cartographer lua参数解析

cartographer lua文件

cartographer常用的lua配置文件包括：map_builder.lua、trajectory_builder.lua、pose_graph.lua、trajectory_builder_2d.lua、trajectory_builder_3d.lua。这些文件的位置在

工作空间/src/cartographer/configuration_files

trajectory_builder.lua、trajectory_builder_2d.lua、trajectory_builder_3d.lua负责前端扫描匹配，map_builder.lua和pose_graph.lua负责后端优化。

trajectory_builder.lua

-- Copyright 2016 The Cartographer Authors
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--      http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

include "trajectory_builder_2d.lua"
include "trajectory_builder_3d.lua"

TRAJECTORY_BUILDER = {
  trajectory_builder_2d = TRAJECTORY_BUILDER_2D, -- 表示引用了trajectory_builder_2d.lua文件
  trajectory_builder_3d = TRAJECTORY_BUILDER_3D,
--  pure_localization_trimmer = {
--    max_submaps_to_keep = 3,
--  },
  collate_fixed_frame = true, -- 是否将数据放入阻塞队列中
  collate_landmarks = false,  -- 是否将数据放入阻塞队列中
}

trajectory_builder.lua文件比较简单，主要参数在trajectory_builder_2d.lua和trajectory_builder_3d.lua两个文件中。

trajectory_builder_2d.lua

-- Copyright 2016 The Cartographer Authors
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--      http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

TRAJECTORY_BUILDER_2D = {
  use_imu_data = true,            -- 是否使用imu数据，默认为true
  min_range = 0.,                 -- 雷达数据的最远最近滤波, 保存中间值
  max_range = 30.,				  -- 雷达数据不在min_range和max_range之间的会被扔掉
  min_z = -0.8,                   -- 雷达数据的最高与最低的过滤, 保存中间值
  max_z = 2.,					  -- 点云数据在z轴的分布在min_z和max_z之间才会被采用，可以通过这两个参数减少地面反射的雷达数据对cartographer的干扰
  missing_data_ray_length = 5.,   -- 超过最大距离范围的数据点用这个距离代替，对于雷达数据中的NAN或NAF数据，用这个参数的值代替
  num_accumulated_range_data = 1, -- 几帧有效的点云数据进行一次扫描匹配
  voxel_filter_size = 0.025,      -- 体素滤波的立方体的边长

  -- 使用固定的voxel滤波之后, 再使用自适应体素滤波器
  -- 体素滤波器 用于生成稀疏点云 以进行 扫描匹配
  adaptive_voxel_filter = {
    max_length = 0.5,             -- 尝试确定最佳的立方体边长,边长最大为0.5
    min_num_points = 200,         -- 如果存在 较多点 并且大于'min_num_points', 则减小体素长度以尝试获得该最小点数
    max_range = 50.,              -- 距远离原点超过max_range的点被移除
  },

  -- 闭环检测的自适应体素滤波器, 用于生成稀疏点云 以进行 闭环检测
  loop_closure_adaptive_voxel_filter = {
    max_length = 0.9,
    min_num_points = 100,
    max_range = 50.,
  },

  -- 是否使用 real_time_correlative_scan_matcher 为ceres提供先验信息
  -- 计算复杂度高 , 但是很鲁棒 , 在odom或者imu不准时依然能达到很好的效果
  -- 设置为true会提高计算量，当使用频率较低的单线雷达、建图出现叠图的情况时，可以设置为true，辅助建图
  use_online_correlative_scan_matching = false,
  real_time_correlative_scan_matcher = {
    linear_search_window = 0.1,             -- 线性搜索窗口的大小
    angular_search_window = math.rad(20.),  -- 角度搜索窗口的大小
    translation_delta_cost_weight = 1e-1,   -- 用于计算各部分score的权重
    rotation_delta_cost_weight = 1e-1,
  },

