中文说明：
借助于Matlab信号处理工具箱的强大分析能力，利用双谱估计对信号进行处理,获取频率信息，并提出了判断列车运行不平稳的准则。
English Description：
With the powerful analysis ability of MATLAB signal processing toolbox, bispectrum estimation is used to process the signal to obtain the frequency information, and the criteria for judging the unstable operation of the train are proposed.