旋转机械振动信号形态滤波器的设计与分析

对实测采样振动信号的滤波处理,验证了形态滤波器在抑制信号干扰、保留信号原有特征方面的作用。定量分析了形态滤波器设计中结构元素的形状、宽度、幅值等因素对形态滤波器性能的影响程度以及振动信号的采样频率对结构元素尺寸的影响,并根据数据分析结果得出了在对旋转机械振动信号进行降噪滤波处理时,形态滤波器中结构元素的形状及尺寸的一般设计规律。     

变速机械振动信号的伪同步重采样技术——Ⅱ滤波器设计与信号重采样

在变速回转机械信号等转角采样过程中,采样频率随着机械转速的变化而变化,同时,为防止信号频谱混迭,抗频混滤波器的截止频率必须满足采样定理。而对于伪同步信号重采样,由于重采样频率（瞬时转速）和重采样时刻均为连续时变函数,因此,信号的重采样比也应为连续时变函数。本文将探讨重采样滤波器（自适应信号滤波器）的设计问题,并给出信号重采样公式及其数字阶比谱算例。     

基于EEMD和共振解调的滚动轴承自适应故障诊断

本文为解决滚动轴承原始振动信号信噪比低以及带通滤波器参数选择依赖于人的主观经验等影响传统共振解调技术有效应用的问题,提出了EEMD自适应消噪和自适应共振解调相结合的方法。论文首先利用EEMD自适应地将信号分解成多个分量,通过互相关系数方法进行自适应重构以突出故障特征信号,然后利用谱峭度自动确定带通滤波器的中心频率和带宽,最后对滤波后的信号进行能量算子解调谱分析。数字仿真信号和滚动轴承实验证明了该方法的有效性。     

计及噪声影响的高准确度迭代滤波电网频率测量方法

电网频率是电力系统的关键参数,表征电网运行状态,对电力系统控制和保护至关重要。迭代滤波方法采用时域移频和迭代滤波两步可高效实现电网频率测量。然而,实际测量中,电力信号不可避免地受到噪声干扰而产生频率估计误差,影响频率测量准确度。因此,通过引入迭代滤波过程等效加权滤波器的等效噪声带宽、扇形损失参数以及滤波器重叠相关系数,研究加性高斯白噪声对基于迭代滤波的电力系统频率估计的影响,推导相应的方差表达式。通过设置不同的仿真参数,验证基于迭代滤波频率估计方差表达式的有效性。最后基于所推导的方差表达式,给出通过增加测量间隔和提高迭代次数提升实际测量中频率估计准确度的建议。     

基于全相位HHT的瞬时频率测量

全相位谱分析能够很好地抑制频谱泄漏、优化系统性能,其关键技术在于对数据进行全相位预处理。将这一技术运用于HHT求解瞬时频率中,提出了一种全相位HHT的瞬时频率测量算法,分析了全相位预处理和HHT求解瞬时频率的算法,将信号首先进行全相位预处理,然后用HHT算法求解信号的瞬时频率。这种算法是一种优化算法性能的算法,不会过多增加系统的计算量。通过对一非平稳信号分析,验证了基于全相位HHT的瞬时频率方差更小,具有更高的精确性。     

用相位差分和Wigner分布估计信号瞬时频率

时变信号瞬时频率的测量有许多重要的应用。例如,在地震勘探、雷达、声纳、通信、生物医学中,瞬时频率是一些物理现象的很好描述。Wigner分布是时,频信号分析的有效工具。本文阐述了信号瞬时频率的概念及其定义。论述了用相位差分和用Wigner分布估计瞬时频率的方法。论证了Wigner分布峰值检测可以为高信噪比下线性调频信号提供最佳估计。     

提高采样控制系统带宽的方法研究

影响控制系统带宽的主要因素有机械结构谐振频率、系统加速能力和系统采样频率。对影响采样控制系统带宽的因素作了详细的分析,给出在低采样频率下扩展系统带宽的两种方法棗虚拟采样法和多频率采样控制法,并对虚拟采样法进行了详细的讨论。实验结果表明,虚拟采样器在插值次数小于等于4时,插值精度可以满足要求,能够将系统带宽扩展3倍左右。     

基于广义解调平滑能量分离算法的瞬时频率估计

平滑能量分离算法能够跟踪调幅调频信号的瞬时频率,结合广义解调和复解析Gabor滤波器的优点能够克服平滑能量分离算法只适用于单分量窄带信号以及对噪声敏感的局限性。理论分析了负频干扰对传统广义解调多分量分离方法的影响,在此基础上提出了一种新的基于广义解调的平滑能量分离算法,该方法利用广义解调将非平稳信号转化为准平稳信号,再通过复解析Gabor滤波器对其进行滤波以达到单分量信号分离的效果,分离出来的准平稳信号无需进行逆广义解调,直接采用平滑能量分离算法求取瞬时频率,经过频率补偿得到原始信号的瞬时频率。仿真和试验结果表明该方法能够克服负频率干扰,且比传统方法具有更高的解调精度,进一步扩大了平滑能量分离算法的应用范围。     

