A Novel Phase Difference Measurement Method for Coriolis Mass Flowmeter Based on Correlation Theory

Abstract

Aiming at the poor precision problem in phase difference measurements with unknown frequencies in engineering practice, a new phase difference measurement method is proposed for Coriolis mass flowmeter based on correlation theories. Firstly, the signal frequency was estimated by using an adaptive notch filter, which was applied to filter the waves and determined the integer period of the sampling signals, and the non-integer period sampling signals needed to be extended. Then, the Hilbert transformation was conducted relative to the extended signals, and the correlation functions of these extended signals with the transformed signals can be computed. Finally, the formula of phase difference can be obtained by utilizing the sinusoidal function. Compared to traditional methods, such as the correlation method, the Hilbert transformation method, and sliding Goertzel algorithm, the proposed method is suitable for both integer period and non-integer period sampling signals, and its accuracy, real-time, and dynamic performance is superior. Simulation and experiment results validate the superiority and effectiveness of the proposed method.

Harmonic current variation characteristics of shunt capacitors based on full-phase FFT algorithm

“…In order to make the full-phase fast Fourier transform algorithm more anti-noise performance, this paper proposes to improve it with the phase difference algorithm to obtain the full-phase fast Fourier transform phase difference algorithm [26]. The basic idea is to weight the signal after full-phase processing, making the decay of the spectral lines on both sides of the main flap of the capacitor faster, so as to make the harmonic components interfere with each other smaller, but also effectively reduce the impact of noise.…”

“…Accelerating the decay of the partials can reduce the mutual interference of the harmonic components and can improve the detection accuracy of the algorithm. In order to make the signal decay faster, a polynomial transformation of 𝑋(𝑘) is now performed to obtain a new spectral sequence as (26) In order to accelerate the decay speed so that satisfies:…”

“…(1) Full-phase plus window processing of the harmonic signal for the fast Fourier transform operation, and then the harmonic signal is weighted according to Equation (26). The harmonic signal is processed by traditional fast Fourier transform.…”