Determination of influential factors and diagnostics using multivariate statistical relationships between variables and faults

摘要

This paper proposes a variable influence (VI) index-based on-line method for diagnosing discontinuous processes. The VI index is developed using the concept of contribution plots, and can be used to explain the influence of a process variable on a specific fault. The proposed method consists of two phases: off-line VI model-building and on-line diagnosis via VI index comparison. In the off-line VI model-building phase, the off-line VI model is constructed using off-line fault data and used as a reference model for the on-line diagnosis of a new batch. The on-line diagnosis phase is triggered by an out-of-control signal of a new batch. It calculates the VI index values for new process data available at that time, which are compared with the off-line VI index values of the off-line VI model stored in the data/model base. The proposed method has the advantage that it does not require any process knowledge of operators and can automatically select an assignable cause via the comparison of VI index values. A case study on a PVC batch process is conducted to demonstrate the diagnosis performance of the proposed method. The performance of the proposed method is also evaluated when an on-line mode is not considered in the proposed framework.