  -- ceres匹配的一些配置参数
  ceres_scan_matcher = {
    occupied_space_weight = 1., -- 地图匹配权重
    translation_weight = 10.,	-- 平移权重，匹配位置和先验位置偏差量的权重
    rotation_weight = 40.,		-- 旋转权重，匹配的姿态和先验的姿态偏差量的权重 
    -- 以上三者求參差最小，作为ceres的优化依据
    -- 下面是ceres求解的参数设置
    ceres_solver_options = {
      use_nonmonotonic_steps = false,
      max_num_iterations = 20, -- 最大迭代次数
      num_threads = 1,		   -- 线程数
    },
  },

  -- 为了防止子图里插入太多数据, 在插入子图之前之前对点云数据进行过滤
  motion_filter = {
    max_time_seconds = 5.,
    max_distance_meters = 0.2,
    max_angle_radians = math.rad(1.),
  },

  -- TODO(schwoere,wohe): Remove this constant. This is only kept for ROS.
  imu_gravity_time_constant = 10.,

  -- 位姿预测器，一般不用
  pose_extrapolator = {
    use_imu_based = false,
    constant_velocity = {
      imu_gravity_time_constant = 10.,
      pose_queue_duration = 0.001,
    },
    imu_based = {
      pose_queue_duration = 5.,
      gravity_constant = 9.806,
      pose_translation_weight = 1.,
      pose_rotation_weight = 1.,
      imu_acceleration_weight = 1.,
      imu_rotation_weight = 1.,
      odometry_translation_weight = 1.,
      odometry_rotation_weight = 1.,
      solver_options = {
        use_nonmonotonic_steps = false;
        max_num_iterations = 10;
        num_threads = 1;
      },
    },
  },

  -- 子图相关的一些配置
  submaps = {
    num_range_data = 90,          -- 一个子图里插入雷达数据为180个，这个参数在代码里会乘2
    grid_options_2d = {
      grid_type = "PROBABILITY_GRID", -- 地图的种类, PROBABILITY_GRID是概率栅格地图，还可以是tsdf格式
      resolution = 0.05, -- 地图分辨率
    },
    range_data_inserter = {
      range_data_inserter_type = "PROBABILITY_GRID_INSERTER_2D",
      -- 概率占用栅格地图的一些配置
      probability_grid_range_data_inserter = {
        insert_free_space = true,
        hit_probability = 0.55, -- 大于该值表示栅格被占用
        miss_probability = 0.49, -- 小于该值表明栅格为空
      },
      -- tsdf地图的一些配置
      tsdf_range_data_inserter = {
        truncation_distance = 0.3,
        maximum_weight = 10.,
        update_free_space = false,
        normal_estimation_options = {
          num_normal_samples = 4,
          sample_radius = 0.5,
        },
        project_sdf_distance_to_scan_normal = true,
        update_weight_range_exponent = 0,
        update_weight_angle_scan_normal_to_ray_kernel_bandwidth = 0.5,
        update_weight_distance_cell_to_hit_kernel_bandwidth = 0.5,
      },
    },
  },
}

trajectory_builder_3d.lua

trajectory_builder_3d.lua和trajectory_builder_2d.lua的内容基本相同，下面来解析不同的参数。

  -- 在3d slam 时会有2个自适应体素滤波, 一个生成高分辨率点云, 一个生成低分辨率点云
  high_resolution_adaptive_voxel_filter = {
    max_length = 2.,
    min_num_points = 150,
    max_range = 15.,
  },

  low_resolution_adaptive_voxel_filter = {
    max_length = 4.,
    min_num_points = 200,
    max_range = MAX_3D_RANGE,
  },

  ceres_scan_matcher = {
    -- 在3D中,occupied_space_weight_0和occupied_space_weight_1参数分别与高分辨率和低分辨率滤波点云相关
    occupied_space_weight_0 = 1.,
    occupied_space_weight_1 = 6.,
    intensity_cost_function_options_0 = {
        weight = 0.5,
        huber_scale = 0.3,
        intensity_threshold = INTENSITY_THRESHOLD,
    },
    translation_weight = 5.,
    rotation_weight = 4e2,
    only_optimize_yaw = false,
    ceres_solver_options = {
      use_nonmonotonic_steps = false,
      max_num_iterations = 12,
      num_threads = 1,
    },

