Objects repel each other

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lumeqi
Posts: 29
Joined: 04 Dec 2023, 06:20

Objects repel each other

Post by lumeqi »

Hello,
I have two parts with four shafts and four holes respectively, which can complete multi shaft hole assembly. I want to simulate multi axis hole assembly in the simulation. I have set the "Body is responsive" and "Body is dynamic" attributes for them respectively. However, when simulating multi axis hole assembly, they will repel and shake like placing the same level of two magnets together (unable to insert the shaft into the hole). After changing the physics engine, it didn't produce any good results. The engine I am currently using is "Bullet 2.83" because it can complete the grabbing of these two parts by the robotic arm, while other engines have poor grabbing effects. How can I set object properties to simulate multi axis hole assembly?
Thanks.

coppelia
Site Admin
Posts: 10375
Joined: 14 Dec 2012, 00:25

Re: Objects repel each other

Post by coppelia »

Hello,

what kind of shapes are you using to model your two parts? If you use non-convex shapes, this will never be good. You should design your two parts as a compound of primitive shapes (best), or as a compound of convex shapes (not bad either).

The problem when using random non-convex meshes is that the engines won't be able to compute clear penetration depths (required in order to correctly compute repelling forces).

Try to model each part with primitive cylinders, primitive cuboids and primitive spheres. Once done, assemble them into a compound shape.

Cheers

lumeqi
Posts: 29
Joined: 04 Dec 2023, 06:20

Re: Objects repel each other

Post by lumeqi »

Hello,
First of all, thank you for your answer.
The object I am using is my own imported STL model. Is this method of importing external models not recommended? If it is a complex model, I think it will be easier to import it into simulation software after being drawn using professional drawing software than to directly model it using simulation software. If using my own model, how would you like me to make the settings?
thanks

fferri
Posts: 1230
Joined: 09 Sep 2013, 19:28

Re: Objects repel each other

Post by fferri »

Yes you can draw it in external CAD, that it is probably best for mechanics design.

But if you intend to use the model for dynamics simulation, after importing it into coppeliaSim, you have to simplify it, ensure it is convex by doing convex decomposition or approximating it with primitive shapes.

It is all explained in Designing dynamic simulations design considerations 1-2-3.

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