In the development of planetary gear drive, it is found that there is obvious noise in the bench test of several prototypes. Taking various measures, such as replacing gears and other parts to eliminate manufacturing defects, can not eliminate noise. The signal analysis shows that the noise mainly occurs in an asymmetric side frequency of the first-order meshing frequency of 36.38 order (greater than 130dB), the main meshing frequency of 36.99 order, and the modulation frequency of side frequency of planetary carrier of 0.606 order.

The test order diagram under different loads is shown in 4.1, and the results are basically the same. The number of teeth of planetary gear train is 94-61-17 respectively, with three planetary gears. In the following, the cause of this kind of asymmetrical sideband noise will be further analyzed.

Single stage planetary drive (2K-H) is shown in Figure 4.2. The number of planetary gears is p, the input speed of sun gear s is s, s ω, the output speed of planet carrier C is C ω, C ω, and the outer ring gear R is fixed, that is, 0r ω =; R ω = 0r ω =; the number of sun gear, planet gear and ring gear respectively, SZ, P and PZ and R; RZ; the included angle between planet gear P and the first planet gear is positioning angle P (angle P ψ（ p∈[1, P]）。

It is assumed that the order of meshing frequency of planetary gear and ring gear, MF and rotation frequency of planet carrier corresponding to CF are Ω m Ω, C, C Ω. According to the transmission principle, there is the following relationship:

To ensure that the planetary gear can be installed, the following assembly conditions must be met: