基于Hilbert变换科氏流量计相位差测量方法改进

Improvement of phase difference measuring method based on Hilbert transform for Coriolis mass flowmeter

离散Hilbert变换因其计算相位差准确度高,在科氏流量计中得到广泛应用。针对非整周期采样下信号变换失真问题,研究基于采样数据的减小信号变换失真算法,提高流量测量精度。分析离散Hilbert变换四步算法,根据离散变换特征,提出非整周期信号周期化插补算法和信号变换误差计算的区间循移算法。通过实验验证,在非整周期采样时,所研究算法可减小采样信号变换失真,相位差计算精度提高一位,质量流量计算误差小于原来误差1/5。

Discrete-time Hilbert transform is widely applied in Coriolis mass flowmeter due to its high accuracy in calculating phase difference. Under non-integer-period sampling, the discrete-time Hilbert transform will have signal distortion and affect the accuracy of flow measurement. For the problem of signal transformation distortion under non-integer-period sampling, an algorithm used to reduce signal transformation distortion based on the data is studied out to improve flow measurement accuracy. Firstly, the 4-step algorithm of discrete-time Hilbert transform is analyzed. According to the discrete transformation features, period-data interpolation algorithm for non- integer-period and interval shifting algorithm for signal transformation error calculation are studied out. Experiments prove that these two algorithms decrease the signal transformation distortion under non-integer-period sampling, the mass-flow rate error becomes 1/5 smaller than its original error, and the precision of phase difference is raised up.