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Robot State Publisher outputs negative delays

asked 2011-09-30 02:41:45 -0600

joan gravatar image

I have a doubt regarding the robot state publisher node. I am loading an urdf file validated with the check_urdf. When launching the robot state publisher, I obtain some suspicious values on the Average Delay field.

I am running under Electric version and the launch file I am using looks like the following:

<!-- robot urdf model -->
<param name="robot_description" command="cat $(find robot_base)/model/robot_base.urdf" />

<!-- robot state publisher node -->
<node pkg ="robot_state_publisher"
      type="state_publisher"
      name="robot_state_publisher">
</node>

The tf_monitor outputs this result:

RESULTS: for all Frames

Frames:
Frame: /front_laser published by /robot_state_publisher Average Delay: -0.499885 Max Delay: 0
Frame: /rear_laser published by /robot_state_publisher Average Delay: -0.499884 Max Delay: 0
Frame: /vertical_laser published by /robot_state_publisher Average Delay: -0.499883 Max Delay: 0

All Broadcasters:
Node: /robot_state_publisher 51.2438 Hz, Average Delay: -0.499884 Max Delay: 0

I am not sure if this negative Average Delay values are due to some error or not. When adding a new frame from the odometry node which links to the robot_state_publisher base_link, the Average Delay outputs a more coherent value like 9.61504e-05.

Is everything running as expected or I have some bug on my setup?

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2 Answers

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answered 2011-09-30 12:42:44 -0600

Eric Perko gravatar image

See the tf FAQ for the answer to this. This is normal behavior for certain nodes that timestamp data in the future.

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answered 2011-09-30 03:53:51 -0600

DimitriProsser gravatar image

I receive the same on some of my frames, but it's never caused any problem for me. I believe that it arises due to the publish rate, with the negative value meaning that it is published more often than the delay rate is checked.

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Asked: 2011-09-30 02:41:45 -0600

Seen: 595 times

Last updated: Sep 30 '11