LAUSR

In recent years, the signal diagnosis on devices operating under industrial environment has attracted increasing attention. Most data-driven signal diagnosis methods are based on a closed-set assumption that class sets of training and test data are the same. However, in industrial scenarios, during the running process of the device, the operating environment and condition may change over time, continuing generating data belonging to unknown classes with new characteristics and distribution. The unknown classes usually reflect new modes or faults of the device needed to be captured. They are unavailable in training phase, contradicting the closed-set assumption. Existing methods are inappropriate to this type of open-set classification, requiring to classify known classes and recognize unknown classes. To address this challenging problem, this article proposes a generic open-set signal classification method. First, we apply Fourier transform to convert the sensor signals from time domain to frequency domain, then data in the time and frequency domains are fused. Next, a variational encoder-classifier network is proposed to classify known classes and learn the distribution of feature space to extract robust latent features. Finally, based on extreme value theory and entropy, a pair of discriminators determine whether samples belong to unknown or not. The experimental results on two vibration-signal datasets from bearings and nuclear reactor demonstrate the effectiveness and superiority of our proposed open-set signal classification method, especially in practical applications.