ROS2极简总结-SLAM

Posted 2021-09-06 zhangrelay

参考文献：Navigation using ROS 2 Mapping

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SLAM - Simultaneous Localization And Mapping

同步定位和建图

机器人仿真或实际运动环境的最简描述。

建图 - SLAM

• SLAM：同时估计机器人的位置姿态和环境的地图
  • 定位：给定地图推断位置
  • 建图：推断给定位置的地图
  • SLAM：同时学习地图和定位机器人
• SLAM 的目标是创建或增强环境地图。
• 地图表示 2D 或 3D 环境。
• 实际上是一个很难解决的问题！

至少目前没有很好的统一的解决方案，相关算法都在研发和改进中。

地图类型

栅格地图	图形地图	特征地图

ROS2 SLAM工具箱

目前，ROS2 的 SLAM 还没有可靠唯一标准。 一些有力竞争者是：

• LaMa (2D) - IRIS Labs - 新的，可以说是更好的，强有力的竞争者
• Cartographer (2D/3D) - Google - 从 ROS1 移植，经常使用，但没有维护
• SLAM 工具箱 (2D) - Steve Macenski - 当前随 Navigation2 一起提供，需要支持。 如果可以，请参与帮助！

二维SLAM

占用栅格图

• 为每个网格单元计算概率（贝叶斯过滤器）

三维SLAM

用于三维占用地图的八叉树

• 基于树的数据结构

效果引用（github.com/rsasaki0109/li_slam_ros2） 

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此处简单用turtlebot3+cartographer+ros2foxy+webots2021b在win10下，跑一个效果：

• set TURTLEBOT3_MODEL=burger 
• ros2 launch webots_ros2_turtlebot robot_launch.py
• ros2 launch turtlebot3_cartographer cartographer.launch.py use_sim_time:=true
• ros2 run turtlebot3_teleop teleop_keyboard

ros2 launch webots_ros2_turtlebot robot_launch.py

启动webots仿真

"""Launch Webots TurtleBot3 Burger driver."""

import os
import pathlib
from launch.substitutions import LaunchConfiguration
from launch.actions import DeclareLaunchArgument
from launch.substitutions.path_join_substitution import PathJoinSubstitution
from launch import LaunchDescription
from launch_ros.actions import Node
import launch
from ament_index_python.packages import get_package_share_directory
from webots_ros2_core.webots_launcher import WebotsLauncher


def generate_launch_description():
    package_dir = get_package_share_directory('webots_ros2_turtlebot')
    world = LaunchConfiguration('world')
    robot_description = pathlib.Path(os.path.join(package_dir, 'resource', 'turtlebot_webots.urdf')).read_text()
    ros2_control_params = os.path.join(package_dir, 'resource', 'ros2control.yml')

    webots = WebotsLauncher(
        world=PathJoinSubstitution([package_dir, 'worlds', world])
    )

    # TODO: Revert once the https://github.com/ros-controls/ros2_control/pull/444 PR gets into the release
    controller_manager_timeout = ['--controller-manager-timeout', '50'] if os.name == 'nt' else []
    controller_manager_prefix = 'python.exe' if os.name == 'nt' else "bash -c 'sleep 10; $0 $@' "

    diffdrive_controller_spawner = Node(
        package='controller_manager',
        executable='spawner.py',
        output='screen',
        prefix=controller_manager_prefix,
        arguments=['diffdrive_controller'] + controller_manager_timeout,
    )

    joint_state_broadcaster_spawner = Node(
        package='controller_manager',
        executable='spawner.py',
        output='screen',
        prefix=controller_manager_prefix,
        arguments=['joint_state_broadcaster'] + controller_manager_timeout,
    )

    turtlebot_driver = Node(
        package='webots_ros2_driver',
        executable='driver',
        output='screen',
        parameters=[
            {'robot_description': robot_description},
            ros2_control_params
        ],
        remappings=[
            ('/diffdrive_controller/cmd_vel_unstamped', '/cmd_vel')
        ]
    )

    robot_state_publisher = Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        output='screen',
        parameters=[{
            'robot_description': '<robot name=""><link name=""/></robot>'
        }],
    )

    footprint_publisher = Node(
        package='tf2_ros',
        executable='static_transform_publisher',
        output='screen',
        arguments=['0', '0', '0', '0', '0', '0', 'base_link', 'base_footprint'],
    )

