A novel frequency estimation algorithm for wideband signal with sub-Nyquist sampling is proposed in this paper. With the aid of information provided by the auxiliary delayed sampling channel and the aliased frequency ...A novel frequency estimation algorithm for wideband signal with sub-Nyquist sampling is proposed in this paper. With the aid of information provided by the auxiliary delayed sampling channel and the aliased frequency estimation for wideband signal with sub-Nyquist sampling, the frequency aliasing due to sub-Nyquist sampling can be solved. This method can reduce the complexity of the overall hardware at the cost of an auxiliary sampling channel. Furthermore, in order to alleviate the computation burden for its practicability, a more simplified algorithm is put forward and its validity is proved by our numerical simulation results. The Cramer-Rao Lower Bound (CRLB) of the frequency estimation is also derived at the end of this paper.展开更多
Roll eccentricity is an important factor causing thickness variations during hot strip rolling and might define the limit of strip thickness control accuracy. An improved multi-resolution wavelet transform algorithm w...Roll eccentricity is an important factor causing thickness variations during hot strip rolling and might define the limit of strip thickness control accuracy. An improved multi-resolution wavelet transform algorithm was proposed to compensate for the roll eccentricity. The wavelet transform method had good localization characteristics in both the time and frequency domains for signal analysis; however, the wavelet method had a frequency-aliasing problem owing to the less than ideal cut-off frequency characteristics of wavelets. This made its component reconstruction of an inaccurate signal. To eliminate inherent frequency aliases in the wavelet transform, fast Fourier transform （FFT） and inverse fast Fourier transform （IFFT） were combined with the Mallat algorithm. This synthesis was described in detail. Then, the roll eccentricity component was extracted from rolling force signal. An automatic gauge control （AGC） system added with a multi-resolution wavelet analyzer was designed. Experimental results showed that the anti-aliasing method could greatly restrain the inverse effect of eccentricity and the thickness control accuracy was improved from ±40 μm to ±15 μm.展开更多
Eccentricity is one of the frequent faults of induction motors,and it may cause rub between the rotor and the stator.Early detection of significant rub from pure eccentricity can prolong the lifespan of induction moto...Eccentricity is one of the frequent faults of induction motors,and it may cause rub between the rotor and the stator.Early detection of significant rub from pure eccentricity can prolong the lifespan of induction motors.This paper is devoted to such mixed-fault diagnosis:eccentricity plus rub fault.The continuous wavelet transform(CWT)is employed to analyze vibration signals obtained from the motor body.An improved continuous wavelet transform was proposed to alleviate the frequency aliasing.Experimental results show that the proposed method can effectively distinguish two types of faults,single-fault of eccentricity and mixed-fault of eccentricity plus rub.展开更多
文摘A novel frequency estimation algorithm for wideband signal with sub-Nyquist sampling is proposed in this paper. With the aid of information provided by the auxiliary delayed sampling channel and the aliased frequency estimation for wideband signal with sub-Nyquist sampling, the frequency aliasing due to sub-Nyquist sampling can be solved. This method can reduce the complexity of the overall hardware at the cost of an auxiliary sampling channel. Furthermore, in order to alleviate the computation burden for its practicability, a more simplified algorithm is put forward and its validity is proved by our numerical simulation results. The Cramer-Rao Lower Bound (CRLB) of the frequency estimation is also derived at the end of this paper.
基金Item Sponsored by National Natural Science Foundation of China (60774032)Provincial Natural Science Foundation of Guangdong Province of China (06025724)+1 种基金Key Project of Guangzhou Scientific Program of China (2007Z2-D0121)Special Research Fund of Ministry of Education of China for College Doctoral Subjects (20070561006)
文摘Roll eccentricity is an important factor causing thickness variations during hot strip rolling and might define the limit of strip thickness control accuracy. An improved multi-resolution wavelet transform algorithm was proposed to compensate for the roll eccentricity. The wavelet transform method had good localization characteristics in both the time and frequency domains for signal analysis; however, the wavelet method had a frequency-aliasing problem owing to the less than ideal cut-off frequency characteristics of wavelets. This made its component reconstruction of an inaccurate signal. To eliminate inherent frequency aliases in the wavelet transform, fast Fourier transform （FFT） and inverse fast Fourier transform （IFFT） were combined with the Mallat algorithm. This synthesis was described in detail. Then, the roll eccentricity component was extracted from rolling force signal. An automatic gauge control （AGC） system added with a multi-resolution wavelet analyzer was designed. Experimental results showed that the anti-aliasing method could greatly restrain the inverse effect of eccentricity and the thickness control accuracy was improved from ±40 μm to ±15 μm.
文摘Eccentricity is one of the frequent faults of induction motors,and it may cause rub between the rotor and the stator.Early detection of significant rub from pure eccentricity can prolong the lifespan of induction motors.This paper is devoted to such mixed-fault diagnosis:eccentricity plus rub fault.The continuous wavelet transform(CWT)is employed to analyze vibration signals obtained from the motor body.An improved continuous wavelet transform was proposed to alleviate the frequency aliasing.Experimental results show that the proposed method can effectively distinguish two types of faults,single-fault of eccentricity and mixed-fault of eccentricity plus rub.
