共查询到19条相似文献,搜索用时 328 毫秒
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李正飞 《机械工程与自动化》2008,(5)
根据小波变换和噪声信号的能量分布特性,提出了一种先用小波变换对含噪图像进行多尺度分解,求出各尺度小波变换高频系数的噪声方差和阈值,利用各尺度的阈值对高频系数进行处理,然后利用小波变换系数重构图像,实现图像降噪的方法;实验结果说明该方法既可以有效地降低噪声,又可以较好地保持图像细节。 相似文献
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小波分析在语音除噪中的应用 总被引:1,自引:2,他引:1
小波分析具有时间平移和多尺度分辨率的特点,是目前信号处理领域中十分活跃的理论。含噪语音信号经过小波变 换后,语音信息主要集中在小波变换尺度较大的低频部分,白噪声主要集中在小波变换尺度较小的高频部分。根据这一特 点,我们可以利用小波变换对含噪语音信号进行除噪处理。 相似文献
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0INTRODUCTIONSincethecoddleofthe1970's,abatchOfcompanieslikeHPinU.S.A.havedevelopedvariousdynamicsignalanalyzersbasedonFrsandhavebeenusedinavarietyofsignalmeasurementsandanalysissuchasstmcturalmodelanalysis,statemonitoringandfaultsdiagnosisofeqUipmentandnoiserealtimeoctaveanalysisetc,thisresultsinbigprogressofdynamicsignalanalysis.However,theFFTdefinedbyRiemafmintegTationisonlyabletoanalyzestaystatistical(smooth)signalsbutinefficienttonon-staystatistical(non-smooth)signalswhicharealso… 相似文献
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子波变换的局域分析特性使它可用于目标阶跃边缘的增强,达到抽取目标轮廓特征的目的。本文中介绍了采用光学及数字方法实现子波变换,抽取目标边缘的理论及实验结果,并通过比较看出,数字方法的结果要好于光学方法 相似文献
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Vibration analysis of rotating machinery using time-frequency analysis and wavelet techniques 总被引:1,自引:0,他引:1
Time-frequency analysis, including the wavelet transform, is one of the new and powerful tools in the important field of structural health monitoring, using vibration analysis. Commonly-used signal analysis techniques, based on spectral approaches such as the fast Fourier transform, are powerful in diagnosing a variety of vibration-related problems in rotating machinery. Although these techniques provide powerful diagnostic tools in stationary conditions, they fail to do so in several practical cases involving non-stationary data, which could result either from fast operational conditions, such as the fast start-up of an electrical motor, or from the presence of a fault causing a discontinuity in the vibration signal being monitored. Although the short-time Fourier transform compensates well for the loss of time information incurred by the fast Fourier transform, it fails to successfully resolve fast-changing signals (such as transient signals) resulting from non-stationary environments. To mitigate this situation, wavelet transform tools are considered in this paper as they are superior to both the fast and short-time Fourier transforms in effectively analyzing non-stationary signals. These wavelet tools are applied here, with a suitable choice of a mother wavelet function, to a vibration monitoring system to accurately detect and localize faults occurring in this system. Two cases producing non-stationary signals are considered: stator-to-blade rubbing, and fast start-up and coast-down of a rotor. Two powerful wavelet techniques, namely the continuous wavelet and wavelet packet transforms, are used for the analysis of the monitored vibration signals. In addition, a novel algorithm is proposed and implemented here, which combines these two techniques and the idea of windowing a signal into a number of shaft revolutions to localize faults. 相似文献
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详述了Fourier变换与小波变换的本质区别,分析了Fourier变换和短时Fourier变换应用于故障检测的不足;介绍了小波变换及其应用于故障检测的优点;指出了小波变换应用于故障检测的理论和方法。 相似文献
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针对双馈风力发电机组在并网运行时,其电力电子变流装置将向电网注入大量谐波电流的问题,将基于LabVIEW的在线谐波分析技术应用到双馈风力发电机组的谐波监测分析中。开展了针对双馈风力发电机组注入电网谐波的傅里叶分析和小波包分析,提出了将傅里叶变换与小波包变换联合使用的方法;在LabVIEW上搭建了仿真平台,对双馈风力发电机组可能存在的谐波进行了仿真分析试验。试验及研究结果表明,对于平稳信号与非平稳信号进行谐波分析时,将傅里叶变换与小波包变换联合使用,两者的效能得到明显的提高,优于单独使用傅里叶变换或小波包变换,且可更准确地获取基波和谐波的实时波形与频域特性,谐波定位更准确,为谐波补偿提供了更可靠、准确的信息。 相似文献
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随着电力电子技术的广泛应用,谐波对电力系统的污染越来越严重,检测、分析和抑制谐波已经成为电力系统环境治理的重要课题.利用小波变换及传统的傅立叶变换对电网中的谐波进行了检测、分析,并通过MATLAB进行了仿真.仿真结果表明,利用小波变换可以将信号中不同频率的谐波有效地提取出来,并进行有针对性的分析,具有更高的分析精度. 相似文献
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