IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: EXPRESS BRIEFS, VOL. 62, NO. 10, OCTOBER 2015 1007
Leader-Following Consensus in Second-Order
Multiagent Systems via Event-Triggered
Control With Nonperiodic Sampled Data
Nankun Mu, Xiaofeng Liao, and Tingwen Huang
Abstract—The problem of leader-following consensus in second-
order multiagent systems is investigated in this brief, where the
data are sampled randomly within a certain known bound and
the data transmission is driven by an event-triggered control pro-
tocol. A distributed event-triggered control protocol is designed,
in which the Zeno behavior is naturally excluded by the strictly
positive sampling intervals and the data transmission is largely
reduced. Under the proposed protocol, the sufficient condition
is derived for assuring the consensus, which declares that the
consensus can be achieved if the control gains and the sampling
intervals are reasonable. Some numerical examples are provided
to demonstrate the effectiveness of the proposed protocol.
Index Terms—Consensus, event-triggered control, nonperiodic
sampling, second-order dynamics.
I. INTRODUCTION
I
N the past decade, the collective behaviors in autonomous
agents have received increasing attention due to their broad
applications in many areas. One of the attractive collective
behavior is consensus, which refers to the problem that an
agreement state can be reached as a result of local data transmis-
sion among multiple autonomous agents, and the reader may
refer to [1]–[11] for the specific studies.
Recently, the event-triggered control protocols have attracted
a lot of research interests due to its advantage of reducing data
transmission. The so-called event-triggered control protocol is
that the data transmission only occurs when a measurement
error increases to a certain threshold; thus, the same control
goal can be achieved with less data transmission. There have
been considerable research efforts on event-triggered control
Manuscript received April 4, 2015; revised April 29, 2015; accepted May 19,
2015. Date of publication July 17, 2015; date of current version September 25,
2015. This work was supported in part by the National Natural Science
Foundation of China under Grant 61170249 and Grant 61472331, by the
Qatar National Research Fund (a member of the Qatar Foundation) through
the National Priorities Research Program under Grant 4-1162-1-181, by the
Graduate Student Research Innovation Project of Chongqing, and by the Talents
of Science and Technology Promote Plan, Chongqing Science Technology
Commission. This brief was recommended by Associate Editor J. Lu.
N. Mu and X. Liao are with the College of Electronic and Informa-
tion Engineering, Southwest University, Chongqing 400715, China (e-mail:
nankun.mu@qq.com; xfliao@swu.edu.cn).
T. Huang is with Texas A&M University at Qatar, Doha 23874, Qatar
(e-mail: tingwen.huang@qatar.tamu.edu).
Color versions of one or more of the figures in this brief are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TCSII.2015.2458036
protocol, including the problem of packet loss [12], time-
dependent threshold [13], periodic sampled data [14], [15],
combinational measurement errors [16]–[20], potential Zeno
behavior [21], time delay [20], pinning control [22], [23], and
second-order dynamics [19].
In practice, it is possible that the sampling interval cannot
be constant [24], [25]; thus, it is natural that the nonperiodic
sampling systems are more favorable than the periodic sam-
pling systems. Additionally, compared with most of the existing
works, the second-order dynamics are more complicated; thus,
the problem of the event-based consensus in such systems is
more challenging. Although the event-triggered control proto-
cols for second-order multiagent systems have been proposed
[13], [19], the effectiveness of the event-triggered control pro-
tocols can be further improved. These discussions motivates
this brief.
In this brief, we consider the problem of leader-following
consensus in second-order multiagent systems via event-
triggered control. The distributed event-triggered control
protocol based on nonperiodic sampled data and original mea-
surement errors and time-dependent threshold is designed.
Then, the analysis on consensus is given, and the sufficient con-
sensus conditions are derived. Finally, the numerical examples
also demonstrate the effectiveness of the proposed protocol.
II. P
RELIMINARIES
The communication topology in a multiagent system, which
consists of a leader and N follower agents, can be modeled as
a directed graph
¯
G = {0}∩G,where{0} denotes the leader,
and G = {V, E, W} is a weighted directed graph of the N
agents, with the set of nodes V = {v
1
,v
2
,...,v
N
},thesetof
directed edges E⊆V×V, and the weighted adjacency matrix
W =(w
ij
) ∈ R
N×N
. If the directed edge (j, i) ∈E, then agent
j is called a neighbor of agent i with w
ij
> 0, and agent
i can receive information from agent j;otherwise,w
ij
=0.
The neighbor index set of agent i is denoted by N
i
= {j ∈
V|(j, i) ∈E}. The Laplacian matrix L =(l
ij
) ∈ R
N×N
is
associated with the adjacency matrix W. The matrix B =
diag{b
1
,b
2
,...,b
N
} is the leader adjacency matrix associated
with the graph
¯
G,whereb
i
> 0 if agent i is a neighbor of the
leader, and b
i
=0otherwise. A graph is said to have a spanning
tree if and only if there is a node that can reach all the other
nodes following the edge directions.
Lemma 1: If and only if
¯
G has a directed spanning tree with
the leader at the root, all eigenvalues of (L + B) have positive
real parts [26].
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