摘要
电磁流量计广泛应用于工业流量测量领域。但是,低频方波励磁及较低的系统运算能力限制了电磁流量计进行高精度、高速度测量及浆液等复杂流体测量的能力。励磁控制及增强系统运算能力成为提高电磁流量计性能特别是浆液测量性能的关键。本文通过理论仿真提出了基于线性电源和基于高低压电源切换的两种方波励磁控制方案,并分别对其进行了电路仿真、设计与实验;采用基于线性电源的励磁控制方案,以DSP芯片TMS320F2812为信号处理和系统控制核心,研制了浆液型电磁流量计系统;采用MATLAB中的GUI设计了上位机监控软件,实现对电磁流量计运行的监控及其采集波形的实时显示;针对水流量和浆液流体测量,分别采用了基于梳状带通滤波和基于统计分析与信号重构的信号处理方法,并分别进行了流速模拟器和纯水的标定实验及浆液流量的测量比照实验。
实验结果表明,所提方波励磁控制方法能在保证信号零点稳定性的前提下大幅拓宽电磁流量计的方波励磁频率范围,结合上位机监控软件,所研制的电磁流量计系统用于流速模拟器及水流量标定精度均优于0.5级,浆液满流量测量稳态波动率小于1%且响应跟随时间短于4s。这从而大幅提高了电磁流量计的测量精度和测量速度,特别是提高了电磁流量计用于浆液流体测量的性能,进而推动了国内电磁流量计技术的进一步发展,并为其进入国际先进行列奠定了一定的基础。
Electromagnetic flowmeter is widely used in industrial flow measurement. But the low-frequency square-wave excitation and the lower system computing power have constrained high-precision and high-speed measurement cability of electromagnetic flowmeter, and its ability of measureing slurry and other complex fluid as well. Excitation control and enhanced system computing power become the key to improve the performance of electromagnetic flowmeter,particularly to improve the performance of slurry measurement. In the paper, by theoretical simulation, the excitation control method based on linear voltage regulator and the method based on high-low voltage power switching are proposed, and the circuit’s simulation, design and experiment are conducted too. Adopting the excitation control method based on linear voltage and using DSP-chip TMS320F2812 as the core of signal processing and system control, slurry-type electromagnetic flowmeter system is developed. And, PC monitor software is designed by the Graphical User Interface of MATLAB to monitor the operation of electromagnetic flowmeter and display signal gathered real-time. Then, the signal processing method based on comb-peak filtering for the measurement of water flow and the method based on statistical analysis and signal reconstruction for the measurement of slurry flow are adopted respectively. Also, the comparing experiments of slurry measurement as well as the calibration experiments for velocity of flow simulator and water flow are conducted.
The experimental results show that, the square-wave excitation control methods can broaden the frequency range of square-wave excitation widely under the premise of ensuring stable signal zero, and combing with PC monitor software, the calibration accuracy of electromagnetic flowmenter system developed is better than 0.5 for water flow as well as velocity of flow simulator, the fluctuating scale of full flow measurement for slurry is lower than 1% with a short response time in 4 seconds. Thereby, this significantly increases the measurement accuracy and speed of electromagnetic flowmeter, particularly improves the performance of electromagnetic flowmeter for slurry measurement. Hence, the study promotes the technology of domestic electromagnetic flowmeter and lays a certain foundation for its going into the international advanced level as well.
引文
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