Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed suc...Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed successfully. By utilizing instantaneous frequencyestimation (IFE) theoretics of TFA technique, and based on IFE of peak searching on thetime-frequency spectrum, order analysis (OA) functions is put forward and implemented, such as orderspectrum, order spectrum matrix, order tracking, order tracking filtering, and order componentextraction, etc. Unlike the home and abroad existing popular characteristic analyzers, which needkey phasing devices such as shaft encoder, phase-locked loop (PLL), phase-locked multiple frequency,tachometer, etc, to implement constant angle sampling directly or indirectly, whereas thisinstrument only uses the vibration signal of rotating machinery to carry out OA. This instrumentmakes up the shortage of these traditional instruments in analyzing the non-stationary signal ofrun-up and run-down process of rotating machinery. Therefore, it is a great breakthrough for theexisting order analyzers.展开更多
The attempt to represent a signal simultaneously in time and frequency domains is full of challenges. The recently proposed adaptive Fourier decomposition （AFD） offers a practical approach to solve this problem. Thi...The attempt to represent a signal simultaneously in time and frequency domains is full of challenges. The recently proposed adaptive Fourier decomposition （AFD） offers a practical approach to solve this problem. This paper presents the principles of the AFD based time-frequency analysis in three aspects： instantaneous frequency analysis, frequency spectrum analysis, and the spectrogram analysis. An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution. The proposed approach performs better than both the Fourier transform and short-time Fourier transform.展开更多
A novel method of Doppler frequency extraction is proposed for Doppler radar scoring systems. The idea is that the time-frequency map can show how the Doppler frequency varies along the time-line, so the Doppler frequ...A novel method of Doppler frequency extraction is proposed for Doppler radar scoring systems. The idea is that the time-frequency map can show how the Doppler frequency varies along the time-line, so the Doppler frequency extraction becomes curve detection in the image-view. A set of morphological operations are used to implement curve detection. And a map fusion scheme is presented to eliminate the influence of strong direct current （DC） component of echo signal during curve detection. The radar real-life data are used to illustrate the performance of the new approach. Experimental results show that the proposed method can overcome the shortcomings of piecewise-processing-based FFT method and can improve the measuring precision of miss distance.展开更多
A method of time-frequency analysis (TFA) based on wavelets is applied to study the phase space structure of three-dimensional asymmetric triaxial galaxy enclosed by spherical dark halo component. The investigation is...A method of time-frequency analysis (TFA) based on wavelets is applied to study the phase space structure of three-dimensional asymmetric triaxial galaxy enclosed by spherical dark halo component. The investigation is carried out in the presence and absence of dark halo component. Time-frequency analysis is based on the extraction of instantaneous frequency from the phase of the continuous wavelet transform. This method is comparatively fast and reliable. This method can differentiate periodic from quasi-periodic, chaotic sticky from chaotic non-sticky, ordered from chaotic and also, it can accurately determine the time interval of the resonance trapping and transitions too. Apart from that, the phenomenon of transient chaos can be explained with the help of time-frequency analysis. Comparison with the method of total angular momentum (denoted as Ltot) proposed recently is also presented.展开更多
This paper provides the results of using ground penetrating radar (GPR) method to detect hydrocarbon products (diesel and gasoline) in a controlled lab test. The work addresses the environmental problem generated by t...This paper provides the results of using ground penetrating radar (GPR) method to detect hydrocarbon products (diesel and gasoline) in a controlled lab test. The work addresses the environmental problem generated by the uncontrolled leakage of hydrocarbon product</span><span style="font-family:"">s</span><span style="font-family:""> and the subsequent contamination </span><span style="font-family:"">of </span><span style="font-family:"">plumes in the subsoil. Most of the research propose</span><span style="font-family:"">s</span><span style="font-family:""> the geophysical techniques to evaluate the plumes but some controversial were discussed on how i</span><span style="font-family:"">t</span><span style="font-family:""> affected the electrical and dielectric response depending on the excitation of the non-invasive method. The present work focuses </span><span style="font-family:"">on</span><span style="font-family:""> a comparative analysis