Z domain to freq domain (bode of closed loop with negative feed back)?

I just want to continous time domain freq response with discrete time freq response closep loop with negative feedback. But i dont know how to go from z domain to frequency domain analytically

Answer 1

[Star Strider]

If you have the Symbolic Math Toolbox, try this:

syms z s Fs
assume(Fs > 0)
H(z) = (z + 1) / (z^2 + 10*z - 5);                      % Create Transfer Function
BilTrns = s == 2*Fs * (z-1)/(z+1);                      % Bilinear Transform, s —> z
Bz = solve(BilTrns, z);                                 % Bilinear Transform, z —> s
H(s) = H(Bz);                                           % Substitute
H(s) = simplify(H(s), 'Steps',20)                       % Desired Result

It may not seem obvious at first, although it is.

EDIT — To do the conversion numerically, use the d2c (link) function.

[mehmet baki]

here my question I

 added one photo

[mehmet baki]

s=tf('s')
g=1/((s+1)*(s+10))
gd=c2d(g,.1,'zoh')
gdcl=feedback(135.5*gd,1)
% my closed loop tf to plot bode

0.48103 (z+0.6945)/(z^2 - 0.7917z + 0.6669)

[Star Strider]

Your system is already continuous. If you want to transform it to discrete, use the related c2d function. Supply a value for the sampling interval, ‘Ts’, and since the assignment wants you to use the zero-order-hold discretization method, be certain to specify that.

If you want the Bode plot of your system, use the bode function.

I leave the rest to you. Please familiarise yourself with the Control system Toolbox (link) functions.

[mehmet baki]

just wanna learn what is wsubw and how to bode this discrete cltf by hand

[mehmet baki]

sir I know bode graphs both as discrete & cont. but I don't know how to graph asymptotically by hand

[Star Strider]

I have no idea what ‘omega_w’ is. You must look at the preceding discussion in the textbook to find out. That information is not on the page you posted, and it not standard notation, at least that I am aware of.