机器人操作系统二（ROS2）- 启程 Departure

是时候放下ROS1，开启ROS2的旅程了。It's time to put down ROS1 and start the journey of ROS2.

ROS2官方在线文档链接 ROS2 official online documentation：https://index.ros.org/doc/ros2/

ROS2教程文档使用说明与为什么选择ROS2？ROS2 tutorial documentation instructions and why choose ROS2?https://blog.csdn.net/ZhangRelay/article/details/93601114

ROS2常规学习路径 ROS2 regular learning path：

demos、navigation2 and moveit2

ROS2进阶学习路径 ROS2 advanced learning path：

others

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学习分享从安装配置开始，首先详细介绍教程，然后是两个专题：Navigation2和MoveIt!2。This article starts with ROS2 installation and configuration, first introduces the tutorial in detail, then two topics: Navigation2 and MoveIt!2.

安装详细过程 Installation detailed tutorial：ROS 2 Dashing Diademata安装和使用文档（含Linux、Windows和OS X）ROS 2 Dashing Diademata installation and documentation (including Linux, Windows and OS X)

ROS教程 ROS 2 tutorials：https://github.com/zhangrelay/ros2_tutorials

配置教程包 Tutorial package configuration：

1. 下载：git clone
2. 编译：colcon build
3. 使用：ros2 run

colcon build

导入编译的环境 Import the compiled environment：

source install/setup.bash

输入ros2 run turtlesim，可以看到如下节点 Enter ros2 run turtlesim, you can see the following nodes：
draw_square        --prefix           turtle_teleop_key  
mimic              turtlesim_node

常用命令如下 Common commands are as follows：

1. ros2 run turtlesim turtlesim_node
2. ros2 topic list
3. ros2 run turtlesim draw_square
4. ros2 topic echo /turtle1/pose
5. ……

更多内容参考下图 For more details, please refer to the following figure：

欢迎大家下载案例调试玩耍， 更多内容后续介绍。You are welcome to download the case, debug and play, more will be introduced in subsequent articles.

思考题 Thinking：

回顾roslaunch， 写一个ros2 launch，同时启动turtlesim_node和draw_spuare。Looking back at roslaunch, write a ros2 launch and start both the turtlesim_node and draw_spuare node.

扩展题 Extended：

对比ROS1和ROS2的turtlesim包，分析和思考两代ROS编程和使用中的差异。Compare the turbulsim package of ROS1 and ROS2, analyze and think about the difference between the two generations of ROS in programming and use.

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 draw_square.launch.py

from launch import LaunchDescription
import launch_ros.actions

def generate_launch_description():
    return LaunchDescription([
        launch_ros.actions.Node(
            node_namespace= "ros2", package='turtlesim', node_executable='turtlesim_node', output='screen'),
        launch_ros.actions.Node(
            node_namespace= "ros2", package='turtlesim', node_executable='draw_square', output='screen'),
    ])

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