Welcome to ROSMASTER X3 Plus repository
7.hector mapping algorithm
7.hector mapping algorithm
7.hector mapping algorithm7.1 Introduction 7.2 Use 7.2.1 Start 7.2.2 Control the robot 7.2.3 Map save 7.3 Topics and Services 7.4 configuration parameters 7.5 TF transformation
hector_slam： http://wiki.ros.org/hector_slam
hector_slam/Tutorials： http://wiki.ros.org/hector_slam/Tutorials/SettingUpForYourRobot
hector_mapping： http://wiki.ros.org/hector_mapping
map_server： https://wiki.ros.org/map_server
7.1 Introduction
Features: hector_slam does not need to subscribe to odometer/odom messages, uses the Gauss-Newton method, and directly estimates odometer information using lidar. However, when the speed of the robot is high, slippage will occur, resulting in deviations in the mapping effect and high requirements for sensors. When building a map, set the rotation speed of the cart as low as possible.
There is no odom coordinate system usage method, taken from Wiki.
7.2 Use
Note: When building a map, the slower the speed, the better the effect(note that if the rotation speed is slower), the effect will be poor if the speed is too fast.
According to different models, you only need to set the purchased model in [.bashrc], X1(ordinary four-wheel drive) X3(Mike wheel) X3plus(Mike wheel mechanical arm) R2(Ackerman differential) and so on. Section takes X3 as an example
Open the [.bashrc] file
sudo vim .bashrc
Find the [ROBOT_TYPE] parameter and modify the corresponding model
xxxxxxxxxxexport ROBOT_TYPE=X3 # ROBOT_TYPE: X1 X3 X3plus R2 X7
7.2.1 Start
Start command(robot side), for the convenience of operation, this section takes [mono + laser + yahboomcar] as an example.
#You need to enter docker first, perform this step more#If running the script to enter docker fails, please refer to 07.Docker-orin/05, Enter the robot's docker container~/run_docker.shroslaunch yahboomcar_nav laser_bringup.launch # laser + yahboomcar roslaunch yahboomcar_nav laser_usb_bringup.launch # mono + laser + yahboomcar roslaunch yahboomcar_nav laser_astrapro_bringup.launch # Astra + laser + yahboomcar Mapping command(robot side)
<Open another terminal and enter the same docker container
xxxxxxxxxxroslaunch yahboomcar_nav yahboomcar_map.launch use_rviz:=false map_type:=hector
- [use_rviz] parameter: whether to enable rviz visualization.
- [map_type] parameter: set the mapping algorithm [hector].
Open the visual interface(virtual machine side)
xxxxxxxxxxroslaunch yahboomcar_nav view_map.launch
The gap at the back of the robot is due to the occlusion of the installation position of the display screen, so a certain range of Lidar data is shielded. The shielding range can be adjusted or not shielded according to the actual situation. For details, see [01. Lidar Basic Course].
7.2.2 Control the robot
- The keyboard controls the movement of the robot
xxxxxxxxxxroslaunch yahboomcar_ctrl yahboom_keyboard.launch #custom
- The handle controls the movement of the robot
Make the robot walk all over the area to be built, and the map is as closed as possible.
There may be some scattered points during the mapping process. If the mapping environment is well closed and regular, the movement is slow, and the scattering phenomenon is much smaller.
7.2.3 Map save
xxxxxxxxxxrosrun map_server map_saver -f ~/yahboomcar_ws/src/yahboomcar_nav/maps/my_map # The first waybash ~/yahboomcar_ws/src/yahboomcar_nav/maps/map.sh # second way
The map will be saved to ~/yahboomcar_ws/src/yahboomcar_nav/maps/ folder, a pgm image, a yaml file.
map.yaml
xxxxxxxxxximage : map.pgmresolution : 0.05origin : [-15.4,-12.2,0.0]negate : 0occupied_thresh : 0.65free_thresh： 0.196
Parameter parsing:
- image: The path of the map file, which can be an absolute path or a relative path
- resolution: the resolution of the map, m/pixel
- origin: The 2D pose(x, y, yaw) of the lower left corner of the map, where yaw is rotated counterclockwise(yaw=0 means no rotation). Many parts of the system currently ignore the yaw value.
- negate: whether to reverse the meaning of white/black, free/occupy(the interpretation of the threshold is not affected)
- occupied_thresh: Pixels with an occupancy probability greater than this threshold will be considered fully occupied.
