Workshop 8 ‐ Mapping

Preliminaries

First, synchronise your fork with the main repository on GitHub (Sync fork) as some structural changes were made and new files were added. Then clone or pull the repository to your local PC and re-open it in the dev container using VSC. Rebuild the updated packages colcon build --symlink-install, and source the workspace source install/setup.bash.

Task 1 - Mapping

• Launch the simulator with the default environment: ros2 launch limo_gazebosim limo_gazebo_diff.launch.py.
• Launch the slam toolbox: ros2 launch slam_toolbox online_async_launch.py use_sim_time:=true.
• Run RViz with the config file from the Limo's navigation toolbox rviz2 -d /opt/ros/lcas/install/limo_navigation/share/limo_navigation/rviz/limo_navigation.rviz.
• Use the teloperation node to drive the robot around and cover the entire environment to complete the map: ros2 run teleop_twist_keyboard teleop_twist_keyboard.
• Save the created map using map_saver: ros2 run nav2_map_server map_saver_cli -f my_map.
• Inspect the created files including my_map.yaml and .pgm. It is a good practice to store these files in the maps folder of your development package (e.g. in cmp9767_tutorial/maps/).
• You can now terminate the slam_toolbox and restart the simulator. To use the newly created map, launch the navigation stack with an additional parameter specifying the map file: ros2 launch limo_navigation limo_navigation.launch.py map:=my_map.yaml use_sim_time:=true. If your map files are stored in the maps folder, remember to source your workspace first and then issue ros2 launch limo_navigation limo_navigation.launch.py map:=src/cmp9767_tutorial/maps/my_map.yaml use_sim_time:=true. Note the performance of the robot localisation component whilst navigating around.

Task 2 - Making Changes

Changes in the Environment

• Modify the simulation environment by adding 2-4 new static obstacles, remap the environment again and save the resulting map. Note the changes in localisation/navigation quality when using the two maps built before and after the modifications.

Changing the slam_toolbox parameters

• Read about the slam_toolbox key parameters.
• A copy of the parameter file for the slam toolbox (mapper_params_online_async.yaml) is stored in the 'cmp9767_tutorial/config' folder. Make changes to some key parameters in that file: e.g. increase the map resolution to 0.01.
• Launch the toolbox with the modified config file: ros2 launch slam_toolbox online_async_launch.py slam_params_file:=src/cmp9767_tutorial/config/mapper_params_online_async.yaml and note the changes to the resulting map. You can just experiment with other parameters and note the behaviour of the mapping toolbox.

Task 3 - The Real Stuff!

• Run the slam_toolbox on the robot, map the lab and use the map with the navigation stack to direct the robot to selected points in the environment. Identify the difficult spots - what might be the reasons for the lower performance in such places?