零点就是使得系统传递函数为0的s的值如果系统的传递函数（Transfer function)是：
G(s) = N(s)/D(s)
N(s)，D(s)是整式，那么满足N(s)=0的s的值就是该传递函数的零点（zeros)，满足D(s)=0（系统的特征方程）的值就是该传递函数的极点(poles)。
比如
G(s) = (s+1)(s-1)(s-12)/[(s+3)(s+5)(s+3-2j)(s+3+2j)]
那么系统的零点就是:1，-1，12(有个别书上将无穷大也算零点，不过一般不写）
极点是：-3，-5，-3+2j，-3-2j
从你的说法看来你把零点和极点弄混淆了，注意区分。
answer from lecturer:
answer from lecturer:
Root locus attempts to trace the closed loop poles as we vary K. This starts from the open loop poles and ends either at infinity or the zeros. All the construction is based on the vector equation: 1 + KGH = 0.. The open loop poles and zeros refer to GH.
也就是说不是看整个T.F,只看GH来决定zeros
难道是 国大和南大不一样？
Root locus attempts to trace the closed loop poles as we vary K. This starts from the open loop poles and ends either at infinity or the zeros. All the construction is based on the vector equation: 1 + KGH = 0.. The open loop poles and zeros refer to GH.
也就是说不是看整个T.F,只看GH来决定zeros
难道是 国大和南大不一样？
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