配置导航参数

前文(ROS机器人底盘(13)-move_base(1))讲了move_base的简单的基础,本文将详细分析下如何配置move_base参数

最简单的配置

再次引用该图

movebase
map_server和amcl都是不必须的，我们就首先配置一个没有map的move_base

fake_move_base_with_out_map.launch

<launch>
  <include file="$(find pibot_bringup)/launch/robot.launch"/>
  <param name="use_sim_time" value="false" />
  <include file="$(find pibot_nav)/launch/include/move_base_with_out_map.launch.xml" />
</launch>

• robot.launch为Pibot的驱动，其他底盘可替换为自己的驱动
• move_base_with_out_map.launch.xml

<launch>
  <arg name="model" default="$(env PIBOT_MODEL)" doc="model type [apollo, zeus]"/>

  <node pkg="move_base" type="move_base" respawn="false" name="move_base" output="screen" clear_params="true">
    <rosparam file="$(find pibot_nav)/params/costmap_common_params_$(arg model).yaml" command="load" ns="global_costmap" />
    <rosparam file="$(find pibot_nav)/params/costmap_common_params_$(arg model).yaml" command="load" ns="local_costmap" />
    <rosparam file="$(find pibot_nav)/params/local_costmap_params_withoutmap.yaml" command="load" />
    <rosparam file="$(find pibot_nav)/params/global_costmap_params_withoutmap.yaml" command="load" />
    <rosparam file="$(find pibot_nav)/params/dwa_local_planner_params_$(arg model).yaml" command="load" />
    <rosparam file="$(find pibot_nav)/params/move_base_params.yaml" command="load" />
    <rosparam file="$(find pibot_nav)/params/global_planner_params.yaml" command="load" />
  </node>
</launch>

• 配置文件详情

1.costmap_common_params_apollo.yaml

max_obstacle_height: 0.60  # assume something like an arm is mounted on top of the robot

# Obstacle Cost Shaping (http://wiki.ros.org/costmap_2d/hydro/inflation)
#robot_radius: 0.16  # distance a circular robot should be clear of the obstacle (kobuki: 0.18)
footprint: [[0.10, -0.07], [0.10, 0.18], [-0.10, 0.18], [-0.10, -0.07]]
# footprint: [[x0, y0], [x1, y1], ... [xn, yn]]  # if the robot is not circular

map_type: voxel

obstacle_layer:
  enabled:              true
  max_obstacle_height:  0.6
  origin_z:             0.0
  z_resolution:         0.2
  z_voxels:             2
  unknown_threshold:    15
  mark_threshold:       0
  combination_method:   1
  track_unknown_space:  true    #true needed for disabling global path planning through unknown space
  obstacle_range: 2.5
  raytrace_range: 3.0
  origin_z: 0.0
  z_resolution: 0.2
  z_voxels: 2
  publish_voxel_map: false
  observation_sources:  scan
  scan:
    data_type: LaserScan
    topic: scan
    inf_is_valid: true
    marking: true
    clearing: true
    min_obstacle_height: 0.05
    max_obstacle_height: 0.35
  #bump:
    #data_type: PointCloud2
    #topic: mobile_base/sensors/bumper_pointcloud
    #marking: true
    #clearing: false
    #min_obstacle_height: 0.0
    #max_obstacle_height: 0.15
  # for debugging only, let's you see the entire voxel grid

#cost_scaling_factor and inflation_radius were now moved to the inflation_layer ns
inflation_layer:
  cost_scaling_factor:  2.5  # exponential rate at which the obstacle cost drops off (default: 10)
  inflation_radius:     1.2  # max. distance from an obstacle at which costs are incurred for planning paths.

static_layer:
  enabled:              false

2.local_costmap_params_withoutmap.yaml

local_costmap:
   global_frame: /odom
   robot_base_frame: /base_link
   update_frequency: 1.0
   publish_frequency: 2.0
   static_map: false
   rolling_window: true
   width: 4
   height: 4
   resolution: 0.05
   transform_tolerance: 0.5
   plugins:
    - {name: obstacle_layer,      type: "costmap_2d::VoxelLayer"}
    - {name: inflation_layer,     type: "costmap_2d::InflationLayer"}

3.global_costmap_params_withoutmap.yaml

global_costmap:
   global_frame: /map
   robot_base_frame: /base_link
   update_frequency: 1.0
   publish_frequency: 0.5
   static_map: false
   rolling_window: true
   width: 12
   height: 12
   resolution: 0.05
   transform_tolerance: 0.5
   plugins:
     - {name: obstacle_layer,          type: "costmap_2d::VoxelLayer"}
     - {name: inflation_layer,         type: "costmap_2d::InflationLayer"}

4.dwa_local_planner_params_apollo.yaml

DWAPlannerROS:

# Robot Configuration Parameters - Kobuki
  max_vel_x: 0.25
  min_vel_x: 0.05

  max_vel_y: 0
  min_vel_y: 0

  max_trans_vel: 0.35 # choose slightly less than the base's capability
  min_trans_vel: 0.001  # this is the min trans velocity when there is negligible rotational velocity
  trans_stopped_vel: 0.05

  # Warning!
  #   do not set min_trans_vel to 0.0 otherwise dwa will always think translational velocities
  #   are non-negligible and small in place rotational velocities will be created.

  max_rot_vel: 0.6  # choose slightly less than the base's capability
  min_rot_vel: 0.4  # this is the min angular velocity when there is negligible translational velocity
  rot_stopped_vel: 0.1
  
  acc_lim_x: 1 # maximum is theoretically 2.0, but we 
  acc_lim_theta: 1.5 
  acc_lim_y: 0      # diff drive robot

