• 学习ros机器人导航从精读nav2导航launch文件开始

    nav2导航launch文件经过了多层套娃，真的是让初学者哭晕在厕所，今天我们就拆解一下他的launch文件，还原他最简单的状态，看看他到底启动了什么节点。

    一 tb3仿真机器人启动文件：tb3_simulation_launch.py

    1 文件目录结构 

    文件取自：Nav2 — Navigation 2 1.0.0 文档

    2 文件源代码 

    1. # Copyright (c) 2018 Intel Corporation
    2. #
    3. # Licensed under the Apache License, Version 2.0 (the "License");
    4. # you may not use this file except in compliance with the License.
    5. # You may obtain a copy of the License at
    6. #
    7. #     http://www.apache.org/licenses/LICENSE-2.0
    8. #
    9. # Unless required by applicable law or agreed to in writing, software
    10. # distributed under the License is distributed on an "AS IS" BASIS,
    11. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12. # See the License for the specific language governing permissions and
    13. # limitations under the License.
    14.  
    15. """This is all-in-one launch script intended for use by nav2 developers."""
    16.  
    17. import os
    18.  
    19. from ament_index_python.packages import get_package_share_directory
    20.  
    21. from launch import LaunchDescription
    22. from launch.actions import DeclareLaunchArgument, ExecuteProcess, IncludeLaunchDescription
    23. from launch.conditions import IfCondition
    24. from launch.launch_description_sources import PythonLaunchDescriptionSource
    25. from launch.substitutions import LaunchConfiguration, PythonExpression
    26. from launch_ros.actions import Node
    27.  
    28.  
    29. def generate_launch_description():
    30.     # Get the launch directory
    31.     bringup_dir = get_package_share_directory('nav2_bringup')
    32.     launch_dir = os.path.join(bringup_dir, 'launch')
    33.  
    34.     # Create the launch configuration variables
    35.     slam = LaunchConfiguration('slam')
    36.     namespace = LaunchConfiguration('namespace')
    37.     use_namespace = LaunchConfiguration('use_namespace')
    38.     map_yaml_file = LaunchConfiguration('map')
    39.     use_sim_time = LaunchConfiguration('use_sim_time')
    40.     params_file = LaunchConfiguration('params_file')
    41.     default_bt_xml_filename = LaunchConfiguration('default_bt_xml_filename')
    42.     autostart = LaunchConfiguration('autostart')
    43.  
    44.     # Launch configuration variables specific to simulation
    45.     rviz_config_file = LaunchConfiguration('rviz_config_file')
    46.     use_simulator = LaunchConfiguration('use_simulator')
    47.     use_robot_state_pub = LaunchConfiguration('use_robot_state_pub')
    48.     use_rviz = LaunchConfiguration('use_rviz')
    49.     headless = LaunchConfiguration('headless')
    50.     world = LaunchConfiguration('world')
    51.  
    52.     # Map fully qualified names to relative ones so the node's namespace can be prepended.
    53.     # In case of the transforms (tf), currently, there doesn't seem to be a better alternative
    54.     # https://github.com/ros/geometry2/issues/32
    55.     # https://github.com/ros/robot_state_publisher/pull/30
    56.     # TODO(orduno) Substitute with `PushNodeRemapping`
    57.     #              https://github.com/ros2/launch_ros/issues/56
    58.     remappings = [('/tf', 'tf'),
    59.                   ('/tf_static', 'tf_static')]
    60.  
    61.     # Declare the launch arguments
    62.     declare_namespace_cmd = DeclareLaunchArgument(
    63.         'namespace',
    64.         default_value='',
    65.         description='Top-level namespace')
    66.  
    67.     declare_use_namespace_cmd = DeclareLaunchArgument(
    68.         'use_namespace',
    69.         default_value='false',
    70.         description='Whether to apply a namespace to the navigation stack')
    71.  
    72.     declare_slam_cmd = DeclareLaunchArgument(
    73.         'slam',
    74.         default_value='False',
    75.         description='Whether run a SLAM')
    76.  
    77.     declare_map_yaml_cmd = DeclareLaunchArgument(
    78.         'map',
    79.         default_value=os.path.join(bringup_dir, 'maps', 'turtlebot3_world.yaml'),
    80.         description='Full path to map file to load')
    81.  
    82.     declare_use_sim_time_cmd = DeclareLaunchArgument(
    83.         'use_sim_time',
    84.         default_value='true',
    85.         description='Use simulation (Gazebo) clock if true')
    86.  
    87.     declare_params_file_cmd = DeclareLaunchArgument(
    88.         'params_file',
    89.         default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
    90.         description='Full path to the ROS2 parameters file to use for all launched nodes')
    91.  
    92.     declare_bt_xml_cmd = DeclareLaunchArgument(
    93.         'default_bt_xml_filename',
    94.         default_value=os.path.join(
    95.             get_package_share_directory('nav2_bt_navigator'),
    96.             'behavior_trees', 'navigate_w_replanning_and_recovery.xml'),
    97.         description='Full path to the behavior tree xml file to use')
    98.  
    99.     declare_autostart_cmd = DeclareLaunchArgument(
    100.         'autostart', default_value='true',
    101.         description='Automatically startup the nav2 stack')
    102.  
    103.     declare_rviz_config_file_cmd = DeclareLaunchArgument(
    104.         'rviz_config_file',
    105.         default_value=os.path.join(bringup_dir, 'rviz', 'nav2_default_view.rviz'),
