Chinese Journal of Electronics
Vol.21, No.3, July 2012
An Extended Multi-scale Principal Component
Analysis Method and Application in Anomaly
Detection
∗
WEN Chenglin
1
, ZHOU Funa
2
,WENChuanbo
3
and CHEN Zhiguo
2
(1.Institute of Information and Controll, Hangdian University, Hangzhou 310018, China)
(2.Institute of Advanced Control and Intelligent Information Processing, Henan University, Kaifeng 475004, China)
(3.Electric Engineering College, Shanghai Dianji University, Shanghai 200240, China)
Abstract — Multi-scale principal component analysis
(MSPCA) can well implement multivariate information
extracting on different scales, but theory foundation of
MSPCA is still an open question. Using spectral decompo-
sition of a matrix and multi-scale representation of spectral
as well as multi-scale transform of a signal, an Extended
multi-scale PCA (EMSPCA) method is proposed to ana-
lyze the reason why multi-scale detection method does well
than single scale method. Under the uniform projection
frame of EMSPCA, the relation between multi-scale de-
tection model and those on each scale is established. Thus
multi-scale anomaly detection can be implemented without
establishing another new PCA model of the reconstructed
data. Simulation shows the efficiency of EMSPCA anomaly
detection algorithm.
Key words — Spectral decomposition, Projection, Ex-
tended multi-scale PCA (EMSPCA), Principal component
analysis (PCA), Fault detection.
I. Introduction
With the development of industry technology, large scale
system becomes more and more complicated and automatic.
All parts of the system are tightly connected, and they are
operating as a whole. Failure in a part may cause breakdown
of the whole system or even result in disastrous accident
[1−3]
.
Research on fault diagnosis has received widely attention from
experts both in academic and application
[1−8]
.
Principal component analysis (PCA) is a commonly used
method in the field of data driven abnormal detection
[9−13]
.
Multi-scale principal component analysis (MSPCA) com-
bines the ability of PCA to decorrelate multivariate with
that of wavelet analysis to extract deterministic features.
Simulation shows that MSPCA can well extract feature
information
[14−16]
. But existed methods on MSPCA can’t the-
oretically analyze the intrinsic reason why MSPCA is better
than PCA.
Spectrum decomposition of covariance matrix and multi-
scale decomposition of spectrum are first studied. Then ex-
tended MSPCA is established to theoretically analyze the in-
trinsic reason why MSPCA is better than PCA. Finally, an
EMSPCA based abnormal detection algorithm is proposed.
II. PCA
The essence of PCA is a linear transform corresponding to
axis rotation
[9,11,12]
V = B
T
Y (1)
where Y =[y(1), y(2), ···, y(n)] ∈ R
p×n
is the observation
matrix, p is the number of observation variable, n is the num-
ber of samples; V =[v(1), v(2), ···, v(n)] ∈ R
p×n
is score
matrix.
PCA provides a method of observation matrix decompos-
ing observation in Eq.(2)
Y =
υ
i=1
b
i
V
i
+ E (2)
where b
i
=[b
i1
,b
i2
, ···,b
ip
]
T
is loading vector, is after PCA
transform, eigenvalue corresponding to each b
i
is descendly
sorted as λ
1
≥···≥λ
p
≥ 0. V
i
=[v
i
(1), ···,v
i
(n)] ∈ R
1×n
is
the projection of Y on b
i
,thatis
V
i
= b
T
i
Y (3)
E =
p
i=υ+1
b
i
V
i
is the residual matrix, υ is the number of key
principal components
[9−12]
.
III. MSPCA
MSPCA implement PCA to wavelet coefficients at each
scale to filter unwanted components. The main idea of
MSPCA can be shown in Fig.1
[13−15]
.
∗
Manuscript Received Apr. 2011; Accepted Nov. 2011. This work is supported by the National Natural Science Foundation of China
(No.60934009, No.61034006, No.60804026, No.61174112, No.60801048).