~<name>/global_frame (string, default: "/map")
The global frame for the costmap to operate in.代价地图在哪一个坐标系的基础上制作
~<name>/robot_base_frame (string, default: "base_link")
The name of the frame for the base link of the robot.传感器数据转换为地图上数据的桥梁
~<name>/transform_tolerance (double, default: 0.2)
Specifies the delay in transform (tf) data that is tolerable in seconds. This parameter serves as a safeguard to losing a link in the tf tree while still allowing an amount of latency the user is comfortable with to exist in the system. For example, a transform being 0.2 seconds out-of-date may be tolerable, but a transform being 8 seconds out of date is not. If the tf transform between the coordinate frames specified by the global_frame and robot_base_frame parameters is transform_tolerance seconds older than ros::Time::now(), then the navigation stack will stop the robot.延迟时间，和实时性要求有关，这个时间参数实际上是允许TF传输延迟，参数设置过大会影响机器人的行为。

~<name>/update_frequency (double, default: 5.0)
The frequency in Hz for the map to be updated.图的更新频率，需要配合传感器数据的发布频率。考虑机器人处理器速度。
~<name>/publish_frequency (double, default: 0.0)
The frequency in Hz for the map to be publish display information.发布频率，主要被RViz接收，需要考虑地图大小来设置发布频率。

~<name>/rolling_window (bool, default: false)
Whether or not to use a rolling window version of the costmap. If the static_map parameter is set to true, this parameter must be set to false.
~<name>/always_send_full_costmap (bool, default: false)
If true the full costmap is published to "~<name>/grid" every update. If false only the part of the costmap that has changed is published on the "~<name>/grid_updates" topic.

~<name>/width (int, default: 10)
The width of the map in meters.地图的几何参数，也会影响路径规划精度。
~<name>/height (int, default: 10)
The height of the map in meters.
~<name>/resolution (double, default: 0.05)
The resolution of the map in meters/cell.
~<name>/origin_x (double, default: 0.0)
The x origin of the map in the global frame in meters.
~<name>/origin_y (double, default: 0.0)
The y origin of the map in the global frame in meters. 

~<name>/observation_sources (string, default: "")
A list of observation source names separated by spaces. This defines each of the <source_name> namespaces defined below.
Each source_name in observation_sources defines a namespace in which parameters can be set:
~<name>/<source_name>/topic (string, default: source_name)
The topic on which sensor data comes in for this source. Defaults to the name of the source.
~<name>/<source_name>/sensor_frame (string, default: "")
The frame of the origin of the sensor. Leave empty to attempt to read the frame from sensor data. The frame can be read from both sensor_msgs/LaserScan, sensor_msgs/PointCloud, and sensor_msgs/PointCloud2 messages.
~<name>/<source_name>/observation_persistence (double, default: 0.0)
How long to keep each sensor reading in seconds. A value of 0.0 will only keep the most recent reading.
~<name>/<source_name>/expected_update_rate (double, default: 0.0)
How often to expect a reading from a sensor in seconds. A value of 0.0 will allow infinite time between readings. This parameter is used as a failsafe to keep the navigation stack from commanding the robot when a sensor has failed. It should be set to a value that is slightly more permissive than the actual rate of the sensor. For example, if we expect a scan from a laser every 0.05 seconds we might set this parameter to be 0.1 seconds to give a generous buffer and account for some amount of system latency.
~<name>/<source_name>/data_type (string, default: "PointCloud")
The data type associated with the topic, right now only "PointCloud", "PointCloud2", and "LaserScan" are supported.
~<name>/<source_name>/clearing (bool, default: false)
Whether or not this observation should be used to clear out freespace.
~<name>/<source_name>/marking (bool, default: true)
Whether or not this observation should be used to mark obstacles.
~<name>/<source_name>/max_obstacle_height (double, default: 2.0)
The maximum height in meters of a sensor reading considered valid. This is usually set to be slightly higher than the height of the robot. Setting this parameter to a value greater than the global max_obstacle_height parameter has no effect. Setting this parameter to a value less than the global max_obstacle_height will filter out points from this sensor above that height.
~<name>/<source_name>/min_obstacle_height (double, default: 0.0)
The minimum height in meters of a sensor reading considered valid. This is usually set to be at ground height, but can be set higher or lower based on the noise model of your sensor.
~<name>/<source_name>/obstacle_range (double, default: 2.5)
The maximum range in meters at which to insert obstacles into the costmap using sensor data.
~<name>/<source_name>/raytrace_range (double, default: 3.0)
The maximum range in meters at which to raytrace out obstacles from the map using sensor data.
~<name>/<source_name>/inf_is_valid (bool, default: false)
Allows for Inf values in "LaserScan" observation messages. The Inf values are converted to the laser maximun range.

