d_ =d (V(e)+e)儿 4头防 :V"=0 -西d-y小,卧 :V(0)=0,r(0)=0→C=Ve@=V@ V-o V(=)+6.)r=V5 v日间- →r=VE +可后- VA VVA 在一d附近.主轨迹有Ve,=0,=0,就是之轴,无须讨论,2 2 1 A r z z r z z A A A A d V r z d V d V V V = + − = + − ( ( ) )( ( ( ) ) ) ( ( ( ) ) ) ( ( ) ) ( ) ( ) ( ( ) ) ( ( ) ) ( ) 0 0 0 0 0 0 0 0 1 0 4 0 0 0 0 0 1 d 1 1 2 2 d d z z z z r r z r z z z r z r z A z z z A A r r r z r z z A A A A z z V z V z r V r V V z r V z r C v v V r C v v V z r r z V z V V z z d d d V V r z z z z V V V d V d z z d d + + + = = + = + = = = + = = + = = = = + = + − + + = , = 2 2 2 2 1 1 1 r A z z A A z A z z r A A z z z z z z A A A A A d V r d V d d d V V r V V d d d V V V V V + − − = − = − + + − + = − + + − = − + −