Tutorial for Mapping

In this tutorial we create a map of an environment using grid mapping from slam_toolbox

Prerequisites

If not already done, install following packages

sudo apt-get install ros-humble-slam-toolbox ros-humble-navigation2 ros-humble-nav2-bringup ros-humble-teleop-twist-keyboard

Make sure you have connected to the wifi network Robile5G. In one of terminals, ssh to the robot (please add these as aliases in ~/.bashrc for convenience)

-  ssh -x studentkelo@192.168.0.101   [while connecting to Robile1]
-  ssh -x studentkelo@192.168.0.102   [while connecting to Robile2]
-  ssh -x studentkelo@192.168.0.103   [while connecting to Robile3]
-  ssh -x studentkelo@192.168.0.104   [while connecting to Robile4]

  • Password (for all robiles): area5142

  • It is recommended to ssh to robot only to launch the robot and to kill the robot. For all other purposes, it is recommended to use the terminal of your system

  • Make sure to set the environment variable ROS_DOMAIN_ID to respective robot id while publishing/subscribing to any ros topics from your terminal. Eg: while using Robile1, export ROS_DOMAIN_ID=1

To launch the robot in simulation, run the following command in a new terminal

ros2 launch robile_gazebo gazebo_4_wheel.launch.py

To launch the real-robot, run the bringup launch file in a tmux session (refer to Demo Communication for more details on tmux). Main steps are as follows,

Create a new session by running the following command in the terminal where the robot’s terminal is ssh-ed (replace session_name with any name of your choice)

tmux new -s session_name

Now run the following command to launch the robot drivers

ros2 launch robile_bringup robot.launch.py

To detach the tmux session, press Ctrl+b and then press d. To attach the tmux session, run the following command (replace session_name with the name of the session you created)

tmux attach -t session_name [or] tmux a -t session_name

Creating a Map

Run mapping node, and move the robot around the environment

ros2 launch robile_navigation online_async.launch.py

If using the robot in simulation, control the robot using teleop keys

ros2 run teleop_twist_keyboard teleop_twist_keyboard

To visualize the robot in rviz2 while using real robot, run the following command in a new terminal. Make sure that the ROS_DOMAIN_ID is set to the respective robile number. For example, for Robile4, it is set to the number 4. Please don’t leave space between the equal sign and the number

export ROS_DOMAIN_ID=4
rviz2

To load the rviz2 config file, click on the Open Config button in the top left corner of the rviz2 window and select the file robile.rviz from folowing path

robile_navigation/config/robile_ros2_nav.rviz

  • Now you should see the map being built in rviz2 while moving the robot around the environment

Saving the Map

Run the map saver: After traversing the map, go to the maps directory under robile_navigation package and run the following command to save the map. In the following command, replace map_name with the name of the map that you want to save

ros2 run nav2_map_server map_saver_cli -f map_name --occ 0.65 --free 0.15 --ros-args -p save_map_timeout:=20.0

This will create two files: a map_name.pgm and map_name.yml. Please use desired name for the map inplace of map_name. Now you can kill the mapping node

Finally, to use the map that you just created you need to check which map will be loaded by the navigation stack

echo $ROBOT_ENV

If it is not same as map_name that you have set, then you need to set the environment variable ROBOT_ENV to the map name that you want to use

export ROBOT_ENV=map_name
Eg: export ROBOT_ENV=map_c069

Note

Environment variables are only set for the current terminal session. ROBOT_ENV needs to be set in the terminal where you are launching the map_server node, which is discussed under localization