yade-users team mailing list archive

[chiara modenese <c.modenese@xxxxxxxxx>]

2010/4/19 Václav Šmilauer <eudoxos@xxxxxxxx>

>
> >
> > Yes, I confirm (by myself :-) ) that doing so we account for the
> > applied displacement twice. Actually this fact is already documented
> > and avoid in JumpChangeSe3 class. Maybe we can add a comment also in
> > TranslationEngine so that if one wants to use it on dynamic bodies, it
> > knows that in such a way you apply the displacement (giving velocity
> > as input) twice.
> > Actually I do not see another way to apply TranslationEngine to
> > dynamic bodies avoiding this problem. In fact, one could use
> > JumpChangeSe3 on dynamic bodies as well, but not using ScGeom since it
> > needs velocities.
>
> There is actually https://bugs.launchpad.net/yade/+bug/398089 which is
> closely related.
>
> Reading JumpChangeSe3 (wouldn't it be better to call it StepChangeSe3,
> or rather StepChange... something else?) code, positions are updated "by
> hand"
>
>  if(!setVelocities || (setVelocities && !b->isDynamic))
>
> i.e. either (1st case) NewtonIntegrator will not update position because
> velocity is zero, or (2nd case) NewtonIntegrator will not update
> position because the body is not dynamic.
>
> TranslationEngine doesn't make this distinction, it wasn't really
> (probably) conceived for such fine-grained control.
>

I personally think this is a very basic task, so we should be able in Yade
to run a simulation in displacement control (totally working, I mean). Any
advice how to do that? Say that one simply wants to apply a displacement
(fixed or whatever) at each time step being the bodies dynamic..

cheers, Chiara



>
> One could add a flag to JumpChangeSe3 so that the delta wouldn't mean
> delta in one timestep, but in 1 second; that would make it functionally
> superset of TranslationEngine actually.
>
> (I was also planning -- or I've written but never commited --
> interpolating engine between start and end position&orientation for a
> particle....)
>
> Cheers, v.
>
>
>
>
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