ROS2：如何将Cartographer和Navigation2一起使用（2）：使用纯定位和Nav2进行导航_amcl和cartographer

作者：煮酒与君饮 | 2024-07-24 22:01:48

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amcl和cartographer

ROS2中的navigation2使用AMCL和map_server来估计自己的位置并自主移动。

map_server发布/map主题，AMCL根据/map和雷达的/scan、里程计/odom信息估计自己的位置，并将/tf发布到/odom。

通过将AMCL和map_server分别替换成cartographer_node、cartographer_occupancy_grid_node而不是AMCL，Cartographer可以单独进行纯定位并在导航中运行它，同时估计自己的位置。

实现在ROS2中的Cartographer纯定位可以在上篇文章中发现，本文将讲解Cartographer替换AMCL配合Nav2实现导航仿真。

ROS2：如何将Cartographer和Navigation2一起使用（1）：从SLAM到纯定位_什么都不会的码小白的博客-CSDN博客

Nav2操作

首先检查Navigation2默认状态下的操作。


export TURTLEBOT3_MODEL=burger
ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py

当在Gazebo环境中运行Nav2时，务必将use_sim_time设置为true。

运行turtlebot3包中的navigation2.launch可以使用下面的命令。


export TURTLEBOT3_MODEL=burger
ros2 launch turtlebot3_navigation2 navigation2.launch.py use_sim_time:=true

单击Rviz命令面板上的2D Pose Estimate设置初始位置，然后用Nav2 Goal拖动地图上的目标位置，使用Turtlebot3向目标位置移动。

创建启动文件启动Cartographer和Nav2

Nav2中的bringup_launch.py是在navigation2.launch.py中调用的，而执行amcl和map_server的localization_launch.py是在bringup_launch.py中执行的。
通过重写bringup_launch.py来创建新的启动文件，以运行上一篇文章中创建的cartographer_localization.launch.py而不是localization_launch。

在launch文件夹下创建一个新的启动文件bringup_launch_cartographer.launch.py，以下是启动文件内容的示例。


import os
 
from ament_index_python.packages import get_package_share_directory
 
from launch import LaunchDescription
from launch.actions import (DeclareLaunchArgument, GroupAction,
                            IncludeLaunchDescription, SetEnvironmentVariable)
from launch.conditions import IfCondition
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration, PythonExpression
from launch_ros.actions import Node
from launch_ros.actions import PushRosNamespace
from nav2_common.launch import RewrittenYaml
 
 
def generate_launch_description():
    # Get the launch directory
    bringup_dir = get_package_share_directory('nav2_bringup')
    launch_dir = os.path.join(bringup_dir, 'launch')
    cartographer_launch_dir = os.path.join(get_package_share_directory('turtlebot3_cartographer'), 'launch')
 
    # Create the launch configuration variables
    namespace = LaunchConfiguration('namespace')
    use_namespace = LaunchConfiguration('use_namespace')
    slam = LaunchConfiguration('slam')
    map_yaml_file = LaunchConfiguration('map')
    use_sim_time = LaunchConfiguration('use_sim_time')
    params_file = LaunchConfiguration('params_file')
    autostart = LaunchConfiguration('autostart')
    use_composition = LaunchConfiguration('use_composition')
    use_respawn = LaunchConfiguration('use_respawn')
    log_level = LaunchConfiguration('log_level')
 
    remappings = [('/tf', 'tf'),
                  ('/tf_static', 'tf_static')]
 
    configured_params = RewrittenYaml(
        source_file=params_file,
        root_key=namespace,
        param_rewrites={},
        convert_types=True)
 
    stdout_linebuf_envvar = SetEnvironmentVariable(
        'RCUTILS_LOGGING_BUFFERED_STREAM', '1')
 
    declare_namespace_cmd = DeclareLaunchArgument(
        'namespace',
        default_value='',
        description='Top-level namespace')
 
    declare_use_namespace_cmd = DeclareLaunchArgument(
        'use_namespace',
        default_value='false',
        description='Whether to apply a namespace to the navigation stack')
 
    declare_map_yaml_cmd = DeclareLaunchArgument(
        'map',
        default_value='',
        description='Full path to map yaml file to load')
 
    declare_use_sim_time_cmd = DeclareLaunchArgument(
        'use_sim_time',
        default_value='false',
        description='Use simulation (Gazebo) clock if true')
 
    declare_params_file_cmd = DeclareLaunchArgument(
        'params_file',
        default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
        description='Full path to the ROS2 parameters file to use for all launched nodes')
 
    declare_autostart_cmd = DeclareLaunchArgument(
        'autostart', default_value='true',
        description='Automatically startup the nav2 stack')
 
    declare_use_composition_cmd = DeclareLaunchArgument(
        'use_composition', default_value='True',
        description='Whether to use composed bringup')
 
    declare_use_respawn_cmd = DeclareLaunchArgument(
        'use_respawn', default_value='False',
        description='Whether to respawn if a node crashes. Applied when composition is disabled.')
 
