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Strange numbers in "Create your own urdf file" URDF's tutorial

asked 2017-12-24 23:15:24 -0500

SerSav gravatar image

Hello! I recently started studying ROS and now I'm considering this tutorial

I don't understand how the axis xyz values (from Completing the Kinematics) was calculated. The follow values are given at first:

  <axis xyz="0 1 0" />

for joint2 and

<axis xyz="-0.707 0.707 0" />

for joint1.

But after that in the general .XML file are given:

 <axis xyz="-0.707 0.707 0" />

for joint2 and

<axis xyz="-0.9 0.15 0" />

for joint1.

As i know vectors for axis xyz should be normalized, but "-0.9 0.15 0" is not normalized. What are the correct values? Thanks.

I use Ubuntu 16.04 and ROS kinetic.

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Just divide each each component by the magnitude. Then, perhaps, you can update the wiki to help others out.

jayess gravatar image jayess  ( 2017-12-26 11:02:16 -0500 )edit

I think it's an error since 0 1 0 is already normalized. It should be 0 1 0 in my opinion.

Airuno2L gravatar image Airuno2L  ( 2018-01-26 06:46:40 -0500 )edit

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answered 2018-01-26 05:31:09 -0500

nd gravatar image

According to my view it depends on your joint type if it is revolute or translational joint. Ex. if your joint is revolute and axis of rotation is around z axis, simply put

<axis xyz="0 0 1"/>

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Asked: 2017-12-24 23:11:28 -0500

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Last updated: Jan 26 '18