RE: scaling

Dear Ali

Sorry about the delay in replying.

At the outset we decided from knowledge of the problem that a variation in
thrust of 7.5 % of maximum thrust was of equal importance to a 5% variation
in surge margin, etc. This is therefore an apriori decision that an engineer
familiar with the problem would have to make.

The outputs are therefore scaled so that a unit variation in the output
corresponds to these changes.

Let y be the thrust output, and let M be the maximum thrust. Then y is
scaled by 100/(7.5M). Note that if the scaled output y*100/(7.5M) is equal
to 1 then y is equal to 7.5M/100 ie 7.5% of M as required.

Similarly for the other outputs.

Hope this is clear

Regards

Ian Postlethwaite

-----Original Message-----
From: Ali Karimpour
To: ixp@leicester.ac.uk
Cc: a_karimpour@hotmail.com
Sent: 07/10/2000 06:09
Subject: Re: scaling

Dear Prof. Ian Postlethwaite
Hello,
I am a Ph.D student in Electrical Engineering Department,
Ferdowsi University of Mashad. Regarding the "scaling" of "aero engine
example" (chapter 12 of your book), I have difficulty in understanding
the
scaling weights of thrust related and surge margin related outputs.
How do you choose the scale of thrust related outputs that each unit
after
scaling represents 7.5% of maximum thrust? How do you get 7.5%?
Similarly,
how do you get the 5% for the surge margin and 2.2% for spool speed? And
how
can we make sure (before the completion of controller design) that
"The outputs are scaled such that equal magnitudes of cross-coupling
              into each of the outputs is equally undesirable"

Thank you
Ali Karimpour

Ali Karimpour
Department of Electrical Engineering
Faculty of Eng.
P.O.Box 91775-1111
Mashhad-Iran

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Received on Sun Oct 15 18:02:30 2000