Re: Control toolbox: Problems emulating M*TLAB's cloop

[A Scottedward Hodel]

The OCST data structures only admit proper (causal) transfer functions.
The MATLAB toolbox was updated to admit nonproper (i.e., PID) transfer
functions in its tf and zpk forms.  State space systems, of course, can't
represent a derivative except by approximating with a high-pass filter.

It's sloppy, but the only way I know to do PID design in the OCST is
to have both y and ydot (output and its derivative) available in the
plant model.

By the way, you can also use the OCST command "sysconnect" to construct
closed-loop systems.  I need to improve the star-product function interface
so that it's less confusing (to me) to use.

> With Octaves's developmental version I tried to investigate a system
> controlled with a PID controller. In an tutorial I saw MATLAB's cloop()
> function, which I was able to mimick using buildssic() for a "plant"
> and a proportional conroller (as systems s1 and s2).
> Now I wanted to test the same with a PID controller, which Octave does
> not accept, because it has "more zeros than poles".
>
> Does anybody know how to construct the closed loop system, consisting of
> the plant and PID controller using OCST?
>
> Thomas.
>
>
>
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--
A S Hodel Assoc. Prof. Dept Elect and Computer Eng, Auburn Univ,AL 36849-5201
On leave at NASA Marshall Space Flight Center (256) 544-1426
Address until 31 July 2000:Mail Code TD-55, MSFC, Alabama, 35812
http://www.eng.auburn.edu/~scotte



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