Cartographer_ros解讀

本文轉載自查看原文 2019-11-19 21:33 1134 cartographer_ros

Cartographer_ros主要實現Topics的訂閱與發布。訂閱是指從IMU，激光雷達，里程計取數據，然后傳給Cartographer庫。發布是指從Cartographer拿處理的結果，然后發布給ROS，然后可以在rivz上顯示。

1. cartographer_ros/docs/source/ros_api.rst

此文件描述了Cartographer_ros訂閱與發布了哪些topics及服務。

2.運行 cartographer_ros

roslaunch cartographer_ros demo_revo_lds.launch

3.revo_lds.lua

此配置文件，描述了發布哪些Topics及名稱。在源碼中。訂閱的Topic在源碼中通過ratio of the pulse（脈沖的比率）的方式來定時調用。發布是通過定時器的方式，定時發布。具體值，可以通過此配置文件配置。

1)定時器方式

wall_timers_.push_back(node_handle_.createWallTimer(

::ros::WallDuration(node_options_.submap_publish_period_sec),

&Node::PublishSubmapList, this));

2)ratio方式

void Node::HandlePointCloud2Message(

const int trajectory_id, const std::string& sensor_id,

const sensor_msgs::PointCloud2::ConstPtr& msg) {

absl::MutexLock lock(&mutex_);

if (!sensor_samplers_.at(trajectory_id).rangefinder_sampler.Pulse()) {

return;

}

map_builder_bridge_.sensor_bridge(trajectory_id)

->HandlePointCloud2Message(sensor_id, msg);

}

4. cartographer_node

Cartographer_ros中的一個重要節點

1.請先查看：cartographer_ros/docs/source/ros_api.rst 文檔

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Subscribed Topics：

scan (`sensor_msgs/LaserScan`_)

echoes (`sensor_msgs/MultiEchoLaserScan`_)

points2 (`sensor_msgs/PointCloud2`_)

imu (`sensor_msgs/Imu`_)

odom (`nav_msgs/Odometry`_)

Published Topics：

submap_list (`cartographer_ros_msgs/SubmapList`_)

Services：

submap_query (`cartographer_ros_msgs/SubmapQuery`_)

start_trajectory (`cartographer_ros_msgs/StartTrajectory`_)

trajectory_query (`cartographer_ros_msgs/TrajectoryQuery`_)

finish_trajectory (`cartographer_ros_msgs/FinishTrajectory`_)

write_state (`cartographer_ros_msgs/WriteState`_)

get_trajectory_states (`cartographer_ros_msgs/GetTrajectoryStates`_)

read_metrics (`cartographer_ros_msgs/ReadMetrics`_)

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2. 運行cartographer_ros

roslaunch cartographer_ros demo_revo_lds.launch

================================

3.revo_lds.lua

demo_revo_lds.launch 指定加載revo_lds.lua 配置文件。指定topic的名稱，發布的Topic的時間間隔。

map_frame = "map",

tracking_frame = "scan",

published_frame = "scan",

odom_frame = "odom",

provide_odom_frame = false,

use_odometry = false,

use_nav_sat = false,

use_landmarks = false,

publish_frame_projected_to_2d=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,

rangefinder_sampling_ratio = 1.,

odometry_sampling_ratio = 1.,

fixed_frame_pose_sampling_ratio = 1.,

imu_sampling_ratio = 1.,

landmarks_sampling_ratio = 1.,

===========

map_frame:一般為“map”.用來發布submap的ROS幀ID.

tracking_frame:SLAM算法要跟蹤的ROS 幀ID.?

published_frame:用來發布pose的幀ID.?

odom_frame:只要當有里程計信息的時候才會使用。即provide_odom_frame=true.

provide_odom_frame:如果為true，the local, non-loop-closed, continuous pose將會在map_frame 里以odom_frame發布?

publish_frame_projected_to_2d：如果為true，則已經發布的pose將會被完全成２D的pose，沒有 roll,pitch或者z-offset？

use_odometry:如果為true，需要提供里程計信息，並話題/odom會訂閱nav_msgs/Odometry類型的消息，在SLAM過程中也會使用這個消息進行建圖

use_nav_sat:如果為true，會在話題/fix上訂閱sensor_msgs/NavSatFix類型的消息，並且在 globalSLAM中會用到

use_landmarks:如果為true，會在話題/landmarks上訂閱cartographer_ros_msgs/LandmarkList類型的消息，並且在SLAM過程中會用到

num_laser_scans:SLAM可以輸入的/scan話題數目的最大值

num_muti_echo_laser_scans:SLAM可以輸入sensor_msgs/MultiEchoLaserScan話題數目的最大值

num_subdivisions_per_laser_scan:將每個接收到的（multi_echo）激光scan分割成的點雲數。細分 scam可以在掃描儀移動時取消scanner獲取的scan。有一個相應的trajectory builder option可將細分掃描累積到將用於scan_matching的點雲中。

num_point_clouds:SLAM可以輸入的sensor_msgs/PointCloud2話題數目的最大值

lookup_transform_timeout_sec:使用tf2查找transform的超時時間（秒）。

submap_publish_period_sec:發布submap的時間間隔（秒）

pose_publish_period_sec:發布pose的時間間隔，值為5e-3的時候為200HZ

trajectory_publish_period_sec:發布trajectory markers（trajectory的節點）的時間間隔，值為30e-3 為30ms

rangefinder_samping_ratio:測距儀的固定采樣ratio

imu_sampling_ratio:IMU message的固定采樣ratio

landmarks_sampling_ratio:landmarks message的固定采樣ratio,(單位是啥？)

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4.RVIZ 訂閱的topic

1)TF

2)/submap_list

3)/scan_matched_points2

4)/trajectory_node_list

5)/landmark_poses_list

6)/constraint_list

5.App

cartographer_assets_writer

cartographer_dev_trajectory_comparison

cartographer_offline_node

cartographer_rosbag_validate

cartographer_dev_pbstream_trajectories_to_rosbag

cartographer_node

cartographer_pbstream_map_publisher

cartographer_dev_rosbag_publisher

cartographer_occupancy_grid_node

cartographer_pbstream_to_ros_map

6. Note.cpp 源碼分析

0.Node構造函數

1) 定義各種topic

submap_list_publisher_ =

node_handle_.advertise<::cartographer_ros_msgs::SubmapList>(

kSubmapListTopic, kLatestOnlyPublisherQueueSize);

trajectory_node_list_publisher_ =

node_handle_.advertise<::visualization_msgs::MarkerArray>(

kTrajectoryNodeListTopic, kLatestOnlyPublisherQueueSize);

landmark_poses_list_publisher_ =

node_handle_.advertise<::visualization_msgs::MarkerArray>(

kLandmarkPosesListTopic, kLatestOnlyPublisherQueueSize);

constraint_list_publisher_ =

node_handle_.advertise<::visualization_msgs::MarkerArray>(

kConstraintListTopic, kLatestOnlyPublisherQueueSize);

scan_matched_point_cloud_publisher_ =

node_handle_.advertise<sensor_msgs::PointCloud2>(

kScanMatchedPointCloudTopic, kLatestOnlyPublisherQueueSize);

2)定義各種服務的發布器。