    106.         description='Full path to the RVIZ config file to use')
    107.  
    108.     declare_use_simulator_cmd = DeclareLaunchArgument(
    109.         'use_simulator',
    110.         default_value='True',
    111.         description='Whether to start the simulator')
    112.  
    113.     declare_use_robot_state_pub_cmd = DeclareLaunchArgument(
    114.         'use_robot_state_pub',
    115.         default_value='True',
    116.         description='Whether to start the robot state publisher')
    117.  
    118.     declare_use_rviz_cmd = DeclareLaunchArgument(
    119.         'use_rviz',
    120.         default_value='True',
    121.         description='Whether to start RVIZ')
    122.  
    123.     declare_simulator_cmd = DeclareLaunchArgument(
    124.         'headless',
    125.         default_value='False',
    126.         description='Whether to execute gzclient)')
    127.  
    128.     declare_world_cmd = DeclareLaunchArgument(
    129.         'world',
    130.         # TODO(orduno) Switch back once ROS argument passing has been fixed upstream
    131.         #              https://github.com/ROBOTIS-GIT/turtlebot3_simulations/issues/91
    132.         # default_value=os.path.join(get_package_share_directory('turtlebot3_gazebo'),
    133.         #                            'worlds/turtlebot3_worlds/waffle.model'),
    134.         default_value=os.path.join(bringup_dir, 'worlds', 'waffle.model'),
    135.         description='Full path to world model file to load')
    136.  
    137.     # Specify the actions
    138.     start_gazebo_server_cmd = ExecuteProcess(
    139.         condition=IfCondition(use_simulator),
    140.         cmd=['gzserver', '-s', 'libgazebo_ros_init.so', world],
    141.         cwd=[launch_dir], output='screen')
    142.  
    143.     start_gazebo_client_cmd = ExecuteProcess(
    144.         condition=IfCondition(PythonExpression([use_simulator, ' and not ', headless])),
    145.         cmd=['gzclient'],
    146.         cwd=[launch_dir], output='screen')
    147.  
    148.     urdf = os.path.join(bringup_dir, 'urdf', 'turtlebot3_waffle.urdf')
    149.  
    150.     start_robot_state_publisher_cmd = Node(
    151.         condition=IfCondition(use_robot_state_pub),
    152.         package='robot_state_publisher',
    153.         executable='robot_state_publisher',
    154.         name='robot_state_publisher',
    155.         namespace=namespace,
    156.         output='screen',
    157.         parameters=[{'use_sim_time': use_sim_time}],
    158.         remappings=remappings,
    159.         arguments=[urdf])
    160.  
    161.     rviz_cmd = IncludeLaunchDescription(
    162.         PythonLaunchDescriptionSource(os.path.join(launch_dir, 'rviz_launch.py')),
    163.         condition=IfCondition(use_rviz),
    164.         launch_arguments={'namespace': '',
    165.                           'use_namespace': 'False',
    166.                           'rviz_config': rviz_config_file}.items())
    167.  
    168.     bringup_cmd = IncludeLaunchDescription(
    169.         PythonLaunchDescriptionSource(os.path.join(launch_dir, 'bringup_launch.py')),
    170.         launch_arguments={'namespace': namespace,
    171.                           'use_namespace': use_namespace,
    172.                           'slam': slam,
    173.                           'map': map_yaml_file,
    174.                           'use_sim_time': use_sim_time,
    175.                           'params_file': params_file,
    176.                           'default_bt_xml_filename': default_bt_xml_filename,
    177.                           'autostart': autostart}.items())
    178.  
    179.     # Create the launch description and populate
    180.     ld = LaunchDescription()
    181.  
    182.     # Declare the launch options
    183.     ld.add_action(declare_namespace_cmd)
    184.     ld.add_action(declare_use_namespace_cmd)
    185.     ld.add_action(declare_slam_cmd)
    186.     ld.add_action(declare_map_yaml_cmd)
    187.     ld.add_action(declare_use_sim_time_cmd)
    188.     ld.add_action(declare_params_file_cmd)
    189.     ld.add_action(declare_bt_xml_cmd)
    190.     ld.add_action(declare_autostart_cmd)
    191.  
    192.     ld.add_action(declare_rviz_config_file_cmd)
    193.     ld.add_action(declare_use_simulator_cmd)
    194.     ld.add_action(declare_use_robot_state_pub_cmd)
    195.     ld.add_action(declare_use_rviz_cmd)
    196.     ld.add_action(declare_simulator_cmd)
    197.     ld.add_action(declare_world_cmd)
    198.  
    199.     # Add any conditioned actions
    200.     ld.add_action(start_gazebo_server_cmd)
    201.     ld.add_action(start_gazebo_client_cmd)
    202.  
    203.     # Add the actions to launch all of the navigation nodes
    204.     ld.add_action(start_robot_state_publisher_cmd)
    205.     ld.add_action(rviz_cmd)
    206.     ld.add_action(bringup_cmd)
    207.  
    208.     return ld

    二 launch文件究竟启动了什么

    1 第一层套娃启动了什么

    只看launch文件最后面几行。

    1.     # Add any conditioned actions
    2.     ld.add_action(start_gazebo_server_cmd)
    3.     ld.add_action(start_gazebo_client_cmd)
    4.  
    5.     # Add the actions to launch all of the navigation nodes
    6.     ld.add_action(start_robot_state_publisher_cmd)
    7.     ld.add_action(rviz_cmd)
    8.     ld.add_action(bringup_cmd)
    9.  
    10.     return ld

