Unstable model with Revolute joint properties?

[Thomas]

https://mail.kaist.ac.kr/Mail?act=BIGFI ... anguage=ko

Here I attached the scene.
shapes are linked with revolute joint and child/parent relationship.
If we increase the mass of cuboid (for example, to 3000kg)
the revolute joint is broken.

I tried to bind them with collection, but it did't work.

That's because of properties of revolute joint ?
But, I could find any dynamic properties of revolute joint about that problem.
Could you explain and help me?

[coppelia]

Hello Thomas,

this is normal with the Bullet or ODE engine: they require to have a mass/inertia ratio that is not too high (i.e. around 1/10 max.) Have a look at this section, mainly the design consideration 7. You will notice that with the Vortex engine (and to a certain extent with the Newton engine too) this constraint can be greatly loosen.

This means, if you still want to use the Bullet engine, then the wheels of your vehicle should also have a much higher mass (e.g. 1500 Kg).

Cheers

[Thomas]

I solved this problem by using Vortex dynamic engine.

Why does it give us different result?

That's because of performance of each dynamic engine?

Then, can we say " Vortex is better than others" ?

[coppelia]

Yes, physics engine have each different strength, properties, or are intended for different applications. Bullet and ODE are usually considered as game engines, since they are fast, quite stable, but less precise and realistic than Vortex (and Newton). But for a game this is usually fine, also for most robot applications.
But yes, Vortex is usually considered as a more realistic and precise engine (for most applications).

Cheers

[martin_simulation]

Hi Thomas,

Solving a physics problem ends up solving mathematical equations.
You can decide to be fast or accurate. In some situation, a lack of accuracy means less reliable results and may lead to instability.
Vortex puts more emphasis to accuracy and hence is usually more stable and reliable.

Martin