在上篇文章中，我们在ubuntu上搭建了PX4的开发环境。本篇文章将继续开发环境的搭建，完成ROS+gazebo+Mavros的仿真环境搭建，其中mavros可以用来执行offboard控制。

!!!注意：

我的安装过程可能稍有不同，由于在这之前我就已经安装了ROS，而Gazebo则是在上一篇文章中已经安装，因此我在安装的时候没有直接使用安装脚本，而是将脚本逐行执行以避免问题。

如果你之前没有在home下创建过ros工作空间，那你应该直接运行脚本,而不用按照本篇文章的记录，以减少麻烦。

本篇文章分为以下几个部分：

1. mavros的安装

2. offboard控制演示

3. 视频记录

1.mavros的安装

这部分的安装过程是按照官方连接(ROS/Gazebo)来进行的，下面的命令实际上是脚本中的命令逐行运行。

1. 检查系统版本

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n138" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">lsb_release -sc
bionic</pre>

查看自己的输出是否为bionic，确认自己的版本是否是18.04，如果不是，请寻找针对特定版本的教程。

2. 安装仿真依赖项

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n141" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">wget https://raw.githubusercontent.com/PX4/Devguide/master/build_scripts/ubuntu_sim_common_deps.sh
​
./ubuntu_sim_common_deps.sh</pre>

如果下载下来的脚本不是可执行文件，运行

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n143" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">chmod +x ubuntu_sim_common_deps.sh</pre>

安装过程中查看是否输出了：

./ubuntu_sim_common_deps.sh: 行 47: * :语法错误：需要操作数

image

那么你需要自己运行下面的命令来安装fastrtps，虽然这个暂时也没看到有什么用。

进入home目录，运行

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n150" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">(cd eProsima_FastCDR-1.0.8-Linux && ./configure --libdir=/usr/lib && make -j4 && sudo make install)
(cd eProsima_FastRTPS-1.7.1-Linux && ./configure --libdir=/usr/lib && make -j4 && sudo make install)</pre>

来进行安装。

3. 安装ROS+Gazebo

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n153" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">sudo apt-get install protobuf-compiler libeigen3-dev libopencv-dev -y
​

安装的ROS+Gazebo

ROS Gazebo: http://wiki.ros.org/melodic/Installation/Ubuntu

Setup keys

sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654

For keyserver connection problems substitute hkp://pgp.mit.edu:80 or hkp://keyserver.ubuntu.com:80 above.

sudo apt-get update

Get ROS/Gazebo

sudo apt install ros-melodic-desktop-full -y

Initialize rosdep

sudo rosdep init
rosdep update

Setup environment variables

echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc;
source /opt/ros/melodic/setup.bash
​

Install rosinstall and other dependencies

sudo apt install python-rosinstall python-rosinstall-generator python-wstool build-essential -y</pre>

4. 编译MAVROS

<pre spellcheck="false" class="md-fences md-end-block ty-contain-cm modeLoaded" lang="bash" cid="n156" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;"># MAVROS: https://dev.px4.io/en/ros/mavros_installation.html

Install dependencies

sudo apt-get install python-catkin-tools python-rosinstall-generator -y
​

Create catkin workspace

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
catkin init
wstool init src
​
​

Install MAVLink

we use the Kinetic reference for all ROS distros as it's not distro-specific and up to date

rosinstall_generator --rosdistro kinetic mavlink | tee /tmp/mavros.rosinstall
​

Build MAVROS

Get source (upstream - released)

rosinstall_generator --upstream mavros | tee -a /tmp/mavros.rosinstall
​

Setup workspace & install deps

wstool merge -t src /tmp/mavros.rosinstall
wstool update -t src
​
rosdep install --from-paths src --ignore-src -y
​
wget https://raw.githubusercontent.com/mavlink/mavros/master/mavros/scripts/install_geographiclib_datasets.sh
​
./install_geographiclib_datasets.sh
​
catkin build
​

source 空间

echo "source ~/catkin_ws/devel/setup.bash >> ~/.bashrc
source ~/catkin_ws/devel/setup.bash</pre>

2. offboard控制

打开官方MAVROS Offboard control example链接，然后在catkin_ws目录中，运行命令

<pre mdtype="fences" cid="n165" lang="bash" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">catkin_create_pkg offboard_pkg roscpp std_msgs geometry_msgs mavros_msgs</pre>

