In order to verify the effectiveness of the proposed method in planetary gearbox fault diagnosis, a planetary gearbox fault simulation experiment is designed. The experimental system is shown in Figure 1. The test-bed is mainly composed of variable-speed drive motor, torsion sensor and encoder, planetary gearbox, two-stage parallel shaft gearbox and programmable magnetic brake.

In order to simulate the local fault of planetary gear box, a micro through crack with width of 0.15 mm and depth of 1 mm is machined on a tooth of sun gear and planetary gear by wire cutting technology along the tooth root and perpendicular to the tooth center line. The fault gear is shown in Figure 2. In this experiment, pcb352c33 acceleration sensor (measuring range: ± 50g, frequency range: 0.5 ~ 10 kHz, sensitivity: 100 mV / g) is used to collect fault vibration signal.

The acceleration sensor is arranged on the vertical radial, horizontal radial and axial test points on the top of the planetary gearbox. Dt9837 data converter and a notebook computer with DAQ software are selected as the data acquisition system of this experiment. During the experiment, the speed of the sun wheel connected with the motor is 1 380 R / min, the sampling frequency is 5 120 Hz, and the data length is 4 096 points. According to the structural parameters of the planetary gearbox and the speed of the input shaft of the sun gear, the local fault characteristic frequency of each gear under the test conditions is calculated.