# Goal Tolerance Parameters
  yaw_goal_tolerance: 0.2 
  xy_goal_tolerance: 0.15  
  latch_xy_goal_tolerance: false

# Forward Simulation Parameters
  sim_time: 2.0       # 1.7
  vx_samples: 10       # 3
  vy_samples: 1       # diff drive robot, there is only one sample
  vtheta_samples: 20  # 20

# Trajectory Scoring Parameters
  path_distance_bias: 32.0      # 32.0   - weighting for how much it should stick to the global path plan
  goal_distance_bias: 24.0      # 24.0   - wighting for how much it should attempt to reach its goal
  occdist_scale: 0.4            # 0.01   - weighting for how much the controller should avoid obstacles
  forward_point_distance: 0.325 # 0.325  - how far along to place an additional scoring point
  stop_time_buffer: 0.2         # 0.2    - amount of time a robot must stop in before colliding for a valid traj.
  scaling_speed: 0.25           # 0.25   - absolute velocity at which to start scaling the robot's footprint
  max_scaling_factor: 0.2       # 0.2    - how much to scale the robot's footprint when at speed.

# Oscillation Prevention Parameters
  oscillation_reset_dist: 0.05  # 0.05   - how far to travel before resetting oscillation flags

# Debugging
  publish_traj_pc : true
  publish_cost_grid_pc: true
  global_frame_id: odom


# Differential-drive robot configuration - necessary?
#  holonomic_robot: false

5.move_base.yaml

# Move base node parameters. For full documentation of the parameters in this file, please see
#
#  http://www.ros.org/wiki/move_base
#
shutdown_costmaps: false

controller_frequency: 5.0
controller_patience: 3.0


planner_frequency: 1.0
planner_patience: 5.0

oscillation_timeout: 10.0
oscillation_distance: 0.2

# local planner - default is trajectory rollout
base_local_planner: "dwa_local_planner/DWAPlannerROS"

base_global_planner: global_planner/GlobalPlanner #"navfn/NavfnROS" #alternatives: , carrot_planner/CarrotPlanner

6.global_planner_params.yaml

GlobalPlanner:                                  # Also see: http://wiki.ros.org/global_planner
  old_navfn_behavior: false                     # Exactly mirror behavior of navfn, use defaults for other boolean parameters, default false
  use_quadratic: true                           # Use the quadratic approximation of the potential. Otherwise, use a simpler calculation, default true
  use_dijkstra: true                            # Use dijkstra's algorithm. Otherwise, A*, default true
  use_grid_path: false                          # Create a path that follows the grid boundaries. Otherwise, use a gradient descent method, default false
  
  allow_unknown: true                           # Allow planner to plan through unknown space, default true
                                                #Needs to have track_unknown_space: true in the obstacle / voxel layer (in costmap_commons_param) to work
  planner_window_x: 0.0                         # default 0.0
  planner_window_y: 0.0                         # default 0.0
  default_tolerance: 0.5                        # If goal in obstacle, plan to the closest point in radius default_tolerance, default 0.0
  
  publish_scale: 100                            # Scale by which the published potential gets multiplied, default 100
  planner_costmap_publish_frequency: 0.0        # default 0.0
  
  lethal_cost: 253                              # default 253
  neutral_cost: 66                              # default 50
  cost_factor: 0.55                              # Factor to multiply each cost from costmap by, default 3.0
  publish_potential: true                       # Publish Potential Costmap (this is not like the navfn pointcloud2 potential), default true

运行结果

运行roslaunch pibot_navigation fake_move_base_with_out_map.launch
roslaunch pibot_navigation view_nav_with_out_map.launch
选择2D Nav Goal导航可以看到

配置分析

可以看到move_base配置项较多，涉及到cost_map及planner,分别又包括local_cost_map、global_cost_map和local_planner、global_planner
首先看根配置(简单说就是没有前面的namespace的)，除了move_base.yaml,其他文件都是二级配置项

common_cost_map中在move_base_with_out_map.launch.xml都已经指定了namespace

move_base

根配置

• shutdown_costmaps 当move_base在不活动状态时，是不是要关掉move_base node的 costmap

查看源码可知move_base空闲时shutdown_costmaps为true会关掉cost_map,激活是会重新开启

默认false

• controller_frequency 规划频率，太大会占用CPU 这里我们设置为3， 好点的处理器可以设置稍高
• controller_patience

算了还是直接看源码吧

计算速度失败就判断有没有超时，超时就切换状态

• planner_frequency

容易理解这个是全局路径规划的频率；如果为0即只规划一次

• planner_patience 容易理解，规划路径的最大容忍时间
• oscillation_timeout&oscillation_distance

陷在方圆oscillation_distance达oscillation_timeout之久，认定机器人在震荡，从而做异常处理（应该容易理解吧）

• base_local_planner & base_global_planner

最为重要的2个参数，直接指定使用哪种局部规划和全局规划，
具体类分别继承与实现nav_core::BaseLocalPlanner和nav_core::BaseGlobalPlanner接口

rosrun rqt_reconfigure rqt_reconfigure 查看move_base的参数

可以看到还有几个参数，一并看下

• max_planning_retries 最大规划路径的重试次数 -1标识无限次
• recovery_behavior_enabled 是否启用恢复机制
• clearing_rotation_allowed 是否启用旋转的恢复，当然是在recovery_behavior_enabled 为true的基础上的
• recovery_behaviors 一系列的恢复机制，同base_local_planner & base_global_planner 具体类继承于nav_core::RecoveryBehavior
• conservative_reset_dist 清除机制的参数， 决定清除多远外的障碍