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NSolve gives correct solution after splitting real and imaginary equations

Bert Aerts
Posted 1 year ago

I have a second order continuous time system transfer function denominator with as roots: enter image description here

Now I want to go to a discrete time system with the equation:

enter image description here

In fact I want to solve following complex equation, making z equal to the pole of a discrete time system with sampling time 0.01 sec: enter image description here

But Mathematica 13.2 gives a huge answer depending on a constant c1.

When I help Mathematica as follows, by splitting real and imaginary equations, it does find the correct solution: enter image description here

How can I adapt the first formula?
POSTED BY: Bert Aerts
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Bert Aerts
Bert Aerts
Posted 1 year ago

I solved it by giving 2 complex equations for 2 unknowns zeta and omegaN, as there are 2 complex conjugate poles. And now Mathematica immediately finds the solution. enter image description here This method also works for 2 real poles: enter image description here Full Mathematica 13.2 notebook:

POSTED BY: Bert Aerts
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