drone simulation environment setup (PX4, ROS2, gazebo)

Introduction

There are many ways to simulate drones, but this article focuses on a setup aimed at ultimately using the same code for autonomous drone flight on an actual drone.

• PX4: An open-source flight controller, easy to use with hardware like pixhawk
• ROS2: An open-source framework for robots, ROS is also fine
• gazebo: An open-source 3D simulator, lightweight enough for laptop use

In theory, using pixhawk and an onboard Ubuntu computer should make it easy to transfer to an actual drone.

Setup

First, install Ubuntu 22.04.
https://ubuntu.com/tutorials/install-ubuntu-desktop#1-overview

Then install PX4, ROS2, and gazebo.

ROS 2 User Guide | PX4 User Guide (main)

At this point, you should be able to move a drone in gazebo using sample scripts with ROS2 and PX4.

Development

Camera Data Stream

To bring camera image data from gazebo topics to ROS2 requires a bit of work.

Install ros-humble-ros-gzgarden:

sudo apt install ros-humble-ros-gzgarden

You need to create a bridge with either ros_gz_image or ros_gz_bridge.

ros2 run ros_gz_image image_bridge /camera

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

ros_gz_bridge can be used for other topics (like depth) as well, so it seems more versatile.

ros2 run ros_gz_bridge parameter_bridge /camera@sensor_msgs/msg/Image@ignition.msgs.Image 
/camera_info@sensor_msgs/msg/CameraInfo@ignition.msgs.CameraInfo /depth_camera/points@sensor_msgs/msg/PointCloud2@gz.msgs.PointCloudPacked /depth_camera@sensor_msgs/msg/Image@ignition.msgs.Image

ros_gz/ros_gz_bridge at ros2 · gazebosim/ros_gz

Keyboard Control

Since PX4’s sample code is waypoint-based, you’ll need code to control things like the drone’s speed for keyboard operation.

This code makes it easy to use the keyboard, but note that it uses mavsdk, which is different from the px4_ros_com sample code.

PX4-ROS2-Gazebo-YOLOv8/keyboard-mavsdk-test.py at main · monemati/PX4-ROS2-Gazebo-YOLOv8

Trouble Shooting

I spent some time debugging this issue, so I’m including it just in case.

When trying to start PX4, I encountered this error:

ERROR [gz_bridge] timed out waiting for clock message
ERROR [gz_bridge] Task start failed (-1)
ERROR [init] gz_bridge failed to start
ERROR [px4] Startup script returned with return value: 256

This command fixed it:

pkill -9 ruby
unset GZ_IP
unset GZ_PARTITION

Reference:

PX4-SITL stopped working with Gazebo Garden

The PX4 user forum is very active, so it’s recommended to consult there if you get stuck in debugging.