涡街流量计数字信号处理方法分析与比较

Review of Methods of Digital Signal Processing of Vortex Flowmeter

涡街流量计有许多优点, 近年来应用广泛。但它易于受到由管道振动和流场扰动引起的噪声干扰。用传统的处理信号电路制成的流量计在工业现场测量精度不高, 抗干扰性能差, 无法准确测量小流量。而数字信号处理技术可以弥补传统方法的不足。归纳了数字滤波器、谱分析、自适应陷波以及小波变换等几种方法, 介绍了每一种方法的具体实现, 并作了性能分析和比较。指出数字信号处理方法可以很大程度上提高测量精度, 实现真正小流量测量。但实际应用中需要考虑到准确性和实时性要求。通过MATLAB仿真实验, 验证了采用变采样频率和频谱校正等措施对经典周期图法进行改进, 既可以达到较高的精度, 扩展了量程下限, 又能够满足以单片机为核心的流量计低功耗和实时性要求, 实用性较强。

The vortex flowmeter is widely used in recent years as it has many advantages. However, it is easily influenced by the noises caused by pipe vibrations and fluid turbulence. The flowmeters having a conventional signal processing circuit have a poor accuracy in the real-time measurement, poor tolerance to disturbance, and are unable to measure small flows accurately. The digital signal processing methods can complement the drawbacks of the conventional methods. This paper firstly reviews some digital processing methods, such as digital filtering, spectrum analysis, adaptive notch filtering and wavelet transform, and then depicts their implementation algorithm, finally analyzes and compares their performances. It has been shown that methods of digital signal processing can improve the accuracy of measurements significantly and can be used to measure small flows successfully. In actual applications, however, accuracy and real-time deserve consideration. Through many simulations using MATLAB, it proves that the improved cyclic graph method, which takes the shifted sampling-frequency and spectrum correction, can not only achieve a higher accuracy and extend the lower bound of measurement range, but also can meet the requirements of a flowmeter based on micro-controller, which are low power consumption and being able to be used in real-time. This method has been proved to be more practical than others.