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

[David Lu!!]

Hey Jeff,

I can't answer all of your questions, but robot_state_publisher always
flattens the tree. I assume it's for computational efficiency.

-David!!

On Mon, Sep 20, 2010 at 1:55 PM, Jeff Rousseau <drzaiusx11 at gmail.com> wrote:
> 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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