    分别启动了gazebo，机器人模型文件，rviz2，和bringup_cmd，这里关于导航的只有bringup_cmd，其他的只是生成了机器人和在rviz2里面展现出来了，下面只分析最重要的—导航。

    2 第二层套娃启动了什么

    1.  bringup_cmd = IncludeLaunchDescription(
    2.         PythonLaunchDescriptionSource(os.path.join(launch_dir, 'bringup_launch.py')),
    3.         launch_arguments={'namespace': namespace,
    4.                           'use_namespace': use_namespace,
    5.                           'slam': slam,
    6.                           'map': map_yaml_file,
    7.                           'use_sim_time': use_sim_time,
    8.                           'params_file': params_file,
    9.                           'default_bt_xml_filename': default_bt_xml_filename,
    10.                           'autostart': autostart}.items())

    bringup_launch.py  文件目录结构

    bringup_launch.py文件内容 

    1. # Copyright (c) 2018 Intel Corporation
    2. #
    3. # Licensed under the Apache License, Version 2.0 (the "License");
    4. # you may not use this file except in compliance with the License.
    5. # You may obtain a copy of the License at
    6. #
    7. #     http://www.apache.org/licenses/LICENSE-2.0
    8. #
    9. # Unless required by applicable law or agreed to in writing, software
    10. # distributed under the License is distributed on an "AS IS" BASIS,
    11. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12. # See the License for the specific language governing permissions and
    13. # limitations under the License.
    14.  
    15. import os
    16.  
    17. from ament_index_python.packages import get_package_share_directory
    18.  
    19. from launch import LaunchDescription
    20. from launch.actions import (DeclareLaunchArgument, GroupAction,
    21.                             IncludeLaunchDescription, SetEnvironmentVariable)
    22. from launch.conditions import IfCondition
    23. from launch.launch_description_sources import PythonLaunchDescriptionSource
    24. from launch.substitutions import LaunchConfiguration, PythonExpression
    25. from launch_ros.actions import PushRosNamespace
    26.  
    27.  
    28. def generate_launch_description():
    29.     # Get the launch directory
    30.     bringup_dir = get_package_share_directory('nav2_bringup')
    31.     launch_dir = os.path.join(bringup_dir, 'launch')
    32.  
    33.     # Create the launch configuration variables
    34.     namespace = LaunchConfiguration('namespace')
    35.     use_namespace = LaunchConfiguration('use_namespace')
    36.     slam = LaunchConfiguration('slam')
    37.     map_yaml_file = LaunchConfiguration('map')
    38.     use_sim_time = LaunchConfiguration('use_sim_time')
    39.     params_file = LaunchConfiguration('params_file')
    40.     default_bt_xml_filename = LaunchConfiguration('default_bt_xml_filename')
    41.     autostart = LaunchConfiguration('autostart')
    42.  
    43.     stdout_linebuf_envvar = SetEnvironmentVariable(
    44.         'RCUTILS_LOGGING_BUFFERED_STREAM', '1')
    45.  
    46.     declare_namespace_cmd = DeclareLaunchArgument(
    47.         'namespace',
    48.         default_value='',
    49.         description='Top-level namespace')
    50.  
    51.     declare_use_namespace_cmd = DeclareLaunchArgument(
    52.         'use_namespace',
    53.         default_value='false',
    54.         description='Whether to apply a namespace to the navigation stack')
    55.  
    56.     declare_slam_cmd = DeclareLaunchArgument(
    57.         'slam',
    58.         default_value='False',
    59.         description='Whether run a SLAM')
    60.  
    61.     declare_map_yaml_cmd = DeclareLaunchArgument(
    62.         'map',
    63.         description='Full path to map yaml file to load')
    64.  
    65.     declare_use_sim_time_cmd = DeclareLaunchArgument(
    66.         'use_sim_time',
    67.         default_value='false',
    68.         description='Use simulation (Gazebo) clock if true')
    69.  
    70.     declare_params_file_cmd = DeclareLaunchArgument(
    71.         'params_file',
    72.         default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
    73.         description='Full path to the ROS2 parameters file to use for all launched nodes')
    74.  
    75.     declare_bt_xml_cmd = DeclareLaunchArgument(
    76.         'default_bt_xml_filename',
    77.         default_value=os.path.join(
    78.             get_package_share_directory('nav2_bt_navigator'),
    79.             'behavior_trees', 'navigate_w_replanning_and_recovery.xml'),
    80.         description='Full path to the behavior tree xml file to use')
    81.  
    82.     declare_autostart_cmd = DeclareLaunchArgument(
    83.         'autostart', default_value='true',
    84.         description='Automatically startup the nav2 stack')
    85.  
    86.     # Specify the actions
    87.     bringup_cmd_group = GroupAction([
    88.         PushRosNamespace(
    89.             condition=IfCondition(use_namespace),
    90.             namespace=namespace),
    91.  
    92.         IncludeLaunchDescription(
    93.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'slam_launch.py')),
    94.             condition=IfCondition(slam),
    95.             launch_arguments={'namespace': namespace,
    96.                               'use_sim_time': use_sim_time,
    97.                               'autostart': autostart,
    98.                               'params_file': params_file}.items()),
    99.  
    100.         IncludeLaunchDescription(
    101.             PythonLaunchDescriptionSource(os.path.join(launch_dir,
    102.                                                        'localization_launch.py')),
    103.             condition=IfCondition(PythonExpression(['not ', slam])),
    104.             launch_arguments={'namespace': namespace,
    105.                               'map': map_yaml_file,
    106.                               'use_sim_time': use_sim_time,
    107.                               'autostart': autostart,
    108.                               'params_file': params_file,
    109.                               'use_lifecycle_mgr': 'false'}.items()),
    110.  
    111.         IncludeLaunchDescription(
    112.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'navigation_launch.py')),
    113.             launch_arguments={'namespace': namespace,
    114.                               'use_sim_time': use_sim_time,
    115.                               'autostart': autostart,
    116.                               'params_file': params_file,
    117.                               'default_bt_xml_filename': default_bt_xml_filename,
    118.                               'use_lifecycle_mgr': 'false',
    119.                               'map_subscribe_transient_local': 'true'}.items()),
    120.     ])
    121.  
    122.     # Create the launch description and populate
    123.     ld = LaunchDescription()
    124.  
    125.     # Set environment variables
    126.     ld.add_action(stdout_linebuf_envvar)
    127.  
    128.     # Declare the launch options
    129.     ld.add_action(declare_namespace_cmd)
    130.     ld.add_action(declare_use_namespace_cmd)
    131.     ld.add_action(declare_slam_cmd)
    132.     ld.add_action(declare_map_yaml_cmd)
    133.     ld.add_action(declare_use_sim_time_cmd)
    134.     ld.add_action(declare_params_file_cmd)
    135.     ld.add_action(declare_autostart_cmd)
    136.     ld.add_action(declare_bt_xml_cmd)
    137.  
    138.     # Add the actions to launch all of the navigation nodes
    139.     ld.add_action(bringup_cmd_group)
    140.  
    141.     return ld

