node sends a land command just before it quits. If you kill the ROS session normally (with a Ctrl-C) the drone should land as the ROS session dies. However, if the flock_driver node dies unexpectedly while the drone is flying you may have to re-launch and reconnect to get it to land.