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介绍了一种精确计算机械振动信号频谱幅、频、相的方法。在机械振信号频谱分析的基础上,利用改进的傅立叶变换谱,可以大大提高频率分辨率。经计算检验,该方法的精度较高。 相似文献
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同步提取变换(synchroextracting transform, 简称SET)通过提取短时傅里叶变换(short-time Fourier transform, 简称STFT)在瞬时频率位置的时频系数可获得较理想的时频谱,该方法提高了时频分辨率,减少了交叉项的影响,一定程度上抑制了噪声对STFT时频谱的干扰。针对在SET时频谱的基础上进行信号分量的重构与故障诊断拓展方面的应用,提出了一种基于顺序统计滤波器(order statistics filter, 简称OSF)的SET信号分量重构方法。首先,利用边际谱表征SET时频谱中信号的幅值在整个频率范围内随频率变化的情况;其次,采用顺序统计滤波器分割边际谱,将分割所得边界映射至SET时频谱后,利用SET逆变换重构信号分量;最后,利用峭度指标筛选包含丰富故障信息的分量并进行包络分析,提取故障特征。仿真信号及滚动轴承内圈故障信号的处理结果证明了该方法的有效性。 相似文献
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为解决复合叠加信号的分离、高精度、高分辨率频谱分析等问题,将全相位谱分析技术应用在32位数字信号处理器(DSP)中,进行了复合信号检测与分离,提出了双通道同步采样和采样频率自适应的方法。将TMS320F28335优异的信号处理能力和强大的浮点运算能力与先进的全相位谱分析技术相结合,设计出了一台复合信号频率计。系统测试结果表明:该复合信号频率计的频率分辨率高达0.4%,频率精度达10-5级别,全相位谱分析技术具有很高的精度和良好的抑制频谱泄漏性能,开辟了频谱分析的新空间。 相似文献
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研究了贝叶斯频谱估计的基本理论和基本方法,分别对频率扫描法和频差扫描法进行了研究和计算。仿真结果显示,采用加窗方法可有效提高频率扫描法的频率识别精度。在采样信号相同的条件下,频率扫描法的频率采样点数为1000,得到的频率分辨率为1%。差频扫描法的采样点数为100,得到的频率分辨率为0.1%。贝叶斯频谱分析中模型的选取是决定性的因素。 相似文献
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对于机械振动与故障诊断等领域中常见的极高频(接近奈奎斯特频率)信号,传统的离散频谱校正方法存在着较大误差,负频率成分干涉严重是影响其频谱分析精度的重要因素。为提高极高频信号的频谱分析与校正精度,给出了一种计及负频率影响的离散频谱校正新方法。该方法基于Blackman窗,依据离散频谱的周期性并利用局部谱峰附近的3条谱线,建立包含正负频率贡献的离散频谱校正模型,通过对模型的求解获得频率、幅值和相位校正公式。采用频段内扫描的方式对频谱校正公式进行了仿真验证,结果表明所提方法可有效降低负频率成分对极高频信号频谱的干涉影响,提高其频率、幅值和相位校正精度。 相似文献
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常规多频涡流检测技术在谱分析时,一般采用多个频率的正弦信号同时工作,其激励信号峰值因数较大且检测信号频谱为离散谱.文中提出了一种基于调频信号激励和检测信号细化谱分析的多频涡流检测技术,它不仅降低了激励信号峰值因数,而且检测信号频谱为连续谱.对检测信号施加Tukey窗函数改善谱图,采用Chirp-Z变换计算检测信号频谱,提高谱图的频率分辨率.定义谱图能量、谱图重心、谱图峰度和谱图偏度4个特征量应用于缺陷识别和分类.对于内部缺陷,采用谱图差峰值频率点,定量检测内部缺陷的位置.理论分析和实验结果相一致,验证了所采用方法的正确性. 相似文献
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提出一种压缩感知正交匹配追踪(CS-OMP)超谐波测量新算法,即运用压缩感知理论,通过引入插值系数,基于离散傅里叶变换(DFT)系数向量和狄利克雷核矩阵,构建了高频率分辨率的压缩感知模型,并基于正交匹配追踪算法,在不增加被测数据观测时间前提下,将超谐波测量的频率分辨率提高了一个数量级。数值仿真分析以及两种非线性负荷的实测数据验证的结果表明,该算法可将测得数据频率分辨率由2 k Hz细化为200 Hz,能实现对被测信号中超谐波频率成分的精确定位,也可准确求解出其幅值信息,从而有效地弥补了DFT算法存在的观测时间与频率分辨率互相限制的固有缺陷,在更准确测量超谐波方面展现出良好前景。 相似文献
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《Mechanical Systems and Signal Processing》2006,20(3):702-717
Discrimination capacity, i.e. the capacity to resolve signal components, is probably one of the most important properties of the analysis windows. For components separated by more than a DFT bin the discrimination capacity is determined by the bandwidth and shape of the window's spectral main lobe and the side lobe fall-off rate. The new classical paper of Harris is a milestone where a plethora of windows is discussed and compared through the aforementioned parameters. However, those parameters fail to describe situations given by components clustered within a DFT bin bandwidth. In those cases the discrimination capacity is