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1.
基于模态分析和小波变换的声发射源定位新算法研究 总被引:7,自引:4,他引:7
针对传统声发射源定位中,声发射信号到达传感器的时间受设定门槛电压影响很大,导致声发射源定位效果较差,提出了一种声发射源定位新方法。根据模态声发射理论,携带声发射源信息的声发射信号在结构中传播过程中,具有频散现象和多模态特性。因此,声发射源定位应基于同一频率下、同一模态导波到达各个传感器的时间和传播速度。通过对声发射信号进行Gabor小波变换的方法,在时频空间内确定某一频率下某一模态导波到达传感器的时间;并通过数值计算得到该频率处模态导波的群速度,从而实现声发射源的准确定位。通过薄板中声发射线源定位试验,证明了该定位算法的有效性。 相似文献
2.
Jiao Jing-pin He Cun-fu Wu Bin Fei Ren-yuan Wang Xiu-yan 《Frontiers of Mechanical Engineering in China》2006,1(3):341-345
For wave propagation in dispersive media, the arrival time of the acoustic emission signal to the sensor is dependent on the
setting of the threshold voltage, which results in the inaccuracy of the acoustic emission location. Based on the wavelet
transform and the theory of modal acoustic emission, a new method is proposed to improve the accuracy of acoustic emission
source location. It is believed that the acoustic emission signal propagation in the structure has the characteristics of
multi-mode and dispersion, and the acoustic emission source location should use the arrival time to sensors obtained from
the output signals not only at the same mode but also at the same frequency. The wavelet transform is used to resolve the
problem. By utilizing the time-frequency data of the wavelet, the frequency-dependent arrival time traveling is easily obtained;
by numerical computation of the wave’s propagation in structure, the group velocity of the guided mode is also obtained, therefore
the accuracy source location is realized. The acoustic emission source location experiments were conducted in a thin steel
plate and results show that the technique is an effective tool for acoustic emission source location.
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Translated from Chinese Journal of Scientific Instrument, 2005, 26(3) (in Chinese) 相似文献
3.
针对声发射信号频散特性导致基于时延估计的气体管道泄漏定位误差大的问题,提出一种基于模态声发射时频分析的泄漏定位方法。该方法采用平滑伪Wigner-Ville时频分布对两泄漏信号的互相关函数进行时频分析,利用互相关函数的时频谱可同时提取泄漏信号的时间延迟和与之对应的频率;然后根据泄漏声发射信号的主导模态的频散曲线即可确定该频率对应的声速,利用实时确定的声速和时间延迟并根据两传感器之间的距离即可确定泄漏点的位置。实验结果表明,采用时频分析的气体管道泄漏定位误差与互相关相比减少了6倍。所提出的模态声发射时频定位方法能有效抑制泄漏信号的频散,提高泄漏信号的相关性,从而更适合用于声发射管道泄漏定位。 相似文献
4.
实际管网泄漏检测环境中,管内外非泄漏固定噪声(如施工、管道阀门噪声等)叠加在管道泄漏声信号中,传感观测信号间的互相关函数中有多个相关峰值,若不能正确识别峰值来自泄漏还是非泄漏声源,将导致漏点定位错误。以两传感观测信号的自相关函数构建非泄漏和泄漏信号特征提取函数,通过特征提取函数识别出管道传播媒质对两类信号的衰减特征信息,该衰减特征结合互相关函数的相关峰值时延信息,识别出峰值来自泄漏还是非泄漏声源。实际定位应用表明,在管内外非泄漏固定噪声干扰下,漏点定位误差在1 m以内,突破了传统基于时延估计的泄漏定位技术及仪器需要在夜间,或人为关闭某些管道阀门、支路等安静环境下,通过回避干扰噪声才能进行定位的限制。 相似文献
5.
When there are low signal to noise relationships or low coherences between measured pressure and a reference sensor, a pressure
field measured and estimated by NAH (Nearfield Acoustic Holography) becomes noisy on the hologram and source planes. This
paper proposes a method to obtain the high coherent de-noised pressure signals from low coherent noisy ones by combining a
wavelet algorithm with NAH. The proposed method obtains the de-noised field from acoustic fields on a noise source plane reconstructed
through backward propagation of NAH. Thus this method does not need high coherent pressure signals on the hologram surface
while the conventional nearfield acoustic holography requires high-coherent signals. The proposed method was verified by numerical
simulation using noisy signals, composed of original signals and imposed noises distributed on the hologram surface. 相似文献
6.
