Toward robust process monitoring of complex process industries based on denoising sparse auto-encoder

Abstract

Robust industrial process monitoring is crucial to ensure production safety and product quality stability. However, the process monitoring of high-dimensional, nonlinear, complex industrial processes is still challenging due to their inherent complexities, such as multi-phase, multi-field, and tight coupling of multiple sub-processes. In this article, a simple yet robust nonlinear process monitoring scheme based on a kind of denoising sparse auto-encoder (DSAE) is proposed. Specifically, a novel hybrid auto-encoder, namely DSAE, is established, to address the strong redundancy, nonlinearity and noise interference in process variables by integrating a sparse auto-encoder (SAE) and a denoising auto-encoder (DAE). Successively, an online process monitoring model is established by introducing two new process monitoring statistics computed on the DSAE-based feature representation space and residual space, respectively. Moreover, the Kernel density estimation (KDE) approach is adopted to determine the corresponding control limits of the monitoring statistics, which can avoid the conventional empirical assumption of F or Chi-square distribution on monitoring statistics. Extensive confirmative and comparative experiments conducted for the fault monitoring of a nonlinear numerical simulation system, the benchmark Tennessee Eastman process (TEP) and ventilation exhaust fans (VEFs) in the continuous casting process (CCP) from a top steel plant in China show that the proposed method is promising. Specifically, the proposed method performs favorably against the representative process monitoring methods, and it has especially a stronger robustness against noise and uncertain interference in nonlinear process systems.