Accuracy Analysis Of FFT And FT Spectrum Correction And Its Application In Vibration Test Of Powertrain

For single harmonic component and far spaced multi frequency components in discrete spectrum, there are four kinds of methods employed to correct spectrum.They are Ratio Correction of Amplitude Spectrum,Three Convolution Correction of Discrete Spectrum,Continuous Zoom Analysis Fourier Transform of FFT and FT spectrum and Phase Difference Correction.These all have high estimation accuracy when the signals haven't accompanied with noise. However,observed signals are always accompanied with noise in actual application, which will affect estimation accuracy .The parameter estimation error of Continuous Zoom Analysis Fourier Transform of FFT and FT spectrum is studied is studied in this paper. The relation between estimation error of frequency, phase and amplitude and zoom multiples is revealed in the presence of noise-free signal. Parameter estimation accuracy can be improved by increasing zoom multiples, and the maximum error of each parameter is very little when zoom multiples is larger than 40. To the signal with Gaussian white noise, the probability of finding the wrong maximum spectrum line is increased with rise in zoom multiples. Considering the influence of frequency resolution on frequency estimation accuracy and the probability mentioned above, two evaluation indicators is given to provide the best zoom multiples under different signal to noise ratio. Besides, estimation accuracy of phase and amplitude under Gaussian also be studied using the same method.Finally, the FFT and FT spectrum correction method is modified and improved.This paper use FFT and FT correction method to give a precise analysis to the test results of dynamic strain of a Clutch housing and vibration of two engine from a factory , provides a accurate and reliable basis for the further research of the power train vibration properties.