# Ignition Gazebo Simulation

WARNING

Ignition Gazebo supports a single frame (X500 quadcopter) and world (October 2022).

Ignition Gazebo (opens new window) is an open source robotics simulator from the Ignition Robotics Project. It is derived from the popular robotics simulator Gazebo, featuring more advanced rendering, physics and sensor models.

Supported Vehicles: Quadrotor

Note

See Simulation for general information about simulators, the simulation environment, and simulation configuration (e.g. supported vehicles).

# Installation (Ubuntu Linux)

Note

These instructions were tested on Ubuntu 18.04, Ubuntu 20.04, and Ubuntu 22.04

  1. Install the usual Development Environment on Ubuntu LTS / Debian Linux.

  2. Install Ignition Gazebo (sudo may be required):

    sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
    wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
    apt update
    apt install ignition-fortress
    

# Running the Simulation

Ignition Gazebo SITL simulation can be conveniently run through a make command as shown below:

cd /path/to/PX4-Autopilot
make px4_sitl gz_x500

This will run both the PX4 SITL instance and the ignition gazebo client

The supported vehicles and make commands are listed below (click on the links to see the vehicle images).

Vehicle Command
quadrotor(x500) make px4_sitl gz_x500

The commands above launch a single vehicle with the full UI. QGroundControl should be able to automatically connect to the simulated vehicle.

In order to run the simulation without running the ignition gazebo gui, one can use the HEADLESS=1 flag:

HEADLESS=1 make px4_sitl gz_x500

# Usage/Configuration Options

The startup pipeline allows for highly flexible configuration. In particular, it is possible to:

  • Start a new Ignition simulation with an arbitrary world or attach to an already running simulation.
  • Add a new vehicle to Ignition or link a new PX4 instance to an existing one.

These scenarios are managed by setting the appropriate environment variables.

# Syntax

The startup syntax takes the form:

ARGS ./build/px4_sitl_default/bin/px4

where ARGS is a list of environment variables including:

  • PX4_SYS_AUTOSTART (Mandatory): Sets the airframe autostart id of the PX4 airframe to start.

    • Only 4001 (x500 quadcopter) is currently supported.
  • PX4_GZ_MODEL_NAME: Sets the name of an existing model in the gazebo simulation. If provided, the startup script tries to bind a new PX4 instance to the Ignition resource matching exactly that name.

    • The setting is mutually exclusive with PX4_GZ_MODEL.
  • PX4_GZ_MODEL: Sets the name of a new Ignition model to be spawned in the simulator. If provided, the startup script looks for a model in the Ignition resource path that matches the given variable, spawns it and binds a new PX4 instance to it.

    • The setting is mutually exclusive with PX4_GZ_MODEL_NAME.

    Note

    If both PX4_GZ_MODEL_NAME and PX4_GZ_MODEL are not given, then PX4 looks for PX4_SIM_MODEL and uses it as an alias for PX4_GZ_MODEL. However, this prevents the use of PX4_GZ_MODEL_POSE.

  • PX4_GZ_MODEL_POSE: Sets the spawning position and orientation of the model when PX4_GZ_MODEL is adopted. If provided, the startup script spawns the model at a pose following the syntax "x,y,z,roll,pitch,yaw", where the positions are given in metres and the angles are in radians.

    • If omitted, the zero pose [0,0,0,0,0,0] is used.
    • If less then 6 values are provided, the missing ones are fixed to zero.
    • This can only be used with PX4_GZ_MODEL (not PX4_GZ_MODEL_NAME).
  • PX4_GZ_WORLD: Sets the Ignition world file for a new simulation. If it is not given, then default (opens new window) is used.

  • PX4_SIMULATOR=GZ: Sets the simulator, which for Ignition Gazebo must be gz.

The PX4 Ignition worlds and and models databases can be found on Github here (opens new window). They are added to the Ignition search PATH by gazebo_env.sh.in (opens new window) during the simulation startup phase.

Note

gazebo_env.sh.in is compiled and made available in $PX4_DIR/build/px4_sitl/rootfs/gazebo_env.sh

# Examples

Here are some examples of the different scenarios covered above.

  1. Start simulator + default world + spawn vehicle at default pose

    PX4_SYS_AUTOSTART=4001 PX4_GZ_MODEL=x500 ./build/px4_sitl_default/bin/px4
    
  2. Start simulator + default world + spawn vehicle at custom pose (y=2m)

    PX4_SYS_AUTOSTART=4001 PX4_GZ_MODEL_POSE="0,2" PX4_GZ_MODEL=x500 ./build/px4_sitl_default/bin/px4
    
  3. Start simulator + default world + link to existing vehicle

    PX4_SYS_AUTOSTART=4001 PX4_GZ_MODEL_NAME=x500 ./build/px4_sitl_default/bin/px4
    

# Adding New worlds and Models

New worlds files can simply be copied into the PX4 Ignition world directory (opens new window).

To add a new model:

  1. Add an sdf file in the PX4 Ignition model directory (opens new window).

  2. Define an airframe configuration file.

  3. Define the Ignition default parameters in the airframe configuration file (this example is from x500 quadcopter (opens new window)):

    PX4_SIMULATOR=${PX4_SIMULATOR:=gz}
    PX4_GZ_WORLD=${PX4_GZ_WORLD:=default}
    PX4_SIM_MODEL=${PX4_SIM_MODEL:=<your model name>}
    
    • PX4_SIMULATOR=${PX4_SIMULATOR:=gz} sets the default simulator (Ignition Gazebo) for that specific airframe.

    • PX4_GZ_WORLD=${PX4_GZ_WORLD:=default} sets the default world (opens new window) for that specific airframe.

    • Setting the default value of PX4_SIM_MODEL lets you start the simulation with just

      PX4_SYS_AUTOSTART=<your new airframe id> ./build/px4_sitl_default/bin/px4
      

Note

As long as the world file and the model file are in the Ignition search path IGN_GAZEBO_RESOURCE_PATH it is not necessary to add them to the PX4 world and model directories. However, make px4_sitl gz_<model>_<world> won't work with them.

# Multi-Vehicle Simulation

Multi-Vehicle simulation is supported on Linux hosts.

For more information see: Multi-Vehicle Sim with Ignition Gazebo

# Further Information