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Re: Feedback for octave

From: Andrei
Subject: Re: Feedback for octave
Date: Thu, 08 Mar 2007 17:24:15 -0600
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.13) Gecko/20060414

Doug Stewart wrote:

Andrei Gutierrez wrote:

I have a problem to define the arguments for the feedback for control.
for example:
den=[1 10 1];

It is OK, but if My H(s) is not 1, for example H(s) = s + 1 ...

numh=[1 1];

Gives me the error that the zeros are more than the poles, but in the
feedback its common to have a numerator like this.
Any idea?-.
Thank you.

Help-octave mailing list

You can get around this problem by adding a pole out at a "high" frequency so that its influence on the system will be minimal.
So try this

num = 1
den=[1 10 1]

numh=[1 1]

%%now make a pole at 100
%%with a gain of 1
dp=[1 100]
%% now make H  as:


this makes a pole and a zero at about -100 and they cancel each other out. and your step response and and bode will be OK in the region that you are concerned about.

the zero is at -100
the pole of the closed loop using this method are:


the theoretical poles are

If you put the added pole out farther then it even has less effect.

Doug Stewart

Ok thanks it works,
Im doing a program to find the gain (Z) for a specific damping ratio (Z), would it be useful to upload? or theres another function that already does?

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