Stability Analysis for a General Class of
Discrete-Time Polynomial Fuzzy Dynamic Systems
Liwei Ren
Center for Control Theory and
Guidance Technology
Harbin Institute of Technology
Harbin 150001, P. R. China
Email: 14B304020@hit.edu.cn
Xiaojun Ban
Center for Control Theory and
Guidance Technology
Harbin Institute of Technology
Harbin 150001, P. R. China
Email: banxiaojun@hit.edu.cn
Hao Ying*
Department of Electrical and
Computer Engineering
Wayne State University
Detroit, Michigan, 48202, USA
Email: hao.ying@wayne.edu
Abstract—The polynomial fuzzy models are capable of
modeling complex dynamic systems. They have attracted
increasing attention in the recent years as the models of choice
for the development of more advanced fuzzy controllers. Little
effort has been made to study the models themselves though.
Like many other types of models, a polynomial fuzzy model
aims at describing the physical system’s dynamics based on the
measured input-output data of the system. Importantly, a
polynomial fuzzy model that appears to mimic the measured
data reasonably well does not guarantee its validity. One way
to assess model’s quality is to check whether its stability is
consistent with that of the physical system, which is the theme
of our investigation. In this paper, we first propose a type of
discrete-time polynomial fuzzy dynamic models, which
comprises the general Takagi-Sugeno (T-S) fuzzy model as a
special case. Then, based on the Lyapunov’s linearization
method, a necessary and sufficient condition is established for
analytically determining the local asymptotic stability of the
proposed models. A numerical example is given to illustrate the
effectiveness and utility of our method.
Keywords—polynomial fuzzy system; stability analysis;
Lyapunov’s linearization method
I. INTRODUCTION
When facing complex nonlinear systems, we have to
admit system modeling is really more an art than science.
Fuzzy systems technology can play an important role in
modeling nonlinear dynamic systems as well as developing
model-based control systems [1,2], which have advantage in
describing the complex dynamics of the nonlinear behaviors.
One of the various fuzzy systems which attracts a great deal
of attention is the Takagi-Sugeno (T-S) fuzzy system [3,4].
A T-S fuzzy system consists of a number of linear sub-
systems, which represents local input-output relations of a
nonlinear system and facilitates the stability analysis and
controller synthesis in a general framework [5,6].
Attention has focused on the nonfuzzy polynomial
system theory and its application for many years, owing to
its excellent ability in modeling many natural and man-
made systems [7-9]. The study of the polynomial systems
may provide a unified view of different classes of systems.
Recently, the T-S fuzzy systems have been extended to the
polynomial fuzzy systems, a new type of fuzzy systems
whose rule consequents are represented by the polynomials
[10]. There has been a flurry of research activities in the
design of the polynomial fuzzy control systems [11-13].
Little effort has been made to study the polynomial fuzzy
models themselves though.
A polynomial fuzzy model that can imitate a group of
measured input-output data does not necessarily mean the
model is a valid one. Model quality assessment is needed to
ensure its validity. Yet, there exists no analytical method in
the literature for theoretically checking the quality of a
polynomial fuzzy system. Polynomial fuzzy systems will be
more powerful if this problem can be resolved. The purpose
of our research was to develop a model quality assessment
tool for the polynomial fuzzy systems. We realized our goal
through studying the local stability of a general class of
polynomial fuzzy dynamic systems based on the
Lyapunov’s linearization method. This work significantly
extends the scope of our previous work where the local
stability of the general class of T-S fuzzy systems with the
linear rule consequents [14].
The rest of this paper is organized as follows. Section II
is devoted to describing the general polynomial fuzzy
systems. The main result is given in Section III. In Section
IV, a numerical example is presented to illustrate the utility
of our new method and result. We conclude this paper in
Section V.
II. A
GENERAL CLASS OF POLYNOMIAL FUZZY DYNAMIC
SYSTEMS
There are
Ω
rules. The
-th fuzzy rule of a polynomial
fuzzy system in the general class, denoted
, is as follows:
: IF
()
n
is
0
AND
()
1yn−
is
1
AND
"
AND
()
nm−
is
mj
This work is supported by the National Natural Science Foundation o
China (NSFC) under Grant No.61304006, NSFC under Grant No.61273095
and the Fundamental Research Funds for the Central Universities (Gran
o. HIT. NSRIF. 2013036).