基于多普勒效应的速度测量仪 毕业设计.doc

摘要
流场中有各种物理量,比如压力,密度,速度,其中以速度测量最为复杂。传统的测量方法,如热线热膜流速计、压电探头、机械流速仪、电磁流速计等是接触式的,必须把探头插入流场,对流场有较大干扰,影响测量的真实性和可靠性,并且对于一些特殊的流场如高温烟气、喷燃火焰、腐蚀性流体等也不便于进行接触式测量。而激光多普勒测速技术(LDV,Laser Doppler Velocimetry)是一种非接触式测量方法。它以光的多普勒效应为理论基础,利用流体中的散射粒子对入射激光进行散射,并通过光电探测器探测散射光的频率变化,这种频率变化通常称为频移,根据其中包含的速度信息(粒子散射光的频移与粒子速度呈线性关系)得到流体的运动速度。其动态响应快、空间分辨率高、测量范围大,在测量精度以及实时性上都具有突出的优点。
本文分析比较了现有的激光多普勒测速技术。针对已有激光多普勒测速仪适用面窄,信号处理能力有限,稳定性和测量精度较差等缺点,提出了一种基于数字信号处理技术的激光多普勒测速仪设计方案。本文详细介绍了多普勒信号的处理方法,给出了多普勒信号采集卡的硬件实现方案。
第一章叙述了研究该课题的目的和意义。通过对现有激光多普勒测速技术的分析比较,证明了研制数字信号处理式激光多普勒测速仪的可行性和必要性。
第二章分析了激光多普勒测速仪的工作原理,对差动LDV模型进行了简要介绍,推导出激光多普勒信号的数学模型。在参考现有LDV光路系统的基础上对传统的差动式LDV模型进行了改造,给出了一种新的光路系统设计方案:一维差动偏振式光路系统。
第三章详细介绍了数字信号处理式激光多普勒测速仪的设计方案。其中包括基于TMS320C6713的多普勒信号采集卡硬件电路(前向通道、数据存储部分、主机通信部分)和软件设计(外扩EEPROM的在线编程、数据采集卡boot程序、数据采集卡驱动程序)。
第四章给出了多普勒信号处理的具体方法。主要是以FFT变换为基础的周期图法和峰值逼近法。
第五章对全文进行总结,给出了多普勒信号处理的改进措施。
关键词:多普勒效应,激光多普勒测速(LDV),数字信号处理,TMS320C6713,FFT,峰值逼近
The Speed Measuring Instrument Based on Doppler Effect
ABSTRACT
There are various physical quantities in the flow field, such as pressure, density, velocity, of which the plex velocity measurement. Traditional measurement methods, such as HWFA, piezoelectric sensor, mechanical flow meter, ic flow meter, is the contact, and must probe into the flow field, flow field have a greater interference of the true measurement And reliability, and for some special fields such as high temperature gas flow, burner flame, corrosive fluids are not convenient for contact measurement. The laser Doppler velocimetry (LDV, Laser Doppler Velocimetry) is a non-contact measurement method. It is the Doppler effect of light based on the theory, the use of scattering particles in the fluid in the scattering of incident laser and scattered light through the photoelectric detector of the frequency change, this frequency is often referred to as frequency shift, according to which contains Speed ​​information (light scattering frequency shift and a linear relationship between particle velocity) a