LMS Virtual Lab Query

[morris9791]

Dear Folks,

I am currently learning to use LMS Virtual.Lab software. I am starting off by working on simple models. The analysis type is kinematics. This requires that the number of independent constraint equations must equal the number of generalized coordinates in the model.
My model consist of 2 parts joined together by a bracket joint in addition to the 'globalfixedtogroundbody'.
After solution failure, I get the following information from the .info file


>>>>>>Warning: Prior to assembly the number of constraints, drivers and
initial conditions is not equal to the number of generalized
coordinates. The assembly algorithm will be executed but the
result will represent one of several possible solutions.
Number of constraints, drivers, I.C's = 22
Number of generalized coordinates = 28

Does anyone know of a good source where I can begin to understand this information.

Any information will be appreciated.
Kind regards
Ed

 

[GregLocock]

Just guessing but I'd say you have one rigid body that is completely unconstrained. There are other possibilities. If you can write out a text file dump of your model then post it here. LMS may not let you do that.

Any mechanics/dynamics/theory of mechanisms textbook should give you a basic understanding of that error message.

You might do better asking about kinematic models on the LMS forum, or the ADAMS one, or mechanical engineering.






Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

It was quite a while ago, but I used to be an ADAMS guru (c. 1990-1994). At that time DADS & ADAMS both claimed to be able to remove over-constraints. I didn't believe it for one second. An ADAMS/DADS modeller needs to be acutely aware of constraints.

- Steve

 

[morris9791]

Thanks guys,

I didnt realise there was a LMS forum, although it looks pretty dormant to me! Instead I have sent another query to the Adams forum.

Thanks for your help.
REgards
Ed

 

[Rob45]

Ask your friendly local LMS sales guy, or their tech support; both have proved extremely helpful to me in the past.