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Hi everybody,

As nobody answered to my last question, I re-ask this question cause I am completely blocked!

currently, I'm working on 2D navigation with ROS nav_stack and for this reason I'm using DWAL_local_planner. The DWA_local_planner works well but I'm facing an issue when I put an obstacle in its way (the obstacle is put in its global path before it starts to move). As you see in the following picture,

RVIZ view

When the robot recognizes the obstacle, the DWA_local_planner is not able to produce a path as the following error and it stuck.

 [ WARN] [1510564078.318379963, 78.707000000]: DWA planner failed to produce path. 
 [ INFO]  [1510564078.615916578,78.890000000]: Got new plan
 [ WARN] [1510564078.683191056, 78.923000000]: DWA planner failed to produce path.
 [ INFO] [1510564079.038445171, 79.090000000]: Got new plan
 [ WARN] [1510564079.051915033, 79.128000000]: DWA planner failed to produce path.

I have already tried to solve this issue by changing the DWA_local_planner parameters like path_distance_bias, goal_distance_bias, forward_point_distance, sim_time etc. but still I the local planner does not avoid the obstacle.

Do you have any idea why it behaves like this? I would appreciate if you look at this @David Lu. Thanks in advance,

You can find below the navigation parameters

Launch file:

<node pkg="topic_tools" type="relay" name="cmd_vel_to_nav_vel_relay" args="/cmd_vel /navigation/velocity" />

<!--- Run move_base -->
<node respawn="false" pkg="move_base" type="move_base" name="move_base" output="screen">
    <rosparam file="$(find mule)/conf/costmap_common_params.yaml" command="load" ns="global_costmap" />
    <rosparam file="$(find mule)/conf/costmap_common_params.yaml" command="load" ns="local_costmap" />

    <rosparam file="$(find mule)/conf/local_costmap_params.yaml" command="load" />
    <rosparam file="$(find mule)/conf/global_costmap_params.yaml" command="load" />
    <rosparam file="$(find mule)/conf/base_local_planner_params_simulation.yaml" command="load" />

    <!--Default local planner -->
    <!--<param name="base_local_planner" value="base_local_planner/TrajectoryPlannerROS" />  -->
    <!--<param name="base_local_planner" value="teb_local_planner/TebLocalPlannerROS" />  -->
    <param name="base_local_planner" value="dwa_local_planner/DWAPlannerROS" /> 
    <!--<param name="base_local_planner" value="eband_local_planner/EBandPlannerROS" /> -->
    <param name="controller_frequency" value="5.0" />
    <!--<param name="base_global_planner" value="karto_global_planner/KartoGlobalPathPlanner"/>-->
    <param name="base_global_planner" value="global_planner/GlobalPlanner"/>
    <!--<param name="base_global_planner" value="sbpl_lattice_planner/SBPLLatticePlanner"/> -->
    <param name="SBPLLatticePlanner/primitive_filename" value="$(find mule)/conf/4mob_16.mprim" />
    <param name="recovery_behavior_enabled" value="false"/>
    <!--<rosparam param="recovery_behaviors"> [ { name: "backup_recovery", type: "backup_recovery_dwa/BackupRecovery" } ] </rosparam> -->
    <!--<param name="recovery_behaviors" value="[]"/>-->
    <param name="planner_patience" value="5.0"/>
    <param name="controller_patience" value="15.0"/>
    <param name="shutdown_costmaps" value="true"/>
    <param name="oscillation_timeout" value="30.0"/>
    <param name="oscillation_distance" value="0.4"/>
    <param name="planner_frequency" value="0.0"/>
    <param name="max_planning_retries" value="-1"/>
</node>

global_costmap:

    global_costmap:
          global_frame: map
          robot_base_frame: base_link
          update_frequency: 1.0
          track_unknown_space: true
          static_map: true

          transform_tolerance: 0.5 

          static_layer:
                 track_unknown_space: true
                 enabled:              true
                 map_topic:            "/map"

         inflation_layer:
                enabled:              true
                cost_scaling_factor:  10  
                inflation_radius:     2.0  
                track_unknown_space: true

         plugins:
                - {name: static_layer,        type: "costmap_2d::StaticLayer"}
                - {name: inflation_layer,     type: "costmap_2d::InflationLayer"}

