(b) =a2422445△=1 B=a12225A2=1-a4 互不接触=a22 12=a2324 34 14 互不接触 f x2 L2=a223424 L4=a2244只2 1=a22只32 图2-33信号流图 P= (1-a4)12a2a3 (a23a2+a23a34a1+a4+a23a3a2+a23al312)+a23a2a4+a23a3a12a 例2-14利用 Mason' s gain formula求图2-34所示系统的闭环传递函数46 (a) 1 x 2 x 3 x 4 x a1 2 a2 3 3 4 a 4 2 a a3 2 a4 5 a4 4 5 x 3 5 a a5 2 (b) 1 x 2 x 3 x 4 x 5 x P1 =a1 2a2 3a3 4a4 5 1 =1 (c) 2 x1 x 3 x 5 x P1 = a1 2a2 3a3 5 2 =1−a4 4 (d) 互 不 接 触 (e) (f) (g) 互 不 接 触 2 x 2 x 2 x 2 x 3 x 3 x 4 x 4 x 5 x 5 x 1 2 3 3 2 L = a a 2 2 3 3 4 4 2 L = a a a 3 4 4 L = a 4 2 3 3 4 4 5 5 2 L = a a a a 5 2 3 3 5 5 2 L = a a a 1 2 2 3 3 2 4 4 L = a a a 2 2 2 3 3 5 5 2 4 4 L = a a a a 图 2-33 信号流图 23 32 23 34 42 44 23 34 52 23 35 52 23 32 44 23 35 52 44 12 23 34 45 44 12 23 35 1 ( ) (1 ) a a a a a a a a a a a a a a a a a a a a a a a a a a a P − + + + + + + + − = 例 2-14 利用 Mason’s gain formula 求图 2-34 所示系统的闭环传递函数