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Trajectory filters and joint limits over PI

asked 2011-03-13 15:06:49 -0500

arebgun gravatar image

Hello folks,

I ran into trouble with some of the assumptions that trajectory filters make. I have a servo motor that can do 250 degrees of travel, e.g. it's not a continuous servo. I would like to position it in such a way that the joint limits are, for example, -40 to 210 degrees. The problem is that if some trajectory wants to put this joint at anything over 180 degrees it will want to wrap around, but servo won't be able reach that position for obvious reasons. Is there a way around that?

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answered 2011-03-13 15:42:00 -0500

There is at least one bug that I found in planning_environment related to this. Here is a link to the ticket and the patch: https://code.ros.org/trac/ros-pkg/ticket/4741

Although the patch is for cturtle, a quick check confirms that the bug may still exist. Also, I do not use the standard trajectory filters in my use case, so your mileage may vary.

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Mrinal, you are right, that ticket describes the problem I am having and it looks like the attached patch should fix it. I would need to fix a bunch more packages for this to work properly. I was wondering why motion planner thinks a joint angle was at -3.00 radians when it was definitely over +3.00, that would be why :)
arebgun gravatar imagearebgun ( 2011-03-13 15:53:48 -0500 )edit

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Asked: 2011-03-13 15:06:49 -0500

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Last updated: Mar 13 '11