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）-Correlation theory resolved frequency control system test procedures given transfer function and input demand signal control system output. (Theoretical results and feel there are gaps, can be used to refer to the calculation process)