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Gazebo Sim

Image of the Gazebo multirotor sim
Image of a multirotor in the Gazebo simulator.

This guide contains detailed information on using Gazebo Classic with ROSflight sim.

Gazebo Classic is a (now EOL'd) robotic simulator. It was previously supported by ROSflight, so it is supported now. However, it currently does not work on versions newer than ROS2 Humble, and should be replaced with Gazebo (the currently maintained version of Gazebo). In this guide, we often refer to "Gazebo Classic" as Gazebo.

Launch parameters

This document describes a lot of the launch-time arguments that can be passed to the launch files to configure the simulation. To see a complete list of the launch-time arguments, run a launch command with 

ros2 launch <package_name> <launch_file_name> --show-args

Note

To simulate a fixed-wing mav, just change all instances of multirotor in the steps below to fixedwing.

Danger

Gazebo Classic is officially EOL as of January 2025, and does not work with ROS2 Jazzy. If you are using ROS2 Jazzy, please only use the standalone sim or HoloOcean sim. The following instructions assume you are using ROS2 Humble.

We have not yet upgraded to Gazebo, which is not EOL and better. If you would like to help in this effort, please visit the GitHub issue and let us know.

Gazebo Sim architecture

Architecture of ROSflight sim when using Gazebo sim.
ROSflight modules used when using Gazebo Sim and how they interact. See the simulator architecture page for more information.

When using Gazebo as the visualizer, ROSflight Sim uses the modules shown above. See the simulator architecture page for more information.

Also note that Gazebo publishes the /clock topic, so the standalone_time_manager should not be used with Gazebo. Additionally, the Gazebo node only publishes this topic at ~10Hz, which is too slow for most applications (especially the sensors). Thus, we recommend not setting the use_sim_time parameter to true when using Gazebo, or you will get timing errors.

Installation instructions

Installing Gazebo is done automatically for supported distros (i.e. humble) by following the instructions in the installation for sim guide.

Tip

If you don't want to include any Gazebo dependencies when you build, simply remove the gazebo_sim folder from the simulators directory before running the rosdep commands: 

cd ~/rosflight_ws/src/rosflight_ros_pkgs/rosflight_sim/simulators
rm -rf gazebo_sim

Launching Instructions

  • Source the Gazebo Classic setup file if you haven't added it to ~/.bashrc: 
    source /usr/share/gazebo/setup.sh

  • Launch Gazebo Classic with the ROSflight SIL: 

    ros2 launch rosflight_sim multirotor_gazebo.launch.py

  • Gazebo Classic should now be running! Gazebo should open and you should see the STL of the multirotor at the origin.

Image of the Gazebo multirotor sim
Image of a multirotor in the Gazebo simulator.
  • You should have the following rqt_graph. multirotor_launch_rqt_graph

Tip

Run rqt_graph with the command rqt_graph in a new terminal, assuming the -desktop version of ROS2 was installed.

The launch file manages launching several nodes all at once, as shown in the rqt_graph image:

  • /rosflight_io: Handles the communication between the companion computer and the flight controller
  • /standalone_sensors: Simulates sensor measurements given the true state of the robot
  • /rc: Simulates the RC safety pilot connection to the firmware
  • /sil_board: Instantiation of the firmware
  • /gazebo: Visualizer
  • /multirotor/dynamics: Dynamics plugin to Gazebo Classic, computes the aerodynamic forces and moments given motor commands
  • /dynamics: Interface node between the dynamics plugin and the rest of the rosflight_sim modules

For more information on each of these nodes, see the simulator architecture page.

Running nodes individually

As described in the standalone_sim page, you can run each of the simulator modules individually.

Configuring the Gazebo sim

Tip

Command line arguments to launch files can be previewed by appending --show-args to the launch call: 

ros2 launch rosflight_sim multirotor_gazebo.launch.py --show-args

There are several command line arguments you can pass to customize the behavior at runtime. Here are some important ones:

  • aircraft: Defaults to "anaconda". This parameter controls which dynamics and parameter files get loaded, in addition to the STL file for visualization. Make sure this is set to your correct airframe!
  • use_sim_time: By default, set false. This parameter is a parameter of all nodes in ROS2. If set to true on launch, the node will create a subscription to the /clock topic, and will use that as the source of time for its timers. For Gazebo Classic, it is recommended to leave this as false, since Gazebo Classic publishes a /clock topic at 10Hz, which is too slow for most modules. If using the standalone sim, this parameter will allow you to speed up, slow down, or pause time. See the simulation architecture page for more information.
  • use_vimfly: Node that changes the default RC behavior to use VimFly, a program that lets you use Vim commands to fly around in the sim! Vim, of course, is recommended for everyone, but VimFly especially if you don't have access to RC transmitter connected over USB. See the joystick section for more information on what joysticks are supported.

These command line arguments should be passed using the <argument>:=<value> syntax. For example, 

ros2 launch rosflight_sim multirotor_gazebo.launch.py aircraft:=anaconda
would launch the Gazebo multirotor sim, but would use the fixedwing STL file.

After launching

Remember that the SIL tries its best to replicate hardware. That means you have to calibrate and set parameters in the same way you do in hardware. If you need a reminder, please follow the configuration and manual flight tutorial.

See the Parameter Configuration pages in this documentation for instructions on how to perform all preflight configuration before the aircraft will arm.

You can also run 

ros2 launch rosflight_sim multirotor_init_firmware.launch.py
to load all required parameters and perform initial calibrations for a quick simulation setup.

Warning

Remember to verify that all parameters are set to the value that you would expect. Otherwise, the vehicle will behave erratically.

After loading parameters, you can fly autonomously by launching your GNC stack. See the ROScopter or ROSplane tutorials for a reminder on how to run ROScopter or ROSplane.