Dynamics Analysis Of Wind Power Planetary Gear Trains With Local Crack Fault Under Varying Rotate Speed

The lack and the pollution of fossil fuel has become a global problem,wind energy has been widely concerned from each countries as a new green energy,and the industry of wind power developed rapidly.The failure rate of wind turbine gearbox is high,for the reason that the work environment of wind turbines is complex,the wind current is strong and irregular,and the load have a large scope.It has significance to research on influence of fault to dynamic characteristic of planetary gear transmission system,which is an important part in wind turbine gearbox.Take the planetary gear transmission system as research object,whose dynamic characteristics under local crack fault is reached,as the background of wind power.The influence of different gear under local crack fault to dynamic characteristic is analyzed,from meshing stiffness,inherent characteristic and vibration response of planetary gear transmission system.Firstly,a dynamic model is developed to simulate the vibration signals of a planetary gear set based on Lumped Parameter Method,considering the influence of torsional vibration and ignoring the effect of time-varying mesh stiffness and damping of the transmission system.Using weber method to calculate internal and external meshing stiffness of the planetary transmission under healthy condition,sun gear local crack fault and planet gear local crack fault.Inherent characteristic was calculated and the analysis was conducted on normal model and crack fault model.Secondly,considering the time-varying mesh stiffness caused by the changing tooth mesh number and gear mesh contact area.Internal and external time-varying meshing stiffness of a planetary gear set are computed by using potential energy method.Calculating the time-varying mesh stiffness under sun gear local crack fault of different lengths and angles.Then the influence of crack length to the mesh stiffness is analyzed.Lastly,a dynamic model is developed to simulate the vibration signals of a planetary gear set,considering the horizontal vibration,vertical vibration and torsional vibration,internal and external time-varying mesh stiffness and planet gear phase difference of eachcomponent.While the system starts,stops or the load changes,the change of rotating speed will make the vibration signal full of non-stationary characteristics.Setting the planet gear mesh angular displacement as the meshing cycle,transforming the unsteady-state vibration signal into pseudo steady-state vibration signal by transforming the mesh stiffness in time domain into angular domain.The dynamic responses of gear crack fault in time domain and angular domain are obtained.And then the influence of crack fault to dynamic characteristic in time domain is analyzed,using the method of order envelop tracking.