基于FPGA的颗粒群光散射式气溶胶质量浓度测量系统研究

发布时间：2018-05-18 12:00

本文选题：颗粒群光散射 + 气溶胶　；参考：《南京信息工程大学》2017年硕士论文

【摘要】：气溶胶质量浓度是评价大气环境好坏的重要参数之一,该参数的实时监测已迫在眉睫,而颗粒群光散射法具有快速、高精度、宽的浓度范围且能够在线测量的优点。本文研究并设计了一套基于颗粒群光散射法的气溶胶质量浓度测量系统。本文主要工作包括:提出了将经过激光束的粒子群等效为一颗凝聚体粒子,建立了采用凝聚体电压信号幅度分布反演气溶胶质量浓度的分形模型,该模型充分利用了凝聚体粒子的电压信号幅度及信号数目信息且考虑了颗粒形貌因素,能够有效提高反演精度。基于气溶胶质量浓度的分形模型,设计了用于采集和处理信号的多通道电路。该电路由FPGA控制高速ADC进行信号采集,STM32负责相关数据处理和外围器件的控制。在信号采集电路中,采用了非均匀通道划分的方式,该方式可以有效提高系统的反演速度。考虑到颗粒群光散射法测量的气溶胶质量浓度范围较宽,本文提出了分段标定法标定分形模型中的参数。实验结果表明:对于烟尘样品,当相对湿度在60%以内,质量浓度在0.5～13.0 mg/m3的范围之间时,分形模型反演的质量浓度值与实际测量值吻合较好,两组实验的平均相对误差分别为5.6%和6.0%;而采用电压积分量反演的质量浓度平均相对误差分别为11.0%和18.5%。该结果说明采用颗粒凝聚体集合的散射光信号幅度分布反演气溶胶质量浓度更精确。在高湿度情况下,首先利用Mie散射理论,计算了相对湿度对球形粒子散射系数的影响;然后,利用标准仪器与本文实验装置同时对不同相对湿度条件下的颗粒物进行测量,基于PSO算法处理得到了相对湿度与气溶胶质量浓度分形模型中标定参数之间的变化关系,利用该变化关系可以对标定参数实时修正,对比实验结果表明PSO算法可以提高光散射法反演模型实时测量的精度。本文的研究正好符合国家当前对大气环境实时监测的需求,对治理大气污染和保护人类健康有着重大意义。
[Abstract]:Aerosol mass concentration is one of the most important parameters to evaluate the atmospheric environment. The real-time monitoring of aerosol concentration is imminent, and the particle group light scattering method has the advantages of fast, high precision, wide concentration range and can be measured online. An aerosol mass concentration measurement system based on particle group light scattering method is studied and designed in this paper. The main work of this paper is as follows: the particle swarm passing through laser beam is equivalent to a condensed particle, and a fractal model for retrieving aerosol mass concentration using the amplitude distribution of condensate voltage signal is established. The model makes full use of the information of voltage signal amplitude and signal number of condenser particles and takes into account the factors of particle morphology so that the inversion accuracy can be improved effectively. Based on the fractal model of aerosol concentration, a multichannel circuit is designed for collecting and processing signals. The circuit is controlled by FPGA and high speed ADC for signal acquisition. STM32 is responsible for data processing and peripheral device control. In the signal acquisition circuit, non-uniform channel division is adopted, which can effectively improve the inversion speed of the system. Considering the wide range of aerosol mass concentration measured by particle group light scattering method, this paper presents the parameters of fractal model calibrated by piecewise calibration method. The experimental results show that when the relative humidity is less than 60% and the mass concentration is in the range of 0.5 ~ 13.0 mg/m3, the inversion mass concentration of the fractal model is in good agreement with the actual measured value. The average relative errors of the two groups of experiments are 5.6% and 6.0%, respectively, while the average relative errors of mass concentration obtained by the voltage integral inversion are 11.0% and 18.5%, respectively. The results show that the aerosol mass concentration inversion is more accurate by using the scattering light signal amplitude distribution of the aggregate of particle condensate. In the case of high humidity, the influence of relative humidity on scattering coefficient of spherical particles is first calculated by using Mie scattering theory, and then the particles under different relative humidity conditions are measured simultaneously by using standard instrument and experimental apparatus in this paper. Based on the PSO algorithm, the relationship between the calibration parameters in the fractal model of relative humidity and aerosol concentration is obtained and the calibration parameters can be corrected in real time. The experimental results show that the PSO algorithm can improve the accuracy of real time measurement of the inversion model by light scattering method. The research in this paper is in line with the national demand for real-time monitoring of atmospheric environment, which is of great significance to the control of air pollution and the protection of human health.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X513;TN791

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