Yong Woo Shin Min Soo Kim Sang Kwon Lee 《Journal of Mechanical Science and Technology》2010,24(12):2401-2411
For the detection of the impact location in a pipeline system, the correlation method has been the conventional method. For
the application of the correlation method, the diameter of a duct should be small so that the acoustic wave inside the duct
can propagate with nondispersive characteristics, in the form of, for example, a plane wave. This correlation method calculates
the cross-correlation between acoustic waves measured at two acceleration sensors attached to a buried duct. It also gives
information about the arrival time delay of an acoustic wave between two sensors. These arrival time delays are used for the
estimation of the impact location. However, when the diameter of the duct is large, the acoustic waves inside the duct propagate
with dispersive characteristics owing to the reflection of the acoustic wave off of the wall of the duct. This dispersive
characteristic is related to the acoustic modes inside a duct. Therefore, the correlation method does not work correctly for
the detection of the impact location. This paper proposes new methods of accurately measuring the arrival time delay between
two sensors attached to duct line system. This method is based on the time-frequency analyses of the short time Fourier transform
(STFT) and continuous wavelet transform (CWT). These methods can discriminate direct waves (non-dispersive waves) and reflective
waves (dispersive waves) from the measured wave signals through the time-frequency analysis. The direct wave or the reflective
wave is used to estimate the arrival time delay. This delay is used for the identification of the impact location. This systematic
method can predict the impact location due to the impact forces of construction equipment with more accuracy than the correlation
method. 相似文献
7.
针对气体管道泄漏声发射信号的多模态、频散特性导致互相关泄漏定位误差大的问题,提出采用单一非频散模态提取的气体管道泄漏声发射定位方法。对检测信号的互谱加窗,并根据模态波数确定窗参数,可获得泄漏声发射信号的单一非频散模态导波的互谱。对单一非频散模态导波的互谱进行傅里叶反变换,得到泄漏声发射中单一非频散模态信号的互相关函数以及时延估计,就可以采用单一非频散模态声速,更准确计算出泄漏位置。对气体管道泄漏进行定位实验,相比用未经分解的泄漏声发射信号进行定位,由于声发射单一非频散模态信号的相关性增强,且选用的声速更准确,定位相对误差平均降低7%以上。这表明,通过提取泄漏信号互谱的单一非频散模态成分进行时延估计,可以提高泄漏检测的有效性和减小定位误差。 相似文献
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针对天然气管道泄漏定位的问题,提出一种基于经验小波变换(EWT)及互时频的泄漏定位方法。该方法首先采用EWT对泄漏信号进行分解,获得多个分量,进而提出根据互信息的敏感分量自适应选择算法,获取敏感分量;然后采用互时频法对敏感分量进行时频分析,根据互时频图的最大特征峰值计算时延和相关频率;最后根据频散曲线获得相关声波速度,实现对天然气管道泄漏点定位。实验结果表明,该方法能够实现管道泄漏点定位,与基于EMD的互时频法相比,定位精度明显提高。 相似文献
11.
Jiao Jing-pin Fei Ren-yuan He Cun-fu Wu Bin 《Frontiers of Mechanical Engineering in China》2006,1(2):146-150
It is important to analyze the propagation characteristics of guided waves in acoustic leak location in pipelines. In this
paper, the acoustic leak signal is analyzed in the time-frequency domain. Based on the relation of time-frequency distribution
of the acoustic leak signal and the dispersion curves of guided waves, the mode components of acoustic leak signals were obtained.
The research can provide a guideline for the mode selection in pipeline leak location, and help improve the accuracy of leak
location. 相似文献
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IDENTIFICATION OF THE IMPACT LOCATION ON A PLATE USING WAVELETS 总被引:2,自引:0,他引:2
This paper presents an experimental method that has been developed for detecting flexural waves in plates by the use of piezoelectric films. The recorded signals are analysed by a ‘wavelet transform’ to determine arrival times of waves at different frequencies. These arrival times are used in conjunction with an optimisation to identify the location of the impact (i.e. thex- andy-coordinate of the source location). Also, the time lag between the instant of the impact and the recording of the signals together with the group velocity of the dispersive waves are specified. Close agreement is observed between the experimentally determined results and the exact solutions. This technique is a valuable method for identification of source locations that may be applied to problems related to in-service impact loading of structures, seismic data from earthquakes, and to acoustic emission signals from propagating cracks. 相似文献
14.
