说明：  自己编的Allan方差计算函数，经过了反复测试。输入为陀螺频率数据和采样时间间隔。可以自定义只计算部分相关时间对应方差值。
(Allan variance calculation function, after repeated tests. Input is the gyro frequency data and the sampling time interval. The part of the correlation time corresponding to the variance Can customize)