[ros-users] URDF -> robot_state_publisher -> TF confusion

[Jeff Rousseau]

Hi All,

Attached is the output of 'rosrun tf view_frames' showing the
transforms being published by robot_state_publisher based on the URDF
for my iRobot Create (also attached) as well the output of "rosrun
urdf urdf_to_graphiz irobot_create_full.urdf.xacro" showing the links
and joints that make up my URDF.

I'm a bit confused as to why these two trees don't match. Why is
'robot_state_publisher' flattening the URDF tree and rearranging some
connections when outputting to TF? According to the URDF base_link
should be the parent of base_link_left/right_motor_link and the motor
links should be the parent of the wheel links...

I think this is related, but not entirely sure: when I add the model
to rviz I get the following warnings:
----------
caster_wheel_link
No transform from [caster_wheel_link] to [/map]

base_caster_support_link
No transform from [base_caster_support_link] to [/map]
----------

Any input, ideas as to whats going wrong/what I'm doing wrong?
(my guess is that I'm making an incorrect assumption that there is a
1-to-1 correspondence between how gazebo and ros handle coordinate
frames)

PS on a slightly unrelated note: tf_frames.pdf shows gazebo publishing
the /odom topic at 100hz, is there a way to change this rate? I'm
trying to squeeze as many cycles out of my old hardware as I can, so
I'm trying to avoid over-publishing on my topics to cut down CPU usage
(as it is now gazebo in 'top' is claiming 90-100% of my cpu).  I tried
adding a < param name="publish_frequency" type="double" value="10.0"
/> to fake_localization node in my launch file, but it didn't take...

Jeff
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