How to Plot straight lines and 1 more lines using Bode plot.

Good day to everyone,

i have a transfer function =

5000 s + 20000

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

s^3 + 210 s^2 + 2000 s

when i input this into matlab, i get the answer(picture name:bode) as you can see it is a curved blue graph which is the final graph. The picture labeled as bode ans.png is the answer that was shown by the notes.

Does anyone know what must i type in matlab to get that plot? which shows all the different plots?

Currently what i have typed in matlab:

>> num = [5000 20000]

num =

5000 20000

>> den = [1 210 2000 0]

den =

1 210 2000 0

>> sys=tf(num,den)

sys =

5000 s + 20000

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

s^3 + 210 s^2 + 2000 s

Continuous-time transfer function.

>> bode(sys)

Thank you very much!

Answer 1

[Navya Seelam]

Hi,

The plot in bode ans.PNG is obtained by factorizing the transfer function i.e transfer function=G1*G2*G3*G4*G5 and bode plots of each of G1, G2, G3, G4 and G5 have been shown. The plot GOL is the bode plot of the overall transfer function. The reason for difference in GOL of bode ans.PNG and bode.PNG is because in bode ans.PNG the influence of the pole/zero on the magnitude is ignored before the start of pole/zero on the frequency axis and the same explains the sharp points in bode ans.PNG.