[Octave-bug-tracker] [bug #58240] [octave-forge] (control) Function tf2ss in Octave returns wrong result (in Matlab same function works OK)

[Torsten Lilge]

Update of bug #58240 (project octave):

                Severity:              3 - Normal => 2 - Minor              
              Item Group:        Incorrect Result => Matlab Compatibility   

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Follow-up Comment #3:

Aleksandar, you said in your original post that the result in octave is not a
correct answer. But it is correct. A dynamical system generally has exactly
one transfer function but an infinity large number of possible state space
representations. Octave's state space representation leads to the original
transfer function. 

The state space representation that you have given for Matlab does *not*
result in the original transfer function but in num = [1 4], den = [1 4 -3].
The correct matrix should be A1 = [ -4 -3 ; 1 0 ], I guess this is a typo in
your post?

Given that A1 is the above matrix in Matlab, then the similarity
transformation T = [-4 -13 ; 1 4 ] transforms the state space representation
from Matlab into the one from Octave, i.e. A_oct = T*A_mat*inv(T), B_oct =
T*B_mat, C_oct = C_mat*inv(T).

I am changing the item group into "Matlab Compatibility" and the Severity into
minor.



 

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