5.3.3 tf/tf2 ros command line tools – static_transform_publisher

Course subject(s) Module 5. Robot Vision

In this lecture, we will explore the static_transform_publisher command line tool.

Let’s go back to the terminal of last lecture. If you took a break in between, or closed it, just open a new one, and restart the factory simulation. Then, open a new CCS, source it, and run the following command:

$ rosrun tf2_ros static_transform_publisher 0 0 0 0 0 0 1 test_parent test_child

Notice, we have called the parent frame test_parent and the child frame test_child. After running the command above, we see a new ROS node is created, that is publishing a static transform. It will keep running until it is killed.

In another new, and sourced, CCS shell, we can see this nod by looking at rosnode list. You should be able to see the node name from the previous command.

Let’s look at the TF tree again by generating a new TF tree PDF file. Before doing that, you might want to rename the old file instead of overwriting it.
$ rosrun tf view_frames

Take a look at the new PDF file:

  • We have a new pair of frames.
  • We also have two root frames: map, and test_parent.
  • This is an example of a disconnected TF tree! This is almost never wanted behaviour with ROS, with it will work fine if you actually want that.
  • For example, the tf_echo will now throw an error between disconnected transforms:
    $ rosrun tf tf_echo test_child base_link

We can actually kill the transform we created at the start, and make a new one between a new TF, and an already existing transform:
$ rosrun tf2 ros_static_transform_publisher 0 0 0 0 0 0 1 map test_child

Then, if we create the TF tree again, we will see that the tree is completely connected again! If we new ask tf_echo to tell us the connections between test_child and base_link, it will be happy to tell us.

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Hello (Real) World with ROS - Robot Operating System by TU Delft OpenCourseWare is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on a work at https://online-learning.tudelft.nl/courses/hello-real-world-with-ros-robot-operating-systems//.
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