【作者】 卜永波；

【导师】 白凤山；

【作者基本信息】 内蒙古大学 ， 信号与信息处理， 2008， 硕士

【摘要】 信号处理方法是当前机械设备故障诊断中重要的技术基础之一,分析结果的精确程度是诊断成功与否的关键因素。研究频谱分析的校正方法和误差分析,提高谱分析方法的精度是当前主要的发展方向之一。本文系统的评述了目前国内对FFT变换后谱校正的四种方法。第一种是对幅值谱进行校正的比值法,这种方法利用归一化后差值为1的两点窗谱函数比值,建立一个以校正频率为变量的方程,解出频率,再进行幅值和相位的校正。第二种能量重心校正法,从理论上推导了常用离散窗谱函数的能量重心就是坐标原点,由此得到了能量重心法校正频率和相位的公式。第三种离散频谱的相位差校正法—时域平移+改变窗长法,即第二段时域序列比第一段滞后L点,对这两段时域分别作N点和M点的FFT分析,利用对应峰值谱线的相位差进行频谱校正的方法。第四种方法是FFT+FT谱连续细化分析傅立叶变换,对FFT局部进行细化分析,可以得到某个主要频率成份频率、幅值、相位的精确值,极大的提高了频率分辨率。仿真分析了比值校正法和双窗法。误差分析和仿真计算结果表明比值法解决了精确求FFT后幅度、频率和相位,为精确测量信号参数提供了一种有效手段;双窗法从减小栅栏效应带来的幅值估计误差的角度,设计了一个具有平顶窗谱的窗函数,分析对比了它和矩形窗函数的性能差异,在此基础上,提出了用矩形窗和平顶窗谱窗函数联合进行频谱分析的双窗函数频谱估计算法,可在不降低频谱频率分辨率的条件下提高其幅值估计精度。并在DSP平台实现了FFT幅度谱的优化。更多还原

【Abstract】 Signal processing methods are the important technical foundation of current mechanical equipment fault diagnosis, the analysis results are the key factor in accuracy of the diagnosis. On the spectrum of correction methods and error analysis, improving the accuracy of spectral analysis method is one of the main direction of development.This paper reviews the current system of internal transformation of the FFT spectrum correction after the four methods. The first is the Amplitude Spectrum of the Ratio Correction, this approach useing of a margin after a function of the ratio of two spectrum, the establishment of a correction to the frequency of variable equation of the frequency and then the amplitude and phase correction. The second is Energy Centrobaric Correction Method, this paper demonstrates that the energy centroid of discrete spectrum of frequently used windows is near the origin of coord -inate and deduces the correction formula of frequency and phase using Energy Centrobaric Correcting Method. The third is Phase Difference Correcting Method for Calibration, this method including time-domain translation and the change of window width,the second time-domain sequence lags behind the first one with L points,performing N point FFT analysis on the first sequence and M-point FFT analysis on the second one,and finally correcting spectrum by making use of the phase difference of two corresponding peak lines. The fourth is Zoom FFT+FT Spectrum by Fourier Transform,the method get the precise value of some main frequency,and thus greatly improve the frequency discrimation of FFT spectrum.Error analysis and simulation results show that the Ratio Correction method for resolving the precise extent after the FFT, frequency and phase for the accurate measurement of signal parameters provides an effective means; Correction For The Amplitude Error In FFT By Two Window Funtions -A window function which has a flat top in frequency domain is designed to correct the amplitude error caused by Picket-Fence effect.The window function has a wide main lobe,which results in a loss of frequency resolution of the spectrum.To correct the amplitude error and still keep a high frequency resolution in the FFT spectrum,a new algorithm is proposed,which uses two window functions to do spectrum analysis.The one is a rectangular window function and the other is a window function that has a flat top inrequency domain.By combination of the two window functions,a spectrum can be reached which has both the frequency resolution of rectangular window function and the amplitude resolution of the window function that has a flat top in frequency domain. the implememtation of FFT algorithm optimization on the DSP is introuduced.更多还原