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i hc Bch Khoa TPHCM P N KIM TRA GI A K 1. Nm hc 2012-2Khoa in in
T Mn: C s t ng
Bmn KT Ngy thi: 12/10/2012---o0o--- Th i gian lm bi: 60 pht
Bi 1: (2.5 im) Tm hm truy n t ng ng0)()(
)()(
s R N s N
sY sG ca h thng c s khi Hnh 1.
Bi gi i:S dng tn hi u t ng ng : c th v nhiu cch (0.5im)
Cch 1:
Cch 2:
ng tin : (0.5im) Vng kn : (0.5im) P1 = G2G3 L1 = G2G4G1 P2 = G 6
L2 = G3G5
L3 = G2G3G1
R(s) 1
N (s)
G1 G2
1
1 G3 Y (s)
G4 G5
1 1
1
G6
G1(s) R(s) Y (s)
Hnh 1
+ G2(s)
G6(s)
G4(s)
_ +
G5(s)
+ _ G3(s)+
_
N (s)
_ +
-1 G2 N(s) 1 G3
-G 5
Y(s)
-G 4G1
G6
-G1
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L i gi i:Cu 3.1:+ Cc: 1 2 30; 10 p p p (0.25im) +Zero: 1 1 z
;
+ im tch nh p:3 210
1
s s K
s
2 3 20 3 20 1 10 0dK s s s s sds
3 22 13 20 0 s s s
0 ( )
2.5 ( )
4 ( )
s tach
s cuc tieu nhap
s cuc dai tach
(0.5im)
+ Gc ti m cn: 0180 903 2
q ;
+ Giao im tim cn v tr c honh:0 0 10 1
4.53 1OA
(0.25im)
Q NS: (0.75im)
-12 -10 -8 -6 -4 -2 0 2-8
-6
-4
-2
0
2
4
6
8Root Locus
Real Axis
I m a g
i n a r y
A x
i s
+ T Q NS suy ra h thng n nh v i mi K >0 (0.25im)
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Cu 3.2:K=12 PTT ca h thng tr thnh: 3 210 12 12 s s s
Nghim ca PT T: 12,3
8.79
0.605
s
s i
(0.25im)
11
6.02
n
n
6.01
6.0
2
n (0.25im)
st n
qd 67.66.044
; (0.25im)
2
exp exp 0.6 15.18%1
POT
(0.25im)
Bi 4: (3.5 im) Cho h thng nh Hnh 3.
4.1. (2.5 im) Cho K C =1. Vbiu Bode bin v pha c a h h trong mi n
tn s t 0.01 n 20 rad/seXc nh tn sct bin c v tn s ct pha . nh gi tnh
n nh ca hkn.
4.2. (0.5 im) Cho K C =1. Tnh sai s xc l p ca h thng khi tn hi u
vo l hm d c n v. 4.3. (0.5 im) Xc nh mi n gi tr K C sao cho h kn n
nh.
L i gi i:
4.1Hm truy n vng h :0.1
2
100( 0.5)( ) ( )
( 10)( 5)
s
h C
s eG s K G s
s s s
a hm truy n h v dng:0.1
2
(2 1)( )
(0.1 1)(0.2 1)
s
h
s eG s
s s s Cc t n s ct: 1 2 30.5( / ), 5( / ), 10( / )rad s rad s rad
s (0.25im)
Xc nh im A: (0.25im) 0
0
0.1( / ):
( ) 20 log(1) 2* 20 log(0.1) 40
rad s A
L dB
hocdB L
srad A
80)01.0log(*2)1log(20)(
)/(01.0:
0
0
Biu thc pha v b ng: (0.25im) 180
( ) 180 arctan(2 ) arctan(0.1 ) arctan(0.2 ) 0.1
R(s) Y (s)+ _
Hnh 3
K C
)5)(10()5.0(100
)( 21.0
s s se s
sG sG( s)
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L p bng xc nh mt s im: (0.25im)
(rad/s) 0.1 0.5 1 5 10 20( ) (deg) -171 -146 -139 -196 -259
-345
Biu Bode (1.0im), ch :- biu d i y trong mi n 0.1-20rad/s, SV v
trong mi n 0.01 n 20 rad/s v n tnh im.- ch c tr n vn 1 im nu ch
thch y dc, tn s ct, d tr .
Tn s ct bin: )/(2 srad C , tn s ct pha: )/(2 srad d tr bin: )(5
dBGM , d tr pha: 030 M T cc k t qu trn bi u Bode, ta suy ra h kn n
nh. (0.5im)
4.2 (0.5im) H svn tc:
0lim ( )V C s K sK G s
Suy ra, sai s xc l p:1
0 xl V
e K
4.3 (0.5im)T biu Bode ta th y, n u d ch Bode bin ln 5dB th lc d
tr bin s m v h kn s khngnh, do :
52020 log( ) 5 10 1.8C C K K
0 1.8C K L u : do d tr bin xc nh g n ng nn gi tr K C c th khc
nhau. (tnh chnh xc theo
Matlab th 0 2.8C K )
