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How to input transfer function without simplifying it?

Asked by Supermankid on 12 Sep 2017
Latest activity Answered by Teja Muppirala
on 13 Sep 2017
Hi everyone,
Normally, we can give numerator = [ 1 0]; denominator =[1 1 4]; and system1=tf(num,den); but if the transfer function is like:
G(s) = {s + 2}/{s(s − 1)(s + 6)^2}
can I add this transfer function without simpligying (I mean without multiplying the denominators)
=> only from s(s-1)(s+6)^2
May be someone can provide some tips.

  1 Comment

G = tf([1 2],[1 0]) * tf(1,[1 -1]) * tf(1, [1 6])^2

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1 Answer

Answer by Teja Muppirala
on 13 Sep 2017
 Accepted Answer

s = tf('s')
G = (s+2)/(s*(s-1)*(s+6)^2)
This gives a transfer function (tf) with the polynomials expanded
G =
s + 2
----------------------------
s^4 + 11 s^3 + 24 s^2 - 36 s
Or you can express it as a ZPK (zero-pole-gain)
G = zpk((s+2)/(s*(s-1)*(s+6)^2))
Then you get
G =
(s+2)
---------------
s (s+6)^2 (s-1)

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