计及负频率的DFT与DTFT相位差测量误差分析

针对噪声背景下计及负频率的DFT(Discrete Fourier Transform)与DTFT(Discrete Time Fourier Transform)相位差测量误差问题,用误差理论分别推导出高斯白噪声背景下计及负频率的DFT与DTFT相位差估计方差计算公式。对不同的泄漏误差系数、采样序列长度及信噪比,在负频率影响条件下进行计算验证。结果表明,仿真结果与计算结果一致,表明相位差测量误差分析公式的正确性。提升频率估计精度、增加采样序列长度、提高信号信噪比,可有效提升计及负频率的DFT与DTFT相位差测量方法精度。采样序列长度大于2048点或信噪比大于5 d B时,相位差测量精度提升有限,且DTFT相位差测量方法对频率估计精度更敏感。     

基于MSST的旋转机械故障诊断研究

在介绍多变量信号调制模型的基础上,提出了一种基于双变量同步挤压小波变换的旋转机械故障诊断新方法。该方法通过正交采样技术获取互相垂直通道的振动信号并将其组成一个双变量信号;用同步压缩小波变换分别获取每个变量的同步压缩值,并运用自适应频率拼接技术划分双变量带宽的时频域,以识别双变量中的单分量信号,确定在这些频带内存在的瞬时振幅和频率;根据多通道联合瞬时频率概念融合双变量信号中每个通道的瞬时频率和瞬时幅值,得到双变量信号的时频表征。转子双稳态信号、转子松动不对中碰摩复合故障和齿轮减速箱振动信号分析结果证明了所提方法的可行性和有效性。     

Spectral recovery by analytic continuation in crossing-based spectrum analysis

By the use of analytic continuation, the correct spectrum of an undersampled analog input signal f(a) (t) of a true bandwidth B is recovered from an aliased Fourier spectrum that is computed directly from a data set consisting of sinusoid-crossing locations {t(i)}, where the signal f(a) (t) intersects with a reference sinusoid r(t) with a frequency of W 相似文献   

侧壁四电极电容耦合非接触电导检测器(英文)

研制了一种集成于硅基电泳芯片分离沟道末端侧壁的新型四电极电容耦合非接触电导检测器.研究了该电导检测器的等效模型,对等效电路模型中的参数进行了公式推导,并讨论了影响电导检测响应灵敏度的相关因素.采用深刻蚀及离子注入加工技术制得了用于电导检测的立体电极.制作了基于锁相放大原理的信号处理电路,对该电导检测的频率响应及灵敏度进行了测试分析.实验结果表明,当激励信号频率为300 kHz时,该电导检测器具有最佳线性度;不同浓度Na+溶液响应电压差值为5 mV;检测限达到10-8mol/L;且成功实现了Na+和Li+混合无机阳离子的电泳分离在线检测.     

基于离散频谱分析的自由衰减振动信号的幅值恢复

加矩形窗截断后的自由衰减振动信号可以看成无限长谐波信号与单边指数函数及矩形窗的乘积,从理论上证明了其连续谱峰值点的频率和相位就是信号的实际频率和相位。分析了连续谱的离散频谱幅值误差影响因素,提出一种新的求解幅值恢复系数的方法,该方法根据已估计得到的阻尼、频率和相位重构幅值为给定值的新信号,然后求解加有限长度指数窗幅值恢复系数。当理论频率位于某条离散谱线上,幅值基本无误差。理论分析和仿真表明,采样频率、阻尼和频率误差的变化对幅值分析精度的影响很大,并且是相互作用的,但当理论频率与采样频率之比fn/fs在区间(0.25,0.4)内,且阻尼在区间(0.005,0.02)时,不论频率误差多大,分析精度均很高,幅值误差小于5%。相邻频率成分产生严重模态耦合时,不能使用该方法。     

Microprocessor Implementation of a Fast and Simultaneous Amplitude and Frequency Detector for Sinusoidal Signals

A microprocessor-controlled implementation of a fast and simultaneous amplitude and frequency detector for sinusoidal signals is introduced. The method computes the amplitude and frequency from three successive samples of the input signal. A special feature is that the samples are taken within a fraction of the period of the signal being measured, thereby minimizing the measurement time. Automatic selection of the sampling interval is based on the input frequency range.     

Photon Fluctuations,Equivalent Quantum Efficiency,and the Information Capacity of Photographic Images

The equivalent quantum efficiency (EQE) enables the signol-to-noise ratio of a detector to be compared with that attainable by an ideal noiseless detector working under the some conditions. It thus provides a scientific basis for the measurement of photographic speed-to-grain ratios. The limitations of an ideal detector are only those imposed by photon fluctuations in the signal. The signal itself may also be measured in terms of these inherent photon fluctuations, and this enables the information capacity of the detector to be expressed in terms only of the EQE and the ratio of the power spectrum of the signal to that of the photon fluctuations. There are several advantages when the information capaCity is expressed in this manner. Not only is the signal specified in a basic farm, but also, since the EQE is the most fundamental of imaging properties, the information capacity of the photographic process can be rapidly compared with that of any other type of detector by substitution of the appropriate value of the EQE. In this way the information capacity can also be compared with the ultimate capacity, which is that of the signal itself and corresponds to an EQE of 100 per cent. Examples are given of the information capacity for a range of values of the EQE and signal size, and its spatial frequency dependence is demonstrated in terms of the transfer function.     

