can program tell if SISO or MIMO

Hello. I have a task to check if a transfer function is SISO or MIMO. How can this be done in MATLAB.

I have tried issiso() but this tell me that the transfer function is alwasy SISO.

Is there a function that can tell me if a system is SIOS or MIMO for the transfer function?

I am new with MATLAB and i havent had any luck finding anything for this so far.

[Star Strider]

What’s the transfer function?

What Toolboxes are you using?

[Matthew]

G1 = tf([2 0], [1 2]);
G2 = tf([1 -1], [1 6 15]);
sys = series(G1,G2);
issiso(sys)

ans = logical
   1

This is what i am using.

For toolboxes not sure. If there is a way i just need to be pointed in the direct.

Answer 1

[Walter Roberson]

In the case of transfer functions represented in tf() notation, you can look at size() of the function.

This might not work if the code needs to internally convert to tf to some other representation, such as can happen if you do some operations on tf that have I/O delays in them.

G1 = tf([2 0], [1 2]);
G2 = tf([1 -1], [1 6 15]);
sys = series(G1,G2)

sys =
 
        2 s^2 - 2 s
  -----------------------
  s^3 + 8 s^2 + 27 s + 30
 
Continuous-time transfer function.

sys1 = [G1,G2]

sys1 =
 
  From input 1 to output:
   2 s
  -----
  s + 2
 
  From input 2 to output:
      s - 1
  --------------
  s^2 + 6 s + 15
 
Continuous-time transfer function.

sys2 = [G1; G2]

sys2 =
 
  From input to output...
        2 s
   1:  -----
       s + 2
 
           s - 1
   2:  --------------
       s^2 + 6 s + 15
 
Continuous-time transfer function.

isequal(size(sys), [1 1])

ans = logical
   1

isequal(size(sys1), [1 1])

ans = logical
   0

isequal(size(sys2), [1 1])

ans = logical
   0

[Matthew]

Brilliant. That clears things up so much. The part i was missing was from input to output.

Answer 2

[Paul]

Your code looks correct for determining whether or not a system is SISO

G1 = tf([2 0], [1 2]);
G2 = tf([1 -1], [1 6 15]);
sys = series(G1,G2)

sys =
 
        2 s^2 - 2 s
  -----------------------
  s^3 + 8 s^2 + 27 s + 30
 
Continuous-time transfer function.

issiso(sys)

ans = logical
   1

[Walter Roberson]

Yes, issiso() seems to be working

G1 = tf([2 0], [1 2]);
G2 = tf([1 -1], [1 6 15]);
sys = series(G1,G2)

sys =
 
        2 s^2 - 2 s
  -----------------------
  s^3 + 8 s^2 + 27 s + 30
 
Continuous-time transfer function.

sys1 = [G1,G2]

sys1 =
 
  From input 1 to output:
   2 s
  -----
  s + 2
 
  From input 2 to output:
      s - 1
  --------------
  s^2 + 6 s + 15
 
Continuous-time transfer function.

sys2 = [G1; G2]

sys2 =
 
  From input to output...
        2 s
   1:  -----
       s + 2
 
           s - 1
   2:  --------------
       s^2 + 6 s + 15
 
Continuous-time transfer function.

issiso(sys)

ans = logical
   1

issiso(sys1)

ans = logical
   0

issiso(sys2)

ans = logical
   0