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is there anyway to reduce skidding between the bots wheels and the gazebo world?

asked 2016-04-13 09:07:15 -0500

rajnunes gravatar image

how do i prevent skidding between the wheels of my bot(car like 3 wheels) and the world itself?thanks

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answered 2016-04-13 15:54:10 -0500

pcdangio gravatar image

updated 2016-04-13 16:05:46 -0500

Probably the easiest way is to manually set the coefficient of friction for the wheels in your model's SDF file. Here is a tutorial on how to add friction: http://gazebosim.org/tutorials?tut=fr...

In your case, you might want to set the coefficient to a high number (like 100). The higher you set this number, the less likely your wheels will slip/slide against the ground.

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Some materials have friction coefficients >1 (~1.1), so you can do that. Minor note: friction coefficient of 1+ does not mean it will never slide, but it is very "sticky".

hsu gravatar imagehsu ( 2016-04-13 15:59:02 -0500 )edit

Good catch... in the SDF documentation it says that mu and mu2 must be between 0 and 1. But I just read in the ODE documentation that mu and mu2 can be anything from 0 to infinity (matching real world coulomb coefficients of friction), where infinity means the two objects will never slide.

pcdangio gravatar imagepcdangio ( 2016-04-13 16:04:55 -0500 )edit
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answered 2016-04-13 16:06:11 -0500

hsu gravatar image

updated 2016-04-13 16:07:14 -0500

In addition to setting high friction coefficient, you want to make sure the surface elasticity (kp), damping (kd) and in most cases, allow for minimal interpenetration (min_depth) gives you stable contact without high frequency errors. If contact visualization shows flickering blue line (magnitude of contact force), that indicates the contact is not stable, there are high frequency errors that will cause friction to behave incorrectly. Take a look at this example world of boxes sliding down a 45° incline (tilt gravity):

https://bitbucket.org/osrf/gazebo/src...

Where we get exactly whats expected of friction forces. Another example to demonstrate stable contact by using min_depth:

https://bitbucket.org/osrf/gazebo/src...

Lastly, another more complex example with Atlas feet:

https://bitbucket.org/osrf/drcsim/src...

We modeled (in order of magnitude) after rubber material and got stable contact. When in doubt, start with parameters of real materials, then post back on the forum if you run into more issues.

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Asked: 2016-04-13 09:07:15 -0500

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Last updated: Apr 13 '16