Search

Under variable working conditions, the components of gear fault vibration signals had complex time-frequency characteristics that crossing multiple time scales or overlapping time-frequency domains. The traditional decomposition method could not decompose this kind of signals based on local time-scale characteristics. A new MMD method was introduced. The MMD method innovatively regarded the mono-component signals as a linear combination of eigenvectors with different weight coefficients. By iteratively optimizing the weight coefficients, the corresponding component signals were obtained. The problems that large amount of data reduced the decomposition efficiency when MMD analyzed the actual vibration signals with high sampling rate was solved. And the MMD method was applied to analyse gear fault vibration signals under variable rotating speed working conditions.The results show that the method may effectively decompose to the overlapping fault component signals in time-frequency domain, and has obvious advantages compare to the traditional method based on time-scale characteristics.Combined with order analysis, the gear fault feature information may be extracted clearly and accurately. [ABSTRACT FROM AUTHOR]

The issue of the aerodynamic noises from wind turbine blades affecting the surrounding residents life begins to attract researcher's attention. Most of the existing researches are based on CFD software or experimental data fitting method to analyze the aerodynamic noises, so it is difficult to adapt the demand to dynamic analysis of the aerodynamic noises from wind speed variation. In this paper, the operation parameters, the inflow wind speed and the receiver location are considered, and a modified model to calculate aerodynamic noises from wind turbine blades which is based on traditional acoustic formulas is established. The program to calculate the aerodynamic noises from the 2 MW wind turbine blades is compiled using a time-domain analysis method based on the Simulink modular in Matlab software. And the pressure time sequence diagrams of the aerodynamic noises from wind turbine blades are drawn. It has provided a theoretical foundation to develop low noise wind turbine blades. [ABSTRACT FROM AUTHOR]