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tf: Lookup would require extrapolation into the past

asked 2014-07-28 10:56:03 -0500

rkeatin3 gravatar image

I've written the following method for returning the homogeneous transformation matrix between two tf links:

Eigen::Matrix4f getTransformation(std::string parentName, std::string childName){
  parentName.insert(0,"/");
  childName.insert(0,"/");
  tf::StampedTransform transform;
  tf::TransformListener listener;
  ros::Time t = ros::Time::now();
  try{
    listener.waitForTransform(parentName, childName, t, ros::Duration(4.0));
    listener.lookupTransform(parentName, childName, t, transform);
  }
  catch (tf::TransformException ex){
    ROS_ERROR("%s",ex.what());
  }
  tf::Matrix3x3 rot = transform.getBasis();
  tf::Vector3 trans = transform.getOrigin();
  Eigen::Matrix4f tranformation = Eigen::MatrixXf::Identity(4,4);
  Eigen::Matrix3f upleft3x3;
  upleft3x3 << rot[0][0], rot[0][1], rot[0][2],
               rot[1][0], rot[1][1], rot[1][2],
               rot[2][0], rot[2][1], rot[2][2];
  tranformation.block<3,3>(0,0) = upleft3x3;
  tranformation.col(3) = Eigen::Vector4f(trans[0],trans[1],trans[2],1);
  return transformation;
}

When I try to use this method, I get the following error:

Lookup would require extrapolation into the past.  Requested time 1406560524.442721448 but the earliest data is at time 1406560524.444821575, when looking up transform from frame [wrist_3] to frame [base_link]

I tried the solution suggested by Martin Günther on this page, but that just resulted in an infinite while loop.

Adding a ros::Duration(1) to the requested time worked, but obviously that isn't ideal. Any other solutions?

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Comments

When does this happen? Once at the start or all the time?

dornhege gravatar imagedornhege ( 2014-07-28 10:59:26 -0500 )edit

I get the error whenever the function is called.

rkeatin3 gravatar imagerkeatin3 ( 2014-07-28 11:23:10 -0500 )edit

1 Answer

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answered 2014-07-28 12:22:05 -0500

courrier gravatar image

You should ask for the last known transform with Time(0) instead of Time::now()

  ros::Time t = ros::Time(0);
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Comments

That worked. Thanks!

rkeatin3 gravatar imagerkeatin3 ( 2014-07-28 13:23:14 -0500 )edit

Check out this tuto http://wiki.ros.org/tf/Tutorials/tf%20and%20Time%20%28C%2B%2B%29 for details about tf and times

courrier gravatar imagecourrier ( 2014-07-28 16:27:03 -0500 )edit

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Asked: 2014-07-28 10:56:03 -0500

Seen: 12,896 times

Last updated: Jul 28 '14