OCST: Gain Margin

[Doug Stewart]

On Thu, Jul 2, 2009 at 5:51 PM, Lukas Reichlin <
lukas.reichlin at swissonline.ch> wrote:

> Dear Octave Community,
>
> I wrote an objective function to optimize an Aström/Hägglund PID
> Controller numerically by fminsearch. Versions for Octave and Matlab/
> SImulink can be found here:
>
> http://n.ethz.ch/student/lukasre/download/optiPID/
>
> The Octave control package is quite limited. However, I managed to get
> along quite easily except for one thing: the gain margin of a system.
> In Matlab, there's [gamma, phi, w_gamma, w_phi] = margin(sys). I
> couldn't think of a way to calculate the gain margin numerically. Is
> there any control systems engineer out there who knows how to
> implement an algorithm for the problem? Help would be very appreciated.
>
> Regards,
> Lukas
>
> BTW: Despite I implemented the routine quite differently, the
> conformity of the results between Matlab and Octave is simply
> fantastic :-)
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>


If you look at what I did you might get some ideas.

http://dougs.homeip.net/qtoctave/bode1w.m

Doug Stewart
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