Multidimensional Discretization과 Event-Codification 기법을 이용한 레이저 용접 불량 검출

Abstract

In the literature, various stochastic anomaly detection methods, such as limit checking and PCAbased approaches, have been applied to weld defect detection. However, it is still a challenge to identify meaningful defect patterns from very limited sensor signals of laser welding, characterized by intermittent, discontinuous, very short, and non-stationary random signals. In order to effectively analyze the physical characteristics of laser weld signals: plasma intensity, weld pool temperature, and back reflection, we first transform the raw data of laser weld signals into the form of event logs. This is done by multidimensional discretization and event-codification, after which the event logs are decoded to extract weld defect patterns by Naïve Bayes classifier. The performance of the proposed method is examined in comparison with the commercial solution of PRECITEC’s LWM TM and the most recent PCA-based detection method. The results show higher performance of the proposed method in terms of sensitivity (1.00) and specificity (0.98).