of some signal attributes of the GPR traces to determine under what premises the detection is properly done. These signal attributes were from the time and frequency domain as attenuation coefficient, instantaneous amplitude and frequency have been considered to analyze three different soil samples. The laboratory tests consist of buried liquid (total hydrocarbon of petroleum</span><span style="font-family:"">, </span><span style="font-family:"">so called TPH) bags in the soil sample boxes reveal</span><span style="font-family:""> </span><span style="font-family:"">the range of target detection and consistency of data on </span><span style="font-family:"">the </span><span style="font-family:"">controlled test regarding the dielectric soil characterization and the delimiting position and depth. Instantaneous amplitude and time-frequency shift are revealed as promising signal attributes to accura</span><span style="font-family:"">te</span><span style="font-family:""> detection of the TPH presence. Numerical simulation data were also carried out to interpret the signal reflections on radargrams and to confirm experimental trends and the benefits of us</span><span style="font-family:"">ing</span><span style="font-family:""> the above signal attributes in time-frequency domain.展开更多
In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on th...In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects,and recorded the sEMG signals of the flexor carpi ulnaris.sEMG's median frequency(MDF) and mean frequency(MF) were extracted by short term Fourier transform(STFT),and the root mean square(RMS) of wavelet coefficients in the frequency band of 5—45 Hz was obtained by continuous wavelet transform(CWT).The results demonstrate that both MDF and MF show downward trends within 1 min; however,RMS shows an upward trend within the same time.The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8.It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.展开更多
The demodulation algorithm for AM-FM sinusoids proposed in reference[1]canonly deal with complex exponential sequences.In real applications,one needs to con-struct an analytic signal from real samples.Influenced by th...The demodulation algorithm for AM-FM sinusoids proposed in reference[1]canonly deal with complex exponential sequences.In real applications,one needs to con-struct an analytic signal from real samples.Influenced by the Hilbert Transformation,thecomplex noise in the analytic signal is colored.This paper analyzes the colored noise andthe disadvantage caused by the noise in the estimations of the instantaneous frequencyand amplitude factor using the algorithm in[1]and formulates a practical algorithm.展开更多
Because the existing range-Doppler algorithm in inverse synthetic aperture sonar (ISAS) is based on target model of uniform motion, it may be invalidated for maneuvering targets due to the time-varying changes of both...Because the existing range-Doppler algorithm in inverse synthetic aperture sonar (ISAS) is based on target model of uniform motion, it may be invalidated for maneuvering targets due to the time-varying changes of both individual scatter′s Doppler and imaging projection plane. To resolve the problem, a new range-instantaneous Doppler imaging method is proposed for imaging maneuvering targets based on time-frequency analysis. The proposed approach is verified using real underwater acoustic data.展开更多
为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneo...为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneous freguency,IF)位置进行多次迭代,从而获得更高精度的瞬时频率位置。其次,搜索短时傅里叶系数模极大值的位置并上下平移该位置,得到初步估算的频带并将频带外的短时傅里叶系数归零。最后,搜索频率方向上短时傅里叶系数的局部最大值所对应的瞬时频率位置,根据这些位置对时频系数进行重排,进而得到细化的瞬时频带。通过2组数值算例、1个7层钢筋混凝土剪力墙振动台试验和1个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比现有的局部最大同步挤压变换方法,改进算法不仅提高了瞬时频率的估算精度,而且改善了响应信号瞬时频带的时频聚集性。展开更多
为了从复杂的非平振动信号中追踪直升机的传动系统轴转速信息,开发了一种改进的广义解调变换方法。首先,利用广义解调变换对目标信号进行移频,移频后目标分量将由非平稳转换为近似平稳;其次,基于频谱细化的短时傅里叶变换(short time Fo...为了从复杂的非平振动信号中追踪直升机的传动系统轴转速信息,开发了一种改进的广义解调变换方法。首先,利用广义解调变换对目标信号进行移频,移频后目标分量将由非平稳转换为近似平稳;其次,基于频谱细化的短时傅里叶变换(short time Fourier transform,简称STFT)方法计算得到解调信号时频图;然后,估计信号的瞬时频率,利用迭代计算提升频率估计精度;最后,基于估计的转速信息开展同步分析,提高传动系统齿轮故障振动的信噪比。仿真分析和实测分析结果表明:所提出方法估计的轴速度信息具有较高的精度,满足基于速度信息开展同步分析的需求;利用估计的速度开展同步分析可有效提高信噪比,增强阶次谱上的故障特征,便于准确提取齿轮故障特征。展开更多
提出了基于瞬时频率估计(Instantaneous frequency estimation,IFE)实现旋转机械阶比跟踪的新方法,其优点是简化了阶比分析对硬件的要求,用软件的方法实现了阶比跟踪,仿真与实际测试试验验证了本方法的正确性。本方法实现了旋转机械非...提出了基于瞬时频率估计(Instantaneous frequency estimation,IFE)实现旋转机械阶比跟踪的新方法,其优点是简化了阶比分析对硬件的要求,用软件的方法实现了阶比跟踪,仿真与实际测试试验验证了本方法的正确性。本方法实现了旋转机械非平稳振动信号中参考轴瞬时转速的跟踪、估计算法,为阶比分析的实际应用提供了一种新方法,是对原有阶比跟踪技术的有力补充,特别适合于虚拟仪器发展的要求。展开更多
文摘Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed successfully. By utilizing instantaneous frequencyestimation (IFE) theoretics of TFA technique, and based on IFE of peak searching on thetime-frequency spectrum, order analysis (OA) functions is put forward and implemented, such as orderspectrum, order spectrum matrix, order tracking, order tracking filtering, and order componentextraction, etc. Unlike the home and abroad existing popular characteristic analyzers, which needkey phasing devices such as shaft encoder, phase-locked loop (PLL), phase-locked multiple frequency,tachometer, etc, to implement constant angle sampling directly or indirectly, whereas thisinstrument only uses the vibration signal of rotating machinery to carry out OA. This instrumentmakes up the shortage of these traditional instruments in analyzing the non-stationary signal ofrun-up and run-down process of rotating machinery. Therefore, it is a great breakthrough for theexisting order analyzers.
