Tooth faults detection of planetary gearboxes based on tooth root strain signal of ring gear

Condition monitoring and fault diagnosis of planetary gearboxes is still a challenge at present. This work proposes an approach for tooth faults detection of planetary gearboxes based on the tooth root strain signal of ring gear. Firstly, the tooth fault mechanism is analyzed with two steps. A lumped-parameter model is adopted to investigate the influence of the tooth fault on the ring-planet mesh force, and a 2-D finite element model is built to figure out the fault features in the time domain of the ring gear strain signal caused by such abnormal mesh force. Secondly, the monitoring strategy of sun gear and planet gear is proposed. In the strategy, the averaged strain matrix, whose elements correspond to the teeth of the interesting gear, is obtained by using the extracting and averaging operation. The faulty tooth can be identified by comparing the elements in the matrix. The efficiency of the monitoring strategy and the requirement for complete monitoring are also discussed. Finally, experiments are carried out. In the experiments, the monitoring strategy is applied to different faults of planet gear and sun gear in low speed condition and high speed condition. The theoretical fault features can be obviously seen in the time domain of the measured strain signals, which shows the effectiveness of the proposed approach.