Planetary Gearbox Fault Diagnosis Features Extraction Based On Windowed Synchronous Average

Planetary gearbox is one of the important transmission parts of mechanical equipment.Compared with conventional fixed-shaft gearboxes,it takes advantages of small volume,large carrying capacity and stationary work.However,planetary gearbox is usually operating in harsh environments,such as wind turbines.Then,gear prone to pitting,crack and other local faults,which has become an important monitoring target in the field of faults diagnosis.Planetary gear transmission is much more complex than the fixed-shaft gearbox,which includes the sun gear,planet gears,the planet carrier,the ring gear and so on.Planet gears not only spin around their own centers but also revolve around the center of the sun gear.In addition,planet gears are meshed with both the sun gear and the ring gear simultaneously,which is a typical compound movement.If the vibration sensor is mounted on the vertical direction of gearbox casing,the vibration signal generated by the planet gear set,which the position of meshing vibration source relative to the sensor is time-varying.Moreover,in order to load evenly,the number of planet gear is often more than one.The vibration signal is a mixture from planet gears,ring gear and sun gear at different meshing positions.The feature extraction becomes more difficult.The characteristic analysis of vibration signal is a commonly method in mechanical faults diagnosis.By extracting the fault characteristic of vibration,machine faults can be diagnosed effectively.It is one of hotspot in faults diagnosis to extract the characteristic information from strong background noise.It is also the main research content of this paper.The deep study on a typical planet gearbox,which includes a ring gear,a sun gear and several planet gears,has been carried out in this paper.Based on the previous research works,to the time-varying characteristics path of planetary gearbox transmission,the windowed synchronous averaging scheme has been studied in this paper in the angle-domain.It suits for the time-varying transmission paths and varying-speed working conditions of planetary gearbox.Firstly,the fault generated vibration in the time domain is windowed by the Tukey window,which mainly obtain the useful vibration signal and suppress the effect of time-varying transmission paths.Subsequently,the windowed time-domain signal is resampled at constant angle increments according to the computed order tracking(COT).It converts the non-stationary signal in the time domain into the stationary one in the angle domain.Then,the angle-domain signal is processed by signal synchronous average(SA).By which,the non-stationary signal caused by the rotating speed and load fluctuation can be effectively reduced and the non-synchronous interferences and noise are suppressed.According to the above researches,a narrowband demodulation scheme for teeth faults detection of planetary gearboxes with frequency shift and spectrum edit has been proposed in this paper.It can extract the main meshing order components of planetary gearbox fault from the automated edited order spectrum and recovering the angle-domain signal.It extracts the fault feature of planetary gearbox effectively.Tests are conducted to verify the validity of proposed methods.