ROS学习（19）机器人SLAM功能包——cartographer

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前言

  cartographer的核心是cartographer_node节点，当运行该节点时，需要一个Lua编写的.lua文件，该文件的主要作用是进行参数配置，这与gmapping、hector在launch文件中直接配置参数不同。
  cartographer的亮点在于代码规范与工程化，适合商业应用和二次开发，能有效避免建图过程中环境中移动物体的干扰，支持多传感器数据建图，支持2D-slam和3D-slam建图。
  之前我自定义过一个机器人模型，后来在使用cartographer过程中，感觉有问题，但是这个问题我解决不了，不知道是配置的问题，还是TF的问题，哈哈。所以在本篇开始，舍弃之前自定义的机器人模型，重新自定义一个机器人模型，即使用赵老师的模型，也方便后续kinect的使用。该模型的xacro可以去网上百度下，在这里不再介绍。

一、cartographer_2d.launch文件

launch文件内容如下：

<launch>
  <param name="/use_sim_time" value="true" />

  <node name="cartographer_node" pkg="cartographer_ros"
      type="cartographer_node" args="
          -configuration_directory $(find robot_slam_cartographer)/configuration_files
          -configuration_basename rplidar.lua"
      output="screen">
    <remap from="scan" to="scan" />
    <param name="base_link" value="base_footprint"/>
  node>

  <node name="cartographer_occupancy_grid_node" pkg="cartographer_ros"
      type="cartographer_occupancy_grid_node" args="-resolution 0.05" />

  <node name="rviz" pkg="rviz" type="rviz" required="true"
      args="-d $(find robot_slam_cartographer)/config/default.rviz" />

launch>

该文件主要包含两部分工作，一是运行cartographer_node节点，二是启动rviz可视化界面。当运行cartographer_node节点时，需要用到一个由lua编写的代码文件rplidar.lua，进行参数配置，lua文件内容后面介绍。

二、mbot_sim_gazebo_navigation_world.launch文件

launch文件内容如下：

<launch>
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="worlds/mbot_sim_gazebo_navigation.world"/> 
    <arg name="paused" value="false"/>
    <arg name="use_sim_time" value="true"/>
    <arg name="gui" value="true"/>
    <arg name="headless" value="false"/>
    <arg name="debug" value="false"/>
  include>
launch>

三、robot_gazebo_navigation.launch文件

launch文件内容如下：

<launch>
 	
    <include file="$(find gazebo_ros)/launch/mbot_sim_gazebo_navigation_world.launch">
    include>

    
    <arg name="model" default="$(find xacro)/xacro --inorder '$(find robot_slam_cartographer)/urdf/xacro/robot.xacro'" />
     
    
    <param name="robot_description" command="$(arg model)" />
    
    
    <node name="joint_state_publisher" pkg="joint_state_publisher" type="joint_state_publisher" />

    
    <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" />

      
    <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
          args="-urdf -model mrobot -param robot_description"/> 

    

    

    <include file="$(find robot_slam_cartographer)/launch/cartographer_2d.launch"/>

launch>

四、rplidar.lua文件

文件内容如下：

include "map_builder.lua"
include "trajectory_builder.lua"

options = {
    map_builder = MAP_BUILDER,
    trajectory_builder = TRAJECTORY_BUILDER,
    map_frame = "map",
    tracking_frame = "base_link",
    published_frame = "base_link",
    odom_frame = "odom",
    provide_odom_frame = true,
    use_odometry = false,
    num_laser_scans = 1,
    num_multi_echo_laser_scans = 0,
    num_subdivisions_per_laser_scan = 1,
    num_point_clouds = 0,
    lookup_transform_timeout_sec = 0.2,
    submap_publish_period_sec = 0.3,
    pose_publish_period_sec = 5e-3,
    trajectory_publish_period_sec = 30e-3,


}

MAP_BUILDER.use_trajectory_builder_2d = true

TRAJECTORY_BUILDER_2D.submaps.num_range_data = 35
TRAJECTORY_BUILDER_2D.min_range = 0.3
TRAJECTORY_BUILDER_2D.max_range = 8.
TRAJECTORY_BUILDER_2D.missing_data_ray_length = 1.
TRAJECTORY_BUILDER_2D.use_imu_data = false
TRAJECTORY_BUILDER_2D.use_online_correlative_scan_matching = true
TRAJECTORY_BUILDER_2D.real_time_correlative_scan_matcher.linear_search_window = 0.1
TRAJECTORY_BUILDER_2D.real_time_correlative_scan_matcher.translation_delta_cost_weight = 10.
TRAJECTORY_BUILDER_2D.real_time_correlative_scan_matcher.rotation_delta_cost_weight = 1e-1

SPARSE_POSE_GRAPH.optimization_problem.huber_scale = 1e2
SPARSE_POSE_GRAPH.optimize_every_n_scans = 35
SPARSE_POSE_GRAPH.constraint_builder.min_score = 0.65     

return options

五、编译运行

每一次修改lua文件后，都需要编译，命令如下：

catkin_make_isolated --install --use-ninja

运行launch文件，命令如下：

roslaunch robot_slam_cartographer robot_gazebo_navigation.launch

然后，再运行键盘控制启动文件，命令如下：

rosrun teleop_twist_keyboard teleop_twist_keyboard.py

最后，建图效果如下：

六、保存地图

方法1、使用map_saver直接保存为pgm和yaml文件

切换到map目录，新建map_saver_map文件夹，执行如下命令：

rosrun map_server map_saver -f myMapFile

方法2、先保存为.pbstream文件，再转化为pgm和yaml文件

步骤如下：

1、停止地图构建

rosservice call /finish_trajectory 0

2、生成.pbstream文件

rosservice call /write_state "{filename: '${HOME}/catkin_google_ws/src/robot_slam_cartographer/map/carto_map.pbstream'}"

3、将pbstream转化为pgm和yaml文件

rosrun cartographer_ros cartographer_pbstream_to_ros_map -map_filestem=${HOME}/catkin_google_ws/src/robot_slam_cartographer/map/myMapFile -pbstream_filename=${HOME}/catkin_google_ws/src/robot_slam_cartographer/map/carto_map.pbstream -resolution=0.05

执行效果如下：

地图在功能包中位置如下：