Cartographer 使用方式与典型场景

四、使用方式与典型场景

Cartographer 的日常使用围绕三件事：建图、保存、纯定位。下面给出两个可以直接改参数跑的配置示例。

示例一，一份精简的 2D 建图 Lua 配置骨架。把它放在 cartographer_ros/configuration_files 下，再用 roslaunch 引用。注意 Lua 里的 include 会把官方默认配置先加载进来，你只需要覆盖关心的那几项：

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

options = {
  map_builder = MAP_BUILDER,
  trajectory_builder = TRAJECTORY_BUILDER,
  map_frame = "map",
  tracking_frame = "imu_link",
  published_frame = "base_link",
  odom_frame = "odom",
  provide_odom_frame = true,
  publish_frame_projected_to_2d = true,
  use_odometry = true,
  use_nav_sat = false,
  use_landmarks = 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_BUILDER.use_trajectory_builder_2d = true
MAP_BUILDER.num_background_threads = 4

TRAJECTORY_BUILDER_2D.min_range = 0.12
TRAJECTORY_BUILDER_2D.max_range = 8.0
TRAJECTORY_BUILDER_2D.missing_data_ray_length = 1.0
TRAJECTORY_BUILDER_2D.num_accumulated_range_data = 1
TRAJECTORY_BUILDER_2D.voxel_filter_size = 0.025
TRAJECTORY_BUILDER_2D.submaps.num_range_data = 60

TRAJECTORY_BUILDER_2D.motion_filter.max_time_seconds = 5.0
TRAJECTORY_BUILDER_2D.motion_filter.max_distance_meters = 0.2
TRAJECTORY_BUILDER_2D.motion_filter.max_angle_radians = 0.02

POSE_GRAPH.optimize_every_n_nodes = 35
POSE_GRAPH.constraint_builder.min_score = 0.55
POSE_GRAPH.constraint_builder.global_localization_min_score = 0.6

return options

示例二，加载已有地图做纯定位。做法是把建图得到的 pbstream 通过 launch 参数加载，并把 TRAJECTORY_BUILDER.pure_localization 置为 true，同时把回环搜索范围收窄。纯定位模式下系统不再扩建地图，只估计位姿，CPU 占用显著下降。对应的启动命令形如：

roslaunch cartographer_ros demo_backpack_2d_localization.launch \
  load_state_filename:=$HOME/map.pbstream \
  bag_filename:=$HOME/run2.bag

为纯定位优化的配置片段，关键在于收紧搜索窗口以提升速度，并提高定位门限以保证可靠性：

TRAJECTORY_BUILDER.pure_localization_trimmer = {
  max_submaps_to_keep = 3,
}
POSE_GRAPH.optimize_every_n_nodes = 20
POSE_GRAPH.constraint_builder.sampling_ratio = 0.3
POSE_GRAPH.constraint_builder.global_localization_min_score = 0.65
POSE_GRAPH.constraint_builder.fast_correlative_scan_matcher.linear_search_window = 7.
POSE_GRAPH.constraint_builder.fast_correlative_scan_matcher.angular_search_window = math.rad(30.)

适用与不适用场景的对照如下。