[MBDyn-users] Conditional activation of constraints in a Total joint.

MBDyn users list mbdyn-users at mbdyn.org
Sat Jun 17 23:24:57 CEST 2023


Dejar Pierangelo.

So I will need 2 joints?

Would you please provide an example? What I need is to keep one component
of the position or rotation active up to a certain time, and then
deactivate it for the rest of the simulation. No need to activate it again
after it has been disabled.

 Kind regards.



El sáb., 17 jun. 2023 14:11, MBDyn users list <mbdyn-users at mbdyn.org>
escribió:

> On 17/06/23 18:52, MBDyn users list wrote:
>
> Dear MBDyn users.
>
> I am trying to activate/deactivate components of the constraints of a
> Total joint, as explained in the manual:
>
> "a boolean can be provided in status to indicate that the degree of
> constraint is
> either inactive (0) or active (1); this may be useful, for instance, to
> make constraint activation conditional in parametric input files."
>
> So I have a drive:
>
> drive caller: 1, name,"drive:1", step, 1.0, 0.0, 1.0;
>
>
> and I thought I would be able to use this drive to deactivate the Z
> orientation constraint of a total joint, after one second of simulation
> time, by doing:
>
>
> orientation constraint,
>
> inactive, inactive, string, "model::drive(1, Time)",
>
> single, 0., 0., 1., string, "model::sf::function:20(Time)";
> #<imposed_rotation> [rad]
>
>
> But I get an error: "name expected after type in declaration".
>
>
> Please, what am I getting wrong? Is this because I am using the wrong
> drive?
>
> It doesn't work like that.  You can use a boolean, but it is only
> evaluated at parse time, so no drive caller is allowed there.
>
> To have a joint change by switching off (or on, but that's much trickier)
> one component, you need to define two "driven" elements, identical except
> for the active components, and have one switched off and the other
> simultaneously switched on.
>
> Sincerely, p.
>
>
>
> Thanks in advance.
>
> _______________________________________________
> MBDyn-users mailing listMBDyn-users at mbdyn.orghttps://mail.mbdyn.org/cgi-bin/mailman/listinfo/mbdyn-users
>
>
> --
> Pierangelo Masarati
> Professore Ordinario di Costruzioni e Strutture Aerospaziali
> Dipartimento di Scienze e Tecnologie Aerospaziali
> Politecnico di Milanohttps://www.dona.polimi.it/
>
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