(2)并联 X1(s) Y1(s) G1(s) X(S +Y(s) G2(s) X2(s) Y2(s) X1()=X2(s)=X()Y(s)=H1(s)±Y2(s) G(y)Y(s)H1(s)±Y2(s)G1(s)X1(s)±G2(s)X2s) X(s) X(S) X(S) G1(s)士G2(S) 并联环节总的传递函数等于各环节传递函数之和
(2) 并联 G1(s) X1(s) Y1(s) G2(s) X2(s) Y2(s) X (s) ± Y (s) ( ) ( ) ( ) 1 2 X s = X s = X s ( ) ( ) ( ) 1 2 Y s =Y s Y s ( ) ( ) ( ) X s Y s G s = ( ) ( ) ( ) ( ) ( ) 1 1 2 2 X s G s X s G s X s = ( ) ( ) 1 2 = G s G s ( ) ( ) ( ) 1 2 X s Y s Y s = 并联环节总的传递函数等于各环节传递函数之和
(3)反馈 X(S E(S) Y(S) G(S) X(s) G(S Z(s H(S) 1+G(s)H(s) 负反馈 E(s)=X(S)-Z(s) Z(s)=H(s)Y(s) Y(s)=G(s)E()=G()X(s)-Z(S) G(SIX(S)-H(S)r(S)=G(S)X(S)-G(S)H(S)Y(S) G(S) Y(S)= X(S) 1+G(s)H(S)
(3) 反馈 G (s) E(s) Z(s) H(s) X (s) Y (s) － 1 ( ) ( ) ( ) G s H s G s + X(s) Y(s) 负反馈： E ( s ) = X ( s ) − Z ( s ) = G ( s)[ X ( s ) − Z ( s)] ( ) 1 ( ) ( ) ( ) ( ) X s G s H s G s Y s + = = G ( s)[ X ( s ) − H ( s ) Y ( s)] = G ( s ) X ( s ) − G ( s ) H ( s ) Y ( s ) Z ( s ) = H ( s ) Y ( s ) Y ( s ) = G ( s ) E ( s )
X(SE(S) Y(S) G(S) H(S) Y(S) G(s) G(S) W(S)=X(5)1+G(s)H(s) Y(s)= 1+G(s)H(s) X(S) G(s):前向通道传递函数,H(s):反馈通道传递函数, G(s)H(s):开环传递函数,1+G(s)H(s)=0叫做系统的 闭环特征方程。 G(S) 当1H1时,称为单位反馈系统(S)=1+c(s) 若正反馈: E()=X(s)+Z()W(s) G(s) 1-G(S)H(S
若正反馈： 1 ( ) ( ) ( ) ( ) G s H s G s W s − = G(s)：前向通道传递函数，H(s)：反馈通道传递函数， G(s)H(s)：开环传递函数，1+ G(s)H(s)=0叫做系统的 闭环特征方程。 当H(s)=1时，称为单位反馈系统 1 ( ) ( ) ( ) G s G s W s + = E(s) = X(s) + Z(s) ( ) ( ) ( ) X s Y s W s = 1 ( ) ( ) ( ) G s H s G s + = ( ) 1 ( ) ( ) ( ) ( ) X s G s H s G s Y s + = G (s) E(s) Z(s) H(s) X (s) Y (s) －
例23-1求Y(S),(s),E(S),E(s),2(S),2(S) X(s)F(s) X(s)F(s) X(S) F(S) E(S) X(S G(s) (s) Y(S) H(S) G( Y(S)= X(S) (1)求Y(s)/X(s) 1+G(s)H(S) 设F(s)=0,Y2(s)=0,Y(s)=Y1(s) Y(S) G(s) X()1+G(s)H(S)
例2-3-1 求 ( ) ( ) , ( ) ( ) , ( ) ( ) , ( ) ( ) , ( ) ( ) , ( ) ( ) F s Z s X s Z s F s E s X s E s F s Y s X s Y s (1) 求Y(s)/X(s) ( ) ( ) X s Y s 1 ( ) ( ) ( ) G s H s G s + = 设F(s)=0, Y2 (s)=0, Y(s)=Y1 (s) ( ) 1 ( ) ( ) ( ) ( ) X s G s H s G s Y s + = G (s) E(s) H(s) Z(s) X (s) Y (s) － F(s) Y1 Y2 ＋ G (s) f
F(S) G1(s) (2)求Y(s)F(s) E(S) Y1↓Y2 设X(s)=0, G(s) E(s)=0-Z(s)=Z(s) Y(S) H(S) Y(s)=H1(s)+22(s)=F(sc(s)+E(s)G(s) E(s=Z(s) Z(s)=H(S)Y(S) Y(s)=F(SG(s)-H(sG(sY(s) Y(S) G,(s)F() 1+G(s)H(s) Y(S) G(S) F(S) 1+G(SH(S)
(2) 求Y(s)/F(s) 设X(s)=0， F ( s ) G ( s ) E ( s ) G ( s ) = f + ( ) ( ) F s Y s E ( s ) = − Z ( s ) Z ( s ) = H ( s ) Y ( s ) E(s)=0 -Z(s)= -Z(s) 1 ( ) ( ) ( ) G s H s G s f + = G (s) E(s) H(s) Z(s) X (s) Y (s) － F(s) Y1 Y2 ＋ G ( s ) f Y ( s ) F ( s ) G ( s ) H ( s ) G ( s ) Y ( s ) = f − ( ) 1 ( ) ( ) ( ) ( ) F s G s H s G s Y s f + = ( ) ( ) ( ) 1 2 Y s = Y s + Y s