Dr Xiaoli Li 《The International Journal of Advanced Manufacturing Technology》1998,14(8):539-543
This paper presents a real-time tool breakage detection method for small diameter drills using acoustic emission (AE) and current signals. Using the transmitted properties of the AE signal, apparatus for detecting the AE signal for tool breakage monitoring was developed for a machine centre. The features of tool breakage were obtained from the AE signal using typical signal processing methods. The continuous wavelet transform (CWT) and the discrete wavelet transform (DWT) were used to decompose the spindle current signal and the feed current signal, respectively. The tool breakage features were extracted from the decomposed signals. Experimental results show that the proposed monitoring system possessed an excellent real-time capability and a high success rate for the detection of the breakage of small diameter drills using combined AE and current signals. 相似文献
15.
ZHANG Xinming HE Yongyong HAO Rujiang CHU Fulei State Key Laboratory of Tribology Tsinghua University Beijng China 《机械工程学报(英文版)》2007,20(2):104-108
Morlet wavelet is suitable to extract the impulse components of mechanical fault signals. And thus its continuous wavelet transform (CWT) has been successfully used in the field of fault diagnosis. The principle of scale selection in CWT is discussed. Based on genetic algorithm,an opti-mization strategy for the waveform parameters of the mother wavelet is proposed with wavelet en-tropy as the optimization target. Based on the optimized waveform parameters,the wavelet scalogram is used to analyze the simulated acoustic emission (AE) signal and real AE signal of rolling bearing. The results indicate that the proposed method is useful and efficient to improve the quality of CWT. 相似文献
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研究了基于小波分析的负压波管道泄漏检测与定位技术。并主要对小波分析消噪处理方法进行了分析。先选取合适的小波基和尺度对泄漏信号进行小波分解,再对各尺度下小波分解的高频系数进行阈值量化,并重构小波信号可得消噪后的泄漏信号。运用这种方法,可以更为精确地获得压力突降点,提高泄漏点定位的精度。通过对燃气管道泄漏检测与定位的实例分析,验证了此方法的精确性和有效性。 相似文献
18.
传统的汽车节气门位置信号(throttle position sensor,TPS)处理方法不易消除发动机舱内电磁信号及周边环境的干扰。根据TPS的特征,在MATLAB中选用Daubechies五阶正交小波(dB5)对TPS噪声信号进行4层小波分解,再对分解后得到的各层系数用软阈值法量化处理,最后利用小波重构,实现对信号去噪。最后将获得的去噪信号用于发动机控制,并将控制结果与采用未去噪信号的发动机进行实车对比试验。试验表明:发动机采用去噪的TPS信号运行更平稳,小波变换后的去噪TPS信号对发动机控制具有良好的效果。 相似文献
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Wenhua Han 《Russian Journal of Nondestructive Testing》2008,44(3):184-195
The magnetic flux leakage (MFL) nondestructive evaluation technique is used extensively for in-service inspection of gas and
oil pipelines. Unfortunately, the MFL data obtained from seamless pipeline inspection is usually contaminated by various sources
of noise, which considerably reduces the detectability of defect signals in MFL data. In this paper, a new denoising algorithm
is presented for removing seamless pipe noise (SPN) and system noise contained in MFL data. The algorithm first utilizes the
new wavelet domain adaptive filtering method proposed by combining wavelet transform with the adaptive filtering technique
to remove SPN contained in MFL data and then exploits the coefficient denoising approach with wavelet transform to cancel
the system noise in the output of the wavelet domain adaptive SPN cancellation system. Theoretical analysis shows that the
proposed denoising algorithm has a better overall performance than the existing denoising algorithm. Results of application
of the proposed algorithm to MFL data from field tests are presented to demonstrate the performance of the proposed algorithm
compared with the existing denoising algorithm.
The text was submitted by the author in English. 相似文献