bugGNU Octave - Bugs: bug #41353, control package: step and bode do...


bug #41353: control package: step and bode do not work with constant transfer functions

Submitted by:  None
Submitted on:  Sun 26 Jan 2014 05:42:24 PM UTC  
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Works For Me Assigned to:  None
Originator Name:  Carlos Martinez Originator Email:  -email is unavailable-
Open/Closed:  Closed Release:  3.8.0
Operating System:  GNU/Linux

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Wed 29 Jan 2014 05:32:04 PM UTC, comment #5: 

Please close it, since I cannot reproduce it again myself. Sorry for the waste of time.

Carlos Martinez <moggadeet>
Wed 29 Jan 2014 12:42:25 PM UTC, comment #4: 

Tried your example today with octave 3.8.0 and control 2.6.1 and I can't see any problem when running:

T = tf(1,2);

Andreas Weber <andy1978>
Project Member
Tue 28 Jan 2014 06:45:54 AM UTC, comment #3: 

Thanks for your report. I'm stuck with Octave 3.6.4 on my mac, where it works for me. I'll check it out again as soon as I'm able to update to Octave 3.8.

Lukas Reichlin <paramaniac>
Mon 27 Jan 2014 08:53:20 PM UTC, comment #2: 

The results of ver,

>> ver
GNU Octave Version 3.8.0
GNU Octave License: GNU General Public License
Operating System: Linux 3.11.0-12-generic #19-Ubuntu SMP Wed Oct9 16:12:00 UTC 2013 i686
Package Name  | Version | Installation directory
     control *|   2.6.1 | /home/carlosm/octave/control-2.6.1

I compiled the package myself out of the sources v3.8

Carlos Martinez <moggadeet>
Sun 26 Jan 2014 10:55:03 PM UTC, comment #1: 

I do not get this error with the systems and the plot commands you provided here, using control version 2.6.1. CCing the control package maintainer on this bug report.

Mike Miller <mtmiller>
Project Administrator
Sun 26 Jan 2014 05:42:24 PM UTC, original submission:  

Hello there,

I am reporting a trivial bug with step or bode. The two code portions do the same, but due to internal representation issues the second snippet produces an error.


G = tf(1,[1 -1]);
C = tf([1 -1], 1);
T = G*C/(1+G*C);

Whereas without factorizing the transfer function,

T = tf(1,2);


error: c2d: system is already discrete-time
error: called from:
error:   /home/carlosm/octave/control-2.6.1/@lti/c2d.m at line 67, column 5
error:   /home/carlosm/octave/control-2.6.1/__time_response__.m at line 111, column 7
error:   /home/carlosm/octave/control-2.6.1/step.m at line 89, column 10

I had expected the same results as above.



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  • -email is unavailable- added by andy1978 (Posted a comment)
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  • -email is unavailable- added by moggadeet (Posted a comment)
  • -email is unavailable- added by mtmiller (Posted a comment)
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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2014-01-29 andy1978 Open/ClosedOpen => Closed
    2014-01-26 mtmiller StatusNone => Works For Me
        SummaryStep&bode do not work with constant transfer functions => control package: step and bode do not work with constant transfer functions
        Carbon-Copy- => Added paramaniac

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