Digital Signal Processing 37 (2015) 100–108
Contents lists available at ScienceDirect
Digital Signal Processing
www.elsevier.com/locate/dsp
Recursive least squares parameter identification algorithms for systems
with colored noise using the filtering technique and the auxilary
model
✩
Feng Ding
a,b,∗
, Yanjiao Wang
a
, Jie Ding
c
a
Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Jiangnan University, Wuxi 214122, PR China
b
Control Science and Engineering Research Center, Jiangnan University, Wuxi 214122, PR China
c
School of Automation, Nanjing University of Posts and Telecommunications, Nanjing, 210032, PR China
a r t i c l e i n f o a b s t r a c t
Article history:
Available
online 6 November 2014
Keywords:
Filtering
technique
Parameter
estimation
Recursive
identification
Least
squares
Box–Jenkins
system
This paper focuses on the parameter estimation problems of output error autoregressive systems and
output error autoregressive moving average systems (i.e., the Box–Jenkins systems). Two recursive least
squares parameter estimation algorithms are proposed by using the data filtering technique and the
auxiliary model identification idea. The key is to use a linear filter to filter the input–output data. The
proposed algorithms can identify the parameters of the system models and the noise models interactively
and can generate more accurate parameter estimates than the auxiliary model based recursive least
squares algorithms. Two examples are given to test the proposed algorithms.
© 2014 Elsevier Inc. All rights reserved.
1. Introduction
The development of information and communication technol-
ogy
has had a tremendous impact on our lives, e.g., the informa-
tion
filtering, optimization and estimation techniques [1–4]. In the
areas of signal processing and system identification, the observed
output signals always contain disturbances from process environ-
ments
[5–8]. The disturbances are of different forms (white noise
or colored noise). It is well known that the conventional recursive
least squares (RLS) method generates biased parameter estimates
due to correlated noise or colored noise [9]. Thus the identification
of output error models with colored noise has attracted many re-
search
interests [10]. The bias correction methods have been con-
sidered
very effective to deal with the output error models with
colored noise [11,12]. However, the bias correction methods ignore
the estimation of the noise models [13]. In this paper, we propose
new identification methods for estimating the parameters of the
system model and the noise model.
Since
the noise in real life can be fitted by the autoregressive
(AR) models, the moving average (MA) models [14,15] or the au-
✩
This work was supported by the National Natural Science Foundation of China
(Nos. 61273194, 61203028) and the PAPD of Jiangsu Higher Education Institutions.
*
Corresponding author at: Key Laboratory of Advanced Process Control for Light
Industry (Ministry of Education), Jiangnan University, Wuxi 214122, PR China.
E-mail
addresses: fding@jiangnan.edu.cn (F. Ding), yjwang12@126.com
(Y. Wang),
dingjie@njupt.edu.cn (J. Ding).
toregressive moving average (ARMA) models [16], this paper con-
siders
the output error (OE) model with AR noise as shown in
Fig. 1 (the OEAR model for short), which can be expressed as
y(t) =
B(z)
A(z)
u(t) +
1
C(z)
v(t), (1)
where {u(t)} and {y(t)} are the system input and output se-
quences,
respectively, {v(t)} is a white noise sequence with zero
mean and variance σ
2
, and A(z), B(z) and C(z) are polynomials in
the unit backward shift operator z
−1
[z
−1
y(t) = y(t − 1)]:
A(z) := 1 + a
1
z
−1
+ a
2
z
−2
+ ...+ a
n
a
z
−n
a
,
B(z) := b
1
z
−1
+ b
2
z
−2
+ ...+ b
n
b
z
−n
b
,
C(z) := 1 + c
1
z
−1
+ c
2
z
−2
+ ...+ c
n
c
z
−n
c
.
Assume that the orders n
a
, n
b
and n
c
are known, and u(t) = 0,
y(t) = 0 and v(t) = 0for t 0. The coefficients a
i
, b
i
and c
i
are the parameters to be estimated from the input–output data
{u(t), y(t)}.
The
model in (1) can be transformed into a new controlled au-
toregressive
moving average (CARMA) form,
A(z)C (z ) y(t) = B(z)C(z)u(t) + A(z)v(t),
or
A
(z) y(t) = B
(z)u(t) + D(z)v(t), A
(z) := A (z)C(z),
B
(z) := B(z)C(z), D(z) := A(z).
http://dx.doi.org/10.1016/j.dsp.2014.10.005
1051-2004/
© 2014 Elsevier Inc. All rights reserved.