Research On Fault Diagnosis Of Ventilator Based On Second Generation Wavelet Transform

The basic theory and application of second generation wavelet transform, second generation wavelet de-noising in machinery fault diagnosis technology and second generation wavelet signal process system based on matlab are studied in the thesis. Firstly, the purpose and significance of the task are set forth. Secondly, the signal processing method including FFT, wavelet analysis, wavelet packet analysis theory are introduced; Thirdly, the theory and implementation method of second generation wavelet transform is introduced, the solving process and classification of the predictor and updater and the coefficients with different order are computed. the construction method of second generation biorthogonal wavelet based on lifting scheme are studied, the scale and wavelet function figures with two, four, six and eight order are ploted. At last, apply the second generation wavelet transform to extracting fault features of the mine ventilator, the rubbing fault between rotor and stator of the ventilator is diagnosed successfully. The results show that second generation wavelet transform has great advantages including simple algorithm, fast operation, low memory, simple wavelet construction method and so on.The theory of second generation wavelet de-noising, the selecting scheme of shrinkage and shrinkage function are studied, and the simulation signal is used to test the scheme, then apply it to the de-noising of the vibration signal of a mine ventilator and its fault diagnosis, the unsymmetry fault is diagnosed. The results show that this scheme can improve the SNR, decrease the noise from the original signal and improve the accuracy of the fault diagnosis effectively.The second generation wavelet signal process system based on matlab is studied, the second generation wavelet decomposition, recomposition, de-noising, structure scale-function constitution, wavelet function constitution, spectrum analysis are realized.