Homework 4B - More Robot Operating System (ROS)

NOTE: This assignment, like others in this class, is due at the beginning of the class period. This means that if you are even a minute late, you lose 20%. If you are worried about potentially being late, turn in your homework ahead of time. Do this by submitting them to me during office hours or by sliding it under my office door. Do not send assignments to me through email or leave them in my departmental mail box.

As discussed in class, we will be using the Robot Operating System (ROS) in conjunction with TurtleBots in the course this semester. The point of this homework is to take you through some tutorial exercises to help you learn some of the basic features of ROS and TurtleBots. Note that, as with Homework 3, you will not be programming any robots in this homework. However, you will get to drive them around in simulation a bit!

Work through the listed ROS tutorials, completing the following exercises as you go. (Note that you may use the CSN computers in DEH 115 to complete this assignment or you may use your own computer. If you choose to use your own computer, you will need to install ROS Hydro (following the ROS Hydro Installation Instructions) before completing these exercises (or use a virtual machine such as the one prepared by Nootrix).

As you complete these exercises and add items to your completed assignment, number them to correspond to the numbering below as you did with Homework 3 and 4. Note that not all exercises will result in answers being added to your completed assignment.

3. Work through the tutorial on building a map in the TurtleBot simulator. Note that when you try to launch the TurtleBot playground world, many of the models may fail to load. If any model fails to load, download and install it manually by doing the following:

   wget http://gazebosim.org/models/<model_name>/model.tar.gz (where <model_name> is the actual name of the missing model.

   tar xvf model.tar.gz -C ~/.gazebo/models

   rm model.tar.gz

   For example, if the dumpster model fails to load, do this:

   wget http://gazebosim.org/models/dumpster/model.tar.gz

   tar xvf model.tar.gz -C ~/.gazebo/models

   rm model.tar.gz

   As you work through the tutorial, don't customize the simulated TurtleBot — just use it as it is in the launch file.
1. When the Gazebo window appears, position it such that you have a good view of the robot and all of the obstacles in the environment, then do a screen capture of it and include this in your completed assignment.
2. When the RViz window appears, position it such that you have a good view of the robot at about the same scale as the robot in the Gazebo window, then take a screen capture of the RViz window and include that in your completed assignment.
3. Drive the robot around using the keyboard to construct the best map that you can of the environment. Make sure to drive on all sides of all objects in the environment. Then take another screen capture of the RViz window to show the map and include that map in your completed assignment.
4. In your completed assignment, label the screen-captured map from RViz to show the space that is occupied (occluded), empty (free), and unknown. Also label each obstacle with its type.
5. Be sure to save the map you have created in a form that ROS can use (using rosrun map_server map_saver -f <your map name> as instructed in the tutorial). Note that you will include the saved map files (.pgm and .yaml) in your electronic submission in D2L but you won't print them out for your hard copy. Then close out all of your running ROS/Gazebo processes and move on to the next tutorial.


4. Work through the tutorial on autonomously navigating a known map with a TurtleBot. However, note that you will be using a simulated TurtleBot for this assignment. So, rather than bringing up the TurtleBot, you will run Gazebo as with the previous tutorial.
   1. When the RViz window appears, position it such that you have a good view of the robot and the map, similar to screen-captured map you have already included in your completed assignment for Part 3, above. Take a new screen capture of the loaded map from RViz and include it in your completed assignment.
   2. Explain the various colors that surround the obstacles in the loaded map in RViz.
   3. Explain the cluster of green arrows around the robot in RViz.
   4. Tell the robot its current (starting) position (location and orientation), following the instructions for how to do so in the tutorial.
   5. Give the robot a goal position, following the the instructions for how to do so in the tutorial. This position should be within the map you created for the robot but not inside (or extremely close to) one of the obstacles.
   6. Observe the robot as it moves and explain the red and blue lines that appear before the robot as it moves.
   7. Take a screen capture of the robot at the goal location and include this in your completed assignment.
   8. Give the robot another goal position. This position should be in the unknown space on your map, outside of the free space. Take a screen capture of the robot after it executes this command and explain whether the robot was able to reach this goal.
   9. Give the robot a third goal position. This position should be inside one of the mapped obstacles. Take a screen capture of the robot after it executes this command and explain whether the robot was able to reach this goal.

Turn in both an electronic copy (via D2L) and a hard copy of this assignment.