multiple bode plots on same graph

Hi,

Does anyone know how to plot multiple bode plots using the "bode" function? I know that the easiest way to do this would be to use

bode(sys1, sys2)

but this assumes that both of these functions are written in the "tf" form.

The problem i am having is that I would like to plot an array of data, with a 'tf' data on the same plot. However, I can't quite get it to work the way i want.

So what i want is to plot the bode plot first

bode(A)

and then be able to plot the magnitude and phase in the corresponding bode figure which uses the code

semilogx(f, data(:,1)) 
semilogx(f,data(:,2))

for the magnitude.

has anyone done this before?

tia

[aaa]

alternatively, is it possible to split the

bode(a)

call into the magnitude and phase elements? that would be a solution to the problem, but im not sure if this is possible.

[Janamejaya]

I was able to solve the problem, a Prof. at my university helped me.

Here's the code.

semilogx([10 100 200 300 400 500 600 700 800 900 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 ], [2 2.3 13.3 26.3 -6.46 -11.7 -15.6 -18.8 -20.9 -23.4 -25.2 -37.9 -44.8 -50 -53.9 -57 -59.6 -62 -64 -65 ]);

hold on

num=[0 1];

den=[0.000000495 0.000033 1];

system1=tf(num,den);

bode(system1)

best wishes

janmay

[Janamejaya]

http://www.mathworks.in/matlabcentral/answers/44839-how-to-obtain-two-bode-plots-on-the-same-figure-overlapping

Answer 1

[Craig]

You can create an frd object from your data and then plot it like any other LTI object.

[ResponseData,Frequencies]=freqresp(5*tf(1,[1,1,1])); % Example Data

sys1 = tf(1,[1,1]);

sys2 = frd(ResponseData,Frequencies) 

bode(sys1,sys2)

Answer 2

[a a]

It's working for me:

figure(1);

hold on;

bode(W1); %here you need a system or transfer function or space-state model, etc..

bode(W2);

hold off;

Answer 3

[Paulo Silva]

Maybe something with hold on?!

g = tf([1 0.1 7.5],[1 0.12 9 0 0]);
bode(g)
hold on
g = tf([1],[1 0.12 9 0 0]);
bode(g)

Answer 4

[aaa]

unfortunately it is not that simple. my code looks more like

g = tf([1 0.1 7.5],[1 0.12 9 0 0]);
bode(g)
hold on
semilogx(f, data)

the way you have done it assumes both plots are using 'tf'm which could also be plotted just with

bode(g1,g2)

[Patricia Darling]

I have the same question, none of these answers seem to address the issue of having two different types of data sets on the same bode plot. Did you ever resolve this?

Answer 5

[mjcStudent]

For my assignment, I had to plot the same graph with different values of one parameter. I wrote this:

for N = 1: .5 : 3 % 6 values

Jl = .002*N; % the parameter to be changed

% skipping most of code

if N == 1 % only create one figure window on the first iteration

figure

hold on % only turn on 'hold' on the first iteration

end % end if

bode(sys); % plot output

grid

title("Stiffness: MA controller");

end % end for loop

hold off

Produces the following output: