起伏噪声中单矢量传感器预警检测方法

针对现有振动传感器能量检测方法在较低信噪比及环境噪声变化较大时检测性能较差问题,提出矢量传感器协方差检测方法。该方法利用矢量传感器多通道采样数据构造协方差矩阵,并以最大特征值与最小特征值之比为检验统计量进行目标判决。用该方法检测目标不仅无需噪声先验知识,可有效克服噪声起伏变化带来的影响。仿真及实验表明,该方法检测性能良好,计算复杂度小,适合于矢量传感器对目标检测预警。     

减小噪声干扰的热敏电阻传感器动态测量误差补偿

为了补偿热敏电阻的动态测量误差，可在传感器的输出端串接一个动态补偿环节。该环节本质上是一个带通或高通滤波器，补偿环节的增加将引起严重的噪声放大，影响测量系统的精度。研究了在噪声环境下，改善热敏电阻传感器的动态特性的方法，该方法在采用实验数据得到补偿环节系数的同时，采用多项式预测滤波和中值滤波相结合的方法减小测量系统的噪声。仿真实验验证了该方法的有效性。     

减小定向穿越管道地面摩擦阻力的施工方法

本文结合哈尔滨某地供水工程,介绍了一种减小定向穿越管道地面摩擦阻力的施工方法.该施工方法解决了常规施工中遇到的难题,且易操作、施工效率高,具有显著的实用价值和推广价值.     

同振式矢量传感器设计方法的研究

对同振式矢量传感器的工作原理进行了分析,并在此基础上对同振式矢量传感器的结构设计进行了优化。分析了同振式矢量传感器整体平均密度籽和波尺寸ka与被测水质点振动速度v0之间的关系,得出了同振式矢量传感器的优化设计准则和声散射对同振式矢量传感器设计的影响,为同振式高频矢量传感器的研制提供了可参考依据。     

矢量拖线阵流噪声抑制方法研究

通过对矢量拖线阵流噪声各分量功率谱的推导以及流噪声各分量间相关性的分析,提出了基于声强流的流噪声抑制方法。根据湖试数据的验证可以看出,该方法可以将矢量拖线阵流噪声功率谱抑制到低于声压阵流噪声功率谱的水平。     

自适应噪声抵消在矢量传感器方位估计中的应用

矢量传感器能同时拾取声压和质点振速信息．单个矢量传感器就可以估计目标方位,因此非常适合在一些小平台上使用。一般平台的自噪声非常大,这对于目标的方位估计很不利,必须设法抑制自噪声以估计目标方位。文中采用自适应噪声抵消器对平台自噪声进行抑制,介绍了两种噪声抵消的方法,然后进行方位估计。同时对这两种方法作了计算机仿真。结果表明,两种方法都能有效地抑制平台本地噪声。     

加速度矢量水听器定向声呐浮标的定位方法

本文对加速度矢量水听器被动定向声呐浮标中的偶极子方向性形成、罗盘指向信号形成、低频信号调制、接收信号解调和目标方位计算进行了简明的分析,并就其实现方法进行了原理性的探讨。     

减小应变式多维力传感器测量误差的一种方法

针对目前多维力传感器各维间耦合造成的测量误差过大的问题,提出了适用于应变式多维力传感器的互耦补偿电阻解耦方法。理论分析与实际应用结果表明,该方法能有效地消除传感器各维间的耦合作用,大大减小因此而产生的测量误差。     

基于光纤矢量水听器的浅海噪声矢量场特性研究

基于简正波理论分析了浅海噪声矢量场声压和质点振速的强度特性,仿真了浅海声压和质点振速的噪声强度在深度和频率上的变化特性,噪声矢量场强度特性仿真结果与实验测量结果一致。针对声场测量的有效性,给出了加速度通道自噪声谱级和灵敏度必须满足的关系式,并提出了降低自噪声对接收系统影响的两种措施。最后分析并对比了系统自噪声谱级和海洋环境噪声谱级,结果表明,声压通道的自噪声比环境噪声谱级低20 d B左右,Y通道和Z通道的自噪声比环境噪声低3.5 d B以上,X通道的自噪声谱级在200 Hz附近与环境噪声谱级最为接近,约比环境噪声低1.5 d B。     