流形学习在机械故障诊断中的应用研究

本文针对信号采集系统的特性对流形学习方法性能的影响尚不明确这一问题,采用理论分析和模拟实验的方法,研究了信号采样系统的非线性、零点漂移等特性对流形学习算法性能的影响.结果表明,当信号采样系统的特性保持相对稳定时,流形学习方法可以在一定程度上容忍系统存在的非线性和零点漂移效应.为了使流形学习算法达到较好的效果,在数据的搜集和预处理过程中,应使得数据容易重构到一个高维空间中且它们之间的相似性易于度量.从而,本文的研究结果为流形学习方法在机械故障诊断中的应用提供了一定的理论基础.     

水声测量中的宽频技术应用方法

讨论一种基于宽频分析技术进行水声测量的方法——宽频噪声比较法。该方法从频域分析的角度出发,根据水声测量的实际需要,通过修改Welch法理论,以噪声为信号源,运用现代信号处理技术和数字化硬件系统,实现了水听器的宽频噪声比较法校准系统在宽频范围内的快速高效测量,是对单频脉冲比较法的一个重要补充。对于高Q值水声换能器的测量,避免信号瞬态效应的影响,采用宽频噪声技术更有优势。还对不同采样频率条件下的测量结果进行了比较．结果表明宽频噪声比较法采用脉冲序列内多个脉冲处理结果累加取平均的方法,可以降低对采样频率的要求,或者在设备最高采样频率一定条件下可以实现更高频率范围的测试。     

Relationship between microscanned image quality and fill factor of detectors

Microscanning is an important technique in high-resolution electro-optical imaging. It can increase the resolution and improve the performance of imaging systems. For optimum design of a staring imaging system with microscanning modes it is necessary to choose the optimum microscanning mode according to the fill factor of the detector. Hence it is important to study the effect of the fill factor on the microscanning image quality. With some assumptions, we introduce the sampling-averaging modulation transfer function of a detector array at the spatial Nyquist frequency with which to study quantitatively the improvement in image quality of various microscanning modes for selected fill factors (1, 2/3, and 1/2). Analytical results show that the amount of improvement is closely associated with the fill factor. Finally, typical sampling imaging of focal plane arrays with these fill factors are simulated. Experimental results qualitatively describe the effect of the fill factor on the microscanning image and show good agreement with theoretical analysis.     

双四象限光电探测器在线测试虚拟仪器

通过监测与所接收的激光弥散斑相对应的输出信号的变化率可以对探测器进行实时非接触测量,从而实现以双四象限探测器为接收器件的产品的在线检测和质量控制。介绍了以Labwindows/CVI为开发平台的双四象限探测器的测试、分析系统。建立了探测器接收弥散斑与输出信号变化率的关系模型,采用三次样条插值函数提高欠采样时ns级极窄光电脉冲信号峰值的求取精度。通过实验得到了探测器接收弥散斑与光敏面直径的最佳比值为0.5。研究结果表明,弥散斑直径测量的分辨力为0.0096mm,峰值电压测量幅值分辨力0.1mV。     

Digital-sampling systems in high-resolution and wide dynamic-range energy measurements: Comparison with peak sensing ADCs

The use of fast digital sampling techniques in Nuclear Physics experiments as a replacement of the standard analog signal processing methods is discussed for applications needing high-resolution signal amplitude measurements. This is for example the case of a solid-state detector with a charge-sensitive preamplifier, processed using fast digital sampling methods. Under very general assumptions, an expression for the achievable resolution and dynamic range of the system is reported, valid for any detector/digitizer/digital-filter combination, taking into account the detector noise and the ADC properties, namely the Effective Number of Bits (ENOB) and the sampling frequency. The system properties are summarized using the parameter PSENOB, i.e. the “Peak-Sensing-Equivalent Number of Bits”. These results can be used to predict the attainable performances in various applications, possibly requiring a resolution/dynamic-range trade-off. Numerical examples for some representative cases in γ-ray spectroscopy and charged particle experiments are reported, demonstrating that the equivalent performances of a 15 bit peak-sensing ADC are feasible with today-available sampling ADCs. For ease of presentation, other non-trivial effects as baseline- and non-linearity-related issues as well as experimental tests of the proposed approach are presented in a companion paper [L. Bardelli, G. Poggi, Digital sampling-systems in high-resolution and wide dynamic-range energy measurements: finite time window, baseline effects, and experimental tests, this issue].