Recently, multivariate statistical methods, such as principal component analysis (PCA), have drawn increasing attention for fault detection applications in industrial processes. However, industrial processes typically have complex multimodal and nonlinear characteristics. In these situations, the traditional PCA method performs poorly due to its assumption that the process data are linear and unimodal. To improve fault detection performance in nonlinear and multimode industrial processes, this paper proposes a new fault detection method based on weighted difference principal component analysis (WDPCA). Weighted difference principal component analysis first eliminates the multimodal and nonlinear characteristics of the original data by using the weighted difference method. Then, PCA is applied to the preprocessed data, neglecting the influences of multimodality and nonlinearity. Two numerical examples and an industrial application in a semiconductor manufacturing process are used to verify the effectiveness of WDPCA. The simulation results demonstrate that WDPCA shows better fault detection performance than the PCA, kernel principal component analysis (KPCA), independent component analysis (ICA), k-nearest neighbor rule (kNN), and local outlier factor (LOF) methods. KEYWORDS fault detection, multimodal data, nonlinear data, principal component analysis, weighted difference principal component analysis
| INTRODUCTIONWith the development of modern automation technology in recent years, industrial systems are constantly increasing in scale, complexity, and degree of integration. However, such improvements also increase the probability of fault occurrence. To address this issue, fault detection technology has been developed and is now widely used in production processes. Data-driven fault detection technology has received extensive attention in academic research. Moreover, multivariate statistical analysis methods, such as principal component analysis (PCA) and independent component analysis (ICA), have developed rapidly, and several new fault detection methods have been derived. [1][2][3][4][5][6][7][8][9] Chemical production is an important industrial production field, and its processes increasingly reflect the nonlinear and multimodal characteristics of more complex control systems. The question of how to effectively extract the important information from the chemical production process data and achieve fault detection in nonlinear and multimode processes has also attracted an increasing amount of attention from scholars. [10][11][12][13][14][15][16][17] Lee proposed ICA to extract the higher order features of data. 18 However, ICA is still unable to address the problem of fault detection for nonlinear data.