Homework 4

Logistics

Create a git repository using the link provided in Canvas.
Your homework will be submitted via this git repository.
I will grade whatever is on the main branch when I clone the repository.
Guidelines provides important information about what you should turn-in, including information about your README.md file.

The goal is to use the simulated robot to map an environment and then navigate within the map using the slam_toolbox

Clone the package nubot, which is a package that simulates a mobile robot with a lidar in ignition gazebo into the source space
Your repository will be next to nubot in the source space as well
I purposely did not put a README.md in this package, so you will need to explore it to find out how it works.
HINT: There is one launchfile that runs the simulation and visualizes it in rviz.
HINT: There are two worlds to use, either will be accepted for the assignment but one is significantly smaller (and hence easier to explore).

Going through the First Time Setup Guide to understand how the navigation stack works (up through Setting up the robot's footprint) will be immensely helpful for this homework.
Much of the setup, however, is already done for you in nubot.
By running the launch file in the nubot package you will be able to see what features required by the nav_stack are already implemented.

Your package will be called nubot_nav
In nubot_nav, write a launch file called manual_explore.launch.xml (or you can use a python launch file).
- Starts the nubot simulation.
- Starts slam_toolbox in async mode.
- Starts the nav2 stack (to create cost-maps and also enable navigation).
  - Make sure to set a parameter to increase the footprint of the robot so that it encompasses the whole robot
  - You may use a circular approximation of the robot
- Starts rviz and displays
  - The robot relative to the /map frame
  - The global costmap
  - The local costmap (with the costmap color scheme)
  - The planned path
Record a video of the robot mapping the environment until at least 1 corridor is mapped.

Write a node called explore that causes the robot to explore the environment autonomously while mapping the world.
The launchfile called explore.launch.py (or .xml) should start all the nodes necessary to allow the robot to explore and map its environment
- This launchfile should call manual_explore.launch.xml and then start the explore node.
Use the map_saver_cli in the nav2_map_server package to save the resulting map and place it within the maps directory of the git repository
Record a video of the robot exploring the environment in rviz

You can use any algorithm you want, but it should be described or cited in your README.md.

The exploration does not need to be complete, perfect, or optimal, but it should be generic (so no hardcoding locations that work for this particular room).
The algorithm will ideally enable the robot to explore at least two "rooms" in the environment
- A well-known strategy is called Frontier Exploration.
- See Robot Frontier for a friendly description, in particular Detecting Frontiers
- You can subscribe to the /map topic output by slam_toolbox to get information about the map

The README.md should contain your name, and a description or citation to the exploration algorithm used.
It should also have the ros2 launch commands needed to run the manual and autonomous exploration
It should embed both of the required videos directly in the README so that they can viewed on github