Gazebo Simulation

Gazebo is a powerful 3D simulation environment for autonomous robots that is particularly suitable for testing object-avoidance and computer vision. This page describes its use with SITL and a single vehicle. Gazebo can also be used with HITL and for multi-vehicle simulation.

Supported Vehicles: Quad (Iris and Solo, Hex (Typhoon H480), Generic quad delta VTOL, Tailsitter, Plane, Rover, Submarine (coming soon!)

Gazebo is often used with ROS, a toolkit/offboard API for automating vehicle control. If you plan to use PX4 with ROS you should instead follow the instructions here to install Gazebo as part of ROS!

GazeboPluginMAVLinkSITL

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

Installation

Gazebo 8 setup is included in our standard build instructions:

Additional installation instructions can be found on gazebosim.org.

Running the Simulation

You can run a simulation by starting PX4 SITL and gazebo with the airframe configuration to load (multicopters, planes, VTOL, optical flow and multi-vehicle simulations are supported).

The easiest way to do this is to open a terminal in the root directory of the PX4 Firmware repository and call make for the targets as shown in the following sections.

You can use the instructions below to keep Gazebo running and only re-launch PX4. This is quicker than restarting both.

For the full list of build targets run make posix list_vmd_make_targets (and filter on those that start with gazebo_).

Quadrotor

cd ~/src/Firmware
make posix_sitl_default gazebo

Quadrotor with Optical Flow

make posix gazebo_iris_opt_flow

3DR Solo

make posix gazebo_solo

3DR Solo in Gazebo

Standard Plane

make posix gazebo_plane

Plane in Gazebo

Standard VTOL

make posix_sitl_default gazebo_standard_vtol

Standard VTOL in Gazebo

Tailsitter VTOL

make posix_sitl_default gazebo_tailsitter

Tailsitter VTOL in Gazebo

Ackerman vehicle (UGV/Rover) 

make posix gazebo_rover

Rover in Gazebo

HippoCampus TUHH (UUV: Unmanned Underwater Vehicle) 

make posix_sitl_default gazebo_hippocampus

Submarine/UUV

Change World

The current default world is the iris.world located in the directory worlds. The default surrounding in the iris.world uses a heightmap as ground. This ground can cause difficulty when using a distance sensor. If there are unexpected results with that heightmap, we recommend you change the model in iris.model from uneven_ground to asphalt_plane.

Taking it to the Sky

Please refer to the Installing Files and Code guide if you run into any errors.

This will bring up the PX4 shell:

[init] shell id: 140735313310464
[init] task name: px4

______  __   __    ___
| ___ \ \ \ / /   /   |
| |_/ /  \ V /   / /| |
|  __/   /   \  / /_| |
| |     / /^\ \ \___  |
\_|     \/   \/     |_/

px4 starting.


pxh>

Right-clicking the quadrotor model allows to enable follow mode from the context menu, which is handy to keep it in view.

Gazebo UI

The system will print the home position once it finished intializing (telem> home: 55.7533950, 37.6254270, -0.00). You can bring it into the air by typing:

pxh> commander takeoff

Usage/Configuration Options

Set Custom Takeoff Location

The default takeoff location in SITL Gazebo can be overridden using environment variables.

The variables to set are: PX4_HOME_LAT, PX4_HOME_LON, and PX4_HOME_ALT.

As an example:

export PX4_HOME_LAT=28.452386
export PX4_HOME_LON=-13.867138
export PX4_HOME_ALT=28.5
make posix gazebo

Using a Joystick

Joystick and thumb-joystick support are supported through QGroundControl (setup instructions here).

Simulating GPS Noise

Gazebo can simulate GPS noise that is similar to that typically found in real systems (otherwise reported GPS values will be noise-free/perfect). This is useful when working on applications that might be impacted by GPS noise - e.g. precision positioning.

GPS noise is enabled if the target vehicle's SDF file contains a value for the gpsNoise element (i.e. it has the line: <gpsNoise>true</gpsNoise>). It is enabled by default in many vehicle SDF files: solo.sdf, iris.sdf, standard_vtol.sdf, delta_wing.sdf, plane.sdf, typhoon_h480, tailsitter.sdf.

To enable/disable GPS noise:

  1. Build any gazebo target in order to generate SDF files (for all vehicles). For example:
    make posix_sitl_default gazebo_iris

    The SDF files are not overwritten on subsequent builds.