     还是从后看，启动了一个导航组：bringup_cmd_group

    1.  # Specify the actions
    2.     bringup_cmd_group = GroupAction([
    3.         PushRosNamespace(
    4.             condition=IfCondition(use_namespace),
    5.             namespace=namespace),
    6.  
    7.         IncludeLaunchDescription(
    8.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'slam_launch.py')),
    9.             condition=IfCondition(slam),
    10.             launch_arguments={'namespace': namespace,
    11.                               'use_sim_time': use_sim_time,
    12.                               'autostart': autostart,
    13.                               'params_file': params_file}.items()),
    14.  
    15.         IncludeLaunchDescription(
    16.             PythonLaunchDescriptionSource(os.path.join(launch_dir,
    17.                                                        'localization_launch.py')),
    18.             condition=IfCondition(PythonExpression(['not ', slam])),
    19.             launch_arguments={'namespace': namespace,
    20.                               'map': map_yaml_file,
    21.                               'use_sim_time': use_sim_time,
    22.                               'autostart': autostart,
    23.                               'params_file': params_file,
    24.                               'use_lifecycle_mgr': 'false'}.items()),
    25.  
    26.         IncludeLaunchDescription(
    27.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'navigation_launch.py')),
    28.             launch_arguments={'namespace': namespace,
    29.                               'use_sim_time': use_sim_time,
    30.                               'autostart': autostart,
    31.                               'params_file': params_file,
    32.                               'default_bt_xml_filename': default_bt_xml_filename,
    33.                               'use_lifecycle_mgr': 'false',
    34.                               'map_subscribe_transient_local': 'true'}.items()),
    35.     ])

    导航最核心的部分，定位  导航

    很不容易懂得一个地方，condition=IfCondition(), 条件启动，弄懂这个启动文件又精简很多。

    第一个条件语句块

    1. PushRosNamespace(
    2.             condition=IfCondition(use_namespace),
    3.             namespace=namespace),

    IfCondition条件语句，IfCondition(use_namespace) use_namespace是真这个语句启动，如果是假这个语句块想当于不存在，结合上下文 use_namespace 默认值false，所以这段语句块相当于不存在。

    第二个条件语句块

    1. IncludeLaunchDescription(
    2.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'slam_launch.py')),
    3.             condition=IfCondition(slam),
    4.             launch_arguments={'namespace': namespace,
    5.                               'use_sim_time': use_sim_time,
    6.                               'autostart': autostart,
    7.                               'params_file': params_file}.items()),

    这段的意思是是否用slam_launch.py建图。

    slam的默认取值default_value='False'，如果按默认启动这段语句也可以忽略。

    如果想导航同时建图需要把slam传入True或者直接把默认值改成True。

    第三个条件语句块

    1. IncludeLaunchDescription(
    2.             PythonLaunchDescriptionSource(os.path.join(launch_dir,
    3.                                                        'localization_launch.py')),
    4.             condition=IfCondition(PythonExpression(['not ', slam])),
    5.             launch_arguments={'namespace': namespace,
    6.                               'map': map_yaml_file,
    7.                               'use_sim_time': use_sim_time,
    8.                               'autostart': autostart,
    9.                               'params_file': params_file,
    10.                               'use_lifecycle_mgr': 'false'}.items()),

