Journal of Control Theory and Applications 2007 5 (4) 351–356 DOI 10.1007/s11768-006-6051-x
Robust exponential stability of uncertain discrete
time impulsive switching systems with state delay
Guangdeng ZONG
1,2
, Yuqiang WU
2
, Baoyong ZHANG
1
, Yangyang KONG
2
(1. School of Automation, Nanjing University of Science and Technology, Nanjing Jiangsu 210094, China;
2. Institute of Automation, Qufu Normal University, Qufu Shandong 273165, China )
Abstract: A new class of hybrid impulsive and switching models are introduced and their robust exponential stability
and control synthesis are addressed. The proposed switched system is composed of stable subsystems and unstable subsys-
tems, which not only involves state delay and norm-bounded time-varying parameter uncertainties, but also contains the
impulsive switching effects between the subsystems. Based on the extension of the system dimension and the concept of
average dwell time, a kind of practically useful switching rule is presented which guarantees the desired robust exponential
stability. A switched state feedback controller is also given.
Keywords: Exponential stability; Switched systems; Switching control; State delay; Average dwell time
1 Introduction
In recent years, there has been growing interest in the sta-
bility analysis and controller design of switched systems
(see e.g., [1∼4] for some details). Switched systems are
an important class of hybrid dynamic systems consisting
of a family of continuous time or discrete time subsystems
and a switching rule specifying the switching among them.
The motivation for studying switched systems or switching
control mainly comes from three aspects. 1) Many systems
encountered in practice exhibit switching phenomena be-
tween several subsystems due to the inherent multi-model
or various environmental factors [1, 2]. 2) The methods of
intelligent control design are based on the idea of switch-
ing between different controllers [1, 5]. 3) Switching con-
trollers can achieve a better performance than the traditional
feedback controllers. For example, Narendra and Balakrish-
nan improved system performance using a set of switching
adaptive controllers [6].
Stability analysis is a hot issue in system studies. The sta-
bility of switched systems has been studied using the multi-
ple Lyapunov function method. Although the multiple Lya-
punov function method can also be used to study the robust
stability and exponential stability of switched linear sys-
tems, it is very difficult to find the Lyapunov functions for
unstable subsystems. To ensure the exponential stability of
switched systems, a piecewise Lyapunov function together
with dwell time is utilized. For systems without impulsive
effect, it is shown in [9] that if all the subsystems are sta-
ble and the dwell time (i.e. the time between consecutive
switchings) is sufficiently long, the entire system is expo-
nentially stable for any switching between the subsystems.
In [10], Hespanha extends the dwell time concept to the av-
erage case in the sense that a switching signal has finite av-
erage dwell time if the number of discontinuities it exhibits
in any given interval grows no longer than linearly with the
length of the interval. It is proved that if the average dwell
time is sufficiently large, the given switched system is expo-
nentially stable. However, the considered switched systems
in [9, 10] are only composed of stable subsystems. Moti-
vated by the previous work, Hu et al. [11] and Zhai et al.
[12] considered a more general class of switched systems,
in which both stable subsystems and unstable subsystems
exist. Based on the average dwell time concept and by us-
ing the idea of specifying the total activation time period ra-
tio between the stable subsystems and unstable subsystems,
the exponential stability is guaranteed. Similar to [12], [13]
considered the exponential stability of a class of discrete
time switched systems.
As is well known, time delays commonly appear in many
real control systems, which give rise to instability and poor
performance. During the past decades, the stability of con-
trol systems with time delay has been widely studied. How-
ever, few results for switched systems have considered the
factor of time delay. In [3], based on the switched Lyapunov
function technique, the authors present two different linear
matrix inequality conditions, which guaranteed the asymp-
Received 27 March 2006; revised 3 April 2007.
This work was supported by the National Natural Science Foundation of China (No. 60674027), China Postdoctoral Science Foundation (No. 200704
10336), and the Postdoctor Foundation of Jiangsu Province (No. 0602042B).