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From: "Waleed Najy" <waldo90009@hotmail.com>
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Subject: sisotool
Date: Fri, 9 May 2008 23:00:31 +0000 (UTC)
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My question is about feedback control. The open-loop process
I'm working with is G = tf(5000,[1 1020 20000 0]). I added
this to the "sisotool" as "G" and used a PD controller (i.e.
added a zero), and stabilised it.

Then I added a design constraint; percentage overshoot < 5%.
And this is where the problem comes: even when all the poles
are within the constraint, I'm still getting an overshoot
largely in excess of 5% and I can't understand why.

Could someone please try it and tell me what the problem is?
I would be very grateful.