2s2+4s+3 1(s) U1(s) 3(S+2.2+2s+1) 2(S)= s°+2.2+2+11(s) h()、U23)Rl2(s) h U1(s)U/1(s)s3+2s2+2s+1 2s2+4s+3 H2(S)= (s)3(s3+252+2s+1)( ) 3( 2 2 1) 2 4 3 ( ) 3 2 1 2 1 U s s s s s s I s + + + + + = ( ) 2 2 1 1 ( ) 2 3 2 1 U s s s s I s + + + = 2 2 1 1 ( ) ( ) ( ) ( ) ( ) 3 2 1 2 1 2 1 + + + = = = U s s s s RI s U s U s H s 3( 2 2 1) 2 4 3 ( ) ( ) ( ) 3 2 2 1 1 2 + + + + + = = s s s s s U s I s H s