Theta star planner fails to get path when goals falls in unknown space, where tile value = NO_INFORMATION

[pepisg]

Bug report

Required Info:

• Operating System:
  • Ubuntu 22
• ROS2 Version:
  • Humble
• Version or commit hash:
  • 0d86469 (latest humble branch)
  • cyclone DDS

Steps to reproduce issue

Launch the turtlebot3 simulation with these paramters:

global_costmap:
  global_costmap:
    ros__parameters:
      update_frequency: 1.0
      publish_frequency: 1.0
      global_frame: map
      robot_base_frame: base_link
      rolling_window: true
      width: 20
      height: 20
      robot_radius: 0.22
      resolution: 0.05
      track_unknown_space: true
      plugins: ["obstacle_layer", "inflation_layer"]
      obstacle_layer:
        plugin: "nav2_costmap_2d::ObstacleLayer"
        enabled: True
        observation_sources: scan
        scan:
          topic: /scan
          max_obstacle_height: 2.0
          clearing: True
          marking: True
          data_type: "LaserScan"
          raytrace_max_range: 3.0
          raytrace_min_range: 0.0
          obstacle_max_range: 2.5
          obstacle_min_range: 0.0
      static_layer:
        plugin: "nav2_costmap_2d::StaticLayer"
        map_subscribe_transient_local: True
      inflation_layer:
        plugin: "nav2_costmap_2d::InflationLayer"
        cost_scaling_factor: 3.0
        inflation_radius: 0.55
      always_send_full_costmap: True

planner_server:
  ros__parameters:
    expected_planner_frequency: 20.0
    planner_plugins: ["GridBased"]
    GridBased:
      plugin: "nav2_theta_star_planner/ThetaStarPlanner"
      how_many_corners: 8
      w_euc_cost: 1.0
      w_traversal_cost: 2.0
      w_heuristic_cost: 1.0

They are basically the default parameters but they use a rolling global costmap without a static layer (so we can easily send the robot to an unknown tile) and the defaults for the Theta Star planner.

Then try to send the robot to a place marked as unknown in the global costmap.

Expected behavior

The theta star planner generates a path to the requested goal even if it lies on a tile whose value is NO_INFORMATION,

Actual behavior

The theta star planner fails to compute a path and shows the following error message: Either of the start or goal pose are an obstacle!

Additional information

This is likely due to the way a safe tile is defined in the theta star planner, where any cost above LETHAL_OBSTACLE (defined as 252) is treated as unsafe; howerver NO_INFORMATION tiles are set to 255, which is in fact greater than 252 but should not be considered as an obstacle.

[SteveMacenski]

Sounds like this planner could use a allow_unknown option like NavFn and Smac Planners have! Sounds like a great contribution 😄

[pepisg]

Done in #3286

[tosa-no-onchan]

Hi, I had same error.
But I copy https://github.com/ros-navigation/navigation2/tree/main/nav2_theta_star_planner describe.
It goes well.

planner_server:
  ros__parameters:
    planner_plugin_types: ["nav2_theta_star_planner::ThetaStarPlanner"]
    planner_plugin_ids: ["GridBased"]
    GridBased:
      how_many_corners: 8
      w_euc_cost: 1.0
      w_traversal_cost: 2.0