| Mechanical equipment becomes larger,faster and more intelligent and this asking for a higher requirement for mechanical equipments.Because of large transmission ratio,compact structure,strong carrying capacity,high transmission efficiency,smooth and efficient transmission and many other advantages,it is widely used in the transmission system and plays an important role in mechanical equipment.As the planetary gearbox often works in low-speed,heavy-duty harsh environments and it has a complex structure,important components of the planetary gearbox often fail.Once the planetary system fails,it will bring huge losses to the society.For this reason,it is of great practical significance to study the fault diagnosis of planetary gearbox.However,the planetary gearbox structure is complex.It has unique vibration characteristics.For example,the various modulation modes of the vibration signal are confused with each other.The vibration sources are complex.The phase and amplitude of the vibration signal caused by the change of the transmission path are nonlinear.Moreover,the vibration of different gear meshing pairs are nonlinearly coupled and the frequency components of dynamic responses are often also coupled.These characteristics make it difficult to extract the fault characteristics effectively by the fault diagnosis method based on vibration signal analysis.This research is supported financially by the National Natural Science Foundation of China "Planetary Gear Transmission System Failure Mechanism and Sparse Diagnosis of the Study"(No.51405321)and also by the Jiangsu Provincial Natural Science Foundation."Wind Turbine Planetary Gearbox Failure Evolution Mechanism and Sparse Diagnosis Method"(No.BK20140339).Based on the combination of the direct problem and the inverse problems,this paper studies the fault evolution mechanism and fault feature extraction of planetary gearbox as the target technology and establishes the meshing stiffness calculation model of tooth root crack.It reveals the variation law of the integrated stiffness of the meshing pair under different fault conditions.Then,a multi-degree-of-freedom dynamic model of the planetary gearbox is constructed and the systematic vibration response is studied under different fault conditions.According to the characteristics of the fault signal,the sparse representation method based on the TQWT is studied to extract the fault characteristics of the planetary gearbox.And an experiment is designed to verify the correctness of the fault evolution mechanism and the effectiveness of the method based on TQWT for the fault feature extraction of the planetary gearbox.Stiffness excitation is the main resource of gear meshing,and the calculation of the meshing stiffness is the basis of gear dynamics analysis.In this paper,the calculation models for the external meshing pairs and the inernal meshing pairs of the planetary gearbox are established.Aiming at the typical fault,tooth root crack,the geometrical models of the tooth root crack of the external and inernal meshing pairs of the planetary gearbox are established,respectively.And then the calculation model of the meshing stiffness of the planetary gearbox is established by the energy method.The meshing stiffness under the different fault location(sun gear,planet gear,ring gear)or different crack size is calculated.Finally,the influence of crack location and crack size on the meshing stiffness of the system is analyzed.Then,the translation-torsion model of the planetary gearbox is established by using the concentrated parameter method.The dynamic equation of the planetary gearbox transmission is deduced.The dynamic response of the system is solved.And the influence of crack location,crack fault size and transmission path on the vibration signal is analyzed.Based on the characteristics of the meshing component and the impact component coupling in the time domain waveform under the crack condition of the planetary gear train,a sparse decomposition method based on the signal oscillation behavior is introduced.According to the oscillation behavior of the meshing component and the impact component in the fault gear vibration signal,a sparse representation method based on TQWT is introduced.This method is a nonlinear decomposition method based on signal oscillation behaviors.The sparse decomposition of the objective function is solved by using the Splitting Augmented Lagrangian Shrinkage Algorithm.Finally,a planetary gearbox fault simulation experimental table is designed to gain the vibration response signal of the planetary gearbox.The sparse representation method based on TQWT is used to analyze the vibration.The validity of the research on the mechanism of the crack failure of planetary gearbox and the effectiveness of the sparse representation method based on TQWT in the fault feature extraction of planetary gearbox are verified. |
