Classification of the operating state of rolling bearings with the convolutional neural network with variable dilation factors

Abstract

The work describes rolling bearings operation data processing, and their use in the problem of constructing a mathematical model of the binary classification of the operating state of bearings by the method of a convolutional neural network with varying factors of dilatation of the kernel of convolutional layers. To classify bearings with defects, we used vibration acceleration data from our own test bench and a publicly available data set. The work also investigated a method for generalizing the classification of bearing signals obtained as a result of fundamentally different experiments and having different standard sizes. To unify signals, the following processing method is proposed: select data areas with displacement, go to the frequency space using fast Fourier transform, cut off frequencies exceeding 10 times the shaft rotation frequency, restore the signal while maintaining 10 shaft rotation periods, scale the received signal by dividing it by its diameter orbits of the rolling body and interpolate the signal at 2048 points. This algorithm also allows to generate a balanced sample for building a mathematical model. This feature is provided by varying the step of splitting the initial signal. The advantage of this algorithm over the classical methods of oversampling or undersampling is the generation of new objects that specify the statistical parameters of the general population. The signal processing algorithm was used both for binary classification problems within one dataset, and for training on one and testing on another. To increase the data set for training and testing the mathematical model, the bootstrapping method is used, based on multiple generation of samples using the Monte Carlo method. The quality of the mathematical model of binary classification was assessed by the proportion of correct answers. The problem is formulated as the problem of minimizing binary cross entropy. The results obtained are presented in the form of graphs demonstrating the neural network training process and graphs of the distribution density of metrics.