Why tf2ss and ss(sys) gives different results?

This code gives different results. However the tfs are the same. Can anybody exxplain it why?

   [A1,B1,C1,D1]=tf2ss([25.61 6.2],[24.78 29.74 6.202])
    sys=tf([25.61 6.2],[24.78 29.74 6.202]);
    ss(sys)

Answer 1

[Arkadiy Turevskiy]

This is explained in the doc page for ss. Please click here, and scroll down to click on "Algorithms" in the "More About" section.

Arkadiy

[Arash Mohammadi]

what is the algorithm for ss2tf?

Answer 2

[Azzi Abdelmalek]

your are using two different function tf2ss and ss. Also LTI system have an infinite number of state space representation. Check it by using ss2tf for your two results

If (a,b,c,d) and (a1,b1,c1,d1) are your two different state space representation.

[N1,D1]=ss2tf(a,b,c,d]
[N2,D2]=ss2tf(a1,b1,c1,d1)

You will find that the two models represent the same system