[MBDyn-users] Driver Questions

masarati at aero.polimi.it masarati at aero.polimi.it
Thu May 27 04:02:50 CEST 2010


> Pierangelo,
>
>
>
> I'm using an "array" drive to add an "element" drive to a "streaming file
> drive.  The code segment is as follows.
>
>
>
> Array, 2,
>
>    File, 0, 1,
>
>    Element 5, joint, string, "vx",
>
>       Linear, 0.0, -0.1;
>
>
>
> The joint is a "viscous body", and the element drive acts as a damping
> feedback loop.  This all works well.  My questions are as follows:
>
>
>
> a)  At time-step N, I assume the "element" drive updates its "vx" value to
> be the resultant from time-step N-1.  Yes?

No, it's the current value of "vx" during the iterative solution of the
nonlinear problem.  So it is the (yet unknown) value at time-step N.  In
detail, while computing iteration i of time step N, it is the value of
"vx" at iteration i-1.

> b)  I assume the "element" value "vx" is identical to the value in the
> *.mov
> file for timestep N-1, rotated by the rotation matrix for N-1.  Yes?

No, see above.  At convergence, it will be equal to the value "vx" in .mov
at time N.  During the solution, it is whatever value "vx" has during the
solution at the previous iteration.

> c)  The streaming file driver is specified to update every 33 steps.  Does
> the Array drive update every time-step, even though one of the drives in
> the
> array updates every 33 steps?  Or, does the "array" drive retain its value
> for 33 time-steps until the streaming file drive updates?

The array updates each time it is evaluated.  While updating, it will call
the file driver, and the file driver will not update except every 33 time
steps.  The "element" drive will update each time it is evaluated.

Cheers, p.



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