基于高斯拟合的光纤法珀相关解调算法研究

为了提高非扫描式互相关解调系统的解调精度,通过分析非扫描式解调系统的信号特征,研究了一种基于高斯拟合的解调算法.该算法使用最大值寻峰算法解调出峰值位置,提取出峰值位置附近的光强数据,利用高斯函数对提取出的数据进行曲线拟合,提高了解调的精度.仿真结果表明,该算法具有良好的解调稳定性、解调准确性以及一定的抗干扰能力,仿真中测得该算法的解调误差标准差能达到0.288 6 nm.为了验证算法的实际解调效果,建立了基于现场可编程逻辑门阵列(FPGA)结合数字信号处理器(DSP)的硬件系统,对算法进行实际试验,试验结果表明,该算法拥有比较高的解调精度,解调结果均方差可达到1.6 nm,算法在DSP中的运行时间为700μs.     

基于PSO-ESPRIT算法的SAW温度传感器解调方法

目的 为了提高声表面波(Surface acoustic wave,SAW)温度传感器的测量精度,设计一种基于PSO-ESPRIT算法的高精度SAW温度传感器解调方法。方法 以ESPRIT谱估计方法为基础,把Hankel矩阵的时间窗长度与计算噪声方差时的K值作为粒子群优化(Particle swarm optimization, PSO)算法的输入变量,并以频率估计标准差作为粒子的适应度函数,利用PSO对ESPRIT算法中的参数进行优化,以改善频率估计精度,从而提高SAW回波信号频率估计的分辨率,实现SAW温度传感器的高精度解调。结果 仿真和实验结果表明,所设计的方法与其他谱估计算法相比,其对SAW回波信号估计的频率误差最小,标准差小于0.66kHz。把设计的算法用于SAW温度传感器的温度解调,得到的温度值与实际温度的误差小于0.4℃。结论 测试结果说明,设计的温度解调方法提高了SAW回波信号频率解调精度,可用于SAW温度传感器的解调,实现了对食品包装储运过程中温度的实时监测。     

基于卡尔曼滤波的光纤压力信号解调方法

针对光纤法布里-珀罗传感系统长时间运行时,数据采集等电路部分热噪声过大,造成压力信号相位解调误差过大的问题,建立了基于卡尔曼滤波算法的压力解调算法模型,使用卡尔曼滤波算法对光纤压力信号进行去噪处理.经过计算,当信噪比为15 dB的情况下相位解调误差低于0.1 rad,标准差缩小1 000倍,不同信噪比下,滤波后的相位解调标准差稳定在0.012~0.026 rad之间,绝对相位拟合直线的截距稳定在75.8~76.7.实验结果表明,经过降噪滤波处理的信号解调出的结果精度明显改善,提高了系统在噪声条件下的解调精度和整体稳定性.     

振动调频信号的循环平稳解调原理与实现方法

含有齿轮、滚动轴承等零部件的机械故障振动信号中，有一类信号称为频率调制信号（或称调相信号）。运用循环平稳分析理论，推导调频信号的循环自相关函数结果，并从理论上推导和分析了运用平方解调（或广义检波滤波解调）的方法实现对循环自相关函数的低频切片函数和高频切片函数进行解调的原理和方法，仿真验证理论推导正确，解调效果很好。最后通过对齿轮箱实测故障信号进行分析，验证该方法有很好的解调效果。     

广义解调算法中能量因子的引入与配置原理的研究

广义解调算法在振动信号时频谱应用中效果显著,而在分析解调频谱时对频率的初始值非常敏感。提出了能量因子可调的广义解调算法,将其应用到轴承振动信号的处理中并进行有效性评估。为获得轴承信号的相位函数,使用峰值搜索算法在包络信号中检测瞬时故障特征频率,估计拟合函数;引入了能量因子的概念,根据拟合函数配置能量因子,按照提出方法对原始信号进行重构;参考能量因子对重构信号的相位函数进行估计;对重构信号进行解调,得到关于能量因子的解调信号。根据特征频率的解调值与通过测得转速计算的理论值进行对比,评价能量因子配置的合理性。仿真和实测信号的处理,证明了算法的有效性。     

基于部分解调提前反馈的光纤陀螺振动误差抑制技术

振动环境下光纤陀螺性能的变化称为振动误差,抑制或消除振动误差是光纤陀螺实用化的必然要求。分析了全数字闭环光纤陀螺反馈延迟对闭环跟踪性能的影响,揭示了振动误差的机理是振动环境引入的扰动不能得到较好的抑制,从而引入附加相移误差。为了抑制附加相移误差,在保证闭环稳定的条件下,提出了部分解调提前反馈方法。理论和仿真分析了不同提前反馈比例下陀螺闭环的附加相移误差,在振动测试台上实测了不同提前反馈比例时引入的附加相移及陀螺输出,结果表明增加提前反馈比例时附加相移误差减小,陀螺振动误差同步相应减小。部分解调提前反馈方法适用于不同的调制方式,可在不修改结构、光路等硬件设计的条件下提高光纤陀螺振动环境适应性。     

