ROS2机器人实验报告提示05➡寻路⬅Nav2

上一节，构建了有机器人和一些障碍物仿真元宇宙。

如何让机器人具备自主导航的能力呢？？？

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先介绍偷懒的方式：

安装turtlesim3包，然后使用官方教程即可。

• sudo apt update 
• sudo apt install ros-galactic-turtlebot3-gazebo ros-galactic-turtlebot3-msgs ros-galactic-turtlebot3-simulations 

直接运行：

•   ros2 launch nav2_bringup tb3_simulation_launch.py

查看是否报错！

如果打不开，多尝试几次！

export TURTLEBOT3_MODEL=waffle
export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:/opt/ros/galactic/share/turtlebot3_gazebo/models

如上环境一定要争取配置，推荐添加到bash文件中。

 

 

 

 

 

更多内容参考博客相关章节或观看钉钉直播课回放。

• ROS2机器人个人教程博客汇总（2021共6套）

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思考题：

对比ros2 launch nav2_bringup tb3_simulation_launch.py和ros2 launch sam_bot_description display.launch.py。

实现机器人自动导航，需要哪些功能包，如何实现。

tb3_simulation_launch.py

# Copyright (c) 2018 Intel Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""This is all-in-one launch script intended for use by nav2 developers."""

import os

from ament_index_python.packages import get_package_share_directory

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument, ExecuteProcess, IncludeLaunchDescription
from launch.conditions import IfCondition
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration, PythonExpression
from launch_ros.actions import Node


def generate_launch_description():
    # Get the launch directory
    bringup_dir = get_package_share_directory('nav2_bringup')
    launch_dir = os.path.join(bringup_dir, 'launch')

    # Create the launch configuration variables
    slam = LaunchConfiguration('slam')
    namespace = LaunchConfiguration('namespace')
    use_namespace = LaunchConfiguration('use_namespace')
    map_yaml_file = LaunchConfiguration('map')
    use_sim_time = LaunchConfiguration('use_sim_time')
    params_file = LaunchConfiguration('params_file')
    autostart = LaunchConfiguration('autostart')

    # Launch configuration variables specific to simulation
    rviz_config_file = LaunchConfiguration('rviz_config_file')
    use_simulator = LaunchConfiguration('use_simulator')
    use_robot_state_pub = LaunchConfiguration('use_robot_state_pub')
    use_rviz = LaunchConfiguration('use_rviz')
    headless = LaunchConfiguration('headless')
    world = LaunchConfiguration('world')

    # Map fully qualified names to relative ones so the node's namespace can be prepended.
    # In case of the transforms (tf), currently, there doesn't seem to be a better alternative
    # https://github.com/ros/geometry2/issues/32
    # https://github.com/ros/robot_state_publisher/pull/30
    # TODO(orduno) Substitute with `PushNodeRemapping`
    #              https://github.com/ros2/launch_ros/issues/56
    remappings = [('/tf', 'tf'),
                  ('/tf_static', 'tf_static')]

    # Declare the launch arguments
    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_slam_cmd = DeclareLaunchArgument(
        'slam',
        default_value='False',
        description='Whether run a SLAM')

    declare_map_yaml_cmd = DeclareLaunchArgument(
        'map',
        default_value=os.path.join(
            bringup_dir, 'maps', 'turtlebot3_world.yaml'),
        description='Full path to map file to load')

    declare_use_sim_time_cmd = DeclareLaunchArgument(
        'use_sim_time',
        default_value='true',
        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_rviz_config_file_cmd = DeclareLaunchArgument(
        'rviz_config_file',
        default_value=os.path.join(
            bringup_dir, 'rviz', 'nav2_default_view.rviz'),
        description='Full path to the RVIZ config file to use')

    declare_use_simulator_cmd = DeclareLaunchArgument(
        'use_simulator',
        default_value='True',
        description='Whether to start the simulator')

    declare_use_robot_state_pub_cmd = DeclareLaunchArgument(
        'use_robot_state_pub',
        default_value='True',
        description='Whether to start the robot state publisher')

    declare_use_rviz_cmd = DeclareLaunchArgument(
        'use_rviz',
        default_value='True',
        description='Whether to start RVIZ')

    declare_simulator_cmd = DeclareLaunchArgument(
        'headless',
        default_value='False',
        description='Whether to execute gzclient)')

    declare_world_cmd = DeclareLaunchArgument(
        'world',
        # TODO(orduno) Switch back once ROS argument passing has been fixed upstream
        #              https://github.com/ROBOTIS-GIT/turtlebot3_simulations/issues/91
        # default_value=os.path.join(get_package_share_directory('turtlebot3_gazebo'),
        # worlds/turtlebot3_worlds/waffle.model')
        default_value=os.path.join(bringup_dir, 'worlds', 'waffle.model'),
        description='Full path to world model file to load')

