| The gearbox is the key component of variable speed in a wind turbine,and is easy to occur crack and wear faults due to the alternating load,which affects the safe and reliable operation of a wind turbine.The vibration analysis method is often used to fault detection of the gearbox,but the signal will be affected due to the different transmission path in the process from the meshing position to the surface of the gearbox.In addition,the tooth surface friction generates a large amount of heat at the meshing point,and then the contact temperature increases,resulting in the changes of tooth profile and meshing characteristics.Therefore,the dynamic model of a wind turbine gearbox considering tooth contact temperature is established,and the nonlinear dynamic and transmission characteristics of the system under crack and wear faults are studied,which have important theoretical significance and engineering application value for the fault condition monitoring of a wind turbine gearbox.The main research contents and achievements of this paper are as follows:(1)The temperature and deformation of the tooth surface are calculated respectively using the Blok’s flash temperature theory and thermal deformation formula,and the meshing stiffness caused by the tooth contact temperature is obtained using the Hertz theory.For the gearbox with two-stage fixed gear and one-stage planetary gear,the pure torsional dynamic model is established considering the tooth contact temperature,damping,time-varying meshing stiffness,comprehensive transmission error and backlash using the lump mass method,and the vibration differential equations are derived and solved by Runge-Kutta method.(2)The meshing stiffness of high-speed driving gear with crack is analyzed,the influence of tooth contact temperature on the dynamic behaviors of the system under different crack length is studied,and the numerical results in the time-frequency domain are compared with those of the test without considering the flash temperature.The results show that the flash temperature makes the impact amplitude caused by the crack in the time domain increase,the fault side frequency be more complex,the phase diagram expand and the number of discrete points in Poincaré section increase,and the changes are more obvious with the increasing of the crack length.(3)The depth and time-varying meshing stiffness of the tooth surface wear are calculated using Archard equation and potential energy method,respectively,and the gearbox dynamic model considering the high-speed gears wear is established.The effects of the tooth contact temperature,comprehensive transmission error and wear on the dynamic characteristics are studied through the analysis of bifurcation,time domain,spectrum,phase and Poincaré section diagram,and the frequency domain values of gear wear are compared with experiment data.The results show that the tooth contact temperature makes the chaotic motion region increase and the motion state of the system change,the stability decreases with the increase of comprehensive transmission error,and for the gearbox considering the contact temperature,the gear wear makes the paroxysmal periodic motion appear and chaotic region increase obviously.(4)Based on the ARMAX identification model,the input signal is the numerical simulation results and the output signal is the experimental vibration signal,the model parameters are estimated using the recursive-maximum likelihood method,and the transfer function of the system is obtained.The amplitude frequency responses at different meshing positions are analyzed,and the transmission characteristics of the gearbox system under normal and fault conditions are studied.The results show that the crack and wear faults make the peak of the amplitude frequency characteristics of the signal from the high-speed meshing point to the near measuring point change,and there is no obvious change for the signal from the high-speed meshing point to the far measuring point. |
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