ROS package implementing a 2D exploration framework for 3D mapping with RGBD camera(s).

It works along with the rtabmap_ros ROS package. More information and instructions in their Github page.

It can work with any RGBD camera (and laser scan) configuration allowed in rtabmap_ros. The point cloud ground projection is used for exploration purposes.

This framework allow to choose many strategic decision from command line.

When should the robot replan a new navigation goal? Many replanning conditions can be selected such that if any of them is met, a new evaluation of the frontiers is performed to choose the next exploration target. Current conditions:

• not_moving: The robot is currently not heading to any goal.
• too_much_time_near_goal: Spending too much time near the goal. It votes for replanning if the robot has spent some time near its current goal and it's properly oriented with the goal.
• isolated_goal: The goal is not close to any frontier. It is activated when none of the cells in an arbitrary large neighborhood of the goal corresponds to a frontier.

Which is the cost function for evaluate a frontier as a exploration target? It is described by a weighted sum of frontier evaluation functions. Current frontier evaluation functions:

• Maximum size: It favors larger frontiers over smaller ones.
• Minimum euclidean distance: It favors frontiers which are closer to the robot position, regardless of the obstacles in between.
• Minimum A distance*: The function favors the frontiers with shorter distances, taking as distance the path found by A* algorithm.

Once a frontier is selected, where should the robot go exactly? The function to find a proper 2D navigation point from a frontier is a parameter of the ROS parameter server. Currently one single goal selection function is used:

• Mid point: Selects a navigation goal from where the middle point of the frontier is visible.

The file standard/config.yaml contains an example file containing a possible configuration.

To use this package rtabmap_ros has to be configured according to your robot. Example files are contained in the launch folder. Once the package is compiled and visible for your ROS system and rtabmap is running, launch the cam_exploration node:

roslaunch cam_exploration cam_exploration.launch