  2. Open the SDF file for your target vehicle (e.g. ./Tools/sitl_gazebo/models/iris/iris.sdf).
  3. Search for the gpsNoise element:
    <plugin name='gps_plugin' filename='libgazebo_gps_plugin.so'>
  <robotNamespace/>
  <gpsNoise>true</gpsNoise>
</plugin>
    • If it is present, GPS is enabled. You can disable it by deleting the line: <gpsNoise>true</gpsNoise>
    • If it is not preset GPS is disabled. You can enable it by adding the gpsNoise element to the gps_plugin section (as shown above).

The next time you build/restart Gazebo it will use the new GPS noise setting.

Starting Gazebo and PX4 Separately

For extended development sessions it might be more convenient to start Gazebo and PX4 separately or even from within an IDE.

In addition to the existing cmake targets that run sitl_run.sh with parameters for px4 to load the correct model it creates a launcher targets named px4_<mode> that is a thin wrapper around original sitl px4 app. This thin wrapper simply embeds app arguments like current working directories and the path to the model file.

To start Gazebo and PX4 separately:

  • Run gazebo (or any other sim) server and client viewers via the terminal:
    make posix_sitl_default gazebo_none_ide
  • In your IDE select px4_<mode> target you want to debug (e.g. px4_iris)
  • Start the debug session directly from IDE

This approach significantly reduces the debug cycle time because simulator (e.g. gazebo) is always running in background and you only re-run the px4 process which is very light.

Video Streaming

PX4 SITL for Gazebo supports UDP video streaming from a Gazebo camera sensor attached to a vehicle model. You can connect to this stream from QGroundControl (on UDP port 5600) and view video of the Gazebo environment from the simulated vehicle - just as you would from a real camera. The video is streamed using a gstreamer pipeline.

Video streaming from Gazebo and the Gazebo widget to turn streaming on/off are not enabled by default. This article explains how to enable them. In the near future we expect these features to be enabled by default.

Prerequisites

Install Gstreamer 1.0 and its dependencies:

sudo apt-get install $(apt-cache --names-only search ^gstreamer1.0-* | awk '{ print $1 }' | grep -v gstreamer1.0-hybris) -y

Enable GStreamer Plugin

This step will not be required once video streaming is enabled by default.

Enable the GStreamer Plugin (if disabled) by changing the BUILD_GSTREAMER_PLUGIN option to "ON" in <Firmware>/Tools/sitl_gazebo/CMakeLists.txt (as shown below):

option(BUILD_GSTREAMER_PLUGIN "enable gstreamer plugin" "ON")

Once the plugin is enabled you can run SITL with Gazebo in the normal way:

make clean
make posix gazebo_typhoon_h480

How to View Gazebo Video

The easiest way to view the SITL/Gazebo camera video stream is in QGroundControl. Simply open Settings > General and set Video Source to UDP Video Stream and UDP Port to 5600:

QGC Video Streaming Settings for Gazebo

The video from Gazebo should then display in QGroundControl just as it would from a real camera.

It is also possible to view the video using the Gstreamer Pipeline. Simply enter the following terminal command:

gst-launch-1.0  -v udpsrc port=5600 caps='application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264'
! rtph264depay ! avdec_h264 ! videoconvert ! autovideosink fps-update-interval=1000 sync=false

Gazebo GUI to Start/Stop Video Streaming

This feature is supported for Gazebo version 7.

Video streaming can be enabled/disabled using the Gazebo UI Video ON/OFF button.

Video ON/OFF button

To enable the button:

  1. Open the "world" file to be modified (e.g. <Firmware>/Tools/sitl_gazebo/worlds/typhoon_h480.world).

  2. Within the default world name="default" section, add the gui section for the libgazebo_video_stream_widget (as shown below): 

    <?xml version="1.0" ?>
<sdf version="1.5">
  <world name="default">

        <gui>
      <plugin name="video_widget" filename="libgazebo_video_stream_widget.so"/>
    </gui>

     <!-- A global light source -->
 <include>
 ...

    This section present in typhoon_h480.world - you just need to uncomment the section.

  3. Rebuild SITL:

    make clean
make posix gazebo_typhoon_h480

Extending and Customizing

To extend or customize the simulation interface, edit the files in the Tools/sitl_gazebo folder. The code is available on the sitl_gazebo repository on Github.

The build system enforces the correct GIT submodules, including the simulator. It will not overwrite changes in files in the directory.

Interfacing to ROS

The simulation can be interfaced to ROS the same way as onboard a real vehicle.

Further Information

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