[MBDyn-users] control the type of position constraint in total joint

Andrea Zanoni a.zanoni.mbdyn at gmail.com
Wed Dec 21 13:58:23 CET 2016


Hi Zhenkai,

if you want to change the behavior of the total joint prior to the 
beginning of the simulation, you can use a boolean variable instead of 
the keywords "active" or "inactive".
If you are working on a linux (or OsX) environment, than you can also 
set the value of the variable to match the one of an environmental 
variable.

The case in which you want to change the behavior of the joint during 
the simulation is a bit different and has to be handled though the 
"driven" directive: see section 8.17.2 of the input manual for reference.

Cheers
Andrea

Il 21/12/2016 13:08, Zhenkai Zhao ha scritto:
> hi, guys,
>
> I am using total joint to describe the relative motions of two nodes like below:
>
> joint: JoTotj_Ground_body1,
>          total joint,
>              Node_Ground,
>                  position, reference, Ref_Link1, null,
>                  rotation orientation, reference, Ref_Link1, eye,
>              Node_body1,
>                  position, reference, Ref_Link1, null,
>                  rotation orientation, reference, Ref_Link1, eye,
>              position constraint,
>                  active, inactive, active,
>                  component,
>                  const, 0.,
>                  const, 0.,
>                  const, 0.,
>              orientation constraint,
>                  active, active, inactive,
>                  component,
>                  const, 0.,
>                  const, 0.,
>                  const, 0.;
>
> the part I am interested in is in the position constraint. As you can see in the x direction position constraint, currently it is active, which means there is no DoF in x position.
>
> Is there a way to automatically change 'active' to 'inactive' by using something like If statements or other ways to do that in MBDyn?
>
> Thanks a lot for your help.
>
> Regards,
>
> ZHENKAI ZHAO
>
>
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> MBDyn-users at mbdyn.org
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-- 
---
Andrea Zanoni
Dipartimento di Scienze e Tecnologie Aerospaziali
Politecnico di Milano
Ph. (+39) 02 2399 8035



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