基金supported by the UM Multi-Year Research Grant under Grant No.MYRG144(Y3-L2)-FST11-ZLM
文摘The attempt to represent a signal simultaneously in time and frequency domains is full of challenges. The recently proposed adaptive Fourier decomposition （AFD） offers a practical approach to solve this problem. This paper presents the principles of the AFD based time-frequency analysis in three aspects： instantaneous frequency analysis, frequency spectrum analysis, and the spectrogram analysis. An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution. The proposed approach performs better than both the Fourier transform and short-time Fourier transform.
基金the Ministerial Level Advanced Research Foundation(020045089)
文摘A novel method of Doppler frequency extraction is proposed for Doppler radar scoring systems. The idea is that the time-frequency map can show how the Doppler frequency varies along the time-line, so the Doppler frequency extraction becomes curve detection in the image-view. A set of morphological operations are used to implement curve detection. And a map fusion scheme is presented to eliminate the influence of strong direct current （DC） component of echo signal during curve detection. The radar real-life data are used to illustrate the performance of the new approach. Experimental results show that the proposed method can overcome the shortcomings of piecewise-processing-based FFT method and can improve the measuring precision of miss distance.
文摘A method of time-frequency analysis (TFA) based on wavelets is applied to study the phase space structure of three-dimensional asymmetric triaxial galaxy enclosed by spherical dark halo component. The investigation is carried out in the presence and absence of dark halo component. Time-frequency analysis is based on the extraction of instantaneous frequency from the phase of the continuous wavelet transform. This method is comparatively fast and reliable. This method can differentiate periodic from quasi-periodic, chaotic sticky from chaotic non-sticky, ordered from chaotic and also, it can accurately determine the time interval of the resonance trapping and transitions too. Apart from that, the phenomenon of transient chaos can be explained with the help of time-frequency analysis. Comparison with the method of total angular momentum (denoted as Ltot) proposed recently is also presented.
文摘This paper provides the results of using ground penetrating radar (GPR) method to detect hydrocarbon products (diesel and gasoline) in a controlled lab test. The work addresses the environmental problem generated by the uncontrolled leakage of hydrocarbon product</span><span style="font-family:"">s</span><span style="font-family:""> and the subsequent contamination </span><span style="font-family:"">of </span><span style="font-family:"">plumes in the subsoil. Most of the research propose</span><span style="font-family:"">s</span><span style="font-family:""> the geophysical techniques to evaluate the plumes but some controversial were discussed on how i</span><span style="font-family:"">t</span><span style="font-family:""> affected the electrical and dielectric response depending on the excitation of the non-invasive method. The present work focuses </span><span style="font-family:"">on</span><span style="font-family:""> a comparative analysis of some signal attributes of the GPR traces to determine under what premises the detection is properly done. These signal attributes were from the time and frequency domain as attenuation coefficient, instantaneous amplitude and frequency have been considered to analyze three different soil samples. The laboratory tests consist of buried liquid (total hydrocarbon of petroleum</span><span style="font-family:"">, </span><span style="font-family:"">so called TPH) bags in the soil sample boxes reveal</span><span style="font-family:""> </span><span style="font-family:"">the range of target detection and consistency of data on </span><span style="font-family:"">the </span><span style="font-family:"">controlled test regarding the dielectric soil characterization and the delimiting position and depth. Instantaneous amplitude and time-frequency shift are revealed as promising signal attributes to accura</span><span style="font-family:"">te</span><span style="font-family:""> detection of the TPH presence. Numerical simulation data were also carried out to interpret the signal reflections on radargrams and to confirm experimental trends and the benefits of us</span><span style="font-family:"">ing</span><span style="font-family:""> the above signal attributes in time-frequency domain.