  submaps = {
    -- 2种分辨率的地图
    high_resolution = 0.10,           -- 用于近距离测量的高分辨率hybrid网格 for local SLAM and loop closure, 用来与小尺寸voxel进行精匹配
    high_resolution_max_range = 20.,  -- 在插入 high_resolution map 之前过滤点云的最大范围
    low_resolution = 0.45,
    num_range_data = 160,             -- 用于远距离测量的低分辨率hybrid网格 for local SLAM only, 用来与大尺寸voxel进行粗匹配
    range_data_inserter = {
      hit_probability = 0.55,
      miss_probability = 0.49,
      num_free_space_voxels = 2,
      intensity_threshold = INTENSITY_THRESHOLD,
    },

map_builder.lua

-- Copyright 2016 The Cartographer Authors
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--      http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

include "pose_graph.lua"

MAP_BUILDER = {
  use_trajectory_builder_2d = false,--use_trajectory_builder_2d和use_trajectory_builder_3d要有一个为true
  use_trajectory_builder_3d = false,
  num_background_threads = 4, -- 后台线程数
  pose_graph = POSE_GRAPH,	-- 加载pose_graph.lua的参数
  collate_by_trajectory = false,
}

pose_graph.lua

-- Copyright 2016 The Cartographer Authors
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--      http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

POSE_GRAPH = {
  -- 每隔多少个节点执行一次后端优化，可以设置为num_range_data的2倍，每插入2*num_range_data的雷达数据，子图会更新一次，optimize_every_n_nodes设置的太小会导致在子图无变化时多次优化。
  optimize_every_n_nodes = 90,

  -- 约束构建的相关参数
  constraint_builder = {
    sampling_ratio = 0.3,                 -- 对局部子图进行回环检测时的计算频率, 数值越大, 计算次数越多
    max_constraint_distance = 15.,        -- 对局部子图进行回环检测时能成为约束的最大距离
    min_score = 0.55,                     -- 对局部子图进行回环检测时的最低分数阈值，小于该值可认为回环检测失败
    global_localization_min_score = 0.6,  -- 对整体子图进行回环检测时的最低分数阈值
    loop_closure_translation_weight = 1.1e4,
    loop_closure_rotation_weight = 1e5,
    log_matches = true,                   -- 打印约束计算的log
    
    -- 基于分支定界算法的2d粗匹配器
    fast_correlative_scan_matcher = {
      linear_search_window = 7.,
      angular_search_window = math.rad(30.),
      branch_and_bound_depth = 7,
    },

    -- 基于ceres的2d精匹配器
    ceres_scan_matcher = {
      occupied_space_weight = 20.,
      translation_weight = 10.,
      rotation_weight = 1.,
      ceres_solver_options = {
        use_nonmonotonic_steps = true,
        max_num_iterations = 10,
        num_threads = 1,
      },
    },

    -- 基于分支定界算法的3d粗匹配器
    fast_correlative_scan_matcher_3d = {
      branch_and_bound_depth = 8,
      full_resolution_depth = 3,
      min_rotational_score = 0.77,
      min_low_resolution_score = 0.55,
      linear_xy_search_window = 5.,
      linear_z_search_window = 1.,
      angular_search_window = math.rad(15.),
    },

    -- 基于ceres的3d精匹配器
    ceres_scan_matcher_3d = {
      occupied_space_weight_0 = 5.,
      occupied_space_weight_1 = 30.,
      translation_weight = 10.,
      rotation_weight = 1.,
      only_optimize_yaw = false,
      ceres_solver_options = {
        use_nonmonotonic_steps = false,
        max_num_iterations = 10,
        num_threads = 1,
      },
    },
  },

  matcher_translation_weight = 5e2,
  matcher_rotation_weight = 1.6e3,

  -- 优化残差方程的相关参数
  optimization_problem = {
    huber_scale = 1e1,                -- 值越大,（潜在）异常值的影响就越大
    acceleration_weight = 1.1e2,      -- 3d里imu的线加速度的权重
    rotation_weight = 1.6e4,          -- 3d里imu的旋转的权重
    
