Added Diff drive example

[ahcorde]

Signed-off-by: ahcorde ahcorde@gmail.com

🎉 New feature

Summary

Added Diff drive example

Test it

In one terminal:

ros2 launch ign_ros2_control_demos cart_diff_drive.launch.py

in other terminal:

ros2 run ign_ros2_control_demos example_diff_drive

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[mjcarroll]

Since this is 2-D odometry, I believe the convention is to zero out the covariance for z, roll, pitch, y_dot, and z_dot.

Suggested change

	pose_covariance_diagonal : [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]
	twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]
	pose_covariance_diagonal : [0.001, 0.001, 0, 0, 0, 0.01]
	twist_covariance_diagonal: [0.001, 0, 0, 0, 0, 0.01]

[mjcarroll]

Not to be addressed here, but do you know why these aren't ROS parameters versus command line arguments?

[ahcorde]

To be honest I don't know, but maybe because the compatibility between ros and ros2 it's easy and it's a ignition tool more than a ros. Just guessing

[mjcarroll]

Tested with ROS 2 Foxy and Ignition Fortress and the diff drive controller example works as expected. I just have the one comment about the covariance and this should be good to go.