Gazebo 仿真

Gazebo 是用于自主机器人的强大3D模拟环境，其特别适用于测试物体避障和计算机视觉。 本文描述了如何使用它来进行单机的软件在环仿真。 Gazebo 也可以适用于 硬件在环仿真 和 多机仿真 。

Supported Vehicles: Quad (Iris and Solo, Hex (Typhoon H480), Generic quad delta VTOL, Tailsitter, Plane, Rover, Submarine/UUV.

Gazebo is often used with ROS, a toolkit/offboard API for automating vehicle control. If you plan to use PX4 with ROS you should follow the ROS Instructions to install both ROS and Gazebo (and thereby avoid installation conflicts).

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

Installation

Gazebo 9 的安装在标准的环境编译已有说明。

• macOS： Mac 上的开发环境
• Linux: Development Environment on Ubuntu LTS / Debian Linux > Gazebo, JMAVSim and NuttX (Pixhawk) Targets
• Windows：还不支持。

其他安装说明可在 gazebosim.org 上找到。

运行仿真

您可以通过启动 PX4 SITL和 Gazebo 来运行模拟，并加载机身配置（支持多旋翼飞机，飞机，VTOL，光流和多机仿真）。

最简单的方法是在 PX4 Firmware 存储库的根目录中打开一个终端，并为目标调用make，如以下部分所示。

你可以使用 instructions below 来保持 Gazebo 在后台运行然后只重启 PX4。 这样比同时重启两者要快一些。 You can also run the simulation in Headless Mode which does not start the Gazebo UI (this uses fewer resources and is much faster).

使用命令 make px4_sitl list_vmd_make_targets 获取所有支持的平台（你还可以过滤掉以 gazebo_ 开头的平台）。

The Installing Files and Code guide is a useful reference if there are build errors.

四旋翼

cd ~/src/Firmware
make px4_sitl gazebo

带光流的四旋翼

make px4_sitl gazebo_iris_opt_flow

3DR Solo (Quadrotor)

make px4_sitl gazebo_solo

Typhoon H480 (Hexrotor)

make px4_sitl gazebo_typhoon_h480

This target also supports video streaming simulation.

Standard Plane

make px4_sitl gazebo_plane

Standard VTOL

make px4_sitl gazebo_standard_vtol

Tailsitter VTOL

make px4_sitl gazebo_tailsitter

Ackerman vehicle (UGV/Rover)

make px4_sitl gazebo_rover

HippoCampus TUHH (UUV: Unmanned Underwater Vehicle)

make px4_sitl gazebo_uuv_hippocampus

Boat (USV: Unmanned Surface Vehicle)

make px4_sitl gazebo_boat

Taking it to the Sky

The make commands above first build PX4, and then run it along with the Gazebo simulator.

Once PX4 has started it will launch the PX4 shell as shown below.

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

px4 starting.

INFO  [px4] Calling startup script: /bin/sh etc/init.d-posix/rcS 0
INFO  [param] selected parameter default file eeprom/parameters_10016
[param] Loaded: eeprom/parameters_10016
INFO  [dataman] Unknown restart, data manager file './dataman' size is 11798680 bytes
INFO  [simulator] Waiting for simulator to connect on TCP port 4560
Gazebo multi-robot simulator, version 9.0.0
Copyright (C) 2012 Open Source Robotics Foundation.
Released under the Apache 2 License.
http://gazebosim.org
...
INFO  [ecl/EKF] 5188000: commencing GPS fusion

The console will print out status as PX4 loads the airframe-specific initialisation and parameter files, waits for (and connects to) the simulator. Once there is an INFO print that [ecl/EKF] is commencing GPS fusion the vehicle is ready to arm.

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

You can bring it into the air by typing:

pxh> commander takeoff

Usage/Configuration Options

Headless Mode

Gazebo can be run in a headless mode in which the Gazebo UI is not launched. This starts up more quickly and uses less system resources (i.e. it is a more "lightweight" way to run the simulation).

Simply prefix the normal make command with HEADLESS=1 as shown:

HEADLESS=1 make px4_sitl gazebo_plane

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.

For example:

export PX4_HOME_LAT=28.452386
export PX4_HOME_LON=-13.867138
export PX4_HOME_ALT=28.5
make px4_sitl gazebo

Change Simulation Speed

The simulation speed can be increased or decreased with respect to realtime using the environment variable PX4_SIM_SPEED_FACTOR.

export PX4_SIM_SPEED_FACTOR=2
make px4_sitl_default gazebo

For more information see: Simulation > Run Simulation Faster than Realtime.

Using a Joystick

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

Improving Distance Sensor Performance

The current default world is PX4/sitl_gazebo/worlds/iris.world), which uses a heightmap as ground.

This can cause difficulty when using a distance sensor. If there are unexpected results we recommend you change the model in iris.model from uneven_ground to asphalt_plane.

