Automatica 49 (2013) 1986–1995
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Automatica
journal homepage: www.elsevier.com/locate/automatica
Distributed consensus of linear multi-agent systems with adaptive
dynamic protocols
✩
Zhongkui Li
a,1
, Wei Ren
b
, Xiangdong Liu
c
, Lihua Xie
d
a
State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering,
Peking University, Beijing 100871, China
b
Department of Electrical Engineering, University of California, Riverside, CA, 92521, USA
c
School of Automation, Beijing Institute of Technology, Beijing 100081, China
d
School of Electrical and Electronic Engineering, Nanyang Technological University, 639798, Singapore
a r t i c l e i n f o
Article history:
Received 16 November 2011
Received in revised form
23 November 2012
Accepted 1 March 2013
Available online 23 April 2013
Keywords:
Multi-agent system
Consensus
Cooperative control
Adaptive control
Distributed tracking
a b s t r a c t
This paper considers the distributed consensus problem of multi-agent systems with general continuous-
time linear dynamics for both the cases without and with a leader whose control input might be nonzero
and time varying. For the case without a leader, based on the relative output information of neighboring
agents, two types of distributed adaptive dynamic consensus protocols are proposed, namely, the edge-
based adaptive protocol which assigns a time-varying coupling weight to each edge in the communication
graph and the node-based adaptive protocol which uses a time-varying coupling weight for each node.
These two adaptive protocols are designed to ensure that consensus is reached in a fully distributed
fashion for all undirected connected communication graphs. It is shown that the edge-based adaptive
consensus protocol is applicable to arbitrary switching connected graphs. For the case where there
exists a leader whose control input is possibly nonzero and bounded, a distributed continuous adaptive
protocol is designed to guarantee the ultimate boundedness of the consensus error with respect to
any communication graph which contains a directed spanning tree with the leader as the root and
whose subgraph associated with the followers is undirected, requiring neither global information of the
communication graph nor the upper bound of the leader’s control input. A distributed discontinuous
protocol is also discussed as a special case. Simulation examples are finally given to illustrate the
theoretical results.
© 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Consensus is an important problem in the area of cooperative
control of multi-agent systems. The main idea of consensus is
to develop distributed control policies that enable a group of
agents to reach an agreement on certain quantities of interest.
Due to its potential applications in broad areas such as spacecraft
formation flying and sensor networks, the consensus problem has
been extensively studied by numerous researchers from various
✩
This work was supported by the National Natural Science Foundation of China
under grants 61104153 and 61225013, National Science Foundation under CAREER
Award ECCS-1213291, and National Research Foundation of Singapore under grant
NRF-CRP8-2011-03. The material in this paper was partially presented at the 2012
American Control Conference (ACC2012), June 27–29, 2012, Montreal, Canada. This
paper was recommended for publication in revised form by Associate Editor Tamas
Keviczky under the direction of Editor Frank Allgöwer.
E-mail addresses: zhongkli@gmail.com (Z. Li), ren@ee.ucr.edu (W. Ren),
xdliu@bit.edu.cn (X. Liu), elhxie@ntu.edu.sg (L. Xie).
1
Tel.: +86 1062765037; fax: +86 1062765037.
perspectives; see Jadbabaie, Lin, and Morse (2003), Li, Fu, Xie, and
Zhang (2011), Olfati-Saber, Fax, and Murray (2007), Olfati-Saber
and Murray (2004), Ren and Beard (2005), Ren, Beard, and Atkins
(2007) and references therein. Existing consensus algorithms
can be roughly categorized into two classes, namely, consensus
without a leader (i.e., leaderless consensus) and consensus with
a leader. The case of consensus with a leader is also called
leader–follower consensus or distributed tracking.
A pioneering work on consensus is (Jadbabaie et al., 2003)
which provides a theoretical explanation for the linearized Vic-
sek model (Vicsek, Czirók, Ben-Jacob, Cohen, & Shochet, 1995)
by using tools from algebraic graph theory. In Olfati-Saber and
Murray (2004), a general framework of the consensus problem
for networks of integrators with fixed or switching topologies
is proposed. The controllability of leader–follower multi-agent
systems is considered in Rahmani, Ji, Mesbahi, and Egerstedt
(2009) from a graph-theoretic perspective. Distributed tracking
control for multi-agent consensus with an active leader is ad-
dressed in Hong, Chen, and Bushnell (2008) and Hu and Feng
(2010) by using neighbor-based state estimators. Consensus of net-
works of double- and high-order integrators is studied in Jiang
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http://dx.doi.org/10.1016/j.automatica.2013.03.015