    是否启动定位。

    condition=IfCondition(PythonExpression(['not ', slam])),

    这句很不好理解，直接的意思就是salm取False，整个语句块启动，salm取True，整个语句块不启动。

    这个条件语句和上面的条件语句其实是二选一

    如果slam取True，slam_launch.py建图启动，localization_launch.py 定位不启动。

    如果slam取False，slam_launch.py建图不启动，localization_launch.py 定位启动。

    按默认启动的话只是启动 localization_launch.py

    导航语句块

    1.  IncludeLaunchDescription(
    2.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'navigation_launch.py')),
    3.             launch_arguments={'namespace': namespace,
    4.                               'use_sim_time': use_sim_time,
    5.                               'autostart': autostart,
    6.                               'params_file': params_file,
    7.                               'default_bt_xml_filename': default_bt_xml_filename,
    8.                               'use_lifecycle_mgr': 'false',
    9.                               'map_subscribe_transient_local': 'true'}.items()),

    通过前面的定位，这里才是启动导航的核心程序 navigation_launch.py

    3 第三层套娃

    localization_launch.py

    这个文件的目录结构

    文件内容

    1. # Copyright (c) 2018 Intel Corporation
    2. #
    3. # Licensed under the Apache License, Version 2.0 (the "License");
    4. # you may not use this file except in compliance with the License.
    5. # You may obtain a copy of the License at
    6. #
    7. #     http://www.apache.org/licenses/LICENSE-2.0
    8. #
    9. # Unless required by applicable law or agreed to in writing, software
    10. # distributed under the License is distributed on an "AS IS" BASIS,
    11. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12. # See the License for the specific language governing permissions and
    13. # limitations under the License.
    14.  
    15. import os
    16.  
    17. from ament_index_python.packages import get_package_share_directory
    18.  
    19. from launch import LaunchDescription
    20. from launch.actions import DeclareLaunchArgument, SetEnvironmentVariable
    21. from launch.substitutions import LaunchConfiguration
    22. from launch_ros.actions import Node
    23. from nav2_common.launch import RewrittenYaml
    24.  
    25.  
    26. def generate_launch_description():
    27.     # Get the launch directory
    28.     bringup_dir = get_package_share_directory('nav2_bringup')
    29.  
    30.     namespace = LaunchConfiguration('namespace')
    31.     map_yaml_file = LaunchConfiguration('map')
    32.     use_sim_time = LaunchConfiguration('use_sim_time')
    33.     autostart = LaunchConfiguration('autostart')
    34.     params_file = LaunchConfiguration('params_file')
    35.     lifecycle_nodes = ['map_server', 'amcl']
    36.  
    37.     # Map fully qualified names to relative ones so the node's namespace can be prepended.
    38.     # In case of the transforms (tf), currently, there doesn't seem to be a better alternative
    39.     # https://github.com/ros/geometry2/issues/32
    40.     # https://github.com/ros/robot_state_publisher/pull/30
    41.     # TODO(orduno) Substitute with `PushNodeRemapping`
    42.     #              https://github.com/ros2/launch_ros/issues/56
    43.     remappings = [('/tf', 'tf'),
    44.                   ('/tf_static', 'tf_static')]
    45.  
    46.     # Create our own temporary YAML files that include substitutions
    47.     param_substitutions = {
    48.         'use_sim_time': use_sim_time,
    49.         'yaml_filename': map_yaml_file}
    50.  
    51.     configured_params = RewrittenYaml(
    52.         source_file=params_file,
    53.         root_key=namespace,
    54.         param_rewrites=param_substitutions,
    55.         convert_types=True)
    56.  
    57.     return LaunchDescription([
    58.         # Set env var to print messages to stdout immediately
    59.         SetEnvironmentVariable('RCUTILS_LOGGING_BUFFERED_STREAM', '1'),
    60.  
    61.         DeclareLaunchArgument(
    62.             'namespace', default_value='',
    63.             description='Top-level namespace'),
    64.  
    65.         DeclareLaunchArgument(
    66.             'map',
    67.             default_value=os.path.join(bringup_dir, 'maps', 'turtlebot3_world.yaml'),
    68.             description='Full path to map yaml file to load'),
    69.  
    70.         DeclareLaunchArgument(
    71.             'use_sim_time', default_value='false',
    72.             description='Use simulation (Gazebo) clock if true'),
    73.  
    74.         DeclareLaunchArgument(
    75.             'autostart', default_value='true',
    76.             description='Automatically startup the nav2 stack'),
    77.  
    78.         DeclareLaunchArgument(
    79.             'params_file',
    80.             default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
    81.             description='Full path to the ROS2 parameters file to use'),
    82.  
    83.         Node(
    84.             package='nav2_map_server',
    85.             executable='map_server',
    86.             name='map_server',
    87.             output='screen',
    88.             parameters=[configured_params],
    89.             remappings=remappings),
    90.  
    91.         Node(
    92.             package='nav2_amcl',
    93.             executable='amcl',
    94.             name='amcl',
    95.             output='screen',
    96.             parameters=[configured_params],
    97.             remappings=remappings),
    98.  
    99.         Node(
    100.             package='nav2_lifecycle_manager',
    101.             executable='lifecycle_manager',
    102.             name='lifecycle_manager_localization',
    103.             output='screen',
    104.             parameters=[{'use_sim_time': use_sim_time},
    105.                         {'autostart': autostart},
    106.                         {'node_names': lifecycle_nodes}])
    107.     ])

