Only low-order information
of process data (i.e., mean, variance,
and covariance) was considered in the principal component analysis
(PCA)-based process monitoring method. Consequently, it cannot deal
with continuous processes with strong dynamics, nonlinearity, and
non-Gaussianity. To this aim, the statistics pattern analysis (SPA)-based
process monitoring method achieves better monitoring results by extracting
higher-order statistics (HOS) of the process variables. However, the
extracted statistics do not strictly follow a Gaussian distribution,
making the estimated control limits in Hotelling-
T
2
and squared prediction error (SPE) charts inaccurate,
resulting in unsatisfactory monitoring performance. In order to solve
this problem, this paper presents a novel process monitoring method
using SPA and the
k
-nearest neighbor algorithm. In
the proposed method, first, the statistics of process variables are
calculated through SPA. Then, the
k
-nearest neighbor
(kNN) method is used to monitor the extracted statistics. The kNN
method only uses the paired distance of samples to perform fault detection.
It has no strict requirements for data distribution. Hence, the proposed
method can overcome the problems caused by the non-Gaussianity and
nonlinearity of statistics. In addition, the potential of the proposed
method in early fault detection or safety alarm and fault isolation
is explored. The proposed method can isolate which variable or its
statistic is faulty. Finally, the numerical examples and Tennessee
Eastman benchmark process illustrate the effectiveness of the proposed
method.