光子多普勒测速系统信号解调方法比较

光子多普勒测速系统具有抗干扰能力强、测速范围大等优点,适用于信噪比低、信号质量差的测量场合。介绍光子多普勒测速系统的工作原理,详细阐述常用的四种信号解调方法——条纹法、相位解调法、短时傅里叶变换法、小波变换法的原理、特点和近几年的研究现状。利用上述四种信号解调方法对简谐振动调制的多普勒信号进行解调仿真,直观地展示不同信号解调方法的优缺点和适用性。实验结果表明,相位解调法最适合用于光子多普勒测速系统振动信号解调。最后讨论了采用递归希尔伯特变换的方法减小相位解调法的正交性误差的可行性,通过仿真实验验证了此方法的有效性。     

光纤光栅传感器动态解调方式的误差分析

主要介绍了扫描PZT器件法等四种典型动态解调方法的适用性,分析了其误差主要来源,并推导了其计算公式;分析了光强波动对几种解调方法解调精度的影响,评价了其影响程度,并得出了根据被测对象频率来选择解调方式的结论.     

循环自相关函数及其切片的解调原理分析

在具有齿轮、滚动轴承等设备的机械故障诊断中,幅值解调分析是非常有用的工具.分析了的基于循环平稳信号的循环自相关函数的解调原理,提出了一种新的解调方法--循环自相关函数切片法,由于平稳信号没有循环平稳的特点,使得该方法对加性平稳噪声具有自动降噪功能.     

基于MODEM技术的信号远传系统设计与实现

为了实现煤矿井下用电子皮带秤的信号远程传输,满足煤矿产量监控与计量的需要,设计了基于C8051F023和调制解调芯片MC145442的信号传输系统.系统以煤矿内部电话线为传输介质,实现了信号点对点的远程传输.传输过程中,频率信号通过C8051F023采集并进行整形处理,调制解调模块通过UART0与单片机相连,把采集的信号调制成正弦波信号远传到井上的接收单元,井上单元再解调还原出频率信号.现场试验数据表明,该远程数据传输系统性能稳定,抗干扰能力强,具有一定的实用价值.     

Effect of Truncation of Noisy Line Spread Function on the Computed Optical Transfer Function

Theoretical consideration is given to the error of the optical transfer function caused by noise and truncation of the measured line spread function. The error due to noise is shown to be an increasing function of the scanning range of the line spread function. An optimum scanning range is found to exist that minimizes the total error resulting from noise and truncation. Numerical calculation is presented for the case of an aberration-free circular aperture and the change in total error with varying scanning range and noise level is illustrated.     

超薄弹性层超声反射波频域测厚法

为了克服超声体积波测量方法只适用于测试厚度大于声波波长的弹性层的缺点,提出了频域相对传递函数法测量超薄弹性层的厚度的新方法.在推导超薄弹性层相对反射传递函数的基础上,用相对反射传递函数幅度谱、相位谱和复谱定征超薄弹性的厚度,分析了影响估计准确性的各种因素,研究了相对反射传递函数对厚度的灵敏度函数在误差传递中的意义.实验结果表明:相对传递函数法能够测量厚度为波长百分之一的铝薄层的厚度,相对误差小于2.5%,其中用幅度谱定征得到的结果最准确.这表明相对传递函数法可以有效地测量超薄弹性层的厚度,在实际应用中更加实用,其定征的准确性主要由相对传递函数对厚度灵敏度函数和测量误差共同决定.     

Systematic Errors that are Due to the Monochromatic-Equivalent Radiative Transfer Approximation in Thermal Emission Problems

An underlying assumption of data assimilation models is that the radiative transfer model used by them can simulate observed radiances with zero bias and small error. For practical reasons a fast parameterized radiative transfer model is used instead of a highly accurate line-by-line model. These fast models usually replace the spectral integration of the product of the transmittance and the Planck function with a monochromatic equivalent, namely, the product of a spectrally averaged transmittance and a spectrally averaged Planck function. The error of using this equivalent form is commonly assumed to be negligible. However, this error is not necessarily negligible and introduces a systematic height-dependent bias to the assimilation scheme. Although the bias could be corrected by a separate bias correction scheme, it is more effective to correct its source, the fast radiative transfer model. I examine the magnitude of error when the monochromatic-equivalent approach is used and demonstrate how a fast parameterized radiative model with Planck-weighted mean transmittances can effectively reduce if not eliminate these errors at source. I focus on channel 12 of the High-Resolution Infrared Radiation Sounder onboard the National Oceanic and Atmospheric Administration (NOAA)-14 satellite that, among all the channels of this instrument, displays the largest error.     