~<name>/max_obstacle_height (double, default: 2.0)障碍高度
The maximum height of any obstacle to be inserted into the costmap in meters. This parameter should be set to be slightly higher than the height of your robot.
~<name>/obstacle_range (double, default: 2.5)障碍范围：多少米范围内的障碍物被标识出来
The default maximum distance from the robot at which an obstacle will be inserted into the cost map in meters. This can be over-ridden on a per-sensor basis.
~<name>/raytrace_range (double, default: 3.0)不知道啊，只知道raytrace是一种代价值传播的方法。
The default range in meters at which to raytrace out obstacles from the map using sensor data. This can be over-ridden on a per-sensor basis.

~<name>/track_unknown_space (bool, default: false)
Specifies whether or not to track what space in the costmap is unknown, meaning that no observation about a cell has been seen from any sensor source.

~<name>/origin_z (double, default: 0.0)
The z origin of the map in meters.
~<name>/z_resolution (double, default: 0.2)
The z resolution of the map in meters/cell.
~<name>/z_voxels (int, default: 10)
The number of voxels to in each vertical column, the height of the grid is z_resolution * z_voxels.
~<name>/unknown_threshold (int, default: ~<name>/z_voxels)
The number of unknown cells allowed in a column considered to be "known"
~<name>/mark_threshold (int, default: 0)
The maximum number of marked cells allowed in a column considered to be "free".
~<name>/publish_voxel_map (bool, default: false)
Whether or not to publish the underlying voxel grid for visualization purposes. 

~<name>/inflation_radius (double, default: 0.55) 
The radius in meters to which the map inflates obstacle cost values.
~<name>/cost_scaling_factor (double, default: 10.0)
A scaling factor to apply to cost values during inflation. The cost function is computed as follows for all cells in the costmap further than the inscribed radius distance and closer than the inflation radius distance away from an actual obstacle: exp(-1.0 * cost_scaling_factor * (distance_from_obstacle - inscribed_radius)) * (costmap_2d::INSCRIBED_INFLATED_OBSTACLE - 1), where costmap_2d::INSCRIBED_INFLATED_OBSTACLE is currently 254. NOTE: since the cost_scaling_factor is multiplied by a negative in the formula, increasing the factor will decrease the resulting cost values. 

~base_global_planner (string, default: "navfn/NavfnROS" For 1.1+ series)
The name of the plugin for the global planner to use with move_base, see pluginlib documentation for more details on plugins. This plugin must adhere to the nav_core::BaseGlobalPlanner interface specified in the nav_core package. (1.0 series default: "NavfnROS")
~base_local_planner (string, default: "base_local_planner/TrajectoryPlannerROS" For 1.1+ series)
The name of the plugin for the local planner to use with move_base see pluginlib documentation for more details on plugins. This plugin must adhere to the nav_core::BaseLocalPlanner interface specified in the nav_core package. (1.0 series default: "TrajectoryPlannerROS")
~recovery_behaviors (list, default: [{name: conservative_reset, type: clear_costmap_recovery/ClearCostmapRecovery}, {name: rotate_recovery, type: rotate_recovery/RotateRecovery}, {name: aggressive_reset, type: clear_costmap_recovery/ClearCostmapRecovery}] For 1.1+ series) 
~controller_frequency (double, default: 20.0)
The rate in Hz at which to run the control loop and send velocity commands to the base.
~planner_patience (double, default: 5.0)
How long the planner will wait in seconds in an attempt to find a valid plan before space-clearing operations are performed.
~controller_patience (double, default: 15.0)
How long the controller will wait in seconds without receiving a valid control before space-clearing operations are performed. 

~conservative_reset_dist (double, default: 3.0)
The distance away from the robot in meters at which obstacles will be cleared from the costmap when attempting to clear space in the map. Note, this parameter is only used when the default recovery behaviors are used for move_base.
~recovery_behavior_enabled (bool, default: true)
Whether or not to enable the move_base recovery behaviors to attempt to clear out space.在本项目中应该为否
~clearing_rotation_allowed (bool, default: true)
Determines whether or not the robot will attempt an in-place rotation when attempting to clear out space. Note: This parameter is only used when the default recovery behaviors are in use, meaning the user has not set the recovery_behaviors parameter to anything custom.在本项目中应该为否
~shutdown_costmaps (bool, default: false)
Determines whether or not to shutdown the costmaps of the node when move_base is in an inactive state
~oscillation_timeout (double, default: 0.0)
How long in seconds to allow for oscillation before executing recovery behaviors. A value of 0.0 corresponds to an infinite timeout. New in navigation 1.3.1
~oscillation_distance (double, default: 0.5)
How far in meters the robot must move to be considered not to be oscillating. Moving this far resets the timer counting up to the ~oscillation_timeout New in navigation 1.3.1
~planner_frequency (double, default: 0.0)
The rate in Hz at which to run the global planning loop. If the frequency is set to 0.0, the global planner will only run when a new goal is received or the local planner reports that its path is blocked. New in navigation 1.6.0

~<name>/sim_granularity (double, default: 0.017)
The distance in radians between checks for obstacles when checking if an in-place rotation is safe. Defaults to 1 degree.
~<name>/frequency (double, default: 20.0)
The frequency in HZ at which to send velocity commands to the mobile base.