Automatica 46 (2010) 1994–1999
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Automatica
journal homepage: www.elsevier.com/locate/automatica
Brief paper
Leader-following consensus of second-order agents with multiple time-varying
delays
✩
Wei Zhu
a,b,∗
, Daizhan Cheng
b
a
Key Laboratory of Network Control & Intelligent Instrument of Ministry of Education, Chongqing University of Posts and Telecommunications, Chongqing, 400065, PR China
b
Key Laboratory of Systems and Control, AMSS, Chinese Academy of Sciences, Beijing, 100080, PR China
a r t i c l e i n f o
Article history:
Received 19 April 2009
Received in revised form
10 June 2010
Accepted 13 July 2010
Available online 1 September 2010
Keywords:
Multi-agent system
Consensus
Time-varying delay
Fixed topology
Switching topology
a b s t r a c t
In this paper, a leader-following consensus problem of second-order multi-agent systems with fixed
and switching topologies as well as non-uniform time-varying delays is considered. For the case of
fixed topology, a necessary and sufficient condition is obtained. For the case of switching topology, a
sufficient condition is obtained under the assumption that the total period over which the leader is
globally reachable is sufficiently large. We not only prove that a consensus is reachable asymptotically
but also give an estimation of the convergence rate. An example with simulation is presented to illustrate
the theoretical results.
© 2010 Elsevier Ltd. All rights reserved.
1. Introduction
In recent years, the problem of coordinating the motion of
multiple agents has attracted great attention. This is due to the
fact that multi-agent systems can be found in many application
areas, such as formation control (Fax & Murray, 2004) and
flocking (Jadbabaie, Lin, & Morse, 2003; Vicsek, Cziroók, Ben-Jacob,
Cohen, & Shochet, 1995). A critical problem for coordinated control
is to design appropriate protocols and algorithms such that the
group of agents can reach a consensus on the shared information
in the presence of limited and unreliable information exchange as
well as communication delays (Sun, Wang, & Xie, 2008). The effect
of communication time delays on agents’ consensus behavior was
first analyzed for a continuous-time model in Saber and Murray
(2004). Based on a reduced-order Lyapunov–Krasovskii functional
✩
This work is supported partly by the National Natural Science Foundation
of China under Grant 60736022, 60821091, 10971240, and the Natural Science
Foundation Project of CQ CSTC 2009BB2417, 2008BB2364. The material in this paper
was not presented at any conference. This paper was recommended for publication
in revised form by Associate Editor Hideaki Ishii under the direction of Editor Ian R.
Petersen.
∗
Corresponding author at: Key Laboratory of Network Control & Intelligent In-
strument of Ministry of Education, Chongqing University of Posts and Telecom-
munications, Chongqing, 400065, PR China. Tel.: +86 23 62461624; fax: +86 23
62460360.
E-mail addresses: zhuwei@cqupt.edu.cn, zhuwei@amss.ac.cn (W. Zhu),
dcheng@iss.ac.cn (D. Cheng).
and linear matrix inequalities (LMIs), Lin and Jia (2008) studied
the average consensus problem with switching topology and
uniform time delays. Seuret, Dimarogonas, and Johansson (2008)
investigated the consensus under non-uniform communication
constant delays by using Lyapunov–Krasovskii techniques given in
terms of LMIs. Moreau (2005) discussed the stability of multi-agent
systems with time-dependent communication links.
In this paper, we consider the leader-following consensus
problem of a group of second-order dynamic agents with non-
uniform multiple time-varying delays as well as fixed and
switching topologies. In Saber and Murray (2004), the authors
also discussed the consensus problem of multi-agent systems with
communication time delays by a frequency domain approach, but
the systems are of first order and without a leader, and the time
delay is uniform. Moreover, as said in Lin and Jia (2009), the
frequency domain approach is limited to the fixed topology case
and is invalid when the topologies dynamically change, whereas
the Lyapunov-based approach and the passivity-based approach
are hard to apply to the case of general directed graphs with time
delay and switching topologies. This paper proposes an inequality
technique, which can not only prove that the consensus of multi-
agent is reachable asymptotically, but also give an estimate of the
convergence rate.
2. Model description
We consider a system consisting of N agents and a leader
which is depicted by a graph G . It contains N agents (related to
0005-1098/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.automatica.2010.08.003