ugv_random_walk

This package performs random walk coverage with an unmanned ground vehicle (UGV). It is part of the swarm behaviors library.

Dependencies

This package depends on the following message definitions:

• cpswarm_msgs

The following library packages of the swarm behaviors library are required:

• swarm_behaviors_position

The following packages of the swarm functions library are required:

• target_monitor (only if single_target=true)

The following packages of the sensing and actuation library are required:

• area_provider
• obstacle_detection

Further required packages are:

• roscpp
• actionlib
• random_numbers

Execution

Run the launch file

roslaunch ugv_random_walk ugv_random_walk.launch

to launch the ugv_random_walk node.

The launch file can be configured with following parameters:

• id (integer, default: 1) The identifier (ID) of the CPS used for name spacing in simulation.
• output (string, default: screen) Whether to show the program output (screen) or to write it to a log file (log).

In the param subdirectory there is the parameter file ugv_random_walk.yaml that allows to configure the behavior of the ugv_random_walk node.

Nodes

ugv_random_walk

The ugv_random_walk performs coverage using the random walk algorithm. The random walk is a mathematical movement model, where an agent moves straight for a specific distance. Then, it changes its direction randomly into a direction that is clear of obstacles and moves straight again. If it arrives at the environment boundary, it reflects to continue its walk. When the parameter single_target is set to true, the UGV succeeds once a target has been found and returns the target ID and position.

Action Goal

• ugv_coverage/goal (cpswarm_msgs/CoverageGoal) A goal that starts the random direction coverage behavior.

Action Result

• ugv_coverage/result (cpswarm_msgs/CoverageResult) ID and position of the target that has been found.

Subscribed Topics

• target_found (cpswarm_msgs/TargetPositionEvent) Position and ID of a target detected by the target monitor. Only subscribed when single_target is set to true.

Services Called

• obstacle_detection/get_clear_sector (cpswarm_msgs/GetSector) Get the circular sector that is clear of obstacles.
• area/closest_bound (cpswarm_msgs/ClosestBound) Get the coordinates of the closest boundary in order to reflect from it.

Parameters

• ~loop_rate (real, default: 5.0) The frequency in Hz at which to run the control loops.
• ~queue_size (integer, default: 1) The size of the message queue used for publishing and subscribing to topics.
• ~single_target (boolean, default: true) Whether the algorithm will succeed / terminate once a target has been found.
• ~step_size (real, default: 3.0) The distance in meter that a UGV travels in one step.
• /rng_seed (integer, default: 0) The seed used for random number generation. In the default case, a random seed is generated.

Code API

ugv_random_walk package code API documentation

Changelog for package ugv_random_walk

1.3.0 (2020-01-03)

1.2.0 (2019-12-29)

• Changed: Refactor library structure
• Changed: Read RNG seed from parameter, use random seed otherwise
• Changed: Return state aborted once coverage finishes
• Changed: Check if movement was successful
• Changed: Targets handled by swarm functions library
• Fixed: Correctly handle state of behavior algorithm
• Fixed: Force C++11
• Fixed: Returning of target
• Initial release of ugv_random_walk
• Contributors: Micha Sende