     依然从后面看

    1.        Node(
    2.             package='nav2_map_server',
    3.             executable='map_server',
    4.             name='map_server',
    5.             output='screen',
    6.             parameters=[configured_params],
    7.             remappings=remappings),
    8.  
    9.         Node(
    10.             package='nav2_amcl',
    11.             executable='amcl',
    12.             name='amcl',
    13.             output='screen',
    14.             parameters=[configured_params],
    15.             remappings=remappings),
    16.  
    17.         Node(
    18.             package='nav2_lifecycle_manager',
    19.             executable='lifecycle_manager',
    20.             name='lifecycle_manager_localization',
    21.             output='screen',
    22.             parameters=[{'use_sim_time': use_sim_time},
    23.                         {'autostart': autostart},
    24.                         {'node_names': lifecycle_nodes}])
    25.     ])

     分别启动了

    executable='map_server',   #地图服务

    executable='amcl',             #amcl定位

    executable='lifecycle_manager',   #生命周期管理

    这里注意  remappings = [('/tf', 'tf'), ('/tf_static', 'tf_static')]

    机器人默认发布的是话题是'/tf'    '/tf_static'   定位和导航需要接收的话题是 'tf'    'tf_static' ，需要重映射话题的节点需要加上 remappings=remappings 这也是容易产生迷惑的地方。

    navigation_launch.py

    文件内容

    1. # Copyright (c) 2018 Intel Corporation
    2. #
    3. # Licensed under the Apache License, Version 2.0 (the "License");
    4. # you may not use this file except in compliance with the License.
    5. # You may obtain a copy of the License at
    6. #
    7. #     http://www.apache.org/licenses/LICENSE-2.0
    8. #
    9. # Unless required by applicable law or agreed to in writing, software
    10. # distributed under the License is distributed on an "AS IS" BASIS,
    11. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12. # See the License for the specific language governing permissions and
    13. # limitations under the License.
    14.  
    15. import os
    16.  
    17. from ament_index_python.packages import get_package_share_directory
    18.  
    19. from launch import LaunchDescription
    20. from launch.actions import DeclareLaunchArgument, SetEnvironmentVariable
    21. from launch.substitutions import LaunchConfiguration
    22. from launch_ros.actions import Node
    23. from nav2_common.launch import RewrittenYaml
    24.  
    25.  
    26. def generate_launch_description():
    27.     # Get the launch directory
    28.     bringup_dir = get_package_share_directory('nav2_bringup')
    29.  
    30.     namespace = LaunchConfiguration('namespace')
    31.     use_sim_time = LaunchConfiguration('use_sim_time')
    32.     autostart = LaunchConfiguration('autostart')
    33.     params_file = LaunchConfiguration('params_file')
    34.     default_bt_xml_filename = LaunchConfiguration('default_bt_xml_filename')
    35.     map_subscribe_transient_local = LaunchConfiguration('map_subscribe_transient_local')
    36.  
    37.     lifecycle_nodes = ['controller_server',
    38.                        'planner_server',
    39.                        'recoveries_server',
    40.                        'bt_navigator',
    41.                        'waypoint_follower']
    42.  
    43.     # Map fully qualified names to relative ones so the node's namespace can be prepended.
    44.     # In case of the transforms (tf), currently, there doesn't seem to be a better alternative
    45.     # https://github.com/ros/geometry2/issues/32
    46.     # https://github.com/ros/robot_state_publisher/pull/30
    47.     # TODO(orduno) Substitute with `PushNodeRemapping`
    48.     #              https://github.com/ros2/launch_ros/issues/56
    49.     remappings = [('/tf', 'tf'),
    50.                   ('/tf_static', 'tf_static')]
    51.  
    52.     # Create our own temporary YAML files that include substitutions
    53.     param_substitutions = {
    54.         'use_sim_time': use_sim_time,
    55.         'default_bt_xml_filename': default_bt_xml_filename,
    56.         'autostart': autostart,
    57.         'map_subscribe_transient_local': map_subscribe_transient_local}
    58.  
    59.     configured_params = RewrittenYaml(
    60.             source_file=params_file,
    61.             root_key=namespace,
    62.             param_rewrites=param_substitutions,
    63.             convert_types=True)
    64.  
    65.     return LaunchDescription([
    66.         # Set env var to print messages to stdout immediately
    67.         SetEnvironmentVariable('RCUTILS_LOGGING_BUFFERED_STREAM', '1'),
    68.  
    69.         DeclareLaunchArgument(
    70.             'namespace', default_value='',
    71.             description='Top-level namespace'),
    72.  
    73.         DeclareLaunchArgument(
    74.             'use_sim_time', default_value='false',
    75.             description='Use simulation (Gazebo) clock if true'),
    76.  
    77.         DeclareLaunchArgument(
    78.             'autostart', default_value='true',
    79.             description='Automatically startup the nav2 stack'),
    80.  
    81.         DeclareLaunchArgument(
    82.             'params_file',
    83.             default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
    84.             description='Full path to the ROS2 parameters file to use'),
    85.  
    86.         DeclareLaunchArgument(
    87.             'default_bt_xml_filename',
    88.             default_value=os.path.join(
    89.                 get_package_share_directory('nav2_bt_navigator'),
    90.                 'behavior_trees', 'navigate_w_replanning_and_recovery.xml'),
    91.             description='Full path to the behavior tree xml file to use'),
    92.  
    93.         DeclareLaunchArgument(
    94.             'map_subscribe_transient_local', default_value='false',
    95.             description='Whether to set the map subscriber QoS to transient local'),
    96.  
    97.         Node(
    98.             package='nav2_controller',
    99.             executable='controller_server',
    100.             output='screen',
    101.             parameters=[configured_params],
    102.             remappings=remappings),
    103.  
    104.         Node(
    105.             package='nav2_planner',
    106.             executable='planner_server',
    107.             name='planner_server',
    108.             output='screen',
    109.             parameters=[configured_params],
    110.             remappings=remappings),
    111.  
    112.         Node(
    113.             package='nav2_recoveries',
    114.             executable='recoveries_server',
    115.             name='recoveries_server',
    116.             output='screen',
    117.             parameters=[configured_params],
    118.             remappings=remappings),
    119.  
    120.         Node(
    121.             package='nav2_bt_navigator',
    122.             executable='bt_navigator',
    123.             name='bt_navigator',
    124.             output='screen',
    125.             parameters=[configured_params],
    126.             remappings=remappings),
    127.  
    128.         Node(
    129.             package='nav2_waypoint_follower',
    130.             executable='waypoint_follower',
    131.             name='waypoint_follower',
    132.             output='screen',
    133.             parameters=[configured_params],
    134.             remappings=remappings),
    135.  
    136.         Node(
    137.             package='nav2_lifecycle_manager',
    138.             executable='lifecycle_manager',
    139.             name='lifecycle_manager_navigation',
    140.             output='screen',
    141.             parameters=[{'use_sim_time': use_sim_time},
    142.                         {'autostart': autostart},
    143.                         {'node_names': lifecycle_nodes}]),
    144.  
    145.     ])

