DJI Tello ROS2

• DJI Tello driver for ROS 2 based on DJITelloPy that uses the official SDK for the drone.
• Can be used to control multiple drones both using the swarm functionality (only for Tello EDU) or using multiple WLAN with regular Tello drones.
• This project was developed as a way of learning ROS 2 and evaluate the viability of moving other in progress projects from ROS 1 to ROS 2.
• Ii is recommended to update the Tello firmware to the latest version available
• Project workspace is divided into sub-workspaces that contain different logic.
  • tello package is the main package, includes access to the drone information, camera image and control.
  • tello_msg package defines custom messages to access specific Tello data.
    • Defines the TelloStatus, TelloID and TelloWifiConfig messages
  • tello_control package is a sample control package that displays the drone image and provides keyboard control.
    • T used for takeoff, L to land the drone, F to flip forward, E for emergency stop, WASD and arrows to control the drone movement.

• Bellow is the list of topics published and consumed by the tello package
• The list of published topics alongside their description and frequency. These topics are only published when some node subscribed to them, otherwise they are not processed.

• The list of topics subscribed by the node, these topics can be renamed in the launch file.

• The list of parameters used to configure the node. These should be defined on a launch file.

Camera Calibration

• To allow the drone to be used for 3D vision tasks, as for example monocular SLAM the camera should be first calibrated.
• A sample calibration file is provided with parameters captures from the drone used for testing but it is recommended to perform individual calibrations for each drone used.
• Calibration can be achieved using the camera_calibration package. Calibration pattern can be generated using the calib.io pattern generator tool.

ros2 run camera_calibration cameracalibrator --size 7x9 --square 0.16 image:=/image_raw camera:=/camera_info

• Take as many frame as possible and measure your check board grid size to ensure good accuracy in the process. When the process ends a calibrationdata.tar.gz will be created in the /tmp path.

Launch File

• Launch files in ROS2 are now defined using python code. To launch the main node of the project add the following code to your launch.py file.

Node(
    package='tello',
    executable='tello',
    namespace='/',
    name='tello',
    parameters=[
        {'tello_ip': '192.168.10.1'}
    ],
    remappings=[
        ('/image_raw', 'camera')
    ],
    respawn=True
)

Overheating Problems

• The motor drivers in the DJI Tello overheat after a while when the drone is not flying. To cool down the drivers i have removed the plastic section on top of the heat spreader (as seen in the picture).
• If you are comfortable with leaving the PCB exposed removing the plastic cover should result in even better thermals.
• If possible place the drone on top of an old computer fan or use a laptop cooler to prevent the drone from shutting down due to overheating.

Install

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