然后定位到目录~/catkin_ws/src/offboard_pkg/src/，新建一个文件offboard_node.cpp。

将代码复制进去(官方示例):

<pre mdtype="fences" cid="n171" lang="c++" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">/**

• @file offb_node.cpp
• @brief Offboard control example node, written with MAVROS version 0.19.x, PX4 Pro Flight
• Stack and tested in Gazebo SITL
  */
  ​

include <ros/ros.h>

include <geometry_msgs/PoseStamped.h>

include <mavros_msgs/CommandBool.h>

include <mavros_msgs/SetMode.h>

include <mavros_msgs/State.h>

​
mavros_msgs::State current_state;
void state_cb(const mavros_msgs::State::ConstPtr& msg){
current_state = *msg;
}
​
int main(int argc, char **argv)
{
ros::init(argc, argv, "offb_node");
ros::NodeHandle nh;
​
ros::Subscriber state_sub = nh.subscribe<mavros_msgs::State>
("mavros/state", 10, state_cb);
ros::Publisher local_pos_pub = nh.advertise<geometry_msgs::PoseStamped>
("mavros/setpoint_position/local", 10);
ros::ServiceClient arming_client = nh.serviceClient<mavros_msgs::CommandBool>
("mavros/cmd/arming");
ros::ServiceClient set_mode_client = nh.serviceClient<mavros_msgs::SetMode>
("mavros/set_mode");
​
//the setpoint publishing rate MUST be faster than 2Hz
ros::Rate rate(20.0);
​
// wait for FCU connection
while(ros::ok() && !current_state.connected){
ros::spinOnce();
rate.sleep();
}
​
geometry_msgs::PoseStamped pose;
pose.pose.position.x = 0;
pose.pose.position.y = 0;
pose.pose.position.z = 2;
​
//send a few setpoints before starting
for(int i = 100; ros::ok() && i > 0; --i){
local_pos_pub.publish(pose);
ros::spinOnce();
rate.sleep();
}
​
mavros_msgs::SetMode offb_set_mode;
offb_set_mode.request.custom_mode = "OFFBOARD";
​
mavros_msgs::CommandBool arm_cmd;
arm_cmd.request.value = true;
​
ros::Time last_request = ros::Time::now();
​
while(ros::ok()){
if( current_state.mode != "OFFBOARD" &&
(ros::Time::now() - last_request > ros::Duration(5.0))){
if( set_mode_client.call(offb_set_mode) &&
offb_set_mode.response.mode_sent){
ROS_INFO("Offboard enabled");
}
last_request = ros::Time::now();
} else {
if( !current_state.armed &&
(ros::Time::now() - last_request > ros::Duration(5.0))){
if( arming_client.call(arm_cmd) &&
arm_cmd.response.success){
ROS_INFO("Vehicle armed");
}
last_request = ros::Time::now();
}
}
​
local_pos_pub.publish(pose);
​
ros::spinOnce();
rate.sleep();
}
​
return 0;
}</pre>

然后打开目录~/catkin_ws/src/offboard_pkg/下的CMakeLists.txt添加下面的两行：

<pre mdtype="fences" cid="n177" lang="cmake" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">add_executable(offboard_node src/offboard_node.cpp)
target_link_libraries(offboard_node ${catkin_LIBRARIES})</pre>

然后到目录~/catkin_ws下，运行命令

<pre mdtype="fences" cid="n181" lang="bash" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">catkin build</pre>

等待编译完成后，如果你要在gazebo中仿真，运行命令

<pre mdtype="fences" cid="n187" lang="bash" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">make px4_sitl gazebo_iris</pre>

打开QGroundControl。

然后在终端下运行命令：

<pre mdtype="fences" cid="n191" lang="bash" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">roslaunch mavros px4.launch fcu_url:="udp://:14540@127.0.0.1:14557"</pre>

启动PX4与Mavros之间的连接，然后运行命令

<pre mdtype="fences" cid="n195" lang="bash" class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); --select-text-font-color: #fff; font-size: 0.9rem; line-height: 1.71429em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(218, 218, 218); position: relative !important; margin-bottom: 3em; margin-left: 2em; padding-left: 1ch; padding-right: 1ch; width: inherit; color: rgb(31, 9, 9); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">rosrun offboard_pkg offboard_node</pre>

然后进入gazebo中进行观察。

3. 视频记录

同时，我还将我的安装过程录制成了视频，请点击这里查看。**如果想看offboard控制的效果，可以直接看视频13:00处。