采用统计方法减小黑体辐射源比较分度噪声等效温差

分析了黑体辐射源比较测量过程的特点,采用消除辐射温度计线性漂移的比较测量方法,抑制辐射温度计输出非线性漂移和随机噪声影响统计平均处理方法,减小辐射温度计的噪声等效温差.使用不同的统计平均数量,得到相应测量条件下黑体辐射源比较分度的测量水平.测量结果中噪声等效温差可以优于0.01℃.统计处理方法不仅可以应用在黑体辐射源比较分度中,而且可以扩展应用在与黑体辐射源比较分度类似比较测量过程.     

基于AR谱的声矢量传感器阵方位估计

1.引言 水声信号处理中研究的对象是声场,基于传统的声压传感器阵的水声信号处理只拾取声场的声压,而具有方向敏感性的矢量传感器可以同时测得质点振速等矢量信号,即同时获得p,Vx,Vy,Vz四个关于目标信息的物理量,由于获得的关于声场信息量的增加,基于矢量传感器阵的定向精度必将得到改善[1].常规的波束形成法如Bartlett法,Capon法是一种非参数谱估计法,没有将信号的可用信息结合到估计中[2],本文将AR模型法引入声矢量阵信号处理,将信号的模型结合到谱估计算法中,获得了更精确,分辨率更高的谱估计.     

声矢量阵列的求根 MUSIC算法及其性能分析

在传统声压传感器阵列的求根MUSIC算法的基础上,提出了基于矢量传感器阵列的求根MUSIC算法及其修正形式,通过接收阵列信号的空间谱,选择合适的引导方位,可实现声源的波达方向(DOA)估计.理论推导和仿真实验表明,采用均匀矢量传感器线性阵列的求根MUSIC算法在低信噪比、小快拍数情况下的估计性能要优于传统声压传感器阵列的求根MUSIC算法,同时该算法的计算量远远小于矢量传感器列的MUSIC算法.     

悬臂梁式光纤声传感器研究

光纤声传感器种类很多，但大多着眼于水声，作水听器用。现在本文提出一种可用于空气声检测的悬臂梁式光纤声传感器。本文给出了该种传感器的实验装置，谐振频率，灵敏度的计算，同时给出了它们的实验值。用这种传感器在实验室内可测到最低声正为１×１０－４Ｐａ（１００Ｈｚ时）     

压电膜片传感器的声发射特性研究

现代自动化工业中,声发射传感器已被广泛应用于材料损伤监测,旧式商用声发射传感器因为结构脆弱,在实际应用中需直接粘于被测结构表面,导致二次利用率不高.为使所应用的监测系统效益比更高,本文提出一种采用压电隔膜作为敏感芯体的传感器结构.利用铅笔断裂法对其声学特性进行表征,测试结果显示,压电隔膜传感器和传统AE(声发射)商用传...     

连续流流态下基于声矢量传感器的引气管路设计

基于气流速度测量模型,运用流体动力学的知识,建立了在连续流流态下的引气管路的动态响应模型,推导了引气管路的传递函数。通过传递函数,分析了引气管路的动态特性,提出了引气管路的设计准则,并通过Fluent流体实验验证了引气管路的动态响应模型和设计准则。     

Acoustic Wave Flow Sensor Using Quartz Thickness Shear Mode Resonator

A quartz thickness shear mode (TSM) bulk acoustic wave resonator was used for in situ and real-time detection of liquid flow rate in this study. A special flow chamber made of 2 parallel acrylic plates was designed for flow measurement. The flow chamber has a rectangular flow channel, 2 flow reservoirs for stabilizing the fluid flow, a sensor mounting port for resonator holding, one inlet port, and one outlet port for pipe connection. A 5-MHz TSM quartz resonator was edge-bonded to the sensor mounting port with one side exposed to the flowing liquid and other side exposed to air. The electrical impedance spectra of the quartz resonator at different volumetric flow rate conditions were measured by an impedance analyzer for the extraction of the resonant frequency through a data-fitting method. The fundamental, 3rd, 5th, 7th, and 9th resonant frequency shifts were found to be around 920, 3572, 5947, 8228, and 10 300 Hz for flow rate variation from 0 to 3000 mL/min, which had a corresponding Reynolds number change from 0 to 822. The resonant frequency shifts of different modes are found to be quadratic with flow rate, which is attributed to the nonlinear effect of quartz resonator due to the effective normal pressure imposing on the resonator sensor by the flowing fluid. The results indicate that quartz TSM resonators can be used for flow sensors with characteristics of simplicity, fast response, and good repeatability.     