    # Specify the actions
    start_gazebo_server_cmd = ExecuteProcess(
        condition=IfCondition(use_simulator),
        cmd=['gzserver', '-s', 'libgazebo_ros_init.so', world],
        cwd=[launch_dir], output='screen')

    start_gazebo_client_cmd = ExecuteProcess(
        condition=IfCondition(PythonExpression(
            [use_simulator, ' and not ', headless])),
        cmd=['gzclient'],
        cwd=[launch_dir], output='screen')

    urdf = os.path.join(bringup_dir, 'urdf', 'turtlebot3_waffle.urdf')

    start_robot_state_publisher_cmd = Node(
        condition=IfCondition(use_robot_state_pub),
        package='robot_state_publisher',
        executable='robot_state_publisher',
        name='robot_state_publisher',
        namespace=namespace,
        output='screen',
        parameters=[{'use_sim_time': use_sim_time}],
        remappings=remappings,
        arguments=[urdf])

    rviz_cmd = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            os.path.join(launch_dir, 'rviz_launch.py')),
        condition=IfCondition(use_rviz),
        launch_arguments={'namespace': '',
                          'use_namespace': 'False',
                          'rviz_config': rviz_config_file}.items())

    bringup_cmd = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            os.path.join(launch_dir, 'bringup_launch.py')),
        launch_arguments={'namespace': namespace,
                          'use_namespace': use_namespace,
                          'slam': slam,
                          'map': map_yaml_file,
                          'use_sim_time': use_sim_time,
                          'params_file': params_file,
                          'autostart': autostart}.items())

    # Create the launch description and populate
    ld = LaunchDescription()

    # Declare the launch options
    ld.add_action(declare_namespace_cmd)
    ld.add_action(declare_use_namespace_cmd)
    ld.add_action(declare_slam_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_rviz_config_file_cmd)
    ld.add_action(declare_use_simulator_cmd)
    ld.add_action(declare_use_robot_state_pub_cmd)
    ld.add_action(declare_use_rviz_cmd)
    ld.add_action(declare_simulator_cmd)
    ld.add_action(declare_world_cmd)

    # Add any conditioned actions
    ld.add_action(start_gazebo_server_cmd)
    ld.add_action(start_gazebo_client_cmd)

    # Add the actions to launch all of the navigation nodes
    ld.add_action(start_robot_state_publisher_cmd)
    ld.add_action(rviz_cmd)
    ld.add_action(bringup_cmd)

    return ld

sam_bot_description display.launch.py

import launch
from launch.substitutions import Command, LaunchConfiguration
import launch_ros
import os

def generate_launch_description():
    pkg_share = launch_ros.substitutions.FindPackageShare(package='sam_bot_description').find('sam_bot_description')
    default_model_path = os.path.join(pkg_share, 'src/description/sam_bot_description.urdf')
    default_rviz_config_path = os.path.join(pkg_share, 'rviz/urdf_config.rviz')
    world_path=os.path.join(pkg_share, 'world/my_world.sdf')
    
    robot_state_publisher_node = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description': Command(['xacro ', LaunchConfiguration('model')])}]
    )
    joint_state_publisher_node = launch_ros.actions.Node(
        package='joint_state_publisher',
        executable='joint_state_publisher',
        name='joint_state_publisher',
        condition=launch.conditions.UnlessCondition(LaunchConfiguration('gui'))
    )
    rviz_node = launch_ros.actions.Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        arguments=['-d', LaunchConfiguration('rvizconfig')],
    )
    spawn_entity = launch_ros.actions.Node(
    	package='gazebo_ros', 
    	executable='spawn_entity.py',
        arguments=['-entity', 'sam_bot', '-topic', 'robot_description'],
        output='screen'
    )
    robot_localization_node = launch_ros.actions.Node(
         package='robot_localization',
         executable='ekf_node',
         name='ekf_filter_node',
         output='screen',
         parameters=[os.path.join(pkg_share, 'config/ekf.yaml'), {'use_sim_time': LaunchConfiguration('use_sim_time')}]
    )

    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument(name='gui', default_value='True',
                                            description='Flag to enable joint_state_publisher_gui'),
        launch.actions.DeclareLaunchArgument(name='model', default_value=default_model_path,
                                            description='Absolute path to robot urdf file'),
        launch.actions.DeclareLaunchArgument(name='rvizconfig', default_value=default_rviz_config_path,
                                            description='Absolute path to rviz config file'),
        launch.actions.DeclareLaunchArgument(name='use_sim_time', default_value='True',
                                            description='Flag to enable use_sim_time'),
        launch.actions.ExecuteProcess(cmd=['gazebo', '--verbose', '-s', 'libgazebo_ros_factory.so', world_path], output='screen'),

        joint_state_publisher_node,
        robot_state_publisher_node,
        spawn_entity,
        robot_localization_node,
        rviz_node
    ])

能否修改sam_bot_description display.launch.py，是其不仅具备SLAM还具备导航功能呢？

?_?

^_^

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