Local_cost_map:

    local_costmap:
         global_frame: map
         robot_base_frame: base_link
         update_frequency: 5.0
         publish_frequency: 1.0
         static_map: false
         rolling_window: true
         width: 4.0
         height: 4.0
         resolution: 0.02
         transform_tolerance: 0.5 #0.5

     obstacle_layer:
         enabled: true
         obstacle_range: 5.0
         raytrace_range: 4.5
         inflation_radius: 0.5
         track_unknown_space: true
         combination_method: 1
         observation_sources: laser_scan_sensor
         laser_scan_sensor: {sensor_frame: laser, data_type: LaserScan, topic: /scan, marking: true, clearing: true, 
         expected_update_rate: 0.25, obstacle_range: 19.0, raytrace_range: 19.0}


    inflation_layer:
        enabled:              true
        cost_scaling_factor:  10  # exponential rate at which the obstacle cost drops off (default: 10)
        inflation_radius:     0.5  # max. distance from an obstacle at which costs are incurred for planning paths.
        track_unknown_space: true


    plugins:
        - {name: obstacle_layer,      type: "costmap_2d::ObstacleLayer"}
        - {name: inflation_layer,     type: "costmap_2d::InflationLayer"}

Common_costçmap:

footprint: [[0.725, -0.4], [0.725, 0.4], [-0.725, 0.4], [-0.725,-0.4]]

observation_sources: laser_scan_sensor
laser_scan_sensor: {sensor_frame: laser, data_type: LaserScan, topic: /scan, marking: true, clearing: true}

transform_tolerance: 0.2   
map_type: costmap

DWA_local_planner:

DWAPlannerROS:

  # Robot Configuration Parameters
   max_vel_x: 1
   max_vel_x_backwards: 0.2
   min_vel_x: 0.1 

   max_trans_vel: 1
   min_trans_vel: 0.1

   max_vel_y: 0.0 
   min_vel_y: 0.0 

  max_trans_vel: 1.0
  min_trans_vel: 0.0

  max_rot_vel: 0.4 # 1.0
  min_rot_vel: 0.2 # could set this lower


  acc_lim_x: 0.2
  acc_lim_th: 0.05 # 1.0 
  acc_lim_y: 0.0 # diff drive robot


  # Goal Tolerance Parameters
  yaw_goal_tolerance: 0.15 
  xy_goal_tolerance: 0.5 
  latch_xy_goal_tolerance: false

  # Forward Simulation Parameters
  sim_time: 3 
  sim_granularity: 0.025
  vx_samples: 20 
  vy_samples: 0 
  vtheta_samples: 30 
  controller_frequency: 5
  #meter_scoring: true
  #penalize_negative_x: false

  # Trajectory Scoring Parameters
  path_distance_bias: 32.0
  goal_distance_bias: 20.0
  occdist_scale: 0.01
  forward_point_distance: 0 # Default 0.325 
  stop_time_buffer: 0.5
  scaling_speed: 0.25
  max_scaling_factor: 0.2
  #cheat_factor: 2 
  #scaled_path_factor: 0.75 

  # Oscillation Prevention Parameters
  oscillation_reset_dist: 0.05 

  # Global Plan Parameters
  prune_plan: true

Originally posted by Mobile_robot on ROS Answers with karma: 264 on 2017-11-22

Post score: 1

Original comments

Comment by Humpelstilzchen on 2017-11-23:
Did you tried that with a smaller obstacle? Or by moving the obstacle more to the site?

Comment by Mobile_robot on 2017-11-23:
Thank you for your comment. Yes, I have tried different obstacle size with different position but nothing has been changed.

Comment by Humpelstilzchen on 2017-11-23:
Can you include a picture with both costmaps? (local & global)

Comment by Mobile_robot on 2017-11-23:
I have changed the figure by the one including the global_costmap.

Comment by Humpelstilzchen on 2017-11-24:
Do you see anything on the cmd_vel topic?

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3 Answers 3

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I suggest to restart the navigation stack with default parameters first, and see what happens. Then, change only one param at time. For instance, try to reduce only the inflation radius with something very small (e.g. 0.2) just to see the behavior. I suggest also to use the Trajectory Rollout instead DWA, which was more suitable for me in certain situations.

Originally posted by rastaxe with karma: 620 on 2017-11-23

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Post score: 1

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Have you tried using different dynamic parameters? I'm thinking that acc_lim_th: 0.05 is just a too low angular acceleration to make hard turnings like the one required to avoid that obstacle.

Originally posted by IvanV with karma: 329 on 2017-11-23

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Original comments

Comment by Mobile_robot on 2017-11-23:
Thanks a lot for your answer. Yes, actually I just tried with acc_lim_th: 0.4 but still I have the same problem.

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I agree with rastaxe below. This stuff can be tricky to troubleshoot and the only way to do it is one parameter at a time.

From my brief look, your footprint looks pretty big - 1.45m x 0.8 m? Other things that come to mind are acceleration limits as mentioned above and inflation radius.

Good luck

Originally posted by mcarr with karma: 145 on 2017-11-28

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