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the robot is rotating by iteself without any forces or input. why and how can i stop it ?

asked 2019-07-24 12:18:27 -0500

IamAdi gravatar image

updated 2019-07-24 12:25:35 -0500

https://github.com/AdithyaVenkateshMo...

this above link contains my robots urdf file. the robot is a simple differential drive robot.

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answered 2019-07-24 12:57:54 -0500

bhej gravatar image

updated 2019-07-24 12:59:03 -0500

Try setting friction parameters to the wheel links and ensuring that your wheels have contact with the ground. Otherwise, there is nothing to stop your wheels from rotating. It would be helpful to visualize the wheel contacts in Gazebo and make sure that they are not jittery. If they are, you need to tune your minDepth, kp, and kd tags.

For example:

<gazebo reference="left_wheel">
    <mu1>0.9</mu1>
    <mu2>0.9</mu2>
  <minDepth>0.001</minDepth>
    <kp>100000000</kp>
    <kd>1</kd>
</gazebo>

<gazebo reference="right_wheel">
    <mu1>0.9</mu1>
    <mu2>0.9</mu2>
  <minDepth>0.001</minDepth>
    <kp>100000000</kp>
    <kd>1</kd>
</gazebo>

Guide on Friction: http://gazebosim.org/tutorials?tut=fr...

I would also recommend setting <implicitSpringDamper> to true to get better performance.

<gazebo reference="left_wheel_hinge">
       <implicitSpringDamper>true</implicitSpringDamper>
</gazebo>

<gazebo reference="right_wheel_hinge">
       <implicitSpringDamper>true</implicitSpringDamper>
</gazebo>
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Hi, thanks a lot I tried your suggestions, seems to work but there is still some very small rotations and movements without any forces applied to the bot. I also used the contact-point view to see what's going wrong. it also seems a little jittery. I think I should tune the coefficients little more to probably eliminate it.

Would you have any suggestions on the optimal way to tune coefficients? I can't find a proper explanation on the internet.

Thanks a lot again!!

IamAdi gravatar imageIamAdi ( 2019-07-26 17:33:30 -0500 )edit

I am not sure of an optimal way to tune these coefficients. I have had difficulty tuning them myself and had to resort to some trial and error in finding what works best. It could be helpful to look at this question: https://answers.ros.org/question/3053...

I would also recommend taking a look at the ODE manual and learning more about the friction model, CFM & ERP and how it relates to kp and kd: http://ode.org/ode-latest-userguide.pdf

bhej gravatar imagebhej ( 2019-07-29 11:28:25 -0500 )edit
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Asked: 2019-07-24 12:11:31 -0500

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Last updated: Jul 24