I can not zero my transfer function

how do you do this ?

[Stephan]

Why did you delete the question? How do i do what?

Answer 1

[Stephan]

Hi,

i assume you want to use zero instaed of zeros. The first is for control - the second creates an array of all zeros, which makes no sense in your context. Also note that you wrote

z=zero(Tfx)

instead of

z=zero(TFx)

Both is fixed here and works:

clear all
close all
clc
syms X Y s    
F1 = (5*s^2+12*s+5)*X-(8*s+4)*Y;  %laplace by hand
F2 = (3*s^2+8*s+5)*Y-(8*s+4)*X-(5/s);
[A B] = equationsToMatrix([F1 F2],[X Y]);
sol = inv(A)*B;
x = sol(1);
y = sol(2);
[Numx,Denx] = numden(x);
[Numy,Deny] = numden(y);
Nx = sym2poly(Numx);
Dx = sym2poly(Denx);
[r p k] = residue(Nx,Dx)
TFx = tf(Nx,Dx)
xp=poles(x)
yp = poles(y)
z=zero(TFx)

Best regards

Stephan