Re: SIMO systems

[Geraint Paul Bevan]

Mauro Casse wrote:
> Hi, I can't find how to do this, I must obtain the space state 
> representation of the followig transfer function with single input and 
> two outputs
>                     1                [  1  ]
> G(s) = ------------------- * |       | (this is a column vector)
>              s^2+5*s+1       [ s+1]
>
> the following commands works in Matlab, but octave return this error
>
> octave:26> num = [ 0 1; 1 1];
> octave:27> den = [ 1 5 6 ];
> octave:28> [ A, B, C, D] = tf2ss(num,den)
> error: num(2x2) must be a vector
> error: evaluating if command near line 51, column 3
> error: called from /usr/local/share/octave/2.1.50/m/control/sys


tf2ss requires the numerator to have only one column, i.e. it only works 
with simple gains in the numerator. You can create the state space 
representation manually however:


octave> [A,B,C1,D1] = tf2ss (    1  , [1,5,6] );
octave> [A,B,C2,D2] = tf2ss ( [1,1] , [1,5,6] );
octave> C = [C1;C2];
octave> D = [D1;D2];
octave> A,B,C,D
A =

   0   1
  -6  -5

B =

  0
  1

C =

  1  0
  1  1

D =

  0
  0


--
Geraint Bevan
Department of Mechanical Engineering
University of Glasgow
Tel: +44 (0)141 330 5917



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