ROS2 & PX4 Precision Landing with ArUco Markers

Master the integration of ROS2, PX4, and OpenCV to achieve precision landing using ArUco marker detection. This tutorial delves into how to leverage ROS2’s robust communication framework and PX4’s flight control system to implement highly accurate landings for autonomous drones. You’ll learn how to configure your environment, process camera feeds, and detect ArUco markers in real-time, enabling your drone to land precisely at designated targets. Whether you’re new to drone development or an experienced engineer, this guide provides a step-by-step approach to achieving reliable precision landing with seamless integration into your ROS2 and PX4 projects.

ArUco Markers

Aruco markers are square fiducial markers used in computer vision for tasks like pose estimation, camera calibration, and augmented reality (AR). Each marker has a unique binary pattern inside a black border, allowing it to be easily detected and identified. They help in determining the position and orientation of cameras or objects in a scene, making them valuable in robotics, navigation, and AR applications. https://docs.opencv.org/4.x/d5/dae/tutorial_aruco_detection.html

Video Walkthrough

Watch the video on YouTube

Prerequisites

• Ubuntu 22.04
• ROS2 Humble
• PX4 Autopilot with an ArUco Marker and downward facing camera
• Micro XRCE-DDS Agent
• QGroundControl Daily Build
• OpenCV 4.10.0
• ROS_GZ bridge

You can find the required instructions collected below

https://docs.px4.io/main/en/ros2/user_guide.html https://docs.qgroundcontrol.com/master/en/qgc-user-guide/releases/daily_builds.html

You need the lates PX4-Autopilot, that will contain the required drone with the downward facing camera and the world that has the aruco marker in it To get ros_gz bridge

sudo apt install ros-humble-ros-gzgarden

https://github.com/gazebosim/ros_gz

For the OpenCV part follow the instructions below

Usage

Setup the Workspace

Make sure you source ROS2 Humble in the terminal you are using.

source /opt/ros/humble/setup.bash

OR Just add the line above to your bashrc, in that case it is going to be sourced every time you open a terminal.

nano ~/.bashrc

Navigate to the directory you would like to place the worskpace and then run the following

git clone https://github.com/ARK-Electronics/tracktor-beam.git

Then navigate into the workspace:

cd tracktor-beam

Install OpenCV from source

./install_opencv.sh 

Install the submoduls

git submodule update --init --recursive

Build the workspace

colcon build

After this runs, we do not need to build the whole workspace again, you can just build the individual packages you have modified

colcon build --packages-select precision_land

Source the workspace

source install/setup.bash 

Run the example

Run the simulation environment

Launch PX4 sim

make px4_sitl gz_x500_mono_cam_down_aruco

Launch micro dds

MicroXRCEAgent udp4 -p 8888

Launch the ros_gz_bridge for getting the camera topic

ros2 run ros_gz_bridge parameter_bridge /camera@sensor_msgs/msg/Image@gz.msgs.Image

Launch the ros_gz_bridge for getting the camera info topic (this is how we get camera intrinsics)

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