ROS2与launch入门教程-创建ROS2的launch(启动)文件

ROS2与launch入门教程-创建ROS2的launch(启动)文件

说明：

• 介绍创建launch文件以运行复杂的ROS2系统
• 测试环境: ubuntu 20.04 galactic
• 创建一个launch文件来启动两个小海龟

准备:

• 更新软件源

sudo apt update 

• 安装turtlesim

sudo apt install ros-galactic-turtlesim

• 安装rqt

sudo apt install ~nros-galactic-rqt*

独立launch文件测试:

• 创建luanch目录

mkdir -p ~/launch_ws

• 新建launch文件turtlesim_mimic.launch.py

cd ~/launch_ws
vim turtlesim_mimic.launch.py 

• 内容如下

#引用launch相关包
from launch import LaunchDescription
from launch_ros.actions import Node

#定义launch描述
def generate_launch_description():
    return LaunchDescription([
        #调用节点turtlesim_node,生成第一个小海龟
        Node(
            package='turtlesim',
            namespace='turtlesim1',
            executable='turtlesim_node',
            name='sim'
        ),
        #调用节点turtlesim_node,生成第二个小海龟
        Node(
            package='turtlesim',
            namespace='turtlesim2',
            executable='turtlesim_node',
            name='sim'
        ),
        #调用节点mimic,实现跟随
        Node(
            package='turtlesim',
            executable='mimic',
            name='mimic',
            remappings=[
                ('/input/pose', '/turtlesim1/turtle1/pose'),
                ('/output/cmd_vel', '/turtlesim2/turtle1/cmd_vel'),
            ]
        )
    ])

• mimic的/input/pose话题重映射到/turtlesim1/turtle1/pose
• /output/cmd_vel的话题/turtlesim2/turtle1/cmd_vel
• 根据海龟1的位置,评估海龟2的速度,并发布给海龟2执行,从而实现海龟2跟随海龟1走同样的路径

• 启动launch文件

cd ~/launch_ws
ros2 launch turtlesim_mimic.launch.py 

• 控制海龟1运行

ros2 topic pub -r 1 /turtlesim1/turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: -1.8}}"

• 效果图：　

• 查看节点

rqt_graph

　- 效果图：