Increasing mapping based hidden Markov model for dynamic process monitoring and diagnosis

• An increasing mapping based hidden Markov model (IMHMM) is proposed.
• Parameter re-estimation formulas are based on increasing mappings.
• An IMHMM based expandable process monitoring and fault diagnosis framework.
• An index considering serial correlation is used for dynamical process.

Hidden Markov models (HMMs) perform parameter estimation based on the forward–backward (FB) procedure and the Baum–Welch (BW) algorithm. The two algorithms together may increase the computational complexity and the difficulty to understand the algorithm structure of HMMs clearly. In this study, an increasing mapping based hidden Markov model (IMHMM) is proposed. Between the observation sequence and possible state sequence an increasing mapping is established. The re-estimation formulas for the model parameters are derived straightforwardly based on these mappings instead of FB variables. The IMHMM has simpler algorithm structure and lower storage requirement than the HMM. Based on IMHMM, an expandable process monitoring and fault diagnosis framework for large-scale dynamical process is developed. To characterize the dynamic process, a novel index considering serial correlation is used to evaluate process state. The presented methodology is carried out in Tennessee Eastman process (TEP). The results show improvement over HMM in terms of memory complexity and training time of the model. Also, the power of IMHMM can be observed compared with principal component analysis (PCA) based methods.