Research On Typical Failure Mechanism And Diagnosis Method Of Planetary Gearboxes

Most studies reported in current literature on planetary gearboxes have few results based on the vibration mechanism.And few dynamic models are focused on the studies of fault characteristics under various conditions.Aiming at these shortcomings,a dynamic model of planetary gear sets was established.Using the dynamic model,the fault response characteristics under various fault conditions of the planetary gear were obtained.Moreover,the extraction of fault feature is quite difficult in planetary gearboxes with complicated structure,because of the weak fault response,the extremely serious noise pollution,and the complex sideband of the response signal spectra.To solve the problems in fault diagnosis of planetary gearboxes,an adaptive stochastic resonance method based on frequency information exchange was proposed.Through the analysis of test data in different conditions,the validity of the established model and the proposed fault diagnosis method are verified.The main research work in this thesis is as follows:(1)The characteristics and difficulties of the planetary gearbox system fault diagnosis and the existing problems in current research are discussed.And the significance of establishing dynamic model based on failure and proposing efficient feature extraction method for planetary gearboxes is introduced.(2)A dynamic model of planetary gear sets was established.The model considered the static transmission error,the backlash and the time-varying meshing stiffness of the meshing gear pairs.Furthermore,the time-varying effects of transmission paths at runtime were mentioned in the model.The expression of the time-varying meshing stiffness under the planetary gear fault conditions was calculated,and the meshing stiffness expression under various failure conditions was deduced by introducing fault factors.Using the dynamic model,the fault response characteristics under various conditions of the planetary gear were obtained.(3)An adaptive stochastic resonance method based on frequency information exchange was proposed.Frequency information exchange overcomes the limitations of small parameters of stochastic resonance,and avoids the impact of other harmonic components by only processing the frequency band cared about.Ant Colony Algorithm was utilized to optimize the parameters of bi-stable system adaptively to achieve the best matching with the input signal.The method analyzed the envelope spectra of the planetary gearboxes response signals,which can avoid complex sideband analysis.Through processing and analyzing the simulated signal,the effectiveness of the proposed method is preliminarily verified.(4)A planetary gearbox fault diagnosis test rig was built.The model simulation result was compared with the test result.The comparison verifies the validity of the established model.Meanwhile,the test signals with planetary gear faults including a tooth crack and a missing tooth were processed and analyzed with this method,then the fault features are effectively extracted,and the validity of the method is verified.Compared with the existing methods,such as adaptive stochastic resonance based on re-scaling frequency,the results showed that the proposed method is more effective for the fault diagnosis of the planetary gearboxes.(5)The research work in this thesis was summarized,and the improvement measures and further research directions were put forward.