tustin method resutls in an improper function

[clear]

Hi,

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,

Clear

[MobyJ]

Hi,
It must be a long time that you left the university
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
MobyJ

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