Random Walk Global Planner Baseline¶

The Random Walk Planner serves as a baseline global planner for stress testing system autonomy. Unlike more informed and intelligent planners, the Random Walk Planner generates a series of random trajectories to evaluate system robustness. Using the map published by VDB, the planner will generate and publish multiple linked straight-line trajectories, checking for collisions along these paths.

random walk image The blue line is the global plan generated by the random walk. The yellow line shows the past trajectory followed by the local planner when pursuing the previous random global plans.

Functionality¶

Upon activation by the behavior tree, the Random Walk Planner will:

Generate a specified number of straight-line path segments.
Continuously monitor the robot's progress along the published path.
Once the robot completes the current path, a new set of paths will be generated.

This loop continues, allowing the system to explore various trajectories and stress test the overall autonomy stack.

Parameters¶

Parameter	Description
`num_paths_to_generate`	Number of straight-line paths to concatenate into a complete trajectory.
`max_start_to_goal_dist_m`	Maximum distance (m) from start to goal for each straight-line segment.
`checking_point_cnt`	Number of points along each segment to check for collisions.
`max_z_change_m`	Maximum allowed change in height (z-axis) between start and goal points.
`collision_padding_m`	Extra padding (m) around a voxel when checking for collisions.
`path_end_threshold_m`	Distance threshold (m) for considering the current path completed.
`max_yaw_change_degrees`	Maximum allowed yaw change between consecutive segments.
`robot_frame_id`	Frame name for the robot base, used for transform lookups.

Task Executor¶

This node is a task executor: it runs as a ROS 2 action server and is activated on demand via an ExplorationTask goal. It does not plan continuously — planning only happens while a goal is active.

Action server: /{robot_name}/tasks/exploration
Type: task_msgs/action/ExplorationTask

Cascade¶

Random walk delegates navigation to the local planner via a second action:

behavior_executive  →  ExplorationTask  →  random_walk_planner
                                               ↓
                                        NavigateTask (/{robot_name}/tasks/navigate)
                                               ↓
                                          droan_gl (local planner)
                                               ↓
                                       trajectory_controller

Goal parameters¶

Field	Type	Description
`search_bounds`	geometry_msgs/Polygon	Bounding polygon for search (empty = unbounded)
`min_altitude_agl`	float32	Minimum flight altitude above ground (m)
`max_altitude_agl`	float32	Maximum flight altitude above ground (m)
`min_flight_speed`	float32	Minimum flight speed (m/s)
`max_flight_speed`	float32	Maximum flight speed (m/s)
`time_limit_sec`	float32	Maximum task duration in seconds (0 = no limit)

Feedback (published ~1 Hz)¶

Field	Type	Description
`status`	string	`"planning"` or `"navigating"`
`progress`	float32	Elapsed / time_limit (0 if no time limit)
`current_position`	geometry_msgs/Point	Current robot position

Result¶

Field	Type	Description
`success`	bool	True if time limit reached normally; false if cancelled or error
`message`	string	Human-readable completion reason

CLI test¶

# Send a 30-second unbounded exploration goal with feedback
ros2 action send_goal /robot_1/tasks/exploration task_msgs/action/ExplorationTask \
  '{min_altitude_agl: 3.0, max_altitude_agl: 8.0, min_flight_speed: 1.0, max_flight_speed: 3.0, time_limit_sec: 30.0}' \
  --feedback

# Ctrl-C cancels the goal; the node returns success=false, message="Task cancelled"

Subscriptions¶

Topic	Type	Description
`vdb_map_visualization`	visualization_msgs/Marker	Occupancy map from VDB mapping
`odometry`	nav_msgs/Odometry	Robot state estimate

Publications¶

Topic	Type	Description
`~/global_plan`	nav_msgs/Path	Generated path (also sent as NavigateTask goal)
`~/goal_point_viz`	visualization_msgs/Marker	Goal point visualization
`~/traj_viz`	visualization_msgs/Marker	Trajectory visualization