An Intelligent Deep Feature Learning Method With Improved Activation Functions for Machine Fault Diagnosis

Rotating machinery has been developed with high complexity and precision, and bearings and gears are crucial components in the machinery system. Deep learning has attracted considerable attention from researchers in this area. The convolutional neural network (CNN) is a typical deep learning model that has a strong capability for automatically extracting features from raw data. This capability minimizes dependence on expert knowledge during feature extraction and selection. In CNN, hyperparameters, such as activation functions, can directly influence the performance of the model. In this study, the improved rectified linear units (ReLU)-CNNs are proposed for machinery fault diagnosis. The model's input are raw vibration signals without feature extraction and selection. It is experimentally validated for fault diagnosis using bearing and gearbox datasets. Results show that the proposed method can obtain satisfactory accuracy with enhanced convergence speed. For both datasets, the proposed method gives better diagnosis accrues than the other compared models. The proposed model can take advantages of standard ReLU-CNN, and these advantages can overcome traditional activation functions' vanishing gradient problems. Meanwhile, the improved ReLU-CNN has a new property that makes it perform better than the standard ReLU-CNN.