光纤传感器中偏振开关法消偏振衰落技术

针对低双折射光纤双光束干涉型传感器两臂偏振态随机变化引起的信号衰落,提出的一种新型消偏振方式可以在可见度略有下降的情况下,较好地消除偏振态变化引起的干涉信号可见度的随机变化。该方案是通过相互正交的两个偏振态,补偿由于其中一个偏振态变化导致的干涉信号衰落。通过自动增益控制电路（AGC）可以使传感信号稳定,能够在信噪比有所下降的情况下消除偏振衰落的影响,实现干涉型光纤传感器的消偏振衰落。     

岩石中爆炸应变波信号测试与分析

针对岩石爆破过程中爆炸应变波信号易失真、难测试的特点,建立了一套稳定可靠的超动态应变测试系统.实测了小药量耦合装药在岩石模型中爆炸产生的径向爆炸应变波信号,得到了装药爆炸应变波形的特点以及应变峰值与药包长径比、药量、相对距离的变化关系.试验结果表明:(1)岩石爆破过程中爆炸波综合作用时间约为10μs,表现出初始以压应力为主,持续的压、拉应力交替现象,爆炸加载应变率以104 s-1的数量级变化;(2)药包长径比和药量的变化对应变峰值变化幅度影响在爆源近距离处较大,在相对距离大于45后影响较小;(3)长径比大的药包的爆炸能量对介质作用较为分散,有利于提高炸药的能量利用率.     

基于Brillouin散射的分布式光纤拉伸应变传感器的理论分析

分布式光纤拉伸应变传感器具有非常重要的应用前景。本文中着重从理论上分析讨论了光纤拉伸应变与由此引起的Ｂｒｉｌｌｏｕｉｎ散射光相对于入射光频移量的变化关系。计算结果表明：其理论和实验数据基本吻合。     

Performance Analysis of a Terminal-reflected Fibre Ring-resonant Sensor

An all-fibre terminal-reflected ring resonator is proposed as a highly sensitive sensor. An analysis has been made of the performance characteristics, which depend on the coupling condition of a directional coupler forming a fibre ring, fibre parameters and the time-coherence of a laser source. If the laser source has a phase-coherence factor larger than 0·95, the sensing system proposed would be practical. The system can be doubly sensitized to the fibre ring resonator only, and is not susceptible to the noise-like phase perturbations induced in the feeding fibre.     

RF Spectrum of a Signal after Frequency Multiplication; Measurement and Comparison with a Simple Calculation

A novel experimental technique is introduced and used to measure the effect of frequency multiplication on the RF spectrum of an oscillator. This technique makes it possible to produce the RF spectrum at X band?where measurements are relatively straightforward?that would have been produced by frequency multiplication of the 5-MHz source to any frequency from 9.2 GHz to 100 THz (1014 Hz). A simplified theory is developed and shown to reproduce the experimental results for the relative power in the carrier and noise pedestal, and the shape and the width of the carrier and noise pedestal, to within the measurement uncertainty of 2 or 3 dB, from 5 MHz to 10 THz. The calculations are easily made using analytical techniques from the measurement of the spectral density of phase fluctuations of the source, the effective input spectrum density and the bandwidth of the multiplier chain, and the frequency multiplication factor. It is shown that present 5-MHz-crystal-controlled oscillators are useful as a precision source to ~500 GHz. Suggestions for extending their range to ~100 THz are made.     

Analysis of Large Heterogeneous Repairable System Reliability Data With Static System Attributes and Dynamic Sensor Measurement in Big Data Environment

ABSTRACT

In the age of Big Data, one pressing challenge facing engineers is to perform reliability analysis for a large fleet of heterogeneous repairable systems with covariates. In addition to static covariates, which include time-invariant system attributes such as nominal operating conditions, geo-locations, etc., the recent advances of sensing technologies have also made it possible to obtain dynamic sensor measurement of system operating and environmental conditions. As a common practice in the Big Data environment, the massive reliability data are typically stored in some distributed storage systems. Leveraging the power of modern statistical learning, this article investigates a statistical approach which integrates the random forests algorithm and the classical data analysis methodologies for repairable system reliability, such as the nonparametric estimator for the mean cumulative function and the parametric models based on the nonhomogeneous Poisson process. We show that the proposed approach effectively addresses some common challenges arising from practice, including system heterogeneity, covariate selection, model specification and data locality due to the distributed data storage. The large sample properties as well as the uniform consistency of the proposed estimator are established. Two numerical examples and a case study are presented to illustrate the application of the proposed approach. The strengths of the proposed approach are demonstrated by comparison studies. Datasets and computer code have been made available on GitHub.     

Strain Measurement in a Shape Memory Alloy with Strain Gauges

Abstract:  The recovery of shape due to temperature-induced martensite to austenite phase transformation in shape memory alloys (SMA), such as nickel titanium alloys, has been investigated and utilised in applications for many years. One of the problems in incorporating SMA in host materials, such as composites, is the poor bonding characteristics of the SMA. A closely related problem in experiments is the measurement of strains in SMA specimens; as thin wires have been used in many of the experimental investigations, strains have been deduced from length measurements. In the current work, electrical resistance strain gauges have been bonded on SMA strips. Tensile strains up to 8% during tensile loading as well as compressive strains during strain recovery due to subsequent heating have been measured. Strains determined by other methods, such as extensometer and length measurements, are also reported and compared. The major contribution of this work is the successful bonding of strain gauges on SMA and the measurement of large strains (up to 8%).     

