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A unity feedback system has G(S) =$\frac{K}{(S(1+S)(1+0.4S)}$, If r(t)= 4t and k=2,

(1) Find steady state error.

(2) If it is desired to have steady state error to be 0.2 find corresponding value of ‘k’

(3) Find steadystate error if input is changed to 2+6t and value of ‘k’ to 10.

1 Answer
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G(S) =$\frac{K}{(S(1+S)(1+0.4S)}$

H(S) =1, unity feedback.

(1) For Ramp input

r (t)=4t,

k=2

Steady state error,

$e_ss$=$\frac{A}{k_v}$

$k_v$= $\lim_(s\to 0)$ S G(S) H(S)

=$\lim_(s\to 0)$ $S\frac{k}{(S(1+S)(1+0.4S)}$

=$\lim_(s\to 0)$ $S\frac{2}{(S(1+S)(1+0.4S)}$ =2/(1)(1)

$k_v $ = 2

$e_ss$=$\frac{A}{k_v}$ ,

As A=2 for Ramp input

$e_ss$=2/2 e_ss=1

(2) $e_ss$=0.2, k=?

same input Ramp of …

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