    分别启动的节点

    1.    Node(
    2.             package='nav2_controller',
    3.             executable='controller_server',
    4.             output='screen',
    5.             parameters=[configured_params],
    6.             remappings=remappings),
    7.  
    8.         Node(
    9.             package='nav2_planner',
    10.             executable='planner_server',
    11.             name='planner_server',
    12.             output='screen',
    13.             parameters=[configured_params],
    14.             remappings=remappings),
    15.  
    16.         Node(
    17.             package='nav2_recoveries',
    18.             executable='recoveries_server',
    19.             name='recoveries_server',
    20.             output='screen',
    21.             parameters=[configured_params],
    22.             remappings=remappings),
    23.  
    24.         Node(
    25.             package='nav2_bt_navigator',
    26.             executable='bt_navigator',
    27.             name='bt_navigator',
    28.             output='screen',
    29.             parameters=[configured_params],
    30.             remappings=remappings),
    31.  
    32.         Node(
    33.             package='nav2_waypoint_follower',
    34.             executable='waypoint_follower',
    35.             name='waypoint_follower',
    36.             output='screen',
    37.             parameters=[configured_params],
    38.             remappings=remappings),
    39.  
    40.         Node(
    41.             package='nav2_lifecycle_manager',
    42.             executable='lifecycle_manager',
    43.             name='lifecycle_manager_navigation',
    44.             output='screen',
    45.             parameters=[{'use_sim_time': use_sim_time},
    46.                         {'autostart': autostart},
    47.                         {'node_names': lifecycle_nodes}]),

    executable='controller_server',   #控制服务器节点

    executable='planner_server',      #规划服务器节点

    executable='recoveries_server', #恢复服务器节点

    executable='bt_navigator',          #行为数节点

    executable='waypoint_follower', #航点跟随节点

    executable='lifecycle_manager', #声明周期管理节点

    三 导航启动的所有节点

    1 机器人生成   

    gazebo仿真：gzserver， gzclient

    这一步如果是实体机器人，gezabo程序不需要启动。

    2 发布机器人模型并展示

    executable='robot_state_publisher',

    executable='rviz2',

    3 定位

    executable='map_server',

    executable='amcl',

    4 导航

    ros2 launch nav2_bringup tb3_simulation_launch.py

    executable='controller_server',   #控制服务器节点

    executable='planner_server',      #规划服务器节点

    executable='recoveries_server', #恢复服务器节点

    executable='bt_navigator',          #行为数节点

    executable='waypoint_follower', #航点跟随节点

    executable='lifecycle_manager', #生命周期管理节点

    至此导航仿真拆解完成。

    四 一边建图一边导航

    ros2 launch nav2_bringup tb3_simulation_launch.py slam:=True

    slam:=True 通过condition=IfCondition(slam)影响了上面的第三步 定位，其他节点不变

    1.  IncludeLaunchDescription(
    2.             PythonLaunchDescriptionSource(os.path.join(launch_dir, 'slam_launch.py')),
    3.             condition=IfCondition(slam),
    4.             launch_arguments={'namespace': namespace,
    5.                               'use_sim_time': use_sim_time,
    6.                               'autostart': autostart,
    7.                               'params_file': params_file}.items()),