Strain Measurement on a Rail Bridge Loaded to Failure Using a Fiber Bragg Grating-Based Distributed Sensor System

The paper reports results obtained from an unusual situation in structural monitoring—a “test-to-destruction,” measuring strain using a series of fiber Bragg gratings (FBGs) sensors on a decommissioned concrete Railway Bridge in ÖrnskÖldsvik, Sweden. The study formed part of the EU “Sustainable Bridges” Project. To undertake the study, FBG-based sensors were chosen and embedded in carbon fiber reinforced polymers (CFRPs) composite rods incorporated into grooves specially created in the concrete structure and interrogated using a compact system based on wavelength-division multiplexing (WDM). Throughout the study, the FBG sensors were continuously monitored, allowing the incremental increases in the strain to be seen and through the yield point of the carbon composite reinforcement. The sensors were able to follow the resulting induced changes in strain of over a range in excess of 4000 $mu varepsilon$ just prior to failure of the bridge and representing extreme levels of strain for such a mechanical structure. The measurements made with the FBG-based system were found to be in agreement with the changes expected in the structure (together with the embedded reinforcement), produced by the loading applied. The study has demonstrated the successful use of FBG-based technology premounted in “smart” carbon fiber composite reinforcements used in a test of this type on a typical bridge structure of a type found widely across the world.      

一种MEMS压力传感器测试分析

MEMS压力传感器由于体积小使得工艺实现存在一定难度,样品的测试分析十分重要。本文对研制的三批样品进行测试分析,判断失效样品的制造原因,通过改进工艺,制备出符合要求样品,给出达标样品测试结果。     

机器人腕力传感器时序建模与频谱分析

从时域和频域两方面研究了机器人六维腕力传感器的动态响应。建立了AR模型,分析了功率谱,计算了传递函数和滞后时间,解决了机器人腕力传感器研究中的若干基础性问题。     

基于超声频域分析的碳纤维复合材料孔隙率检测

提出了一种基于超声波频谱分析理论建模与实验标定的碳纤维复合材料孔隙率的检测方法,对碳纤维复合材料孔隙率的频域检测法进行实验分析和讨论,并通过具体示例进行验证,证实了该检测方法是可行的。     

飞秒脉冲光谱测量对时域波形重建的影响

利用光谱相位还原直接电场重建法对飞秒脉冲激光时域波形进行重建,分析了光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的影响。使用低压汞灯对光谱仪波长校准,根据校准结果,对测量光谱蓝移和红移,通过数值模拟研究波长示值误差对重建脉冲波形的影响;利用光谱辐射照度标准装置对光谱仪光谱辐照度校准,通过增加白噪声模拟分析和各种常用反射片实验测量研究光谱辐照度示值误差对重建脉冲波形的影响。结果表明,光谱测量波长示值误差和光谱辐照度示值误差对于飞秒脉冲光谱测量的相对标准差在1%之内。     

带传感器温度变送器测量值的不确定度分析与评定

本文针对带铂电阻温度变送器的校准过程及校准结果,依据JJF1059.1-2012《测量不确定度评定与表示》对其校准结果的不确定度进行了分析与评定,以期在不确定度给出时提供技术上的参考依据。     

基于F-P标准具和Music算法的FBG动态应变传感系统

提出了基于可调光纤环形激光器结构,并采用F-P标准具解调的光纤布拉格光栅(FBG)动态应变传感系统,具有高达60 dB的光学信噪比.F-P标准具用来作为一个边缘滤波器探测FBG波长的漂移,这样的解调方式具有稳定性高的优点.为了提高动态应变测量系统的分辨率,采用了Music算法进行频谱分析.实验结果显示,在700Hz时的动态应变分辨率达到了0.1με/Hz~(1/2),是传统FFT算法的10倍.     

流量测量中超声多普勒信号的频谱特点及其与管道中流速的关系

研究了工业测流的超声多普勒信号的频谱特点，并以此为依据分析了不同安装方式对多普勒频谱的影响，提出了不同测量环境下，应用多普勒频谱计算流速的公式及必要的修正，为提高检测准确度提供了理论依据。     

水声信号LOFAR谱图的线谱迹图象处理

本文提出了一种对水声信号功率谱瀑布图(L0FAR谱图)的图象处理方法,采用半领域法和区域检测法来滤除因水声信号随机干扰引起的图象噪声,净化LOFAR谱图中的线谱迹.对实际水声信号的处理结果表明,本文方法有明显的去噪效果.     

微波叶尖间隙测量传感器的计算分析

介绍了利用微波相位法测量短距离位移的工作原理,建立了一种基于此原理的谐振腔结构微波传感器模型,并完成了模拟计算。分析了微波传感器测量发动机叶尖间隙的能力,和高温环境对传感器性能的影响。结果显示此传感器能够在高温环境下完成0~6 mm范围内的高精度位移测量,可以很好的应用于航空发动机叶尖间隙的测试。     

基于静力衡量法和光学法的超微容量测量方法对比分析

分别使用静力衡量法和光学法对超微容量进行测量。光学法测量中,按照分光原理分别设计了以时域分光和空域分光为基础的测量系统。2套光学测量系统在1μL和10μL的容量测量数据分别为0.967μL和0.929μL以及9.976μL和9.729μL;时域分光测量系统在1μL和10μL测量点重复性为3.2%和2.54%,空域分光测量系统为3.6%和2.02%。2套光学系统相比,时域分光系统的探测器灵敏度更好,在低浓度超微容量测量中能检测到更多光强信息。光学法与静力衡量法获得了相同的结论,证明了光学法在超微容量测量领域的可行性。光学法与静力衡量法相比,光学法针对液体蒸发的处理方法更加简单,光学元件的设计可以有效减小蒸发的影响。     

直线度测量用片簧式传感器的结构与精度分析

对高精度直线度测量仪用片簧式传感器的结构进行了设计,并给出了相应的误差分析。