[MBDyn-users] Initial assembly phase fails if tolerance is too small: Param_Manip(): divide by zero, probably due to singularity in rotation parameters

Pierangelo Masarati masarati at aero.polimi.it
Wed Apr 11 18:48:46 CEST 2012


On 04/11/2012 04:07 PM, Resch Reinhard wrote:
> Dear Mr. Masarati,
>
> I believe that there is a bug somewhere in the initial assembly code.
>
> If you run the model in the attached file with a initial assembly tolerance of 1e-16 the simulation works fine.

The model assembles correctly with all residual coefficients == 0 and 
only one O(1e-17)

> But if you decrease the initial assembly tolerance to 1e-20 the initial assembly procedure diverges.
>
> Finally I get this error message: Param_Manip(): divide by zero, probably due to singularity in rotation parameters

The error is not specifically meaningful; the reason is that all the 
solution elements grew to 1e+<large value> and thus the orientation 
parameters result in a division by zero.  I believe there is no point in 
setting the tolerance to such a small value.  Indeed there might be a 
bug somewhere in the procedure, but I do not see it as critical.  I'd be 
willing to fix it if you can help singling it out, though.

Cheers, p.

-- 
Pierangelo Masarati
Associate Professor
Dipartimento di Ingegneria Aerospaziale
Politecnico di Milano


More information about the MBDyn-users mailing list