A comparison of transfer function estimators

The response of a linear time-invariant process on a stochastic input signal is characterized by the transfer function. Unknown past inputs and future output are sources of inaccuracy in relating a finite segment of an output signal via an estimated transfer function to the corresponding input segment. These end effects are usually characterized with error bounds on the Fourier transform of the output signal, but the error in an estimated transfer function can be quantified more precisely in terms of bias and variance. The accuracy of three transfer function estimators is compared, showing an infinite variance for the Experimental Transfer Function Estimate (ETFE) and a better efficiency for the estimators which are based on the cross spectrum. The variance due to additive noise depends on whether the input is a stochastic or a deterministic signal     

An instrumented structure to measure avalanche impact pressure: Error analysis from Monte Carlo simulations

Avalanche impact pressure on a flat surface has been quantified by full-scale experiments performed at the Lautaret avalanche test site (France). An inverse analysis method is used to reconstruct the pressure applied on this instrumented structure from the deformations recorded during the impact. The deformation-to-pressure transfer function of this large sensor is determined by analytical modelling and is used to quantify the pressure of an artificially released avalanche on the structure. Advanced sensitivity and error analyses are used to determine the uncertainty of the reconstructed pressure. First the uncertainties of the different parameters and processes involved are identified and estimated in the deformation-to-pressure transfer function through probability distributions. Then the sensitivity of the reconstructed pressures to these parameters is investigated to identify the most important parameters. Finally, the distribution of the uncertainty in terms of the probability density of the total error in the pressure is estimated using Monte Carlo simulations. Results are discussed on the basis of the drag coefficient to Froude number dependence and compared with previous avalanche data.     

Cost function analysis applied to the determination of aorta parameters

It has been shown by Fich and Welkowitz that a model of the aorta which is tapered in area and elastic constant and is essentially reflectionless is a good representation for the calculation of pressure and flow wave propagation in the aorta. If one then measures a steady state pressure transfer function in the aorta and relates it to the steady state pressure transfer function of the model, it is possible to adjust the physical parameter values that appear in the model until the transfer functions coincide. By this means it is possible to determine the physical parameters of the aorta.

Both analog and digital data techniques were developed for efficient handling of the data. Matching of the transfer functions was accomplished by finding the ‘best’ set of parameters that minimized a weighted error cost function derived from the magnitude and phase of the transfer functions.     

An instrumented structure to measure avalanche impact pressure: Error analysis from Monte Carlo simulations

Avalanche impact pressure on a flat surface has been quantified by full-scale experiments performed at the Lautaret avalanche test site (France). An inverse analysis method is used to reconstruct the pressure applied on this instrumented structure from the deformations recorded during the impact. The deformation-to-pressure transfer function of this large sensor is determined by analytical modelling and is used to quantify the pressure of an artificially released avalanche on the structure. Advanced sensitivity and error analyses are used to determine the uncertainty of the reconstructed pressure. First the uncertainties of the different parameters and processes involved are identified and estimated in the deformation-to-pressure transfer function through probability distributions. Then the sensitivity of the reconstructed pressures to these parameters is investigated to identify the most important parameters. Finally, the distribution of the uncertainty in terms of the probability density of the total error in the pressure is estimated using Monte Carlo simulations. Results are discussed on the basis of the drag coefficient to Froude number dependence and compared with previous avalanche data.     

一种氨水水平降膜吸收传热模型

在Navier-Stokes方程的基础上,提出一种新的氨水降膜吸收传热模型,通过对降膜过程中的液膜流动特性进行了一维变换,采用Grank-Nicholson方法对降膜特性进行求解,然后根据实验验证了理论模型的仿真结果,实验数据和仿真数据的误差在17%以内,并根据实验数据拟合出了传热系数公式,确定了不同管径下液膜的最大体积流量。     

Estimation of scattering error in spectrophotometric measurements of light absorption by aquatic particles from three-dimensional radiative transfer simulations

We present an approach based on three-dimensional Monte Carlo radiative transfer simulations for estimating scattering error in measurements of light absorption by aquatic particles with a typical laboratory double-beam spectrophotometer. The scattering error is calculated by combining the weighting function describing the angular distribution of photon losses that are due to scattering on suspended particles with the volume scattering function of particles. We applied this method to absorption measurements made on marine phytoplankton, a diatom Thalassiosira pseudonana and a cyanobacterium Synechococcus. Assuming that the scattering phase function is described by the Henyey-Greenstein formula, we determined the backscatter probability of phytoplankton, which yields the best correction for scattering error at a light wavelength of 750 nm, where true absorption is null. The backscattering ratio estimated for both phytoplankton species is significantly higher than previously reported data based on Mie-scattering calculations for homogeneous spheres. Depending on the type of particles, the corrected absorption spectra obtained with our method may be similar or significantly different from spectra obtained with the null-point correction based on wavelength-independent scattering error.     

工况传递路径分析法原理及其应用

工况传递路径分析法（OTPA）是一种有效振动传递路径的在线测量方法,测试中用振源处的振动加速度或噪声表征振源,用振动传递率表示传递路径,相对于传统传递路径分析（TPA）,不需要测量激励力和力到响应的传递函数（FRF）,测试过程得到简化,并可以在线测量。在推导分析工况传递路径的基本原理的基础上,分析其误差原因。并以一汽车振动噪声分析为例,介绍工况传递路径分析法的基本实施步骤,通过传递路径综合分析得出噪声源排序,并由此提出减振降噪措施建议。