# Multi-UAV Gazebo Simulation

Tutorial for Multi-UAV (Quadcopters) simulation in Gazebo and Ardupilot.

# Installation

# Ubuntu

Ubuntu 20.04 inside a Virtual Machine (VM) used in this tutorial.

# Gazebo

The Gazebo version 11 is used in this tutorial. ROS noetic has gazebo11 but if there is problem with it, you can use steps below to install it:

	sudo 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 –
	sudo apt-get update
	sudo apt-get install gazebo11 libgazebo11-dev

If you are using Ubuntu in a VM and gazebo has graphical problems, put the line below inside your bash (bashrc, zshrc, …):

export SVGA_VGPU10=0

# Ardupilot

The latest version (4.3.6 at the time of writing) used in this tutorial. You can use steps below to install it:

	git clone https://github.com/ArduPilot/ardupilot.git
	cd ardupilot
	git submodule update --init –recursive
	alias waf="$PWD/modules/waf/waf-light"
	waf configure --board=sitl
	waf all
	./Tools/environment_install/install-prereqs-ubuntu.sh -y

# Ardupilot_gazebo

	git clone https://github.com/SwiftGust/ardupilot_gazebo
	cd ardupilot_gazebo
	mkdir build
	cd build
	cmake ..
	make -j2
	sudo make install

After installation of this plugin, you need to add lines below inside your bash (bashrc, zshrc, …):

	source /usr/share/gazebo/setup.sh
	export GAZEBO_MODEL_PATH=~/ardupilot_gazebo/models:${GAZEBO_MODEL_PATH}
	export GAZEBO_MODEL_PATH=~/ardupilot_gazebo/models_gazebo:${GAZEBO_MODEL_PATH}
	export GAZEBO_RESOURCE_PATH=~/ardupilot_gazebo/worlds:${GAZEBO_RESOURCE_PATH}
	export GAZEBO_PLUGIN_PATH=~/ardupilot_gazebo/build:${GAZEBO_PLUGIN_PATH}

# Run single UAV

Open a terminal and run the commands below:

	cd ~/ardupilot/Tools/autotest
	./sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I0

Open a new terminal and run:

gazebo --verbose ~/ardupilot_gazebo/worlds/iris_ardupilot.world

After seeing “APM: EKF2 IMU0 is using GPS” message in console, you can use the commands below in the first terminal for takeoff test:

	mode guided
	arm throttle
	takeoff 5

# Run multiple UAVs

For any number of UAVs that you want to simulate, make a copy of “iris_with_standoffs_demo” from ardupliot_gazebo/models folder (iris_with_standoffs_demo_1, iris_with_standoffs_demo_2, iris_with_standoffs_demo_3, …).Besides,you need to add these folders to /.gazebo folder.
Open “model.sdf” file inside of each iris_with_standoffs_demo folder and change <fdm_port_in> and <fdm_port_out> under plugin name=“arducopter_plugin” tag. For example for the first UAV (iris_with_standoffs_demo_1) use below:

	<plugin name="arducopter_plugin" filename="libArduPilotPlugin.so">
	<fdm_addr>127.0.0.1</fdm_addr>
	<fdm_port_in>9002</fdm_port_in>
	<fdm_port_out>9003</fdm_port_out>

For second UAV (iris_with_standoffs_demo_2) use below:

	<plugin name="arducopter_plugin" filename="libArduPilotPlugin.so">
	<fdm_addr>127.0.0.1</fdm_addr>
	<fdm_port_in>9012</fdm_port_in>
	<fdm_port_out>9013</fdm_port_out>

And so on for each UAV add “10” to each port (9002-9003, 9012-9013, 9022-9023, 9032-9033, …).
Now make a copy of iris_ardupilot.world from ardupilot_gazebo/worlds folder:

	cd ~/ardupilot_gazebo/worlds
	cp iris_ardupilot.world iris_multiuav.world

Open the new iris_multiuav.world file and change the bottom of file from this:

	<model name="iris">
	<pose> 0 0 0 0 0 0 </pose>
	<include>
	<uri>model://iris_with_standoffs_demo</uri>
	<pose> 0 0 0 0 0 0 </pose>
	</include>
	</model>

To this (this is for 4 UAV example):

