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Issue with big model

Issue with big model

Issue with big model

(OP)
I'm trying to simulate in A/View a kind of train consisting of several connected vehicles, with 8 tyres per vehicle. It seems to work fine when I apply no force or motion but the gravity. When the simulation starts it naturally bounds a bit on the floor and finally finds equilibrium. But when I try to set the movement I get miscellaneous errors or lockups. I have tried motions and forces to impose the motion I need, and I get different errors every time. These errors are a kind of random movement of some of the parts, that don't follow their logical movement or physical law...like if the joints exploded.
I don't know the reason of these errors but I guess I may have something to do with the complexity of the model itself (32 tyres, 37 gruebler count, 48 moving parts...) because when I reduce the model to 1 vehicle I can run it without these errors. The model is created in solidworks where the vehicles are built in a parametric way so that the vehicles are supposed to be identical.
Does anyone have an idea of what may be happening or have some heritage in models with a similar complexity?

Any idea or way forward is welcome, and if you are interested (or bored) I can email you the model

Thank you!

RE: Issue with big model

That is not a big model in terms of DOF, but 32 tires is going to be a tedious contact problem to solve unless you have carefully optimised their characteristics.

The typical problem with ADAMS is that you don't get enough of a run to actually see what the problem is. Try running just two or three vehicles and see if that gives you any clues.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Issue with big model

(OP)
Thank you!
The tires are definitely making it tedious. If I remove the wheels there are no errors, whatever motion or constrains I add to the model, and it seems to move well... so it has to do with the tires for sure. Indeed, my feeling is that it has to do with getting them start rolling. But how can I optimize the tires? I'm using a pacejka 2002 tire (from an A/Car default .tir file) which I tunned in stiffness to perform like mine. I know that this tire works in other models, but actually these models have also had some similar errors randomly.

Kind regards

RE: Issue with big model

Ah, that's not quite as bad as I thought. A Pacejka tire is actually a vertical spring from the hub to the ground beneath it. It is not a cylindrical roller.

As such it isn't really a contact problem.

So, back to my suggestion, try two and then three vehicles.

If you can get anything sensible out of 3 vehicles then you are nearly home.







Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

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