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Crazy behaviour from a simple "board-like" model

asked 2016-09-20 19:27:24 -0500

wicked88 gravatar image

Im building a more complex model but i created a simple one to start. It has a very weird behaviour that i documented by video so you can all give your opinions !! VIDEO ---------> VIDEO

In the video it is visible the SDF for the model. I made my world setup using this:

<physics type='ode'>
  <gravity>0 0 -9.8</gravity>

But works the same way with or without it. May be its STL related ? Can figure it out.

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answered 2016-09-20 19:59:54 -0500

chapulina gravatar image

It looks like the center of mass is below the ground. You can check it by choosing View -> Center of Mass

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yea your inertia is also probably wrong

Peter Mitrano gravatar imagePeter Mitrano ( 2016-09-21 00:16:01 -0500 )edit

Yes you are right @chapulinha ! How do i change the center of mass ??? Also, any way to correctly compute the inertia of something ?

wicked88 gravatar imagewicked88 ( 2016-09-21 04:56:36 -0500 )edit

Take a look at the inertial SDF syntax: There are also many examples here: This page has good info on moments of interia:

nkoenig gravatar imagenkoenig ( 2016-09-21 08:47:44 -0500 )edit

Thank you all for your answers ! I've already corrected my center of mass of the models and the building is going fine, no odd stupid behaviours now. Although, i still didnt manage to work on my values for the moments of inertia which are crucial to obtain a truthful simulation

wicked88 gravatar imagewicked88 ( 2016-09-21 09:27:09 -0500 )edit

This tutorial might help you with the inertias:

chapulina gravatar imagechapulina ( 2016-09-21 09:42:06 -0500 )edit
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Asked: 2016-09-20 19:27:24 -0500

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Last updated: Sep 20 '16