	<model name="iris_demo_1">
	<pose> 0 0 0 0 0 0 0 </pose>
	<include>
	<uri>model://iris_with_standoffs_demo_1</uri>
	</include>
	</model>
	<model name="iris_demo_2">
	<pose> -10 -10 0 0 0 0 0 </pose>
	<include>
	<uri>model://iris_with_standoffs_demo_2</uri>
	</include>
	</model>
	<model name="iris_demo_3">
	<pose> -20 0 0 0 0 0 0 </pose>
	<include>
	<uri>model://iris_with_standoffs_demo_3</uri>
	</include>
	</model>
	<model name="iris_demo_4">
	<pose> -10 10 0 0 0 0 0 </pose>
	<include>
	<uri>model://iris_with_standoffs_demo_4</uri>
	</include>
	</model>

Open a terminal for each UAV and run the commands below in each of them (4 UAV example):

	# First terminal:
	cd ~/ardupilot1/Tools/autotest
	./sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I0

	# Second terminal:
	cd ~/ardupilot1/Tools/autotest
	./sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I1

	# Third terminal:
	cd ~/ardupilot1/Tools/autotest
	./sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I2

	# Fourth terminal:
	cd ~/ardupilot1/Tools/autotest
	./sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I3

Open a new terminal and run the command below:

gazebo --verbose ~/ardupilot_gazebo/worlds/iris_multiuav.world

Wait for each UAV to get “APM: EKF2 IMU0 is using GPS” message and then you can control UAVs.

附件：

Ardupilot_gazebo 架构图

	flowchart TB
	subgraph "Gazebo仿真环境"
	GW["Gazebo世界"] --- GP["物理引擎\n(ODE/Bullet)"]
	GP --- Models["车辆/传感器模型"]
	Models --- GPlugin["ArduPilot\nGazebo插件"]
	end

	subgraph "ArduPilot SITL"
	FC["飞控代码"] --- AP["ArduPilot核心"]
	AP --- Protocols["通信协议\n(MAVLink)"]
	end

	subgraph "通信层"
	Socket["UDP Socket\n端口连接"]
	end

	GPlugin <--> Socket
	Protocols <--> Socket

	subgraph "地面站"
	GCS["Mission Planner/\nQGroundControl"]
	end

	Protocols <--> GCS

	subgraph "用户界面/工具"
	Tools["开发工具\n监控界面"]
	end

	GCS --- Tools

	flowchart TB
	classDef ardupilotComponents fill:#f9d5e5,stroke:#333,stroke-width:1px
	classDef gazeboComponents fill:#d5f9e5,stroke:#333,stroke-width:1px
	classDef communicationComponents fill:#e5d5f9,stroke:#333,stroke-width:1px
	classDef userComponents fill:#f9e5d5,stroke:#333,stroke-width:1px

	%% ArduPilot SITL 详细组件
	subgraph ARDUPILOT["ArduPilot SITL系统"]
	direction TB
	SITL_CORE["SITL核心模拟器"]
	AP_FW["ArduPilot固件\n(Copter/Plane/Rover/Sub)"]
	AHRS["姿态航向参考系统\n(AHRS)"]
	EKF["扩展卡尔曼滤波器\n(EKF2/EKF3)"]
	CONTROL["控制系统\n(PID/姿态控制器/位置控制器)"]
	NAV["导航系统\n(航路点/任务规划)"]
	MAVLIB["MAVLink库"]
	COMM_DRIVERS["通信驱动\n(UART/UDP/TCP)"]
	PARAM["参数系统"]
	FENCE["地理围栏"]
	VEHICLE_CODE["车辆特定代码"]
	LOG["数据记录系统"]

	SITL_CORE --> AP_FW
	AP_FW --> AHRS & EKF & CONTROL & NAV & PARAM & FENCE & VEHICLE_CODE & LOG
	AHRS --> EKF
	EKF --> CONTROL
	CONTROL --> NAV
	AP_FW --> MAVLIB --> COMM_DRIVERS
	end

