loading
确定根轨迹和虚轴的交点
令s?j?,特征方程D(s)?(j??2)3?K0?02????6??K0?8?0???0????23 ??3??（舍去）或?K??8???0?K0?64???12??0j?54321?-5-4-3-2-1-1-2-3-4-5
(1) 令s?j???????23 ??K0?64过s平面原点，和实轴负方向夹角为?60作射线，和根轨迹的交
?=0.5?arccos??0.5????60点即为主导极点。由图知，主导极点为?1?j3。又
pc1?pc2?pc3?p1?p2?p3??6?pc3??4
所以
(?4?2)3?K0?0?K0?8
Kp?limG(s)H(s)?lims?08?1
s?0(s?2)3(2) 系统的闭环传递函数可以近似为
C(s)88??2 R(s)(s?pc1)(s?pc2)s?2s?4??2??n?2??n?2??2?? ??n?4???0.5?
??1??2??Mp?e?100%?16.3%
?tp?????1.8138s
2?d?n1??3???5% ts???2% ts?4?n??3s
?n??4s