ROS2 & PX4 CustomMode example

This tutorial is a example on how to utilize custom modes in PX4 using ROS2 and QGC. We would like to provide you with a basic example code that you can customize and utilize for your application.

This project is a customized example of the usage of the Auterions PX4-ROS2 Interface Library

https://github.com/Auterion/px4-ros2-interface-lib

Video Walkthrough

Software

https://youtu.be/L1RO0oUdzqI

Hardware

https://www.youtube.com/watch?v=Sw24kesfpLw

Prerequisites

• Ubuntu 22.04
• ROS2 Humble
• PX4 Autopilot
• Micro XRCE-DDS Agent
• QGroundControl Daily Build

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 can also have a look on our previous tutorial where the steps above are covered:

https://github.com/ARK-Electronics/ROS2_PX4_Offboard_Example

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/px4_ros2_examples_ws

Then navigate into the workspace:

cd px4_ros2_examples_ws

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 custom_mode

Source the workspace

source install/setup.bash 

Run the example

Run the simulation environment

To ensure message compatibility, make sure you are using the same PX4 version as shown in the video. To do this, follow these steps:

cd PX4-Autopilot
git fetch origin
git checkout 8070c70
git submodule update --init --recursive

cd PX4-Autopilot/
make px4_sitl_default gz_x500

Run the Micro XRCE-DDS Agent for the communication stream

MicroXRCEAgent udp4 -p 8888

Run QGC Daily build

Navigate to the directory

./QGroundControl.AppImage

Take off with the drone using the GUI

Launch your custom mode

I created a launch file that you can use. It currently contains only one node, so it might seem limited, but you can expand on it. The file includes three basic patterns: circle, spiral, and figure-8. These are ROS2 parameters that you can set either directly in the launch file or via command line arguments. If no pattern is specified, the default is circle.

cd px4_ros2_examples_ws/
source install/setup.bash 

AND

ros2 run custom_mode custom_mode

OR

ros2 launch custom_mode custom_mode.launch.py

OR

ros2 launch custom_mode custom_mode.launch.py trajectory_type:=spiral

OR

ros2 run custom_mode custom_mode --ros-args -p trajectory_type:=figure_8

Start it from QGC

You can just start the custom node from the GUI or you can also map it to your remote control

Closing remarks

ONce you are done do not forget to close all your terminals

Video

ARK Electronics

For more open-source drone-related material, follow us on LinkedIn and Twitter:

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If you’re interested in US-manufactured drone hardware, please visit our webpage:

ARK Electronics

Questions

Message Patrik Dominik Pordi on the Dronecode Foundation Discord for questions or email me at patrik@arkelectron.com

Additional resources

LinuxCheatSheet ROS2CheatSheet CMakeBasics