Automatica 46 (2010) 953–958
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Automatica
journal homepage: www.elsevier.com/locate/automatica
Technical communique
Asynchronously switched control of switched linear systems with average
dwell time
I
Lixian Zhang
∗
, Huijun Gao
Space Control and Inertial Technology Research Center, Harbin Institute of Technology, Harbin, 150001, China
a r t i c l e i n f o
Article history:
Received 7 June 2009
Received in revised form
5 October 2009
Accepted 2 February 2010
Available online 17 March 2010
Keywords:
Asynchronous switching
Average dwell time
Stabilizing control
Switched linear systems
a b s t r a c t
This paper concerns the asynchronously switched control problem for a class of switched linear systems
with average dwell time (ADT) in both continuous-time and discrete-time contexts. The so-called
asynchronous switching means that the switchings between the candidate controllers and system modes
are asynchronous. By further allowing the Lyapunov-like function to increase during the running time
of active subsystems, the extended stability results for switched systems with ADT in nonlinear setting
are first derived. Then, the asynchronously switched stabilizing control problem for linear cases is solved.
Given the increase scale and the decrease scale of the Lyapunov-like function and the maximal delay
of asynchronous switching, the minimal ADT for admissible switching signals and the corresponding
controller gains are obtained. A numerical example is given to show the validity and potential of the
developed results.
© 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Switched systems, which are used to model many physical
or man-made systems displaying switching features, have been
extensively studied in past years (Hespanha, 2004; Johansson &
Rantzer, 1998; Liberzon, 2003; Lu, Wu, & Kim, 2006; Morse, 1996).
The systems, typically, contain a finite number of subsystems and
a switching signal governing the switching among them. The di-
verse switching signals differentiate switched systems from gen-
eral time-varying systems, since the solutions of the former are
dependent on not only the system’s initial conditions but also the
switching signals (Hespanha, 2004). As a class of switching sig-
nals, average dwell time (ADT) switching means that the number
of switches in a finite interval is bounded and the average time
between consecutive switching is not less than a constant (Hes-
panha & Morse, 1999). Rapid progress in the field has shown that
I
The work was supported by National Natural Science Foundation of
China (60904001/F030107), Doctoral Fund of Ministry of Education of China
(20092302120071), China Postdoctoral Science Foundation (20090460069), Out-
standing Youth Science Fund of China (60825303), 973 Project (2009CB320600)
in China, Major program of National Natural Science Foundation of China
(90916005/A0202), Heilongjiang Postdoctoral Science Foundation, China, and
Overseas Talents Foundation of Harbin Institute of Technology. The material in
this paper was not presented at any conference. This paper was recommended for
publication in revised form by Associate Editor Henri Huijberts under the direction
of Editor André L. Tits.
∗
Corresponding author.
E-mail addresses: lixianzhang@hit.edu.cn, lixianzhanghit@gmail.com
(L. Zhang), hjgao@hit.edu.cn (H. Gao).
ADT switching is more general and flexible than dwell time (DT)
switching (Morse, 1996) in related stability analyses and control
syntheses (Hespanha, 2004; Sun, Zhao, & Hill, 2006; Vu, Chatter-
jee, & Liberzon, 2007).
In switched systems, we often call each subsystem a mode, and
say that control problems are to design a set of mode-dependent
controllers or a mode-independent controller for the unforced
system and find admissible switching signals such that the
resulting system is stable and satisfies certain performance criteria.
Many related reports on this issue are available; see, e.g., Lee
and Dullerud (2006), Lu et al. (2006), Rinehart, Dahleh, Reed, and
Kolmanovsky (2008), Sun and Ge (2005), Xu and Antsaklis (2004)
and the references therein. With an adaptation sense, mode-
dependent controller design is less conservative. However, a very
common assumption in the ‘‘mode-dependent’’ context is that
the controllers are switched synchronously with the switching of
system modes, which is quite unpractical. In reality, it takes time
to identify the system modes and apply the matched controller,
and so phenomena of asynchronous switching between system
modes and controller candidates generally exist.
1
The necessities
of considering asynchronous switching for efficient control design
have been shown in a class of chemical systems (Mhaskar, El-
Farra, & Christofides, 2008). Also, a recent study on a class of
1
In this paper, we slightly abuse the notion of synchronous (or asynchronous)
switching to mean that the switchings of system modes and the switchings of de-
sired mode-dependent controllers are synchronous (respectively, asynchronous).
Correspondingly, the delay of asynchronous switching is the time lag from the con-
trollers switching to the system modes switching.
0005-1098/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.automatica.2010.02.021