    return LaunchDescription([
        DeclareLaunchArgument(
            'world',
            default_value='turtlebot3_burger_example.wbt',
            description='Choose one of the world files from `/webots_ros2_turtlebot/world` directory'
        ),
        joint_state_broadcaster_spawner,
        diffdrive_controller_spawner,
        webots,
        robot_state_publisher,
        turtlebot_driver,
        footprint_publisher,
        launch.actions.RegisterEventHandler(
            event_handler=launch.event_handlers.OnProcessExit(
                target_action=webots,
                on_exit=[launch.actions.EmitEvent(event=launch.events.Shutdown())],
            )
        )
    ])

ros2 launch turtlebot3_cartographer cartographer.launch.py use_sim_time:=true

启动SLAM建图

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch_ros.actions import Node
from launch.substitutions import LaunchConfiguration
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import ThisLaunchFileDir


def generate_launch_description():
    use_sim_time = LaunchConfiguration('use_sim_time', default='false')
    turtlebot3_cartographer_prefix = get_package_share_directory('turtlebot3_cartographer')
    cartographer_config_dir = LaunchConfiguration('cartographer_config_dir', default=os.path.join(
                                                  turtlebot3_cartographer_prefix, 'config'))
    configuration_basename = LaunchConfiguration('configuration_basename',
                                                 default='turtlebot3_lds_2d.lua')

    resolution = LaunchConfiguration('resolution', default='0.05')
    publish_period_sec = LaunchConfiguration('publish_period_sec', default='1.0')

    rviz_config_dir = os.path.join(get_package_share_directory('turtlebot3_cartographer'),
                                   'rviz', 'tb3_cartographer.rviz')

    return LaunchDescription([
        DeclareLaunchArgument(
            'cartographer_config_dir',
            default_value=cartographer_config_dir,
            description='Full path to config file to load'),
        DeclareLaunchArgument(
            'configuration_basename',
            default_value=configuration_basename,
            description='Name of lua file for cartographer'),
        DeclareLaunchArgument(
            'use_sim_time',
            default_value='false',
            description='Use simulation (Gazebo) clock if true'),

        Node(
            package='cartographer_ros',
            executable='cartographer_node',
            name='cartographer_node',
            output='screen',
            parameters=[{'use_sim_time': use_sim_time}],
            arguments=['-configuration_directory', cartographer_config_dir,
                       '-configuration_basename', configuration_basename]),

        DeclareLaunchArgument(
            'resolution',
            default_value=resolution,
            description='Resolution of a grid cell in the published occupancy grid'),

        DeclareLaunchArgument(
            'publish_period_sec',
            default_value=publish_period_sec,
            description='OccupancyGrid publishing period'),

        IncludeLaunchDescription(
            PythonLaunchDescriptionSource([ThisLaunchFileDir(), '/occupancy_grid.launch.py']),
            launch_arguments={'use_sim_time': use_sim_time, 'resolution': resolution,
                              'publish_period_sec': publish_period_sec}.items(),
        ),

        Node(
            package='rviz2',
            executable='rviz2',
            name='rviz2',
            arguments=['-d', rviz_config_dir],
            parameters=[{'use_sim_time': use_sim_time}],
            output='screen'),
    ])

ros2 run turtlebot3_teleop teleop_keyboard

启动键盘遥控机器人

import os
import select
import sys
import rclpy

from geometry_msgs.msg import Twist
from rclpy.qos import QoSProfile

if os.name == 'nt':
    import msvcrt
else:
    import termios
    import tty

BURGER_MAX_LIN_VEL = 0.22
BURGER_MAX_ANG_VEL = 2.84

WAFFLE_MAX_LIN_VEL = 0.26
WAFFLE_MAX_ANG_VEL = 1.82

LIN_VEL_STEP_SIZE = 0.01
ANG_VEL_STEP_SIZE = 0.1

TURTLEBOT3_MODEL = os.environ['TURTLEBOT3_MODEL']

msg = """
Control Your TurtleBot3!
---------------------------
Moving around:
        w
   a    s    d
        x

w/x : increase/decrease linear velocity (Burger : ~ 0.22, Waffle and Waffle Pi : ~ 0.26)
a/d : increase/decrease angular velocity (Burger : ~ 2.84, Waffle and Waffle Pi : ~ 1.82)

space key, s : force stop

CTRL-C to quit
"""

e = """
Communications Failed
"""


