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Re: rlocus


From: Eduardo Adam
Subject: Re: rlocus
Date: Fri, 22 Jun 2007 09:17:00 -0300
User-agent: KMail/1.9.5

Thanks Andrei, your suggestion works very well, however, the following mesage 
is written

octave:2> [ro,k_breaks,roots,gains,x_breaks]=rlocus(tf(n,d),0.1,0,10);
warning: in /usr/share/octave/2.1.73/m/control/base/rlocus.m near line 2, 
column 35:
warning: rlocus: some elements in list of return values are undefined

Anyway, I have what I'm looking for, that is, the roots related to the gain.
One more question, please,
Is there any control toolbox manual in the web?  Because, your suggestion with 
rlocus comand doesn't appear in the trational help.

Thanks.
Eduardo.



> In that case, you should specify the returning parameters:
> [ro,k_breaks,roots,gains,x_breaks]=rlocus(tf(n,d),0.1,0,10)
> and you will get all the roots of the system in variable "roots", with
> their respective gains in vector "gains".
> i.e.
> roots(:,1)     are from    gain(1)
>
> Eduardo Adam wrote:
> >On Thursday 21 June 2007 14:04, Andrei wrote:
> >
> >Andrei
> >
> >>ro in your case is the graph, that is plotted.
> >>the rlocus function returns multiple roots of the system and graph with
> >>different gain (K),
> >
> >This is exactly what I want.  That is, multiple roots for different gain
> > (K) and the comand,
> >[ro,Kr]=rlocus(tf(n,d),0.1,0,10)
> >
> >it doesn't work on my Kubuntu.
> >
> >>if you want a specific root, you should use the feedback function for a
> >>closed loop, convert the system form to a transfer function and get the
> >>roots of the denominator:
> >>octave:1> n=1; d=[1 3 2 0];
> >>octave:2>[num,den]=feedback(tf(n,d),tf(1,1));
> >>octave:3>roots(den)
> >>ans =
> >>    -2.32472 + 0.0000i
> >>    -0.33764 + 0.56228i
> >>    -0.33764 - 0.56228i
> >>
> >>Eduardo Adam wrote:
> >>>Hi everyone,
> >>>
> >>>I'm sorry for this basic question but I'm a new octave user and, I'm
> >>>accustumed to used matlab.  So, I ran the following comands:
> >>>
> >>>octave:1> n=1; d=[1 3 2 0];
> >>>octave:2> [ro,Kr]=rlocus(tf(n,d),0.1,0,10)
> >>>warning: in /usr/share/octave/2.1.73/m/control/base/rlocus.m near line
> >>> 3, column 8:
> >>>warning: rlocus: some elements in list of return values are undefined
> >>>ro = [](0x0)
> >>>Kr =
> >>>
> >>> -0.38490
> >>>  0.38490
> >>>
> >>>
> >>>My question is, why I have the answer ro=[]?
> >>>I'm interested in the closed loop roots and, according to the help,
> >>> rlocus would have to provide the roots
> >>>
> >>>On the other hand, the comand
> >>>octave:3> rlocus(tf(n,d),0.1,0,10)
> >>>
> >>>it works perfectly.
> >>>My octave version is 2.1.73 and I'm working with linux-kubuntu.
> >>>
> >>>
> >>>Thanks to everyone.
> >>>
> >>>Eduardo
> >>>_______________________________________________
> >>>Help-octave mailing list
> >>>address@hidden
> >>>https://www.cae.wisc.edu/mailman/listinfo/help-octave

-- 
********************************************************

  Eduardo J. Adam
  INTEC
  Guemes 3450
  3000 Santa Fe, Argentina
  TE: 54 342 4559174/7 - FAX: 54 342 4550944
  e-mail:   address@hidden
            address@hidden 
  web-page: www.intec.unl.edu.ar/~eadam

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