基于Matlab的列车加速度信号处理

列车加逮度对运行控制系统极为重要，但由于其非高斯特性，使得传统功率谱估计方法受到限制，借助于Matlab信号处理工具箱的强大分析能力，利用双谱估计对信号进行处理，获取频率信息，并提出了判断列车运行不平稳的准则。     

双谱估计结合EEMD的齿轮故障特征提取

以实测齿轮箱振动信号为分析对象,对锥齿轮系统进行故障特征提取。通过总体平均经验模态分解(EEMD)将采集到的振动信号进行分解,对比分析原始信号功率谱密度特性和各本征模态函数(IMF)频谱特性,抽取相关频带的IMF分量进行信号重构;对重构信号利用直接法进行双谱估计,计算重构信号的双谱熵和非高斯性强度并分析其随试验时间的变化趋势。结果表明,双谱熵和非高斯性强度可以有效反映齿轮运行实时状况,可作为故障诊断和趋势预测的故障特征值。     

基于高阶谱的齿轮故障特征提取方法研究

基于高阶谱能够抑制高斯信号,并且可以在较强的背景噪声中提取故障信息的特点,在分析高阶谱的理论基础上,针对齿轮振动信号的非线性、频谱成分多样性等特点,研究了基于高阶谱分析的机械故障特征提取方法,提出了基于双谱估计的齿轮故障诊断方法.试验结果表明,该方法能够有效地将正常及不同裂纹程度的齿轮区分开来.     

双谱分析及其在滚动轴承故障诊断中的应用

双谱是处理非线性、非高斯性信号的有力工具,它包含了高阶谱的所有特性.针对滚动轴承具有非线性和非高斯的特性,利用双谱分析方法研究了不同故障模式下滚动轴承的双谱特性以及同一故障类型在不同程度时的双谱特性.实验结果表明,利用双谱特性能很好地区分滚动轴承的不同故障模式以及故障的严重程度,双谱分析方法在滚动轴承故障诊断中具有良好的工程应用前景.     

基于双谱估计的轴承非线性振动信号模式识别

当滚动轴承发生故障时,其产生的振动信号一般是包含较强噪声的非高斯和非线性耦合信号.本文对把高阶统计量用于滚动轴承非线性振动信号特征模式识别的方法进行了研究,提出了基于双谱估计的滚动轴承故障诊断方法.利用这种方法可以同时获得包含滚动轴承故障信号幅值和相位耦合信息的双谱特征图谱.实验研究表明,利用双谱图谱中不同的非线性耦合其故障特征模式不同的特点,可以快速地识别轴承的工作状态.     

基于双谱分析的滚动轴承故障模式识别

当滚动轴承发生故障时,其产生的振动信号一般是包含较强噪声的非高斯和非线性信号。本文对高阶统计量方法用于滚动轴承故障特征提取进行了研究,提出了基于双谱估计的滚动轴承故障诊断方法。利用这种方法可以同时获得包含滚动轴承故障信号幅值和相位信息的双谱特征图谱。研究表明,双谱图谱可以有效地监测滚动轴承工作状态的模式,因而可以快速地识别滚动轴承不同的故障特征。     

基于系统传递特性的齿轮箱齿根裂纹故障诊断

以齿轮箱整体为一个系统,利用功率谱估计方法求出齿轮箱系统的传递特性,通过对传递特性的时域功率谱分析,可以有效地解决输入出现扭振或转速出现波动对故障诊断精度造成的影响。最后以齿轮箱齿根裂纹故障诊断证明其有效性。     

基于系统传递特性的齿轮箱轴承故障诊断研究

以齿轮箱整体为一个系统，利用功率谱估计方法求出齿轮箱系统的传递特性，通过对传递特性的时域功率谱分析，可以有效地解决输入扭矩出现扭振或转速出现波动以及其它外界干扰对故障诊断精度造成影响的问题。     

齿轮齿面误差的三座标测量与二维谱估计

文中介绍了圆柱齿轮齿面误差采用三座标测量和二维信号处理的测量和数据处理方法,提出了改进的二维Kimura谱估计并用于估计斜齿轮齿面周期误差的频率成份。实验分析表明:(1)改进的Kimura谱估计有尖锐的谱峰和高的分辨率;(2)齿面误差的功率谱估计能很好的揭示圆柱齿轮齿面波形的特征和诊断机床一刀具一工件系统的主要周期误差源。这对齿轮自动化生产中的测量和精度改善是很有实际意义的。     

