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URDF joint limititations

asked 2014-06-13 16:49:33 -0500

cmeaclem gravatar image

updated 2014-06-19 00:52:21 -0500

gvdhoorn gravatar image

Hi all,

I have a SolidWorks model of my robot which I have been able to get into RVIZ/MoveIt. This is tested and generally works well.

Now I need a more accurate model, one feature of which is to properly constrain my joint angles. In the initial model the angles were set up to move between [-pi,pi] which was arbitrary and does not represent the range of motion of the actuators. These constraints were crudely configured by setting them in the URDF exporter plugin. But now I want to limit the joints to what I have configured in SolidWorks using the mates.

In SolidWorks I have setup mates that constrains the joints to the region I want using the "Limit Angle" advanced mate. Whilst this constraint works nicely in SolidWorks, allowing me to move the joints within the correct region, i have not been able to get this same functionality into ROS/URDF.

Ideally I would like to import these mates automatically so that if/when i change the model, this is updated in the URDF upon exporting. Is there a way to do this or am i stuck with manually setting these limits each time in the exporter tool?

Regards and thanks in advance,

Chris.

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answered 2014-06-19 00:51:30 -0500

gvdhoorn gravatar image

updated 2014-06-19 00:53:42 -0500

Is there a way to do this or am i stuck with manually setting these limits each time in the exporter tool?

I'm not sure whether the plug-in can base the urdf limits on the limits of the mates, but as long as you save the export configuration after you've set it up, you should not need to re-set any of those limits again. Re-opening the exporter should pick up on the saved limits.

One thing I've been doing in the past is to write a simple Python script that updates the joint limits in the urdf based on a text file. This makes it very easy to update them, without needing to redo the export in SolidWorks every time you change something (it becomes even easier if you generate the text file from data gathered from your control system fi).

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+1 to the idea of python script to update -- I do that too, and to add missing things like velocity and effort limits.

fergs gravatar imagefergs ( 2014-06-19 22:46:27 -0500 )edit

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Asked: 2014-06-13 16:49:33 -0500

Seen: 473 times

Last updated: Jun 19 '14