Stage and navigation stack tutorial

This entry is based on the following tutorial:
http://www.ros.org/wiki/move_base_stage/Tutorials/stage%20and%20navigation%20stack
Following are the elements of the awesomeros package and a small description of their functions.

1. World file: willow.world

It is located at awesomeros/world/willow.world, it is required by stage and it describes the characteristics of the simulation environment.

2. Map server: willow.yaml

Located at world//willow.yaml. A map is required by navigation stack to work on. The yaml file determines the occupancy, resolution and location characteristics of the map being used.

3. Costmaps: they store information about obstacles in the map

3.1 costmap_common_params.yaml: configurations that both costmaps (local and global) should follow.
3.2 global_costmap_params.yaml: configuration of long-term plans over the entire environment.
3.3 local_costmap_params.yaml: configuration for local planning and obstacle avoidance.

4. Base local planner: base_local_planner_params.yaml

It is responsible for computing velocity commands to send to the mobile base of the robot.

5. Navfn: navfn_params.yaml

It provides a fast interpolated navigation function that can be used to create plans for a mobile base.

6. Move_base: move_base.xml

This package lets you move your robot to the desired position using all the previously mentioned nodes of the navigation stack.

7. Amcl: amcl_node.xml

It is a probabilistic location system for mobile robots in 2D.

8. Rviz: rviz.xml and rviz.vcg.

It is a 3D visualization environment

9. Launch file: launch/robot.launch

It acts as a container for all the elements of the package.

Running the launch file and the rviz configuration file lets us set goals in rviz.

The most significant topics published while running this tutorials are the ones of the move_base node.
And the transforms among frames are broadcasted only by stageros and amcl.