平顶高斯光束通过复杂光学系统的传输特性研究

为研究平顶高斯光束通过高斯光阑-透镜系统的传输特性,基于光学矩阵的方法和Collins公式导出了平顶高斯光束通过该复杂光学系统后的场分布的解析表达式和近轴光强分布值,进而分析了平顶高斯光束通过高斯光阑-透镜系统后的传输特性。研究结果表明,平顶高斯光束通过高斯光阑-透镜系统后,实际焦点位置和几何焦点位置并不重合,即发生焦移现象。焦移量的大小与高斯光阑宽度及光阑与透镜间的距离等因素有关,即在一定条件下,光阑宽度增大,相对焦移量变小,光阑与透镜之间的距离与焦距的比越小,相对焦移量就越小。     

ORDER BISPECTRUM: A NEW TOOL FOR RECIPROCATED MACHINE CONDITION MONITORING

Vibrations and sounds generated by reciprocated machines or by their parts strongly depend on the rotation speed of the main shaft of the tested reciprocating system. At the testing or at common performance of the reciprocated machines, their rotation speed is usually changing. With regard to this fact, signals produced by reciprocating machines are non-stationary ones. Therefore, conventional time-invariant methods of their spectral or bispectral analysis are frequently unable to provide meaningful results. In order to solve this problem in the field of polyspectral signal analysis, the order bispectrum analysis is proposed in this contribution. This approach is based on the bispectrum estimation from the signal which is a function of the angle of roll of the main shaft of reciprocated machine. A digital representation of this signal can be obtained by resampling of the signal conveniently sampled in the time domain. The advantages of the order bispectrum application in comparison with that of the conventional bispectrum approach is illustrated based on the example of an engine set classification.     

Limitations in the use of median frequency for lung sound analysis

The aim of this paper is to investigate methods of standardizing lung sound analysis, with a view to supplementing traditional spirometric air flow measurements to help in the diagnosis of asthma and to provide a measure of the effectiveness of treatment. Lung sounds were measured in nine patients with asthma and five control subjects, alongside air flow measurements of forced expiratory volume (FEV1) and forced vital capacity (FVC). The patients were administered the bronchodilator, salbutamol, to assess how effective these measurement techniques were for quantifying its effect. The results agree with previous studies, that analysis of lung sounds is a potentially useful tool for indicating air flow changes. The results, however, also demonstrate that the emerging standard of 'F50' or 'median frequency' should be treated with great caution because of its high sensitivity to the measurement frequency range. F50 is very unlikely to provide a reliable single indicator of lung condition.     

基于 PVDF 非均匀曲率半径结构的高灵敏度电子听诊器

电子听诊器是利用电子技术收集处理心肺音,并依此辅助判断病人身体状况的一种仪器。针对传统电子听诊器灵敏度低、低频响应差等缺点,基于 PVDF 非均匀曲率半径的弯曲夹紧结构,提出了一种高灵敏度的电子听诊器设计方案。通过建立相应的非齐次弦振动模型,理论分析比较证明了非均匀曲率相比均匀曲率的灵敏度有显著提高,并优选非均匀曲率半径结构灵敏度最大的参数研制出一款新型电子听诊器拾音器。实验测试结果表明,该拾音器的灵敏度达到1.7 mV/Pa,相较近年来研究的均匀曲率半径 PVDF 与硅胶衬底组合结构的拾音器灵敏度提高了13.3%。该拾音器能在2-2 kHz 频带范围中保持平坦的频响特性,涵盖心肺音采集的频响范围,为较完整地获取心肺音信号提供有力保障。     

Sound quality analysis of a passenger car based on electroencephalography

This paper presents the correlation between psychological and physiological acoustics for automobile sounds. The purpose of this paper is to evaluate the quality of the interior sound in passenger cars based on electroencephalogram (EEG). Previous objective evaluation method of sound quality involved the use of sound metrics based on psychological acoustics. The proposed method employed not only the psychological but also the physiological acoustics. In this work, the sounds of seven premium passenger cars were recorded, and they were evaluated subjectively by 33 people. The correlation between the subjective rating and the sound metrics was calculated based on psychological acoustics. Finally, the correlation between the subjective rating and the brain EEG was also calculated. Based on these results, a new evaluation system for evaluating the quality of the interior sounds of passenger cars was developed based on bio-signals.     

