中文说明：互相关原理解决控制后系统频率测试的程序，给定传递函数以及输入信号求控制系统输出。（感觉和理论结果有差距，可以用来参考计算过程）
English Description：
Correlation theory deals with the frequency control system test procedures, a given transfer function control system output and input signals. (Feeling a gap and theoretical results, can be used to refer to the process)