    declare_log_level_cmd = DeclareLaunchArgument(
        'log_level', default_value='info',
        description='log level')
 
    # Specify the actions
    bringup_cmd_group = GroupAction([
        PushRosNamespace(
            condition=IfCondition(use_namespace),
            namespace=namespace),
 
        Node(
            condition=IfCondition(use_composition),
            name='nav2_container',
            package='rclcpp_components',
            executable='component_container_isolated',
            parameters=[configured_params, {'autostart': autostart}],
            arguments=['--ros-args', '--log-level', log_level],
            remappings=remappings,
            output='screen'),
 
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(cartographer_launch_dir,
                                                       'cartographer_localization.launch.py'))),
 
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(launch_dir, 'navigation_launch.py')),
            launch_arguments={'namespace': namespace,
                              'use_sim_time': use_sim_time,
                              'autostart': autostart,
                              'params_file': params_file,
                              'use_composition': use_composition,
                              'use_respawn': use_respawn,
                              'container_name': 'nav2_container'}.items()),
    ])
 
    # Create the launch description and populate
    ld = LaunchDescription()
 
    # Set environment variables
    ld.add_action(stdout_linebuf_envvar)
 
    # Declare the launch options
    ld.add_action(declare_namespace_cmd)
    ld.add_action(declare_use_namespace_cmd)
    ld.add_action(declare_map_yaml_cmd)
    ld.add_action(declare_use_sim_time_cmd)
    ld.add_action(declare_params_file_cmd)
    ld.add_action(declare_autostart_cmd)
    ld.add_action(declare_use_composition_cmd)
    ld.add_action(declare_use_respawn_cmd)
    ld.add_action(declare_log_level_cmd)
 
    # Add the actions to launch all of the navigation nodes
    ld.add_action(bringup_cmd_group)
 
    return ld

对比bringup_launch.py，添加以下部分。


    cartographer_launch_dir = os.path.join(get_package_share_directory('turtlebot3_cartographer'), 'launch')
 
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(cartographer_launch_dir,
                                                       'cartographer_localization.launch.py'))),

创建一个新的bringup_launch，启动bringup_launch_cartographer.launch.py。
*map.yaml 由于不需要pgm，所以与map_dir相关的部分已被删除。

相应的navigation2_cartographer.launch.py代码如下。


import os
 
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node
 
TURTLEBOT3_MODEL = os.environ['TURTLEBOT3_MODEL']
 
def generate_launch_description():
    use_sim_time = LaunchConfiguration('use_sim_time', default='false')
    param_file_name = TURTLEBOT3_MODEL + '.yaml'
    param_dir = LaunchConfiguration(
        'params_file',
        default=os.path.join(
            get_package_share_directory('turtlebot3_navigation2'),
            'param',
            param_file_name))
 
    nav2_launch_file_dir = os.path.join(get_package_share_directory('turtlebot3_navigation2'), 'launch')
 
    rviz_config_dir = os.path.join(
        get_package_share_directory('nav2_bringup'),
        'rviz',
        'nav2_default_view.rviz')
 
    return LaunchDescription([
        DeclareLaunchArgument(
            'params_file',
            default_value=param_dir,
            description='Full path to param file to load'),
 
        DeclareLaunchArgument(
            'use_sim_time',
            default_value='false',
            description='Use simulation (Gazebo) clock if true'),
 
        IncludeLaunchDescription(
            PythonLaunchDescriptionSource([nav2_launch_file_dir, '/bringup_launch_cartographer.launch.py']),
            launch_arguments={
                'use_sim_time': use_sim_time,
                'params_file': param_dir}.items(),
        ),
 
        Node(
            package='rviz2',
            executable='rviz2',
            name='rviz2',
            arguments=['-d', rviz_config_dir],
            parameters=[{'use_sim_time': use_sim_time}],
            output='screen'),
    ])

运行


export TURTLEBOT3_MODEL=burger
ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py


export TURTLEBOT3_MODEL=burger
ros2 launch turtlebot3_navigation2 navigation2_cartographer.launch.py use_sim_time:=true

rviz2显示全局成本图。同样，如果使用 Nav2 Goal 拖动地图上的目标位置，Turtlebot3 也会向目标移动。（无需设置初始位置）

运行时的rqt_graph

tf树

/map --> 发出 /odom 的 TF 的节点变为 cartographer_ros 而不是 amcl。

总结

本文通过结合 Nav2 和使用 cartographer 估计其自身位置，实现机器人的导航。
amcl 需要 /odom，但如果更改cartographer 设置，即使对于无法进行里程计的机器人，也可以使用 Nav2 进行导航。

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