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velocity controller question: updated

asked 2013-09-19 01:58:05 -0500

rnunziata gravatar image

updated 2013-09-23 02:00:14 -0500

Is there a better way to adjust for gravity then adjusting min velocity. I thought PID would control torque to over come gravity but how? Any ideas on how to do this?

update1: I was able to PID and inertia values in the urdf and now I am getting better results. Though I am not sure how to adjust PID values so that lower velocities are favored. Since velocities can sometimes be below threshold needed.

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What is your question?

Boris gravatar image Boris  ( 2013-09-19 01:58:56 -0500 )edit

I updated the question to be more direct.

rnunziata gravatar image rnunziata  ( 2013-09-19 02:33:51 -0500 )edit
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Please stop rewriting the question from scratch every time. It is not a whiteboard to wipe it. Just ADD more details below the original text with the line "EDIT" showing where additional info starts. Otherwise it makes almost impossible for people to track the history of your problem.

Boris gravatar image Boris  ( 2013-09-20 21:08:30 -0500 )edit

sorry. Sometimes my understanding of the problem changes so much. Should I just keep updating as you suggest. Or would it be better to close it and open a new one. Or would either be more acceptable.

rnunziata gravatar image rnunziata  ( 2013-09-21 02:30:31 -0500 )edit

In general, one problem - one question. If you have tried a solution suggested by someone, but there are still issues, then add new info to original question showing what you have tried and what was the result. In case you have questions regarding given answer, then add comments to it (as you did). Once the problem is solved mark the answer as correct.

Boris gravatar image Boris  ( 2013-09-21 02:45:22 -0500 )edit

If a new question arises from your original one (i.e. not more specific details), then leave the original one open and just open a new one.

dornhege gravatar image dornhege  ( 2013-09-21 05:54:26 -0500 )edit

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answered 2013-09-20 06:33:06 -0500

rnunziata gravatar image

I was able to PID and inertia values in the urdf and now I am getting better results. Though I am not sure how to adjust PID values so that lower velocities are favored. Since velocities can sometimes be below threshold needed.

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Please don't add comments as answers.

Adolfo Rodriguez T gravatar image Adolfo Rodriguez T  ( 2013-09-22 21:18:30 -0500 )edit
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answered 2013-09-19 04:22:35 -0500

dornhege gravatar image

Your observation is correct: Given those velocities the robot should be rotating. However in simulation (and reality) there will be a minimum velocity setting that is needed to overcome friction. I suspect that is what's happening. Can you try forcing just higher values that have opposite signs?

For move_base depending on the controller, you might find a parameter like: "min_in_place_rot_vel" that sets this limit and thus will send at least this value.

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I will try but check out my last update to question. I am getting differences in behavior from gazebo and the controller for same values. This is using the Velocity effort controller. I think this may have something to do with pid setting.

rnunziata gravatar image rnunziata  ( 2013-09-19 05:28:07 -0500 )edit

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Asked: 2013-09-19 01:58:05 -0500

Seen: 136 times

Last updated: Sep 23 '13