[Octave-bug-tracker] [bug #58538] [octave forge] (control) step and lsim fail on high order transfer functions

[Torsten Lilge]

Follow-up Comment #2, bug #58538 (project octave):

No, there is a problem with the internal system representation used by step
(). As posted in the help list, this seems to be related to a problem when
discretizing a continuous-time transfer function. To test:


# Get q from the original post

# discretization of the transfer function
# unstable eigenvalues (|lambda| > 1)
sys_tf_dt = c2d (q, 0.01);
sys_dt1   = ss (sys_tf_dt);
lambda = eig (sys_dt1.a)
stable = isstable (sys_dt1)

# discretization of the state space model
# => stable eigenvalues
sys_ss_ct = ss (q);
sys_dt2   = c2d (sys_ss_ct, 0.01);
lambda = eig (sys_dt2.a)
stable = isstable (sys_dt2)


I have attached a script that reads the transfer function q and then does the
test given above.

(file #49237)
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Additional Item Attachment:

File name: bug58538_test.m                Size:1 KB
    <https://savannah.gnu.org/file/bug58538_test.m?file_id=49237>



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