超声液体声学特性测量技术研究

发布时间：2019-06-11 13:29

【摘要】：超声液体声学特性测量在石油化工行业、液态食品行业以及医学诊疗领域都有非常重要的意义。通过测量得到的声速、声阻抗和声衰减等参数进一步推导得到液体的密度、浓度、黏度等理化常数，在各个领域的应用越来越广泛。在这种课题背景下，针对传统测量手段的不足，本文研究了基于线性调频连续波的超声液体声学特性测量系统。本文的主要研究内容和成果如下：（1）基于超声波在不同介质界面处的传播特性，建立了用于测量液体声学特性的三层有界介质透射模型。通过对超声波在测量模型中的传播变化情况详细分析，设计了能够有效测量待测液体声速、声阻抗和声衰减参数的方法和具体步骤。（2）针对三层有界介质透射模型，结合国家移动超声探测工程技术研究中心的高速数据收发系统和DSP数字集成电路构建起完整的超声液体声学特性测量系统。采用具有脉冲压缩特性、抗噪和抗干扰性能优越的大时宽带宽积线性调频连续波作为信号源，并根据探头型号进行参数设置。（3）对传统的恒包络LFM信号做出改进，设计基于幅度补偿的预失真处理方案，经过仿真和实验结果证明，预失真处理能够有效解决接收信号幅度衰减和抖动严重的问题。（4）构建实验验证系统，选用乙醇溶液、橄榄油和牛奶作为三种待测液体分别进行测量，对系统接收到的透射信号采用基于时域互相关的时延估计算法和基于FOCUSS算法的幅度估计进行处理，，并计算得到三种液体声速、声阻抗和声衰减特性参数。通过Matlab仿真和实验结果对比可以看出，这两种算法能够较准确估计出LFM信号的传播时延和幅度衰减，结果误差在合理范围之内。
[Abstract]:Ultrasonic liquid acoustic measurement is of great significance in petrochemical industry, liquid food industry and medical diagnosis and treatment. The physical and chemical constants of liquid, such as density, concentration, viscosity and so on, are further deduced from the measured parameters such as sound velocity, acoustic impedance and acoustic attenuation, which are more and more widely used in various fields. In this paper, an ultrasonic liquid acoustic characteristic measurement system based on linear frequency modulation continuous wave (LFM) is studied to overcome the shortcomings of traditional measurement methods. The main research contents and achievements of this paper are as follows: (1) based on the propagation characteristics of ultrasonic wave at different dielectric interfaces, a three-layer bounded dielectric transmission model for measuring the acoustic characteristics of liquid is established. Based on the detailed analysis of the propagation and variation of ultrasonic wave in the measurement model, a method and concrete steps are designed to effectively measure the sound velocity, acoustic impedance and acoustic attenuation parameters of the liquid to be measured. (2) according to the three-layer bounded dielectric transmission model, a complete ultrasonic liquid acoustic characteristic measurement system is constructed by combining the high-speed data receiving and receiving system of the National Mobile Ultrasonic Detection Engineering Technology Research Center and DSP digital integrated circuit. The large time broadband wide product linear frequency modulation continuous wave with pulse compression characteristics, excellent anti-noise and anti-interference performance is used as the signal source, and the parameters are set according to the probe model. (3) the traditional constant envelope LFM signal is improved, and a pre-distortion processing scheme based on amplitude compensation is designed. The simulation and experimental results show that the pre-distortion processing can effectively solve the problem of serious amplitude attenuation and jitter of the received signal. (4) the experimental verification system was constructed, and ethanol solution, olive oil and milk were selected as three kinds of liquids to be measured respectively. The transmitted signals received by the system are processed by time delay estimation algorithm based on time domain cross correlation and amplitude estimation based on FOCUSS algorithm, and three kinds of liquid sound velocity, acoustic impedance and acoustic attenuation characteristic parameters are calculated. Through the comparison of Matlab simulation and experimental results, it can be seen that the two algorithms can accurately estimate the propagation delay and amplitude attenuation of LFM signal, and the error is within a reasonable range.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB52

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