    拆解slam_launch.py

    目录结构

    slam_launch.py

    1. # Copyright (c) 2020 Samsung Research Russia
    2. #
    3. # Licensed under the Apache License, Version 2.0 (the "License");
    4. # you may not use this file except in compliance with the License.
    5. # You may obtain a copy of the License at
    6. #
    7. #     http://www.apache.org/licenses/LICENSE-2.0
    8. #
    9. # Unless required by applicable law or agreed to in writing, software
    10. # distributed under the License is distributed on an "AS IS" BASIS,
    11. # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12. # See the License for the specific language governing permissions and
    13. # limitations under the License.
    14.  
    15. import os
    16.  
    17. from ament_index_python.packages import get_package_share_directory
    18.  
    19. from launch import LaunchDescription
    20. from launch.actions import DeclareLaunchArgument, IncludeLaunchDescription
    21. from launch.launch_description_sources import PythonLaunchDescriptionSource
    22. from launch.substitutions import LaunchConfiguration
    23. from launch_ros.actions import Node
    24. from nav2_common.launch import RewrittenYaml
    25.  
    26.  
    27. def generate_launch_description():
    28.     # Input parameters declaration
    29.     namespace = LaunchConfiguration('namespace')
    30.     params_file = LaunchConfiguration('params_file')
    31.     use_sim_time = LaunchConfiguration('use_sim_time')
    32.     autostart = LaunchConfiguration('autostart')
    33.  
    34.     # Variables
    35.     lifecycle_nodes = ['map_saver']
    36.  
    37.     # Getting directories and launch-files
    38.     bringup_dir = get_package_share_directory('nav2_bringup')
    39.     slam_toolbox_dir = get_package_share_directory('slam_toolbox')
    40.     slam_launch_file = os.path.join(slam_toolbox_dir, 'launch', 'online_sync_launch.py')
    41.  
    42.     # Create our own temporary YAML files that include substitutions
    43.     param_substitutions = {
    44.         'use_sim_time': use_sim_time}
    45.  
    46.     configured_params = RewrittenYaml(
    47.         source_file=params_file,
    48.         root_key=namespace,
    49.         param_rewrites=param_substitutions,
    50.         convert_types=True)
    51.  
    52.     # Declare the launch arguments
    53.     declare_namespace_cmd = DeclareLaunchArgument(
    54.         'namespace',
    55.         default_value='',
    56.         description='Top-level namespace')
    57.  
    58.     declare_params_file_cmd = DeclareLaunchArgument(
    59.         'params_file',
    60.         default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
    61.         description='Full path to the ROS2 parameters file to use for all launched nodes')
    62.  
    63.     declare_use_sim_time_cmd = DeclareLaunchArgument(
    64.         'use_sim_time',
    65.         default_value='true',
    66.         description='Use simulation (Gazebo) clock if true')
    67.  
    68.     declare_autostart_cmd = DeclareLaunchArgument(
    69.         'autostart', default_value='true',
    70.         description='Automatically startup the nav2 stack')
    71.  
    72.     # Nodes launching commands
    73.     start_slam_toolbox_cmd = IncludeLaunchDescription(
    74.         PythonLaunchDescriptionSource(slam_launch_file),
    75.         launch_arguments={'use_sim_time': use_sim_time}.items())
    76.  
    77.     start_map_saver_server_cmd = Node(
    78.             package='nav2_map_server',
    79.             executable='map_saver_server',
    80.             output='screen',
    81.             parameters=[configured_params])
    82.  
    83.     start_lifecycle_manager_cmd = Node(
    84.             package='nav2_lifecycle_manager',
    85.             executable='lifecycle_manager',
    86.             name='lifecycle_manager_slam',
    87.             output='screen',
    88.             parameters=[{'use_sim_time': use_sim_time},
    89.                         {'autostart': autostart},
    90.                         {'node_names': lifecycle_nodes}])
    91.  
    92.     ld = LaunchDescription()
    93.  
    94.     # Declare the launch options
    95.     ld.add_action(declare_namespace_cmd)
    96.     ld.add_action(declare_params_file_cmd)
    97.     ld.add_action(declare_use_sim_time_cmd)
    98.     ld.add_action(declare_autostart_cmd)
    99.  
    100.     # Running SLAM Toolbox
    101.     ld.add_action(start_slam_toolbox_cmd)
    102.  
    103.     # Running Map Saver Server
    104.     ld.add_action(start_map_saver_server_cmd)
    105.     ld.add_action(start_lifecycle_manager_cmd)
    106.  
    107.     return ld

    加载主要内容

    1.     slam_launch_file = os.path.join(slam_toolbox_dir, 'launch', 'online_sync_launch.py')
    2.     start_slam_toolbox_cmd = IncludeLaunchDescription(
    3.         PythonLaunchDescriptionSource(slam_launch_file),
    4.         launch_arguments={'use_sim_time': use_sim_time}.items())
    5.  
    6.     start_map_saver_server_cmd = Node(
    7.             package='nav2_map_server',
    8.             executable='map_saver_server',
    9.             output='screen',
    10.             parameters=[configured_params])
    11.  
    12.     start_lifecycle_manager_cmd = Node(
    13.             package='nav2_lifecycle_manager',
    14.             executable='lifecycle_manager',
    15.             name='lifecycle_manager_slam',
    16.             output='screen',
    17.             parameters=[{'use_sim_time': use_sim_time},
    18.                         {'autostart': autostart},
    19.                         {'node_names': lifecycle_nodes}])

    executable='sync_slam_toolbox_node',  #slam工具箱 

    executable='map_saver_server',    #地图存储

    executable='lifecycle_manager',    #生命周期管理

    五 总结

    tb3_simulation_launch.py 通过修改gazebo启动项可以迁移到实体机器人导航，通过设置slam:=True 或者slam:=False可以选择是否启动建图时导航，实体机器人导航需要把use_sim_time:=false（使用系统时间）, gezabo仿真导航默认的use_sim_time:=true （使用仿真时间）

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  • 原文地址：https://blog.csdn.net/m0_73694897/article/details/132595252