Theta star planner fails to get path when goals falls in unknown space, where tile value = NO_INFORMATION #3285
Description
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.