def get_key(settings):
    if os.name == 'nt':
        return msvcrt.getch().decode('utf-8')
    tty.setraw(sys.stdin.fileno())
    rlist, _, _ = select.select([sys.stdin], [], [], 0.1)
    if rlist:
        key = sys.stdin.read(1)
    else:
        key = ''

    termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)
    return key


def print_vels(target_linear_velocity, target_angular_velocity):
    print('currently:\\tlinear velocity {0}\\t angular velocity {1} '.format(
        target_linear_velocity,
        target_angular_velocity))


def make_simple_profile(output, input, slop):
    if input > output:
        output = min(input, output + slop)
    elif input < output:
        output = max(input, output - slop)
    else:
        output = input

    return output


def constrain(input_vel, low_bound, high_bound):
    if input_vel < low_bound:
        input_vel = low_bound
    elif input_vel > high_bound:
        input_vel = high_bound
    else:
        input_vel = input_vel

    return input_vel


def check_linear_limit_velocity(velocity):
    if TURTLEBOT3_MODEL == 'burger':
        return constrain(velocity, -BURGER_MAX_LIN_VEL, BURGER_MAX_LIN_VEL)
    else:
        return constrain(velocity, -WAFFLE_MAX_LIN_VEL, WAFFLE_MAX_LIN_VEL)


def check_angular_limit_velocity(velocity):
    if TURTLEBOT3_MODEL == 'burger':
        return constrain(velocity, -BURGER_MAX_ANG_VEL, BURGER_MAX_ANG_VEL)
    else:
        return constrain(velocity, -WAFFLE_MAX_ANG_VEL, WAFFLE_MAX_ANG_VEL)


def main():
    settings = None
    if os.name != 'nt':
        settings = termios.tcgetattr(sys.stdin)

    rclpy.init()

    qos = QoSProfile(depth=10)
    node = rclpy.create_node('teleop_keyboard')
    pub = node.create_publisher(Twist, 'cmd_vel', qos)

    status = 0
    target_linear_velocity = 0.0
    target_angular_velocity = 0.0
    control_linear_velocity = 0.0
    control_angular_velocity = 0.0

    try:
        print(msg)
        while(1):
            key = get_key(settings)
            if key == 'w':
                target_linear_velocity =\\
                    check_linear_limit_velocity(target_linear_velocity + LIN_VEL_STEP_SIZE)
                status = status + 1
                print_vels(target_linear_velocity, target_angular_velocity)
            elif key == 'x':
                target_linear_velocity =\\
                    check_linear_limit_velocity(target_linear_velocity - LIN_VEL_STEP_SIZE)
                status = status + 1
                print_vels(target_linear_velocity, target_angular_velocity)
            elif key == 'a':
                target_angular_velocity =\\
                    check_angular_limit_velocity(target_angular_velocity + ANG_VEL_STEP_SIZE)
                status = status + 1
                print_vels(target_linear_velocity, target_angular_velocity)
            elif key == 'd':
                target_angular_velocity =\\
                    check_angular_limit_velocity(target_angular_velocity - ANG_VEL_STEP_SIZE)
                status = status + 1
                print_vels(target_linear_velocity, target_angular_velocity)
            elif key == ' ' or key == 's':
                target_linear_velocity = 0.0
                control_linear_velocity = 0.0
                target_angular_velocity = 0.0
                control_angular_velocity = 0.0
                print_vels(target_linear_velocity, target_angular_velocity)
            else:
                if (key == '\\x03'):
                    break

            if status == 20:
                print(msg)
                status = 0

            twist = Twist()

            control_linear_velocity = make_simple_profile(
                control_linear_velocity,
                target_linear_velocity,
                (LIN_VEL_STEP_SIZE / 2.0))

            twist.linear.x = control_linear_velocity
            twist.linear.y = 0.0
            twist.linear.z = 0.0

            control_angular_velocity = make_simple_profile(
                control_angular_velocity,
                target_angular_velocity,
                (ANG_VEL_STEP_SIZE / 2.0))

            twist.angular.x = 0.0
            twist.angular.y = 0.0
            twist.angular.z = control_angular_velocity

            pub.publish(twist)

    except Exception as e:
        print(e)

    finally:
        twist = Twist()
        twist.linear.x = 0.0
        twist.linear.y = 0.0
        twist.linear.z = 0.0

        twist.angular.x = 0.0
        twist.angular.y = 0.0
        twist.angular.z = 0.0

        pub.publish(twist)

        if os.name != 'nt':
            termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)


if __name__ == '__main__':
    main()

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