Homework 3 Answer

1

Homework 3 Answer

Problem

1. Find the transfer function C(s)/R(s), C(s)/N(s) of the system shown in

Fig.problem.

2. Try to find ( ) ?nG s in order to eliminate the effect of disturbance on the

system ( ( ) / ( ) 0C s N s ).

Fig.problem

Answer

1. set N=0 , find C/R

1 2 3

1 2 3

2

1 2 3

( )( 1)

( )( ) / ( )

1 ( )

K K KG s

s Ts

K K KG sC s R s

G s Ts s K K K

set R=0 , find C/N

moving the first comparator backwards.

3

3 1 2 321 2

3 2 1 2 31

1( ) / ( ) ( )

11

n nn n

K

K K s K K K GK TsC s N s K G KK Ks Ts s K K K

KTs s

2. to eliminate the effect of disturbance on the system

3 1 2 3

2

1 2 3

1 2

( ) / ( ) 0

( )

n n

nn

K K s K K K GC s N s

Ts s K K K

K sG s

K K