A Comparative Study for Material Selection of Sensor Element Using Analytic Hierarchy Process

Material selection is crucial for sensor elements. Because of the numerous material alternatives available in the market, systematic methods must be employed to select the most suitable sensor material that satisfies technical, metrological and economic criteria. In this study, analytic hierarchy process (AHP) is employed for the selection of sensor material. Twenty common materials are classified in three groups according to their elasticity modulus, and then the best sensor material in each group is determined then the AHP rankings of the materials are calculated. The results show that AISI 4340 steel and CuBe alloy are the most suitable materials within the high- and lower-modulus groups, respectively, and Ni-Span-C is another good alternative sensor element.     

Wireless Acoustic Emission Sensor Network for Structural Monitoring

The paper presents a prototype wireless system for the detection of active fatigue cracks in aging railways bridges in real-time. The system is based on a small low-cost sensor node, called an AEPod, that has four acoustic emission (AE) channels and a strain channel for sensing, as well as the capability to communicate in a wireless fashion with other nodes and a base station. AEPods are placed at fracture-critical bridge locations. The strain sensor detects oncoming traffic and triggers the AEPod out of its hibernation mode. As the train stresses the fracture-critical member, acoustic emission and strain data are acquired. The data are compressed and filtered at the AEPod and transmitted off the bridge using cell-phone communication.     

Acoustic Emission Sensor Calibration for Absolute Source Measurements

This paper describes sensor calibration and signal analysis techniques applicable to the method of acoustic emission (AE) and ultrasonic testing. They are particularly useful for obtaining absolute measurements of AE wave amplitude and shape, which can be used to constrain the physics and mechanics of the AE source. We illustrate how to perform calibration tests on a thick plate and how to implement two different mechanical calibration sources: ball impact and glass capillary fracture. In this way, the instrument response function can be estimated from theory, without the need for a reference transducer. We demonstrate the methodology by comparing calibration results for four different piezoelectric acoustic emission sensors: Physical Acoustics (PAC) PAC R15, PAC NANO30, DigitalWave B1025, and the Glaser-type conical sensor. From the results of these tests, sensor aperture effects are quantified and the accuracy of calibration source models is verified. Finally, this paper describes how the effects of the sensor can be modeled using an autoregressive-moving average (ARMA) model, and how this technique can be used to effectively remove sensor-induced distortion so that a displacement time history can be retrieved from recorded signals.     

Parametric Analysis of Acoustic Emission Signals for Evaluating Damage in Composites Using a PVDF Film Sensor

With the increased utilization of advanced composites in strategic industries, the concept of Structural Health Monitoring (SHM) with its inherent advantages is gaining ground over the conventional methods of NDE and NDI. The most attractive feature of this concept is on-line evaluation using embedded sensors. Consequently, development of methodologies with identification of appropriate sensors such as PVDF films becomes the key for exploiting the new concept. And, of the methods used for on-line evaluation acoustic emission has been most effective. Thus, Acoustic Emission (AE) generated during static tensile loading of glass fiber reinforced plastic composites was monitored using a Polyvinylidene fluoride (PVDF) film sensor. The frequency response of the film sensor was obtained with pencil lead breakage tests to choose the appropriate band of operation. The specimen considered for the experiments were chosen to characterize the differences in the operation of the failure mechanisms through AE parametric analysis. The results of the investigations can be characterized using AE parameter indicating that a PVDF film sensor was effective as an AE sensor used in structural health monitoring on-line.