例已知某负反馈系统开瑞传函为G(S)H(S) S(S+1)(S+2) 试画出其根轨迹 解 qn=60,180°,300° 出[s(S+1)(S+2),=a=0 3a2+6a+2=0 a1=-0.423 1.577( 舍) XX> 2 米00.423 1.577( ) 3 6 2 0 [ ( 1)( 2)] 0 : 1 60 , 180 , 300 . ( 1)( 2) . ( ) ( ) 1 2 2 dsda a 舍 解 试画出其根轨迹 例已知某负反馈系统开环传函为 = − = − + + = + + = = − = + + = =       s  s s s S S S k G S H S      - 2 - 1  0