Research Article
𝐻
∞
Static Output Tracking Control of Nonlinear Systems with
One-Sided Lipschitz Condition
Leipo Liu and Xiaona Song
College of Information Engineering, Henan University of Science and Technology, Luoyang 471003, China
Correspondence should be addressed to Leipo Liu; liuleipo123@163.com
Received 21 July 2014; Revised 30 September 2014; Accepted 3 October 2014; Published 13 October 2014
Academic Editor: Haranath Kar
Copyright © 2014 L. Liu and X. Song. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
is paper is concerned with 𝐻
∞
static output tracking control of nonlinear systems with one-sided Lipschitz condition. e
dimensions of system model and reference model may be dierent. A static output feedback controller is designed to guarantee
thatthesystemoutputasymptoticallytracksthereferenceoutputwith𝐻
∞
disturbance rejection level. A new sucient condition
is derived to obtain the static output feedback gain by linear matrix inequality (LMI), and no equality constraints can be needed.
Finally, an example is given to illustrate the eectiveness of the proposed method.
1. Introduction
Tracking control has been a hot point due to its wide applica-
tions. e main objective of tracking control is to minimize
the error between the state (or output) of the plant and the
state (or output) of a given reference model. So it involves two
related problems, that is, state feedback tracking controller
design [1–3] and output feedback tracking controller design
[4–9].Amongthem,thelatterispaidmuchattentionbecause
ofitsattractivefeaturessuchaslowoverheadsofimple-
menting control, the reliability of control systems, and widely
practical applications where measurement of all the state
variables is not possible. Furthermore, since the static output
feedback case needs much lower costs than an observer-
based approach, a few meaningful results about static output
feedback tracking control have been presented [10–12].
From above results, it has been shown that the solution
of the Riccati equation or LMI depends strongly on the
Lipschitz constant, but when the Lipschitz constant becomes
large, most of the existing results are infeasible. To enlarge
the domain of attraction of nonlinear systems, the one-
sided Lipschitz condition is proposed [13, 14, 14–21]. e
one-sided Lipschitz constant is signicantly smaller than
the Lipschitz constant, which makes it much more suit-
able for estimating the inuence of nonlinear part. One-
sided Lipschitz condition is shown to be an extension of
the Lipschitz condition and is less conservative. Recently, the
problem of tracking control of nonlinear systems with one-
sided Lipschitz condition has been presented [22]. In [22],
the stabilization and signal tracking control for one-sided
Lipschitz nonlinear dierential inclusions are considered;
a nonlinear state feedback tracking controller is designed.
However, to the authors’ knowledge, there are very few
studies concerning static output tracking controller design of
nonlinear systems with one-sided Lipschitz condition. ese
motivate our study.
is paper considers static output tracking control of
nonlinear systems with one-sided Lipschitz condition. e
dimensions of system model and reference model may
be dierent. A design procedure of static output feedback
controller is proposed to guarantee that the system output
asymptotically tracks the reference output with 𝐻
∞
distur-
bance rejection level. A new sucient condition is obtained
by LMI, and no equality constraints can be needed. ese
will reduce the diculty in solving output feedback gain.
Finally, an example is given to illustrate the eectiveness of
the proposed method.
Notations. 𝑅
𝑛
and 𝑅
𝑛×𝑚
denote, respectively, the spaces of 𝑛-
dimensional real numbers and 𝑛×𝑚real matrices. Let 𝑀be
a real symmetric matrix; 𝑀>0means 𝑀is positive denite.
⟨⋅,⋅⟩is the inner product in 𝑅
𝑛
;thatis,given𝑥, 𝑦∈𝑅
𝑛
,then
Hindawi Publishing Corporation
Mathematical Problems in Engineering
Volume 2014, Article ID 742704, 7 pages
http://dx.doi.org/10.1155/2014/742704