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

Lorenz =?utf-8?Q?M=F6senlechner?= moesenle at in.tum.de
Mon Sep 20 19:36:55 UTC 2010


in the TUM ros repository you can find a revamped version of the
robot_state_publisher that publishes the complete tree. You can find it here:



> 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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Lorenz Mösenlechner            | moesenle at in.tum.de
Technische Universität München | Boltzmannstr. 3
85748 Garching bei München     | Germany
http://ias.cs.tum.edu/         | Tel: +49 (89) 289-26910

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