0. 前言

系统要求：Ubuntu20.04

ROS安装版本: Noetic

清华源配置

sudo gedit /etc/apt/sources.list

#清华源
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse

1. ROS1安装

添加 sources.list（设置你的电脑可以从 packages.ros.org 接收软件.）

sudo sh -c '. /etc/lsb-release && echo "deb http://mirrors.tuna.tsinghua.edu.cn/ros/ubuntu/ `lsb_release -cs` main" > /etc/apt/sources.list.d/ros-latest.list'

添加 keys

sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654

安装ROS1桌面完整版

sudo apt update
sudo apt install ros-noetic-desktop-full

环境测试

source /opt/ros/noetic/setup.bash

补全rosdep

sudo apt install python3-rosdep python3-rosinstall python3-rosinstall-generator python3-wstool build-essential
sudo apt install python3-rosdep
sudo rosdep init
rosdep update

2. ROS2安装

确保系统要支持 UTF-8:

sudo locale-gen en_US en_US.UTF-8
sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 export LANG=en_US.UTF-8

设置软件源

sudo apt update
sudo apt install curl gnupg2 lsb-release

# 下面这条语句，我的输出错误： gpg: no valid OpenPGP data found
# curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo apt-key add -
# 解决上面的问题，可以换成下面这条语句：
$ curl http://repo.ros2.org/repos.key | sudo apt-key add - 

# 之后再添加源:
sudo sh -c '. /etc/lsb-release && echo "deb http://mirrors.tuna.tsinghua.edu.cn/ros2/ubuntu/ `lsb_release -cs` main" > /etc/apt/sources.list.d/ros-latest.list'

安装ROS2桌面完整版

sudo apt update
sudo apt install ros-foxy-desktop
sudo apt install python3-colcon-common-extensions

环境测试

source /opt/ros/foxy/setup.bash

自动补全工具

sudo apt update
sudo apt install python3-argcomplete
sudo apt update
sudo apt install ros-foxy-rmw-connext-cpp

安装ros1转换bridge

sudo apt update
sudo apt install ros-foxy-ros1-bridge

ROS1和ROS2混合配置

sudo gedit ~/.bashrc

打开.bashrc文本文件后在末尾加上如下代码，完成环境变量设置。

#source /opt/ros/noetic/setup.bash
echo "ros noetic(1) or ros2 foxy(2)?"
read edition
if [ "$edition" -eq "1" ];then
  source /opt/ros/noetic/setup.bash
else
  source /opt/ros/foxy/setup.bash
fi

ROS1和ROS2差异

编译

catkin_make --> colcon build

catkin_make -DCATKIN_WHITELIST_PACKAGES="" --> colcon build --packages-select  PACKAGE_NAME

bashrc存入

echo "source ~/catkin_ws/devel/setup.bash" >> ~/.bashrc --> echo "source ~/colcon_ws/install/setup.bash" >> ~/.bashrc

terminal 命令

rosrun --> ros2 run
rosnode --> ros2 node
roslaunch --> ros2 launch
rosparam --> ros2 param
rospkg --> ros2 pkg
rosservice --> ros2 service 
rossrv --> ros2 srv
rostopic --> ros2 topic
rosaction --> ros2 action

ROS2写法

有一说一，ROS2的class管理还是比较好的，ROS2相比ROS1在语法上有了很大的改变，在编程思路还是一样。这里给出最简单的topic通讯。

#include <chrono>
#include <functional>
#include <memory>
#include <string>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std::chrono_literals;

/* This example creates a subclass of Node and uses std::bind() to register a
* member function as a callback from the timer. */

class MinimalPublisher : public rclcpp::Node
{
  public:
    MinimalPublisher()
    : Node("minimal_publisher"), count_(0)
    {
      publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);
      timer_ = this->create_wall_timer(
      500ms, std::bind(&MinimalPublisher::timer_callback, this));
    }

  private:
    void timer_callback()
    {
      auto message = std_msgs::msg::String();
      message.data = "Hello, world! " + std::to_string(count_++);
      RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", message.data.c_str());
      publisher_->publish(message);
    }
    rclcpp::TimerBase::SharedPtr timer_;
    rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
    size_t count_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalPublisher>());
  rclcpp::shutdown();
  return 0;
}

对上述代码进行简单分析：
头文件部分

#include <chrono>
#include <functional>
#include <memory>
#include <string>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

命名空间

using namespace std::chrono_literals;

使用面向对象中的继承，类名为MinimalPublisher继承rclcpp::Node这个类，继承方式为public;

class MinimalPublisher : public rclcpp::Node

私有成员有回调函数timer_callback，计时器对象timer_,发布者对象publisher_,统计数量的count_;
该timer_callback函数是设置消息数据和实际发布消息的地方。该RCLCPP_INFO宏确保每个发布的消息都打印到控制台。还有计时器、发布者和计数器字段的声明。

private:
    void timer_callback()
    {
      auto message = std_msgs::msg::String();
      message.data = "Hello, world! " + std::to_string(count_++);
      RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", message.data.c_str());
      publisher_->publish(message);
    }
    rclcpp::TimerBase::SharedPtr timer_;
    rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
    size_t count_;

公有成员:类的构造函数用于对私有成员进行初始化；
公共构造函数命名节点minimal_publisher并初始化count_为 0。在构造函数内部，发布者使用String消息类型、主题名称topic和所需的队列大小进行初始化，以在发生备份时限制消息。接下来，timer_被初始化，这会导致timer_callback函数每秒执行两次。this指的是该节点

public:
    MinimalPublisher()
    : Node("minimal_publisher"), count_(0)
    {
      publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);
      timer_ = this->create_wall_timer(
      500ms, std::bind(&MinimalPublisher::timer_callback, this));
    }

主函数部分
rclcpp::init初始化 ROS 2，并rclcpp::spin开始处理来自节点的数据，包括来自计时器的回调。

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalPublisher>());
  rclcpp::shutdown();
  return 0;
}

创建订阅者

#include <memory>
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
using std::placeholders::_1;

class MinimalSubscriber : public rclcpp::Node
{
  public:
    MinimalSubscriber()
    : Node("minimal_subscriber")
    {
      subscription_ = this->create_subscription<std_msgs::msg::String>(
      "topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));
    }

  private:
    void topic_callback(const std_msgs::msg::String::SharedPtr msg) const
    {
      RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
    }
    rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalSubscriber>());
  rclcpp::shutdown();
  return 0;
}

修改CMakeLists.txt文件，将下面内容复制到文件中并保存

add_executable(talker src/publisher_member_function.cpp)
ament_target_dependencies(talker rclcpp std_msgs)

add_executable(listener src/subscriber_member_function.cpp)
ament_target_dependencies(listener rclcpp std_msgs)

install(TARGETS
  talker
  listener
  DESTINATION lib/${PROJECT_NAME})