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tdrd1-Visitor
1-Visitor
March 8, 2011
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Inverse Laplace problems - MC 14 M020

  • March 8, 2011
  • 2 replies
  • 2843 views

So I'm trying to get MC to find the time-response of a MDOF dynamic system (vibrations problem). I start by defining the transfer function in s-domain and then ask MC to find the inverse Laplace - it doesn't quite do it (see attached).

Interestingly, a friend reports that he DOES get a result on MC 13.

Ideas?

Best answer by AlanStevens

Seems to work if you put in a partial fraction step first.

Alan

Message was edited by: AlanStevens The float 5 I used leads to some numerical inaccuracies, which is why there are some complex coefficients in the result. Changing this to, say, float 15 eliminates the complex terms. However, there are still some small amplitude (real) terms remaining that should surely be zero. Of course, you don't need to use the float command at all!.

2 replies

ValeryOchkov24-Ruby IV
24-Ruby IV
March 8, 2011

Sorry but I think answers on same questions must generate automatically - Mathcad 14/15 has new symbolic engine not from Maple but from MuPAD.

See for example http://communities.ptc.com/message/160505 and others same.

AlanStevens19-TanzaniteAnswer
19-Tanzanite
March 8, 2011

Seems to work if you put in a partial fraction step first.

Alan

Message was edited by: AlanStevens The float 5 I used leads to some numerical inaccuracies, which is why there are some complex coefficients in the result. Changing this to, say, float 15 eliminates the complex terms. However, there are still some small amplitude (real) terms remaining that should surely be zero. Of course, you don't need to use the float command at all!.

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