[Octave-bug-tracker] [bug #59372] lsim function from octave gives incorrect results (matlab lsim is fine)

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?59372>

                 Summary: lsim function from octave gives incorrect results
(matlab lsim is fine)
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Wed 28 Oct 2020 03:19:55 AM UTC
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Nidish Narayanaa Balaji
        Originator Email: nb25@rice.edu
             Open/Closed: Open
                 Release: 5.2.0
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:

I was working on a linear dynamics problem and tried to use lsim from the
control package for time transient simulation. My results were wierd, and
after paying more attention, I discovered that octave's lsim function seems to
result in the wrong results.

As demonstration, I'm attaching a simple sdof simulation code that can be
executed in both octave as well as matlab to lead to completely different
results. 

The attached figures compare the results from lsim, ode45, and my hand written
implementation of average acceleration (code not included). 

This seems almost too simple to be wrong in octave.



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File Attachments:


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Date: Wed 28 Oct 2020 03:19:55 AM UTC  Name: octaveplot.png  Size: 66KiB   By:
None

<http://savannah.gnu.org/bugs/download.php?file_id=50146>
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Date: Wed 28 Oct 2020 03:19:55 AM UTC  Name: matlabplot.png  Size: 42KiB   By:
None

<http://savannah.gnu.org/bugs/download.php?file_id=50147>
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Date: Wed 28 Oct 2020 03:19:55 AM UTC  Name: controlbugrep_lsim.m  Size: 520B 
 By: None

<http://savannah.gnu.org/bugs/download.php?file_id=50148>

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