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tustin method resutls in an improper function


I’m trying to convert a function from continuous to discrete. The function has more zeros than poles, so like in Matlab I used the Tustin method, but Labview returns an error: an improper function (in attached file).

I want get H-1(z) not H(z-1) for that reason I couldn’t use the Digital Filter Model, that only invert the numerator for the denominator.

If someone can answer my question will be very helpful.

Thanks a lot,



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It must be a long time that you left the university Smiley Very Happy
This is Automatica bases which you miss or which you forgot.
When you use a transfer function system model, the order of numerator is always inferior or equal to the denominator order!
If you have a numerator order most important than the denominator order, the system cannot exist, It doesn't have a physical signification
It's why the control design toolkit returns an error.
This is a very powerful tool but it cannot make miracle.
I think Matlab returns an error too and it's logical.
I don't know what you want to do, but it's seems to be a bad solution.
Best regards

Message Edité par MobyJ le 07-19-2007 10:42 AM

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