声学故障诊断中的宽带相关噪声信号分离方法

为了提取混合噪声中待诊设备的噪声信号，利用传声器组构造线性测量阵列流型，建立多声源机器系统的宽带相关噪声混合模型。使用聚集变换技术消除频率对参数估计的影响，并同时消除相关信号功率谱矩阵的奇异性，采用宽带相关MUSIC法估计噪声方差与声源方位，从混合信号频谱中分离噪声源信号频谱。该方法可减小其他噪声源信号的干扰，提高待检设备噪声信号的信噪比。实验结果验证了模型与算法的可行性。     

Effects of amplitude modulation on perception of wind turbine noise

Wind turbine noise is considered to be easily detectable and highly annoying at relatively lower sound levels than other noise sources. Many previous studies attributed this characteristic to amplitude modulation. However, it is unclear whether amplitude modulation is the main cause of these properties of wind turbine noise. Therefore, the aim of the current study is to identify the relationship between amplitude modulation and these two properties of wind turbine noise. For this investigation, two experiments were conducted. In the first experiment, 12 participants determined the detection thresholds of six target sounds in the presence of background noise. In the second experiment, 12 participants matched the loudness of modified sounds without amplitude modulation to that of target sounds with amplitude modulation. The results showed that the detection threshold was lowered as the modulation depth increased; additionally, sounds with amplitude modulation had higher subjective loudness than those without amplitude modulation.     

对风机盘管噪声测试与控制方法的讨论

讨论了空调工程中常用的末端装置-风机盘管机组噪声测试方法和控制措施.依据相关标准规定,对A声压级测试方法进行了讨论.对于大多数末端设备,各种噪声源和路径会带来室内噪声问题.噪声源的控制需要与产品内部结构的设计相符,噪声传播路径的控制着重于使房间或建筑内末端设备安装工艺更合理.     

轴承组件非线性特征的研究

本文通过对一个轴承组件结构在预载和非预载情况下所进行的动态试验,发现轴承组件在这两种情况下具有不同的非线性特征。文中阐述了非线性系统的双谱分析、细化双谱分析等方法,给出双谱的快速估算公式,并利用双谱和细化双谱对轴承组件的试验结果进行分析,得到一些有关轴承组件动态特笥的重要结论。     

电弧声信号与铝合金MIG焊缝塌陷的相关性

针对铝合金MIG焊过程热积累作用强容易产生焊缝突然塌陷从而导致焊接过程失败的问题,建立电弧声信号传感系统并以焊接电弧声为研究对象,运用小波分析方法研究焊接电弧声信号与焊缝塌陷的相关性。研究表明电弧声信号的能量变化与焊缝塌陷有着明显的对应关系,电弧声总能量随着焊缝开始塌陷而增加,对电弧声进行小波分解发现不同频带有着不同的变化规律。研究结果为铝合金MIG焊实时焊接塌陷缺陷的检测提供一种新型有效的方法。     

Investigation of the perception characteristics of multiple impact sounds occurring from the manipulation of electronic devices

Electronic devices must be quiet during manipulation for operations. In addition, the sounds need to show distinct impression to satisfy the user’s auditory experience and indicate the completion of an operation. The sounds occur in a short time from frictional contact and the consequent structural vibration when a user operates a device. In this study, the impact sound during printer cassette insertion is analyzed. The rail vibration during closure movement generates continuous sound. This movement ends with the impact sound from contact between the cassette and printer body. The sounds occur as clicking sounds with double impacts separated by a short interval. This clicking sound is important serving as an indicator of completed insertion. The user’s perception of this complex sound is investigated. A physical index to quantify the generated sound is proposed to assist comparisons between printers. Prony’s method was used to characterize the sound features including duration, double impact interval, magnitudes, and decay rates. From the extracted features, artificial clicking sounds were simulated for sound quality evaluations. Auditory experiments were performed to investigate the user’s preference for the separated rail and impact noises. The just noticeable difference was defined to classify the important factors influencing the perception characteristics.