Assignment: ROS

This assignment focuses on ROS (Robot Operating System). ROS is a framework used to program robots. It is quite complicated, however it is widely used on both industrial and commercial settings. Parts to hand in will be noted in italics.

Problem 1: Creating a Publisher and Subscriber (50 points)

Fill in the corresponding sections in the answers.txt in your handin repository and submit the ROS package you create.

  1. Read understanding nodes.

  2. Use rosnode list to display what nodes are running when you start the

  3. Use rosnode info to find out more about each node. What topics does /flow_pub publish?

  4. Do the ROS tutorial to create a package. Name your package ros_assignment_pkg.

  5. Do the building packages tutorial.

  6. Follow the ROS publisher/subscriber tutorial using the workspace and package you created above. Hand in the entire package.

  7. Start the screen session we use to fly the drone. Use rostopic echo and rostopic hz to examine the results of various topics. What is the frame rate we are publishing images from the camera?

Problem 2: Messages (5 points)

Make all modifications in your ROS package from Problem 1 and hand in the package

  1. Read Creating a ROS msg. You do not need to read the section on services.

  2. In your package from question 1, create a ROS message called MyMessage with a field for a string, called name, and a field for an array of float64, called contents. Edit files such as CMakeLists.txt to ensure your message is compiled and available for use. Make these modifications in the package from problem 1 and hand it in.

Problem 3: Reading the IR Sensor (15 points)

  1. Write a ROS subscriber on your drone to read the values from the infrared sensor topic and print them to stdout. Name the file my_echo.py and submit it.

  2. Write a second ROS subscriber that listens to the infrared sensor topic and calculates the mean and variance over a ten second window using NumPy. Print these values to stdout. Name the file mean_and_variance.py and submit it.

Handin

Hand in your answers using this link. Make sure you hand in:

  • answers.txt
  • my_echo.py
  • mean_and_variance.py
  • ros_assignment_pkg: the ROS package you created