机械声混合及其盲分离技术的研究

盲源分离是一个很有优势的盲信号分析与处理工具,在机械状态监测与故障诊断领域有较好的应用前景.但在实际应用于机械源信号、尤其是机械声源信号分离中,源分离精度还不够高.鉴于此,在分析机械声产生、传播与混合机理以及盲分离算法基础上,提出了新的解决途径,特别是基于带通滤波改进的盲源分离新方法.仿真以及实际的机械声源盲分离实验结果,证实了新方法的有效性.     

机械声源信号的带通滤波盲分离

盲源分离是一个很独特的盲信号分析与处理工具，在机械设备状态监测与故障诊断领域有较好的应用前景。但在实际应用于机械源信号分离中，效果尚不够理想。特别是，当传感观测中存在高斯噪声或调制源时，往往无法获得准确的源波形恢复。本文在分析现有盲源分离算法的基础上，提出一种新的、基于带通滤波的改进盲源分离方法。仿真以及实际的机械声源信号分离实验结果证实了新方法的有效性。     

盲卷积分离及其在机械振动信号消噪中的应用研究

盲源分离应用于机械振动信号的预处理中，提供了一个新的处理机制，在机械状态监测和故障诊断中具有一定的价值。本文研究了盲卷积分离的理论，提出了基于限值VQM检验控制准则的盲分离算法，根据机械振动信号的特点探讨了该方法在机械振动信号瞬态成分和噪声卷积混叠信号分离中的应用，有效地提取了瞬态成分，表明了算法的有效性。     

盲源分离在转子复合故障诊断中的应用

提出了基于盲分离技术的转子复合故障诊断的新思路,采用基于统计量的解相关法对仿真得到的裂纹与碰摩、裂纹与油膜涡动复合故障信号进行了盲分离,各复合故障的主要频谱特征被分离出来.分离结果表明采用盲源分离技术进行转子结构的复合故障诊断是可行的.     

基于盲信号处理的机械噪声监测与故障诊断

摘　要: 在介绍盲信号处理统一模型的基础上,全面归纳了其典型算法,综述了它在机械噪声监测与故障诊断中的研究现状,重点讨论了混合模型、噪声盲源分离与盲解卷积、盲源分离与多种技术的结合、噪声监测与诊断系统研究等方面的应用,并指出需要进一步研究的主要问题。
     

基于EEMD子带提取相关机械振动信号单通道盲源分离

针对传统独立分量分析难以解决机械故障诊断中存在的相关源信号盲分离、欠定盲分离等问题,在相关振源信号部分子带满足统计独立的假设前提下,提出基于总体经验模态分解子带提取相关机械源单通道盲源分离方法。该方法将单通道观测信号进行总体经验模态分解获得到子带观测信号,将单通道信号及子带观测信号组成新的多维信号,利用奇异值分解及贝叶斯准则估计源信号数目;据互信息标准与源信号数目选若干独立性较强的子带观测信号重构,实现信号升维;对重构的观测信号进行白化预处理及联合近似对角化,获得源信号估计。并仿真、实验验证该方法在机械故障诊断中的有效性。     

机械信号处理的BSS算法及其比较研究

在由多个独立振动构成的复杂机械振动的状态监测和故障诊断中,复杂机械信号的分离和识别的效果往往是其故障诊断成功的关键.为了得到最佳的机械信号分离算法,对5类经典的盲源分离(BSS)算法的特点和性能进行了比较研究,提出了一套评价准则,使用典型的仿真机械信号,对其在机械故障诊断中的典型机械信号的分离效果进行了充分的实验和详细评估.之后,运用两组来自真实工业设备部件的振动数据去检验其结果.研究结果表明不同的BSS算法具有各自的特点,对处理不同类型的机械信号有不同的效果,其结果有指导意义.     

基于盲解卷积的柴油机振动信号分离研究

基于振动信号分析的故障诊断方法依赖于机械状态特征的有效提取,盲源分离能够从复杂的信号中分离出源信号,是一种有效的特征提取手段。建立的多通道盲解卷积模型和机械系统的振动模型表明了两个模型的一致性,理论上证明了盲解卷积用于机械振动信号分离的可行性。利用MBLMS算法进行实测柴油机振动信号的分离实验,成功分离出了活塞撞击、燃烧和进气阀关闭信号,试验结果证明了盲解卷积能够有效分离柴油机振动信号。     

旋转机械故障信号的去噪源分析

旋转机械振动信号是其故障特征识别与诊断的重要信息来源,将应用统计特征来分解混合信号的去噪源分离(DSS)引入到旋转机械故障诊断中。研究DSS基本理论及其正切去噪函数,并进行模拟信号分离,其分离后的性能指标及与源信号相似系数均优于盲源分离;并将DSS应用于某燃气轮机的实测故障信号分析,诊断出转子发生不平衡及异频伪共振现象,表明该方法在旋转机械故障诊断中的有效性,为机械设备的状态监测和故障诊断提供新的思路和方法。     

基于盲源分离和AR谱估计的旋转机械故障诊断方法

准确的AR模型能够较好地揭示信号中蕴含的状态特征变化的信息,然而,AR模型对系统的状态变化十分敏感,多个动态变化的源信号的耦合必然会影响其估计结果。基于此,提出了一种基于盲源分离和AR谱估计的旋转机械故障诊断方法。首先,利用盲源分离的方法从混合观测信号中恢复各机械振动源信号;然后,将非平稳性的故障信号通过经验模态分解得到各本征模态函数;最后,对经验模态分解得到的平稳的本征模态函数进行AR谱估计,提取振动信号的故障特征信息。通过仿真研究和实验分析验证了该方法在旋转机械故障诊断中的有效性和可行性。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.