For the failure diagnose of onsite mechanical equipment, which based on vibration noise in section, both characteristic signal and noise influence were contained in vibration signal, which all accepted by the machine. The problem arise when the characteristic signal was weak compare with the useless noise, the useful signal becomes hard to obtain, hence result in lower accuracy of the equipment. In this thesis, a new method based on the delayed autocorrelation demodulation method was analyzed and will be used on demodulation noise reduction: Based on the noise reduction feature of autocorrelation function, the related analysis was taken on vibration signal, then the autocorrelation function for the signal was obtained. Then with proper delay on autocorrelation function to avoid noise effect and envelop demodulation, we could achieve the demodulation result. The theoretical analysis and simulation experiments has proven the delayed autocorrelation demodulation method achieve better anti-noise performance than direct demodulation method, meanwhile, the delayed autocorrelation demodulation method could also highlights the characteristic information.
With the increasing request of the comfort, reduce the vibration and noise of automobile AC generator as the industry wide concern. In this paper, based on a type of vehicle alternator speed section of excessive noise problems, using order analysis method on noise generator is analyzed, the main harmonic component generator noise for 36 harmonic components, and determine the maximum value of the resonance speed noise in 1800rpm, 2400rpm, 3400rpm near the motor load state. On this basis, puts forward the corresponding improvement measures to improve the motor, the motor noise value to the manufacturer's standard.
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