Re: rlocus

[Eduardo Adam]

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
> >_______________________________________________
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