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. 构建任何 gazebo 目标以生成 SDF 文件（适用于所有机型）。 例如： make px4_sitl gazebo_iris >Tip在后续版本中不会覆盖 SDF 文件。
2. 打开目标车辆的 SDF 文件（例如./Tools/sitl_gazebo/models/iris/iris.sdf ）。

3. 搜索 gpsNoise 元素：

    xml
    <plugin name='gps_plugin' filename='libgazebo_gps_plugin.so'>
     <robotNamespace/>
     <gpsNoise>true</gpsNoise>
    </plugin>
   

   • 如果存在，则启用 GPS。 您可以通过删除以下行来禁用它：<gpsNoise> true </gpsNoise>
   • 如果未预设，则禁用 GPS 。 您可以通过将gpsNoise元素添加到gps_plugin部分来启用它（如上所示）。

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

Loading a Specific World

By default Gazebo displays a flat featureless plane, as defined in empty.world.

You can load any of the worlds in PX4/sitl_gazebo/worlds) by specifying them as the final option in the PX4 configuration target. For example, to load the warehouse world, you can append it as shown:

make px4_sitl_default gazebo_plane_cam__warehouse

There are two underscores after the model (plane_cam) indicating that the default debugger is used (none). See Building the Code > PX4 Make Build Targets.

You can also specify the full path to a world to load using the PX4_SITL_WORLD environment variable. This is useful if testing a new world that is not yet included with PX4.

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 specifing an _ide variant:

    sh
    make px4_sitl gazebo___ide or 
  
    sh
    make px4_sitl gazebo_iris_ide
  

• 在 IDE 中选择要调试的px4_ <mode>目标（例如px4_iris）

• 直接从 IDE 启动调试会话

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.

Simulated Survey Camera

The Gazebo survey camera simulates a MAVLink camera that captures geotagged JPEG images and sends camera capture information to a connected ground station. The camera also supports video streaming. It can be used to test camera capture, in particular within survey missions.

The camera emits the CAMERA_IMAGE_CAPTURED message every time an image is captured. The captured images are saved to: Firmware/build/px4sitle_default/tmp/frames/DSC_n.jpg (where n starts as 00000 and is iterated by one on each capture).

To simulate a plane with this camera:

make px4_sitl_default gazebo_plane_cam

The camera also supports/responds to the following MAVLink commands: MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS, MAV_CMD_REQUEST_STORAGE_INFORMATION, MAV_CMD_REQUEST_CAMERA_SETTINGS, MAV_CMD_REQUEST_CAMERA_INFORMATION, MAV_CMD_RESET_CAMERA_SETTINGS, MAV_CMD_STORAGE_FORMAT, MAV_CMD_SET_CAMERA_ZOOM, MAV_CMD_IMAGE_START_CAPTURE, MAV_CMD_IMAGE_STOP_CAPTURE, MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION, MAV_CMD_REQUEST_VIDEO_STREAM_STATUS, MAV_CMD_SET_CAMERA_MODE.

The simulated camera is implemented in PX4/sitl_gazebo/src/gazebo_geotagged_images_plugin.cpp.

Simulated Parachute/Flight Termination

Gazebo can be used to simulate deploying a parachute during Flight Termination (flight termination is triggered by the PWM command that is simulated in Gazebo).

The if750a target has a parachute attached to the vehicle. To simulate the vehicle, run the following command:

make px4_sitl gazebo_if750a

To put the vehicle into flight termination state, you can force it to fail a safety check that has flight termination set as the failsafe action. For example, you could do this by forcing a Geofence violation.

For more information see:

• Flight Termination
• Parachute
• Safety Configuration (Failsafes)

Video Streaming

PX4 SITL for Gazebo supports UDP video streaming from a Gazebo camera sensor attached to a vehicle model. When streaming is enabled, 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 and can be enabled/disabled using a button in the Gazebo UI.

The Gazebo camera sensor is supported/enabled on the following frames:

• Typhoon H480

Prerequisites

Gstreamer 1.0 is required for video streaming. The required dependencies should already have been installed when you set up Gazebo (they are included in the standard PX4 installation scripts/instructions for macOS and Ubuntu Linux).

FYI only, the dependencies include: gstreamer1.0-plugins-base, gstreamer1.0-plugins-good, gstreamer1.0-plugins-bad, gstreamer1.0-plugins-ugly, libgstreamer-plugins-base1.0-dev.

Start/Stop Video Streaming

Video streaming is automatically started when supported by the target vehicle. For example, to start streaming video on the Typhoon H480:

make px4_sitl gazebo_typhoon_h480

Streaming can be paused/restarted using the Gazebo UI Video ON/OFF button..

How to View Gazebo Video

The easiest way to view the SITL/Gazebo camera video stream is in QGroundControl. Simply open Application Settings > General and set Video Source to UDP h.264 Video Stream and UDP Port to 5600:

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

The Typhoon world is not very interesting.

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

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.

Further Information

• ROS with Gazebo Simulation
• Gazebo Octomap