Shuhua Yang

Yuhan Yuan, Xiaomo Jiang, Yanfeng Han et al.

Rolling bearings are critical components of rotating machinery, and their proper functioning is essential for industrial production. Most existing condition monitoring methods focus on extracting discriminative features from time-domain signals to assess bearing health status. However, under complex operating conditions, periodic impulsive characteristics related to fault information are often obscured by noise interference. Consequently, existing approaches struggle to learn distinctive fault-related features in such scenarios. To address this issue, this paper proposes a novel CNN-based model named FEMSN. Specifically, a Fourier Adaptive Denoising Encoder Layer (FADEL) is introduced as an input denoising layer to enhance key features while filtering out irrelevant information. Subsequently, a Multiscale Time-Frequency Fusion (MSTFF) module is employed to extract fused time-frequency features, further improving the model robustness and nonlinear representation capability. Additionally, a distillation layer is incorporated to expand the receptive field. Based on these advancements, a novel deep lightweight CNN model, termed the Frequency-Enhanced Multiscale Network (FEMSN), is developed. The effectiveness of FEMSN and FADEL in machine health monitoring and stability assessment is validated through two case studies.

Haitao Liu, Changjun Liu, Xiaomo Jiang et al.

The demand of probabilistic time series forecasting has been recently raised in various dynamic system scenarios, for example, system identification and prognostic and health management of machines. To this end, we combine the advances in both deep generative models and state space model (SSM) to come up with a novel, data-driven deep probabilistic sequence model. Specifically, we follow the popular encoder-decoder generative structure to build the recurrent neural networks (RNN) assisted variational sequence model on an augmented recurrent input space, which could induce rich stochastic sequence dependency. Besides, in order to alleviate the inconsistency issue of the posterior between training and predicting as well as improving the mining of dynamic patterns, we (i) propose using a lagged hybrid output as input for the posterior at next time step, which brings training and predicting into alignment; and (ii) further devise a generalized auto-regressive strategy that encodes all the historical dependencies for the posterior. Thereafter, we first investigate the methodological characteristics of the proposed deep probabilistic sequence model on toy cases, and then comprehensively demonstrate the superiority of our model against existing deep probabilistic SSM models through extensive numerical experiments on eight system identification benchmarks from various dynamic systems. Finally, we apply our sequence model to a real-world centrifugal compressor forecasting problem, and again verify its outstanding performance by quantifying the time series predictive distribution.