How to find the transfer function of a MIMO System?

The parameters are as follows:

a=[-0.0543 -0.5332 0 -9.7295;-2.7791 -10.3435 8.5100 -1.1732;-0.3403 -2.0302 0 0; 0 0 1 0];
b=[2.4224 0.0224; -20.2054 0; -18.4384 0; 0 0];
c=[1 0 0 0;0 1 0 0;0 0 1 0; 0 0 0 1]
d=[0 0 ;0 0;0 0;0 0]

For the matrix given above, how to find the transfer function (MIMO System)?

While using [num1,den1]=ss2tf(a,b,c,d,1)  and loopsys , I get the following error: "Ill-posed problem -- plant G cannot have more outputs than inputs". Any help would be appreciated.

[Star Strider]

I cannot reproduce that error in R2017a. This works for me:

[num1,den1] = ss2tf(a,b,c,d,1);

figure(1)
bode(num1, den1)

I do not have the loopsys function.

[Akhil Shetty]

Hi, Thank you for the reply.

The part of the code which I have problem with is as follows

a=[-0.0844 0.4354 -4.3589 -9.7483 0; -0.2920 -1.8188 39.7431 -1.0682 0;0.0313 -0.3089 -2.3089 -2.3953 0;0 0 1 0 0; 0.1090 -0.9940 0 40.9624 0]; b=[-0.0494 144.8262; -3.2438 0; 8.6497 -7.2413; 0 0; 0 0]; c=[1 0 0 0 0; 0 1 0 0 0; 0 0 1 0 0 ;0 0 0 1 0;0 0 0 0 1 ]; d=[0 0;0 0; 0 0; 0 0;0 0]; G = ss(a,b,c,d); s = zpk('s'); % Laplace variable s

Gd = 8/s; % desired loop shape % Compute the optimal loop shaping controller K [K,CL,GAM,INFO] = loopsyn(G,Gd);

I have used 'loopsyn' for loopshaping. The error which i had mentioned indicates to the line where I have used the "loopsyn" function. Can you please help me out in this matter. Thank you .

[Star Strider]

I am using R2017a and do not have the loopsyn function. (I very rarely do anything with classical control.)

Answer 1

[Sally Al Khamees]

See if the seggestions in these links help.

http://www.mathworks.com/help/ident/ref/tfest.html

http://www.mathworks.com/help/signal/ref/tfestimate.html