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Moving Window Non-negative Matrix Projection for Adaptive Process Monitoring

An adaptive process monitoring approach is described for the monitoring of a process with operating condition changes. As a famous dimension reduction technique, non-negative matrix factorization (NMF) has been used in diverse scientific fields including process monitoring since its appearance. However, the existing NMF based monitoring method is only for stationary processes. This paper presents a new variant of NMF called moving window non-negative matrix projection (MWNMP) for monitoring the time-varying processes. The proposed technique incorporates the moving window method into the existing generalized non-negative matrix projection (GNMP) based monitoring for updating the model to reflect the operating mode change. The obtained basis matrix could be updated when the process status changes. Then, the monitoring metrics and the corresponding upper control limits would be recalculated too. The MWNMP based adaptive process monitoring approach is applied to a continuous stirred tank reactor (CSTR) process. The monitoring results illustrate the adaptability and feasibility for monitoring the time-varying processes.