Linear Chain Conditional Random Field for Operating Mode Identification and Multimode Process Monitoring

As a supervised machine learning algorithm, conditional random fields are mainly used for fault classification, which cannot detect new unknown faults. In addition, faulty variable location based on them has not been studied. In this paper, conditional random fields with a linear chain structure are utilized for modeling multimode processes with transitions. A linear chain conditional random field model is trained by normal data with mode label. This model is able to distinguish transitions from stable modes well. After mode identification, the expectation of state feature function is developed for fault detection and faulty variable location. Case studies on the Tennessee Eastman process and continuous stirred tank reactor (CSTR) testify the effectiveness of the proposed approach.