Bode Plot and resonant peaks

Hello,

I'm trying to fit these points to get a bode plot and possible transfer function

w = [0.1 0.2 0.3 0.5 0.8 1 2 3 5 8 10 20 30 50 80 100 200 300 500 800 1000 2000 3000 5000 8000];

G = [0 0 0 0 0 0 0 10 22 28 33 38 35 33 30 28 20 14 8 0 0 0 0 0 0];

I know there is a zero at 2 and the increasing is steeper so started with

"s^2+4*s+4" on the numerator

I know there is a resonant peak at x = 20 but I'm unable to do it.

Also. how to make the bode plot stop at 0 ?

you can find my try here with this transfer function :H=((s^2+4*s+4))/((s+30)^3);

with C = 6750

Answer 1

[MULI]

I understand that you are trying to get bode plot with the given data.

You may follow these suggestions:

• There is a zero at s=0 and order can be found by calculating slope of line.
• From the transfer since there is decrease in slope at resonant frequency i.e s=20 there is a pole at s=20, to get order of poles can be found by taking the slope of line.
• Again at s=800 there is change is slope so there is a possibility of zero at that frequency.

After getting the right transfer function you may use the function ‘bode’ to get bode plot.

You may refer to this documentation link for more information on ‘bode’ function.

https://www.mathworks.com/help/releases/R2021a/ident/ref/lti.bode.html