3.在自己的bag上运行Cartographer ROS

1、验证自己的bag

cartographer ROS提供了一个工具cartographer_rosbag_validate来自动分析包中的数据。在尝试调试cartographer之前运行这个工具。

操作方式：

cartographer_rosbag_validate -bag_filename your_bag.bag

2.创建一个.lua配置文件

cartographer非常灵活且可以配置用于任何机器人上。机器人配置读取来自于一个options的数据结构，该数据结构必须定义在一个Lua脚本里面。配置例子定义在文件src/cartographer_ros/cartographer_ros/configuration_files，且安装在install_isolated/share/cartographer_ros/configuration_files/.

注意，理想情况下，一个.lua配置应该是具体机器人的而不是一个具体bag的。

可以通过复制例子中的一个，然后调整以适合自己的需求，

3D SLAM：

cp install_isolated/share/cartographer_ros/configuration_files/backpack_3d.lua install_isolated/share/cartographer_ros/configuration_files/my_robot.lua

2D SLAM：

cp install_isolated/share/cartographer_ros/configuration_files/backpack_3d.lua install_isolated/share/cartographer_ros/configuration_files/my_robot.lua

下面去编辑my_robot.lua来适合于自己的机器人。在options块中定义的值定义了cartographer ros前端应当如何与你的bag进行交互。定义在options段后的值用于调试cartographer的内部信息。

你可能需要调整的值，需要提供环境的TF frame IDs，robot in map_frame, tracking_frame, published_frame and odom_frame.

You can either distribute your robot’s TF tree from a /tf topic in your bag or define it in a .urdf robot definition.

警告：应该信任你的位姿！在机器人和IMU或者LIDAR之间的小的offset可能会导致不相关的地图重构。cartographer通过可以纠正小的位姿误差，但并不是万能的。

需要修改的其他的值有，传感器的数量和类型：

a、num_laser_scans:你使用话题sensor_msgs.LaserScan的数量

b、num_multi_echo_laser_scans:话题num_multi_echo_laser_scans的数量

c、num_point_clouds:话题sensor_msgs/PointCloud2的数量

可以使用use_landmarks和use_nav_sat，来使能路标和GPS作为附加的定位源.在options块中的其他的变量通常保持不变。

然而，有一个全局变量需要调整来适用于自己的bag：

TRAJECTORY_BUILDER_3D.num_accumulated_range_data or TRAJECTORY_BUILDER_2D.num_accumulated_range_data

这个变量定义了构建一个完整激光的信息的数量（通常，是一个完整的分辨率）。如果听从工具cartographer_rosbag_validate的建议，没一帧激光使用100个ROS messages，可以设置这个变量为100。If you have two range finding sensors (for instance, two LIDARs) providing their full scans all at once, you should set this variable to 2.

Create.launch 文件用于自己的SLAM场景

例子中的.launch文件在中src/cartographer_ros/cartographer_ros/launch定义，并安装在install_isolated/share/cartographer_ros/launch/。

可以复制下面的例子

cp install_isolated/share/cartographer_ros/launch/backpack_3d.launch install_isolated/share/cartographer_ros/launch/my_robot.launch
cp install_isolated/share/cartographer_ros/launch/demo_backpack_3d.launch install_isolated/share/cartographer_ros/launch/demo_my_robot.launch
cp install_isolated/share/cartographer_ros/launch/offline_backpack_3d.launch install_isolated/share/cartographer_ros/launch/offline_my_robot.launch
cp install_isolated/share/cartographer_ros/launch/demo_backpack_3d_localization.launch install_isolated/share/cartographer_ros/launch/demo_my_robot_localization.launch
cp install_isolated/share/cartographer_ros/launch/assets_writer_backpack_3d.launch install_isolated/share/cartographer_ros/launch/assets_writer_my_robot.launch

my_robot.launch用于在线的SLAM

demo_my_robot.launch应用于研发的机器人上，并期望一个bag_filename参数来重放记录的数据.这个launch文件也会启动一个rviz窗口用于可视化cartographer的状态。

offline_my_robot.launch非常类似于demo_my_robot.launch，但它尝试执行SLAM尽可能的快.这使得地图构建非常快,它也可以用于多个bag文件的地图构建。

demo_my_robot_localication.launch非常类似于demo_my_robot.launch但是它期望一个load_state_filename参数来指出一个.pbstream，它记录了先前cartographer的执行。先前的记录将作为一个预先计算的地图，然后cartographer只会在这个地图上执行定位。

assets_writer_my_robot.launch用于提取.pstream中的数据，.pstream中记录了先前cartographer的执行。

Again, a few adaptations need to be made to those files to suit your robot.

• Every parameter given to -configuration_basename should be adapted to point to my_robot.lua.
• If you decided to use a .urdf description of your robot, you should place your description in install_isolated/share/cartographer_ros/urdf and adapt the robot_description parameter to point to your file name.
• If you decided to use /tf messages, you can remove the robot_description parameter, the robot_state_publisher node and the lines statring with -urdf.
• If the topic names published by your bag or sensors don’t match the ones expected by Cartographer ROS, you can use <remap> elements to redirect your topics. The expected topic names depend on the type of range finding devices you use.

注意：

• The IMU topic is expected to be named “imu”
• If you use only one sensor_msgs/LaserScan topic, it is expected to be named scan. If you have more, they should be named scan_1, scan_2 etc…
• If you use only one sensor_msgs/MultiEchoLaserScan topic, it is expected to be named echoes. If you have more, they should be named echoes_1, echoes_2 etc…
• If you use only one sensor_msgs/PointCloud2 topic, it is expected be named points2. If you have more, they should be named points2_1, points2_2, etc…

配置好之后，开始启动

roslaunch cartographer_ros my_robot.launch bag_filename:=/path/to/your_bag.bag