- free_thresh: Pixels with an occupancy probability less than this threshold will be considered completely free.
7.3 Topics and Services
| Topic subscription | type | describe |
|---|---|---|
| scan | sensor_msgs/LaserScan | Depth data from lidar scans |
| syscommand | std_msgs/String | system command. If the string is equal to "reset", the map and robot pose are reset to the initial state |
| Topic release | type | describe |
| map_metadata | nav_msgs/MapMetaData | Publish map Meta data |
| map | nav_msgs/OccupancyGrid | Publish map raster data |
| slam_out_pose | geometry_msgs/PoseStamped | Covariance-Free Robot Pose Estimation |
| poseupdate | geometry_msgs /PoseWithCovarianceStamped | Robot Pose Estimation with Gaussian Uncertainty Estimation |
| Serve | type | describe |
| dynamic_map | nav_msgs/GetMap | Get map data |
| reset_map | std_srvs/Trigger | Call this service to reset the map and the hector will create a brand new map from scratch. Note that this will not restart the robot's pose, it will restart from the last recorded pose. |
| pause_mapping | std_srvs/SetBool | Call this service to stop/start processing laser scans. |
| restart_mapping_with_new_pose | hector_mapping/ResetMapping | Call this service to reset the map, the robot's pose, and resume the map(if paused) |
Node view
xxxxxxxxxxrqt_graph
7.4 configuration parameters
| parameter | type | Defaults | describe |
|---|---|---|---|
| ~base_frame | String | "base_link" | Robot base coordinate system for positioning and transformation of laser scan data |
| ~map_frame | String | "map" | The coordinate system of the map |
| ~odom_frame | string | "odom" | Odometer coordinate system(essentially the coordinate system pointed to by map) |
| ~map_resolution | Double | 0.025(m) | map resolution, edge length of grid cells |
| ~map_size | Int | 1024 | the size of the map |
| ~map_start_x | double | 0.5 | The origin of /map [0.0, 1.0] is relative to the grid map on the x-axis |
| ~map_start_y | double | 0.5 | The origin of /map [0.0, 1.0] is relative to the grid map on the y-axis |
| ~map_update_distance_thresh | double | 0.4(m) | The threshold for map update, which is calculated from the first update on the map until the straight distance reaches the parameter value and is updated again |
| ~map_update_angle_thresh | double | 0.9(rad) | The threshold for map update, which is calculated from one update on the map until the rotation reaches this parameter value and then update again |
| ~map_pub_period | double | 2.0 | map release cycle |
| ~map_multi_res_levels | int | 3 | Map Multi-Resolution Grid Series |
| ~update_factor_free | double | 0.4 | The map used to update free cells, the range is [0.0, 1.0] |
| ~update_factor_occupied | double | 0.9 | The map used to update the occupied cells, the range is [0.0, 1.0] |
| ~laser_min_dist | double | 0.4(m) | The minimum distance of the laser scan point, the scan point less than this value will be ignored |
| ~laser_max_dist | double | 30.0(m) | The maximum distance of the laser scan point, the scan point less than this value will be ignored |
| ~laser_z_min_value | double | -1.0(m) | The minimum height relative to the lidar, scan points below this value will be ignored |
| ~laser_z_max_value | double | 1.0(m) | Relative to the lidar's maximum height, scan points above this value will be ignored |
| ~pub_map_odom_transform | bool | true | Whether to publish the coordinate conversion between map and odom |
| ~output_timing | bool | false | Process the output timing information of each laser scan through ROS_INFO |
| ~scan_subscrible_queue_size | int | 5 | Queue size for scan subscribers |
| ~pub_map_scanmatch_transform | bool | true | Whether to publish the coordinate transformation between scanmatcher and map |
| ~tf_map_scanmatch_transform_frame_name | String | "scanmatcher_frame" | Scanmatcher's coordinate system naming |
7.5 TF transformation
| Required TF Transform | describe |
|---|---|
| laser-->base_link | Usually a fixed value, the transformation between the lidar coordinate system and the base coordinate system is generally published by robot_state_publisher or static_transform_publisher |
| Published TF Transform | describe |
| map-->odom | The current estimate of the robot pose within the map frame(only provided if parameter "pub_map_odom_transform" is true). |
View tf tree
xxxxxxxxxxrosrun rqt_tf_tree rqt_tf_tree
