Study On Fault Diagnosis Method Of Non-Stationary Speed Gear

The steering gear transmission speed is affected by load changes in wind turbines, ships and other mechanical equipment, there is a certain level of random fluctuations, resulting in the vibration signal has a strong non-stationary.The traditional fault diagnosis methods of frequency analysis are operating under the assumption that the speed of gearbox is constant,if the variable speed gearbox vibration signals are directly analyzed by traditional spectrum analysis, it will occur "frequency aliasing" phenomenon, fault characteristic frequency can’t be accurately extracted.Therefore, the research on gearbox fault diagnosis of non-stationary speedis essential.The paper uses the software of Automatic Dynamic Analysis of Mechanical Systemsfor studying the feature of gearbox fault vibration signal in non-stationary speed to simulate gear fault vibration signal. And comparative analyses the spectrum of gearbox failure vibration simulation signal under conditions of stationary and non-stationary speed.The paper processes simulation signal of stationary and non-stationary with traditional method of time-frequency analysis to verify the validity of dealing with non-stationary signals in the method.For this research the random fluctuations of speed gearbox, this paper designs and builds non-stationary speed gearbox fault diagnosis system test trials. The paper simulates gear Fault development process by adding a single tooth surface pitting area ratio and develops a program of equiangular sampling and equal time interval sampling in non-stationary speed gear fault diagnosis tests.As non-stationary speed gear fault vibration signal having a non-linear and multi-component characteristics, the paper proposes the frequency analysis method of differential intrinsic time-scale decomposition to deal with fault vibration signals by the way of differential. The method can separate components of closed signal frequency. And then separate multi-component signal into a plurality of physically meaningful instantaneous frequency intrinsic time scale component by ITD. It can separate unrelated interference noise component and improve the signal to noise ratio.For non-stationary speed gear fault vibration signal has a strong non-stationary characteristics,the paper proposesa kind of non-stationary speed estimatedgear fault diagnosis method based on improved Hilbert-Huang Transform. Firstly decompose fault vibration signal by differential intrinsic time-scale decomposition method to remove noise.And then use the improved Hilbert-Huang transform method toestimate the instantaneous frequency of fault vibration signal to get a smooth processing of non-stationary vibration signal.Finally use order tracking method to extract non-stationary speed gear fault feature.