almost completely determined by the spectral phase of the analysis window, while the shape of the window's magnitude spectrum has little effect. This paper is devoted to a specific class of asymmetric analysis windows capable of resolving components separated by less than a DFT bin. Those windows have recently been proposed and analytically discussed. However, a number of important properties have not been tackled. Herein, the asymmetric analysis windows are thoroughly described and compared to the classical analysis windows in various aspects. The main benefits of the proposed windows are extended discrimination capacity, robustness against additive noise and simple generation. These properties make them very good candidates for narrow-band spectrum analysis of mechanical systems. Results for some real-world examples are presented, showing the capability of the new windows to resolve closely spaced vibration modes when there is a lack of spectral resolution due to the finite register length. 相似文献
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In this paper, noise propagation through a two-stage nonlinear algorithm for measurement of harmonic distortion in power systems according to IEC 61000-4-7 is analyzed. Noise generated in the instrument’s input circuitry is considered as an aggregated noise source without detailed characterization of its origin. The first stage of the measurement algorithm is the discrete Fourier transform (DFT) of the input signal. Noise propagation through the DFT is analyzed by means of probability theory. The result of this analysis, the probability density function (pdf) of the DFT spectrum amplitudes, is used for characterization of the second stage of the measurement algorithm – the root-sum-square grouping of several spectrum components into a single harmonic distortion index. In this way, pdfs of the most common harmonic indices are derived and analyzed. 相似文献
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提高FFT谱质量的一种新方法 总被引:10,自引:0,他引:10
论述了DFT连续性,并推出DFT谱的插值公式。提出了通过迭代确定DFT的幅值极大值以寻找信号参数,并编制出寻找DFT幅值峰值的抛物线迭代程序,该迭代只需几步即可得到相当准确的频率。考察了DFT的频率分辨力和精度。比较了窗函数对DFT精度影响,指出全景分析时采用汉宁窗,而局部分析时采用矩形窗。 相似文献
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本文介绍了一种将DFT对称分解进行频谱分析的方法。该方法可以很容易地得到频谱全景,并且再通过简单运算,可以得出感兴趣的频段的细节,其实用性好。 相似文献
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实际的系统都是不满足或不完全满足取样定理条件的,频率混迭是不可避免的。因此DFT(FFT)给出的频谱是有误差的,本文给出了表达式及估算方法。 相似文献
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Vibration monitoring of rolling element bearings by the high-frequency resonance technique is reviewed. It is shown that the procedures for obtaining the spectrum of the envelope signal are well established, but that there is an incomplete understanding of the factors which control the appearance of this spectrum. Until the envelope spectrum can be fully explained, use of the technique is limited 相似文献