ros2-docs/docs/General ROS 2/SLAM and Navigation/Nav2.md

Nav2

What is Nav2

Nav2, or the Navigation 2 Stack, is a powerful and flexible navigation framework for robots in the Robot Operating System 2 (ROS 2). It provides a modular set of tools and algorithms for autonomous robot navigation in complex environments.

Starting Nav2 from the Terminal

Here are the terminal commands for launching the Nav2 toolkit.

# Start robot or robot simulator in this case I wil use the turtlebot3
ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py

ros2 launch nav2_bringup bringup_launch.py use_sim_time:=true map:=Desktop/maps/my_map.yaml
# Launch rviz2 and add the TF visualization and the map visualization
ros2 run rviz2 rviz2

Custom Nav2 Launch File

Here is a custom ROS 2 Launch file

=== "Python"

```python title="nav2.launch.py" linenums="1"
from launch import LaunchDescription
import os
from ament_index_python import get_package_share_directory
from launch_ros.parameter_descriptions import ParameterValue
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node
from launch.actions import DeclareLaunchArgument, IncludeLaunchDescription

def generate_launch_description():

	# Declare the arguments
	use_sim_time = LaunchConfiguration('use_sim_time', default='False')
	map = LaunchConfiguration('map')

	# Define RViz config path
	rviz_config_path = os.path.join(
		get_package_share_directory('locker98_tools_bringup'),
		'rviz', 'nav2_config.rviz'
	)

	# Include the bringup launch file
	bringup_launch_file = os.path.join(
		get_package_share_directory('nav2_bringup'),
		'launch', 'bringup_launch.py'
	)

	# Include the bringup launch file and pass arguments
	include_bringup = IncludeLaunchDescription(
		bringup_launch_file,
		launch_arguments={
			'use_sim_time': use_sim_time,
			'map': map
		}.items()
	)

	# RViz node
	rviz2_node = Node(
		package='rviz2',
		executable='rviz2',
		output='screen',
		arguments=['-d', rviz_config_path]
	)

	# Return LaunchDescription
	return LaunchDescription([
		DeclareLaunchArgument('use_sim_time', default_value='False', description='Use simulation time'),
		DeclareLaunchArgument('map', default_value='', description='Map input'),
		include_bringup,
		rviz2_node
	])
```

=== "XML"

```xml title="nav2.launch.xml" linenums="1"
<launch>
    <!-- Declare Launch Arguments -->
    <arg name="use_sim_time" default="false" description="Use simulation time" />
    <arg name="map" default="" description="Map input" />

    <!-- Include bringup launch file -->
    <include file="$(find-pkg-share nav2_bringup)/launch/bringup_launch.py">
        <arg name="use_sim_time" value="$(var use_sim_time)" />
        <arg name="map" value="$(var map)" />
    </include>

    <!-- RViz node -->
    <node pkg="rviz2" exec="rviz2" output="screen">
        <param name="config" value="$(find-pkg-share locker98_tools_bringup)/rviz/nav2_config.rviz" />
    </node>
</launch>
```