Algorithm Study And Development Of CMF

Coriolis Mass Flowmeter (CMF) is widely used in various industrial fields due to their advantages: measuring the mass flow rate directly, high measurement accuracy, and measuring density of fluids at the same time, etc. This paper uses digital signal processing methods to deal with the signals of CMF.The purpose of this paper is to develop a new generation and top-level digital CMF with high performance and accuracy. In this paper two aspects for the digital signal processing algorithm of CMF have been mainly studied: frequency measurement and phase difference measurement. According to time-stationary and time-varying signal, two kinds of digital signal processing system models are introduced. In addition, the driving circuit and analog filter are studied in this paper, which resolve the practical problem in the laboratory.The main work of this dissertation is as follows:1,Based on the conventional DFT approach applied on CMF digital signal processing algorithms, Chirp-Z algorithm is used on the signal frequency measurement initialization and the frequency tracking. The method of intensive sampling only in narrowband ensures greater accuracy improvement; 2,Referring to the literature in and abroad, time-varying signal model based on random walk model is proposed. Using direct type and lattice type IIR adaptive line enhancer and frequency estimation algorithm to measure and track the signal frequency;3,Sliding Goertzel algorithm is used to calculate the phase difference of CMF signals. This algorithm can avoid the influence of non-integral period sampling and calculate the time interval in real time;4,According to time-stationary and time-varying signal, two kinds of digital signal processing system models are proposed: Using Chirp-Z and sliding Goertzel algorithm to deal with time-stationary signal; applying IIR type adaptive line enhancer and sliding Goertzel algorithm to time-varying signal. The abundance of simulation in MATLAB and DSP5510 environment indicates that we can obtain high accuracy and real time in the time interval calculation;5,The driving circuit and analog filter commonly used now are designed and analyzed based on emulation tool Multisim. The problems in practical circuit are resolved.