Introduction and Resources

The goal of this lab is to gain experience using the tf system in ROS. Unfortunately, the Python API for tf is not very well documented on the ROS wiki. Here are some places you can get information:

• Official tf tutorials
• Using Python tf (A ROS wiki page. This is not very complete.)
• The complete API doesn't seem to exist online in any one place. Some information can be found here:
  • tf.Transformer (This is the base class for other tf classes, but isn't often used directly.)

Warmer-Colder: Practicing with tf

• Log into one of the lab computers as Student. connect to a Turtlebot. Complete steps 2 and 3 from the packaging lab to create a new repository and stu and clone it on your local computer. The folder containing your repository should be named "warmer_colder".
• Download and unzip the warmer_colder package: warmer_colder.zip. The package includes a launch file that will start the Turtlebot as well as the sound_play and goal_publisher nodes.
• Copy the contents of the the warmer_colder package into the local clone of your mercurial repository. Assuming that you unzipped the package in your Downloads folder, the steps should look something like this:

  cp -r ~/Downloads/warmer_colder/* ~/catkin_ws/src/warmer_colder/
  

• Add the contents to your mercurial repository:

  cd ~/catkin_ws/src/warmer_colder
  hg add *
  hg commit -m 'First commit.'
  

• You should now be able to complete steps 4.4 and 4.5 of the packaging lab.
• Take a few minutes to read the code in goal_publisher.py and tf_demo.py. Once you understand those files, start the Turtlebot (or gazebo) and execute the warmer_colder launch. If everything is working correctly the robot should say "Howdy" at three second intervals.

• Modify warmer_colder.py so that its behavior matches the documentation.

Submitting

Commit your completed code using the log message "TF LAB FINAL SUBMISSION". Push the results to stu.