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How do you specify joint location in SDF 1.0 [closed]

asked 2012-11-19 20:55:36 -0500

updated 2014-04-20 14:09:38 -0500

ngrennan gravatar image

Hi all

I'm putting together an arm manipulator My urdf model worked well with rvis and all the joints worked as expected and the kinematics were correct. However I've been trying to convert to SDF1.0 format in order to use plugins but my kinematics are all odd. The joints still have the <origin> tag specified (in order to correctly locate the joint) but even when I modify the pose (which I'm taking to be "x y z r p y", though the documentation is pretty scarce) value, it doesn't change the positioning of the joint.

Any help for converting these files or helping me understand how kinematics are specified in sdf would be great.

Peter

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Closed for the following reason the question is answered, right answer was accepted by PeterMilani
close date 2012-11-29 11:47:39

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answered 2012-11-20 10:40:00 -0500

Okay, got this one to work.

The Joint location is given by the child link origin which is specified as part of the "link " element at the root level. This joint origin needs to be specified in terms of the model origin (my model origin was at 0 0 0 0 0 0) so it could also be the global origin. Therefore you need to work out the positions of the joints initially in this coordinate frame. And it seems to work.

On a side note, this specifying joint locations in this manner is unconventional. The original urdf method of locating the joint in terms of the parent link in the parent links frame is far more conventional and widely used. It requires a lot less initial calculation to boot.

Peter

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I was facing a similar problem, when I converted my urdf ROS file to an sdf file for using my manipulator model in Gazebo. Here is my problem https://answers.ros.org/question/3548...
@PeterMilani can you please help?

aleena_infinitynbeyond gravatar image aleena_infinitynbeyond  ( 2020-06-15 12:17:38 -0500 )edit

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Asked: 2012-11-19 20:55:36 -0500

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Last updated: Nov 20 '12