[Octave-bug-tracker] [bug #43263] Minreal (control toolbox) may generate inaccurate result

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?43263>

                 Summary: Minreal (control toolbox) may generate inaccurate
result
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Sat 20 Sep 2014 03:42:54 AM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: Saul Mtakula
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.1
        Operating System: Microsoft Windows

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Details:

Control toolbox 2.6.5 refers. Code for the m file is shown below. The step
response after manipulations of the transfer functions in the code should be a
damped oscillation. The response obtained is not correct; my suspicion is on
the minreal command because when it is omitted the step response is unbounded.
It could be the feedback command is the problem.


clear
close all
clc

pkg load control

s=tf('s');

Gpff=3/((1+4*s)*(1+6*s));

Gcc=(1+1/(60*s));
Glff=series(Gcc,Gpff);
Gff=minreal(feedback(Glff))


Gplc=0.001111*(1-30*s)/(s*(1+30*s));
Gplc=series(Gplc,Gff)

Gclc=(1+1/(2.5*60*s))*(0.2*60*s+1)/((1+6*s)*(1+1.2*s))

Gllc=minreal(series(Gclc,Gplc))


figure(1)
Gllc_cl=minreal(feedback(Gllc));
step(Gllc_cl);
legend('Level')





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