Characteristic Frequency Extraction And Analysis Of Planetary Gear Sets

Planetary gear sets(PGS) has been widely are commonly used in modern automobile, such as automatic transmission, wheel reducer of heavy vehicle, power distributor of Hybrid cars, etc. The working principle of PGS is very different from those traditional fixed-shaft gear sets, which leads to the complexity of vibration response signal. There are many modulation sidebands in the spectrum of PGS’ vibration signal, which is similar to those fault fixed-shaft gear sets’ signal. Therefore, it’s essential to accurately establish the mathematical model of vibration response signal of PGS based on a further studying on the mechanism of PGS’ vibration signal, which will provide an important theoretical basis for engineering application.The main conclusions of the thesis are as follows:(1) It was deduced by formula that the periodic change of signal transfer path will generate amplitude modulation on PGS’ vibration response signal. A new signal transfer path method is proposed by combining experiment, finite element simulation and numerical fitting, and the mathematical model of the new method was established.(2) It was theoretically deduced that the periodic change of meshing force direction will generate amplitude modulation on PGS’ vibration response signal as well. A dynamic simulation was built to verify this conclusion and the mathematical model of periodic change of meshing force direction was established.(3) Considering about several types of PGS with different numbers of ring gear teeth, sun gear teeth and planet gear, the mathematical models of PGS’ vibration signal were established and numerical simulations were carried out. Sideband harmonics caused by rotating carrier were found in the vicinity of the gear mesh harmonic. The numerical simulations of vibration signal of PGS with different meshing force were carried out as well, and it was found that not only first order but high order modulation sidebands caused by rotating carrier will appear under this circumstances. The effectiveness of the proposed model is verified by experiments.(4) Through analysis of the mathematical model, it is found that, when meshing frequency was constant, the amplitude of modulation sidebands were influenced by the Fourier series expansion coefficients of signal transfer path mathematical model. In addition, these coefficients have little affection on the modulation sidebands.