	%% Gazebo 详细组件
	subgraph GAZEBO["Gazebo仿真环境"]
	direction TB
	WORLD["世界模型\n(.world文件)"]
	PHYSICS["物理引擎\n(ODE/Bullet/Simbody/DART)"]
	MODELS["模型定义\n(.sdf/.urdf文件)"]
	SENSORS["传感器模型\n(IMU/GPS/气压计/相机/雷达)"]
	PLUGIN_LOADER["插件加载器"]
	RENDERING["图形渲染引擎"]
	DYNAMICS["动力学计算"]
	COLLISIONS["碰撞检测"]
	ENV_EFFECTS["环境效应\n(风/湍流/降水)"]

	WORLD --> PHYSICS & MODELS & ENV_EFFECTS
	MODELS --> SENSORS
	PHYSICS --> DYNAMICS & COLLISIONS
	MODELS --> PLUGIN_LOADER
	WORLD --> RENDERING
	end

	%% 通信与中间层
	subgraph COMM["通信层"]
	direction TB
	UDP["UDP套接字\n(端口14550-14557)"]
	FDMSOCKET["FDM Socket\n(物理动态模型接口)"]
	SIM_SOCKET["仿真控制Socket"]
	MAVPROXY["MAVProxy\n(MAVLink代理)"]

	UDP <--> MAVPROXY
	FDMSOCKET <--> SIM_SOCKET
	end

	%% ArduPilot Gazebo 插件详情
	subgraph PLUGIN["ArduPilot Gazebo插件"]
	direction TB
	PLUGIN_INIT["插件初始化"]
	MODEL_INTERFACE["模型接口"]
	SENSOR_UPDATE["传感器数据更新"]
	ACTUATOR["执行器命令处理"]
	SIM_STATE["仿真状态管理"]
	POS_ROT["位置/旋转计算"]
	FORCE_TORQUE["力和力矩应用"]

	PLUGIN_INIT --> MODEL_INTERFACE
	MODEL_INTERFACE --> SENSOR_UPDATE & ACTUATOR
	ACTUATOR --> FORCE_TORQUE
	SENSOR_UPDATE --> POS_ROT
	POS_ROT & FORCE_TORQUE --> SIM_STATE
	end

	%% 用户接口组件
	subgraph USER["用户接口系统"]
	direction TB
	GCS["地面站\n(Mission Planner/QGC)"]
	MAVLINK_INSPECTOR["MAVLink检查器"]
	PLOT["实时数据绘图"]
	JOYSTICK["摇杆控制"]
	HMI["人机交互界面"]

	GCS --> MAVLINK_INSPECTOR & PLOT & JOYSTICK
	MAVLINK_INSPECTOR & PLOT & JOYSTICK --> HMI
	end

	%% 数据流路线
	%% 从 Gazebo 到 ArduPilot 的传感器数据流
	SENSORS --> PLUGIN::SENSOR_UPDATE
	PLUGIN::POS_ROT --> FDMSOCKET
	FDMSOCKET --> SITL_CORE

	%% 从 ArduPilot 到 Gazebo 的控制命令流
	CONTROL --> COMM_DRIVERS
	COMM_DRIVERS --> SIM_SOCKET
	SIM_SOCKET --> PLUGIN::ACTUATOR
	PLUGIN::FORCE_TORQUE --> PHYSICS

	%% MAVLink 通信流
	MAVLIB --> UDP
	UDP --> MAVPROXY
	MAVPROXY --> GCS

	%% 配置和初始化流
	PARAM --> SITL_CORE
	PLUGIN_LOADER --> PLUGIN::PLUGIN_INIT

	%% 应用样式
	class ARDUPILOT,AP_FW,AHRS,EKF,CONTROL,NAV,MAVLIB,COMM_DRIVERS,PARAM,FENCE,VEHICLE_CODE,LOG,SITL_CORE ardupilotComponents
	class GAZEBO,WORLD,PHYSICS,MODELS,SENSORS,PLUGIN_LOADER,RENDERING,DYNAMICS,COLLISIONS,ENV_EFFECTS gazeboComponents
	class COMM,UDP,FDMSOCKET,SIM_SOCKET,MAVPROXY,PLUGIN,PLUGIN_INIT,MODEL_INTERFACE,SENSOR_UPDATE,ACTUATOR,SIM_STATE,POS_ROT,FORCE_TORQUE communicationComponents
	class USER,GCS,MAVLINK_INSPECTOR,PLOT,JOYSTICK,HMI userComponents