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## title = Setup the Navigation Stack for TurtleBot
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## description = Provides a first glimpse of navigation configuration for your robot, with references to other much more comprehensive tutorials.
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<<TableOfContents(4)>>

This tutorial doesn't pretend to be a comprehensive guide for fine tuning TurtleBot navigation, as the [[navigation/Tutorials|navigation tutorials]] do a great job on this. Here we just provide some useful how-tos and tricks that !TurtleBot users sometimes ask. The idea is to save your time, avoiding you the need of digging in the abundant existing documentation!

== Key files ==

The !TurtleBot navigation is ruled (as in almost any other ROS robot) by a combination of launch and yaml files. Both are contained on [[turtlebot_navigation]] package, on launch and param directories respectively.

== Move base ==

!TurtleBot navigation motion is generated by [[move_base]], who maintains a global and a local cost maps so it can create global and local plans. Its behavior is defined on param/move_base yaml files, three for cost maps and base_local_planner_params.yaml for the planner. [[costmap_2d]] configuration is quite tricky, and in most cases is driven by the need of balance between cpu usage and performance, so we will not mention here.

=== Planner ===

 * Change speed limits:
  *  max_vel_x: maximum linear velocity; absolute limit for !TurtleBot 1 is 0.5, and 0.7 for !TurtleBot 2
  *  min_vel_x: minimum linear velocity; maybe you will need to increase when caring heavy loads, in case the robot cannot beat friction at minimum speed
  *  max_rotational_vel: maximum angular velocity; absolute limit for !TurtleBot 2 is 3.14 (not sure for !TurtleBot 1; ''can anyone fill this?'')
  *  min_in_place_rotational_vel: same comment as for minimum linear velocity

 * Goal tolerance. These two parameters allow you to make !TurtleBot more or less accurate when reaching its goal. '''Be careful: very low values can make the robot move around the goal without reaching it!'''
  * yaw_goal_tolerance
  * xy_goal_tolerance
 
 * Cost computing biases. These three parameters define the preference of !TurtleBot when following its global plan:
  * path_distance_bias: increase to make the robot follow the plan more closely
  * goal_distance_bias: increase to make the robot trajectory smoother and more efficient
  * occdist_scale: increase to make the robot more afraid to hit obstacles

== Amcl (localization) ==

!TurtleBot localization is provided by [[amcl]]. You can tweak this algorithm by modifying parameters on launch/includes/_amcl.launch file. But this is not basic stuff, and so out of the scope of this tutorial.

== Gmapping (map building) ==

!TurtleBot maps are build with [[gmapping]]. You can tweak this algorithm by modifying parameters on launch/includes/_gmapping.launch file. But again, this is out of the scope of this tutorial.

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