基金Supported by the National Natural Science Foundation of China(No.81222021 and No.31011130042)the National Key Technology R&D Program of the Ministry of Science and Technology of China(No.2012BAI34B02)
文摘In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects,and recorded the sEMG signals of the flexor carpi ulnaris.sEMG's median frequency(MDF) and mean frequency(MF) were extracted by short term Fourier transform(STFT),and the root mean square(RMS) of wavelet coefficients in the frequency band of 5—45 Hz was obtained by continuous wavelet transform(CWT).The results demonstrate that both MDF and MF show downward trends within 1 min; however,RMS shows an upward trend within the same time.The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8.It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.
文摘The demodulation algorithm for AM-FM sinusoids proposed in reference[1]canonly deal with complex exponential sequences.In real applications,one needs to con-struct an analytic signal from real samples.Influenced by the Hilbert Transformation,thecomplex noise in the analytic signal is colored.This paper analyzes the colored noise andthe disadvantage caused by the noise in the estimations of the instantaneous frequencyand amplitude factor using the algorithm in[1]and formulates a practical algorithm.
文摘Because the existing range-Doppler algorithm in inverse synthetic aperture sonar (ISAS) is based on target model of uniform motion, it may be invalidated for maneuvering targets due to the time-varying changes of both individual scatter′s Doppler and imaging projection plane. To resolve the problem, a new range-instantaneous Doppler imaging method is proposed for imaging maneuvering targets based on time-frequency analysis. The proposed approach is verified using real underwater acoustic data.
文摘为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneous freguency,IF)位置进行多次迭代,从而获得更高精度的瞬时频率位置。其次,搜索短时傅里叶系数模极大值的位置并上下平移该位置,得到初步估算的频带并将频带外的短时傅里叶系数归零。最后,搜索频率方向上短时傅里叶系数的局部最大值所对应的瞬时频率位置,根据这些位置对时频系数进行重排,进而得到细化的瞬时频带。通过2组数值算例、1个7层钢筋混凝土剪力墙振动台试验和1个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比现有的局部最大同步挤压变换方法,改进算法不仅提高了瞬时频率的估算精度,而且改善了响应信号瞬时频带的时频聚集性。
文摘为了从复杂的非平振动信号中追踪直升机的传动系统轴转速信息,开发了一种改进的广义解调变换方法。首先,利用广义解调变换对目标信号进行移频,移频后目标分量将由非平稳转换为近似平稳;其次,基于频谱细化的短时傅里叶变换(short time Fourier transform,简称STFT)方法计算得到解调信号时频图;然后,估计信号的瞬时频率,利用迭代计算提升频率估计精度;最后,基于估计的转速信息开展同步分析,提高传动系统齿轮故障振动的信噪比。仿真分析和实测分析结果表明:所提出方法估计的轴速度信息具有较高的精度,满足基于速度信息开展同步分析的需求;利用估计的速度开展同步分析可有效提高信噪比,增强阶次谱上的故障特征,便于准确提取齿轮故障特征。
文摘提出了基于瞬时频率估计(Instantaneous frequency estimation,IFE)实现旋转机械阶比跟踪的新方法,其优点是简化了阶比分析对硬件的要求,用软件的方法实现了阶比跟踪,仿真与实际测试试验验证了本方法的正确性。本方法实现了旋转机械非平稳振动信号中参考轴瞬时转速的跟踪、估计算法,为阶比分析的实际应用提供了一种新方法,是对原有阶比跟踪技术的有力补充,特别适合于虚拟仪器发展的要求。
