How performing FRF for complex functions

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评论： Star Strider 2023-10-11

Hello,

I'm tryiing to plot phase and magnitude plot for below complex transfor function by performing FRF for say -600 to 600 Hz

1257 s + 3.736e05

-------------------------------------------

s^2 + (1554 - 2e02i) s + (3.736e05 - 2e02i)

Please help

Star Strider 2023-10-5

Try this —

s = tf('s');

H = (1257*s + 3.736e05) / (s^2 + (1554 - 2e02i)*s + (3.736e05 - 2e02i))

H = 1257 s + 373600 ------------------------------------- s^2 + (1554-200i) s + (3.736e05-200i) Continuous-time transfer function.

opts = bodeoptions;

opts.FreqUnits = 'Hz';

opts.FreqScale = 'linear';

figure

bodeplot(H, {0 600*2*pi}, opts) % Plot Transfer Function

grid

[mag,phase,wout] = bode(H, {0 600*2*pi}); % Return Numeric Values ('wout' Will Be In rad/sec, So Divide It By (2*pi) To Get Hz)

mag = squeeze(mag);

phase = squeeze(phase);

Once again thank you so much, Now I'm trying plot the root locus using rlocus(), and it says

Error using DynamicSystem/rlocus (line 65)

Cannot compute the root locus of models with complex data.

May be I need to rewrite my transfer function, I will get back to you if I have any questions.

Star Strider 2023-10-11

My pleasure!

I cannot suggest a work-around for the rlocus problem.

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