    -- 前端结果残差的权重
    local_slam_pose_translation_weight = 1e5,
    local_slam_pose_rotation_weight = 1e5,
    -- 里程计残差的权重
    odometry_translation_weight = 1e5,
    odometry_rotation_weight = 1e5,
    -- gps残差的权重
    fixed_frame_pose_translation_weight = 1e1,
    fixed_frame_pose_rotation_weight = 1e2,
    fixed_frame_pose_use_tolerant_loss = false,
    fixed_frame_pose_tolerant_loss_param_a = 1,
    fixed_frame_pose_tolerant_loss_param_b = 1,

    log_solver_summary = false, --是否保存优化后的结果
    use_online_imu_extrinsics_in_3d = true,
    fix_z_in_3d = false,
    ceres_solver_options = {
      use_nonmonotonic_steps = false,
      max_num_iterations = 50,
      num_threads = 7,
    },
  },

  max_num_final_iterations = 200,   -- 在建图结束之后执行一次全局优化, 不要求实时性, 迭代次数多
  global_sampling_ratio = 0.003,    -- 纯定位时候查找回环的频率
  log_residual_histograms = true,
  global_constraint_search_after_n_seconds = 10., -- 纯定位时多少秒执行一次全子图的约束计算

  --  overlapping_submaps_trimmer_2d = {
  --    fresh_submaps_count = 1,
  --    min_covered_area = 2,
  --    min_added_submaps_count = 5,
  --  },
}

backpack_2d.lua参数解析

以backpack_2d.lua为例，讲解自己的lua文件如何配置。

-- Copyright 2016 The Cartographer Authors
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--      http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

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

options = {
  map_builder = MAP_BUILDER, -- map_builder.lua的参数信息
  trajectory_builder = TRAJECTORY_BUILDER,
  map_frame = "map", --地图坐标系的名字
  tracking_frame = "base_link", -- 将所有传感器数据转换到这个坐标系下，如果有imu,一般设置为imu_link,因为imu的频率非常高（上百hz），而雷达数据的频率相对低（几十hz），如果把imu数据转换到其他坐标系则每秒钟需要转换几百次，比较耗费资源
  published_frame = "base_link", -- 设置为tf树最顶端的坐标系名称，设置完成后cartographer会发布map->published_frame的坐标系
  odom_frame = "odom", -- 里程计的坐标系名字
  provide_odom_frame = true, -- 是否提供odom的tf, 如果为true,则tf树为map->odom->footprint，如果为false，则tf树为map->published_frame
  publish_frame_projected_to_2d = false,-- 是否将坐标系投影到平面上，一般为false
  use_pose_extrapolator = true, --是否使用位姿推测器，一般为false
  -- 通过话题订阅的方式使用里程计、gps、landmark,三者可以同时订阅，但每个只能订阅1个话题
  use_odometry = false, -- 是否使用里程计,如果使用要求一定要有odom的tf
  use_nav_sat = false,-- 是否使用gps
  use_landmarks = false,-- 是否使用landmark 
  --num_laser_scans、num_multi_echo_laser_scans、num_point_clouds三者不能同时为0
  num_laser_scans = 0, -- 是否使用单线激光数据并设置订阅topic的数量
  num_multi_echo_laser_scans = 1,-- 是否使用multi_echo_laser_scans数据
  num_subdivisions_per_laser_scan = 10,-- 1帧数据被分成几次处理,一般为1
  num_point_clouds = 0,-- 是否使用16线点云数据
  
  lookup_transform_timeout_sec = 0.2, -- 查找tf时的超时时间
  submap_publish_period_sec = 0.3, -- 发布数据的时间间隔
  pose_publish_period_sec = 5e-3,
  trajectory_publish_period_sec = 30e-3,

  -- 传感器数据的采样频率
  rangefinder_sampling_ratio = 1., --设置为0.1则表示每10帧数据使用1帧数据
  odometry_sampling_ratio = 1.,
  fixed_frame_pose_sampling_ratio = 1.,
  imu_sampling_ratio = 1.,
  landmarks_sampling_ratio = 1.,
}
--修改之前5个lua文件参数可以使用这种方式
MAP_BUILDER.use_trajectory_builder_2d = true
TRAJECTORY_BUILDER_2D.num_accumulated_range_data = 10

return options