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J
JBlackhole16-Pearl
16-Pearl
November 29, 2016
Solved

statespace solver: A & B matrix must be functions (of t)

  • November 29, 2016
  • 3 replies
  • 2147 views

To all,

Made some minor progress in understanding & using the statespace solver.

As my test case is a 2-dofs system I think I have established the matrices required by the solver.

However the solver needs/wants the A & B matrices to be functions (of time in my case) but cannot set it up correctly (see attached). I did find an old thread on a similar issue but cannot open the file

Any suggestion on the correct syntax?

Thanks

Regards

Best answer by AlanStevens

u(t)  must be a 2x1 vector.

A(t) has C and K the wrong way round.

See attached for corrections.

Alan

3 replies

-
-MFra-21-Topaz II
21-Topaz II
November 29, 2016

Hi JB,

But A (t) does not seem to be correctly defined. You should correct it:

At.jpg

J
JBlackhole16-PearlAuthor
16-Pearl
November 29, 2016

thanks

A
AlanStevens19-TanzaniteAnswer
19-Tanzanite
November 29, 2016

u(t)  must be a 2x1 vector.

A(t) has C and K the wrong way round.

See attached for corrections.

Alan

J
JBlackhole16-PearlAuthor
16-Pearl
November 29, 2016

Thanks

u(t): forgot about that

not sure I understand the K and C being inverted in the A matrix as it seems to correspond to the notes

-
-MFra-21-Topaz II
21-Topaz II
November 29, 2016

The Shannon sampling theorem says that the sampling frequency of a time signal, must be equal to or greater than two times the frequency band of the given signal.

Moreover something is wrong with the index i:

sampling freq.jpg

J
JBlackhole16-PearlAuthor
16-Pearl
November 29, 2016

not sure why I cannot convert the predicted solution (using the ODE) inot a sampled vector to be used in the FFT

look like MC doesn't like starting the sampling at i=0. Starting at 1 seems to be OK eventough I get a flat FFT!

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