【作者】 王雪艳；

【导师】 刘缠牢；

【作者基本信息】 西安工业大学 ， 精密仪器及机械， 2011， 硕士

【摘要】 基于米氏散射理论的激光粒度分析仪由颗粒的散射光强分布来反演颗粒粒度分布,在理论上归结为第一类Fredholm积分方程的求解,由于这是一个典型的不适定问题,粒度反演算法成为激光粒度仪的核心研究内容和热点。因此开展这方面的研究显得十分必要和迫切。本文的研究内容集中在基于米氏散射理论的粒度测试反演算法方面。利用VisualC++6.0软件,结合实验室试验平台,主要完成的工作如下：1)在米氏散射理论和激光粒度仪工作原理的基础上,建立了单个颗粒及颗粒系的光散射模型,进行了理论推导,并以Visual C++6.0为平台编写程序进行了模拟验证,包括米氏散射光强大小及分布规律模拟、不同粒径颗粒散射光的角分布规律模拟等。根据不同粒径范围颗粒系的散射光强角分布规律,设计了相应环形光电探测器的尺寸参数,对其颗粒系的散射光强进行仿真探测。2)研究了典型的非独立模式和独立模式反演算法,总结了非独立模式和独立模式反演算法各自的特点。仿真研究发现：非独立模式反演算法计算简单,但需要事先假设颗粒的粒度分布满足某个特定函数,这在很大程度上限制了其应用。独立模式迭代反演算法理论上可以获得任意颗粒系的粒度分布,但对噪声极其敏感,易于造成粒度测量结果失真。3)在光能列向量上引入随机噪声模拟实测时的光能分布,针对独立模式算法对噪声极其敏感,易于造成粒度测量结果失真的问题,进行了深入研究,论述了光能分布的复杂性以及实际测量中从光能上去噪的不易操作性,引入数据平滑算法,对反演结果进行平滑处理,有效消除了误差影响,提高了粒度测量的精度及其可靠性。4)在现有试验平台上,对标准样品进行大量测试,结合仿真研究,分析试验系统的误差因素,对实验系统提出改进方案和要求。通过本课题的研究,完成了基于米氏散射理论的激光粒度测试系统的理论分析和实验探究。说明其理论模型是可行的,相应的实验研究和结果是可靠的。解决了粒度测试反演算法实际应用受噪声影响使测量失真的问题,满足了现代粉体工业粒度测量精度高、可靠稳定的要求。实验发现,经平滑处理,误差分布趋于一致,通过检校、定标,误差将得到进一步的控制。更多还原

【Abstract】 The laser particle size analyzer based on Mie scattering theory performs inversion of particle size distribution from scattered light intensity distribution of particles and resolved into the solution of Fredholm integral equation of the first kind. Since this is a typical ill-posed problem, particle size inverse algorithm becomes the key research content and hot spot of laser particle size analyzer. Thus it seems to be rather necessary and urgent to carry out this research.The research content of this article is concentrated in particle size test based on Mie theory. The main works completed are as follows, with the help of Visual C++6.0 and in combination with experiment platforms in laboratories:1) On the basis of mastering Mie theory and the working principle of laser particle size analyzer, light scattering modules for single particles and particle systems are established, theoretical derivation is carried out, and a program is written to perform simulation verification with Visual C++6.0 as the platform, including simulation of Mie scattered light intensity and distribution law, simulation of angular distribution law of scattered light of particles in different sizes, and so on. The specification parameters of corresponding annular photodetectors are designed according to different particle size measurement ranges, and simulation detection is performed to the scattered light intensity of their particle systems.2) Typical non-independent-mode and independent-mode particle size inverse algorithms are researched, and the respective characteristics of non-independent mode and independent mode are summarized. It is found out by simulation researches that the inverse algorithm of non-independent mode is easy to calculate, but it is necessary to suppose that the particle size distribution meets a certain function, which greatly limits its applications. The iterative inverse algorithm of independent mode, theoretically, can obtain the particle size application of any particle system, but is extremely sensitive to noise, so that it easily leads to distortion of particle size measurement result.3) The luminous energy distribution at the time of random noise simulation measurement is introduced into the luminous energy column vector. The iterative inverse algorithm of independent mode is extremely sensitive to noise, so that it easily leads to distortion of particle size measurement result. In depth research is conducted on this problem, the complexity of luminous energy distribution and the nonoperability of denoising the luminous energy in practical measurement are discussed, and data smoothing algorithm is introduced to make smoothing processing to the inversion results. This effectively eliminates the influence of errors, and improves the precision and reliability of particle size measurement.4) A great deal of tests are performed to standard samples on the existing experiment platforms, the error factors of the experiment system are analyzed in combination of the simulation research, and improvement proposals and requirements are proposed to the experiment system at last.With the researches of this thesis, system theoretical analysis and experiment researches on the laser particle size test based on Mie theory are completed. This proves that the theoretical model of it is feasible, and corresponding experimental researches and results are reliable. It also solves the problem that influence on practical application of particle size test inverse algorithm from noise leads to measurement distortion, and satisfies the requirements on high precision, reliability and stability of particle size measurement in modern powder industry. Experiments show that after smoothing processing, the error distribution reaches unanimity, and the errors will be further controlled through verification and calibration.更多还原