Running PR2 in Gazebo; 2dnav gives TF errors

asked 2012-01-24 10:50:37 -0500

Ibrahim
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Hi, I'm trying to test some software I wrote in simulation before running it on the real PR2. I created a little Gazebo world that is a somewhat accurate representation of my workspace, and I launch it and it works fine for the most part. I can launch pr2_2dnav_slam.launch and teleop the simulated PR2 around to generate a map of the area. Then I save the map, and I want to load it as a static map using a map_server and then launch the nav stack. However, at this point the nav stack starts throwing a bunch of TF errors that all basically look like

[ERROR] [1327451804.285384190, 15.638000000]: Transform unavailable Lookup would require extrapolation into the past. Requested time 15.288000000 but the earliest data is at time 15.508000000, when looking up transform from frame [/base_footprint] to frame [/base_link]

and becomes basically unusable. I have set ROBOT=sim and I'm using https://code.ros.org/svn/wg-ros-pkg/stacks/wg_robots_gazebo/trunk/pr2_2dnav_gazebo/2dnav-stack-amcl.launch to launch the nav stack which should ensure that it's using the simulated PR2.

Any ideas on what could be wrong? Thanks!

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I do see the same error a couple times on startup, but the error stops and things work correctly. Do you see a continuous stream of the error message?

hsu ( 2012-01-24 13:18:15 -0500 )edit

I didn't try that one, I'll try it out now. For me I get the errors only at the beginning but then I can't actually do anything with the nav stack at that point (eg. I tried publishing an initial pose to localize, didn't work, etc).

Ibrahim ( 2012-01-25 08:08:25 -0500 )edit

Oh thanks! Starting everything together makes it work. I'm guessing I didn't set use_sim_time properly for the other nodes?

Ibrahim ( 2012-01-25 08:41:57 -0500 )edit

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answered 2012-01-24 13:15:37 -0500

hsu
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did you try the launch file: https://code.ros.org/svn/wg-ros-pkg/stacks/wg_robots_gazebo/trunk/pr2_2dnav_gazebo/pr2-empty-amcl.launch for starting everything together?

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answered 2012-01-25 10:12:54 -0500

This post is a wiki. Anyone with karma >75 is welcome to improve it.

John's suggestion "did you try the launch file: https://code.ros.org/svn/wg-ros-pkg/stacks/wg_robots_gazebo/trunk/pr2_2dnav_gazebo/pr2-empty-amcl.launch for starting everything together? - hsu (20 hours ago)" worked.

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answered 2012-01-25 12:38:07 -0500

hsu
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updated 2012-01-25 12:38:56 -0500

Looking at pr2-empty-amcl.launch:

<launch>

  <!-- start up empty world -->
  <include file="$(find gazebo_worlds)/launch/empty_world.launch"/>

  <!-- start up robot -->
  <include file="$(find pr2_gazebo)/pr2.launch"/>

  <!-- Tug Arms For Navigation -->
  <node name="tuckarms" pkg="pr2_tuckarm" type="tuckarm.py" args="b" output="screen" />

  <!-- load map -->
  <node name="map_server" pkg="map_server" type="map_server" args="$(find gazebo_worlds)/Media/materials/textures/map_blank.png 0.1" respawn="true" />

  <!-- nav-stack -->
  <include file="$(find pr2_2dnav_gazebo)/2dnav-stack-amcl.launch"/>

  <!-- for visualization -->
  <include file="$(find pr2_navigation_global)/rviz/rviz_move_base.launch"/>

</launch>

Is it possible that you didn't launch one of the nodes? If you launch each of these nodes by hand, does the navigation stack work for you?

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Running PR2 in Gazebo; 2dnav gives TF errors

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