435 research outputs found
Distributed Average Consensus under Quantized Communication via Event-Triggered Mass Summation
We study distributed average consensus problems in multi-agent systems with
directed communication links that are subject to quantized information flow.
The goal of distributed average consensus is for the nodes, each associated
with some initial value, to obtain the average (or some value close to the
average) of these initial values. In this paper, we present and analyze a
distributed averaging algorithm which operates exclusively with quantized
values (specifically, the information stored, processed and exchanged between
neighboring agents is subject to deterministic uniform quantization) and relies
on event-driven updates (e.g., to reduce energy consumption, communication
bandwidth, network congestion, and/or processor usage). We characterize the
properties of the proposed distributed averaging protocol on quantized values
and show that its execution, on any time-invariant and strongly connected
digraph, will allow all agents to reach, in finite time, a common consensus
value represented as the ratio of two integer that is equal to the exact
average. We conclude with examples that illustrate the operation, performance,
and potential advantages of the proposed algorithm
Dynamic Quantized Consensus of General Linear Multi-agent Systems under Denial-of-Service Attacks
In this paper, we study multi-agent consensus problems under
Denial-of-Service (DoS) attacks with data rate constraints. We first consider
the leaderless consensus problem and after that we briefly present the analysis
of leader-follower consensus. The dynamics of the agents take general forms
modeled as homogeneous linear time-invariant systems. In our analysis, we
derive lower bounds on the data rate for the multi-agent systems to achieve
leaderless and leader-follower consensus in the presence of DoS attacks, under
which the issue of overflow of quantizer is prevented. The main contribution of
the paper is the characterization of the trade-off between the tolerable DoS
attack levels for leaderless and leader-follower consensus and the required
data rates for the quantizers during the communication attempts among the
agents. To mitigate the influence of DoS attacks, we employ dynamic
quantization with zooming-in and zooming-out capabilities for avoiding
quantizer saturation
Time-and event-driven communication process for networked control systems: A survey
Copyright © 2014 Lei Zou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In recent years, theoretical and practical research topics on networked control systems (NCSs) have gained an increasing interest from many researchers in a variety of disciplines owing to the extensive applications of NCSs in practice. In particular, an urgent need has arisen to understand the effects of communication processes on system performances. Sampling and protocol are two fundamental aspects of a communication process which have attracted a great deal of research attention. Most research focus has been on the analysis and control of dynamical behaviors under certain sampling procedures and communication protocols. In this paper, we aim to survey some recent advances on the analysis and synthesis issues of NCSs with different sampling procedures (time-and event-driven sampling) and protocols (static and dynamic protocols). First, these sampling procedures and protocols are introduced in detail according to their engineering backgrounds as well as dynamic natures. Then, the developments of the stabilization, control, and filtering problems are systematically reviewed and discussed in great detail. Finally, we conclude the paper by outlining future research challenges for analysis and synthesis problems of NCSs with different communication processes.This work was supported in part by the National Natural Science Foundation of China under Grants 61329301, 61374127, and 61374010, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany
Decentralized Event-Triggered Consensus of Linear Multi-agent Systems under Directed Graphs
An event-triggered control technique for consensus of multi-agent systems
with general linear dynamics is presented. This paper extends previous work to
consider agents that are connected using directed graphs. Additionally, the
approach shown here provides asymptotic consensus with guaranteed positive
inter-event time intervals. This event-triggered control method is also used in
the case where communication delays are present. For the communication delay
case we also show that the agents achieve consensus asymptotically and that,
for every agent, the time intervals between consecutive transmissions is
lower-bounded by a positive constant.Comment: 9 pages, 5 figures, A preliminary version of this manuscript has been
submitted to the 2015 American Control Conferenc
Self-triggered Consensus of Multi-agent Systems with Quantized Relative State Measurements
This paper addresses the consensus problem of first-order continuous-time
multi-agent systems over undirected graphs. Each agent samples relative state
measurements in a self-triggered fashion and transmits the sum of the
measurements to its neighbors. Moreover, we use finite-level dynamic quantizers
and apply the zooming-in technique. The proposed joint design method for
quantization and self-triggered sampling achieves asymptotic consensus, and
inter-event times are strictly positive. Sampling times are determined
explicitly with iterative procedures including the computation of the Lambert
-function. A simulation example is provided to illustrate the effectiveness
of the proposed method.Comment: 29 pages, 3 figures. To appear in IET Control Theory & Application
Event-Triggered Consensus and Formation Control in Multi-Agent Coordination
The focus of this thesis is to study distributed event-triggered
control for multi-agent systems (MASs) facing constraints in
practical applications. We consider several problems in the
field, ranging from event-triggered consensus with information
quantization, event-triggered edge agreement under
synchronized/unsynchronized clocks, event-triggered
leader-follower consensus with Euler-Lagrange agent dynamics and
cooperative event-triggered rigid formation control.
The first topic is named as event-triggered consensus with
quantized relative state measurements. In this topic, we develop
two event-triggered controllers with quantized relative state
measurements to achieve consensus for an undirected network where
each agent is modelled by single integrator dynamics. Both
uniform and logarithmic quantizers are considered, which,
together with two different controllers, yield four cases of
study in this topic. The quantized information is used to update
the control input as well as to determine the next trigger event.
We show that approximate consensus can be achieved by the
proposed algorithms and Zeno behaviour can be completely excluded
if constant offsets with some computable lower bounds are added
to the trigger conditions.
The second topic considers event-triggered edge agreement
problems. Two cases, namely the synchronized clock case and the
unsynchronized clock case, are studied. In the synchronized clock
case, all agents are activated simultaneously to measure the
relative state information over edge links under a global clock.
Edge events are defined and their occurrences trigger the update
of control inputs for the two agents sharing the link. We show
that average consensus can be achieved with our proposed
algorithm. In the unsynchronized clock case, each agent executes
control algorithms under its own clock which is not synchronized
with other agents' clocks. An edge event only triggers control
input update for an individual agent. It is shown that all agents
will reach consensus in a totally asynchronous manner.
In the third topic, we propose three different distributed
event-triggered control algorithms to achieve leader-follower
consensus for a network of Euler-Lagrange agents. We firstly
propose two model-independent algorithms for a subclass of
Euler-Lagrange agents without the vector of gravitational
potential forces. A variable-gain algorithm is employed when the
sensing graph is undirected; algorithm parameters are selected in
a fully distributed manner with much greater flexibility compared
to all previous work concerning event-triggered consensus
problems. When the sensing graph is directed, a constant-gain
algorithm is employed. The control gains must be centrally
designed to exceed several lower bounding inequalities which
require limited knowledge of bounds on the matrices describing
the agent dynamics, bounds on network topology information and
bounds on the initial conditions. When the Euler-Lagrange agents
have dynamics which include the vector of gravitational potential
forces, an adaptive algorithm is proposed. This requires more
information about the agent dynamics but allows for the
estimation of uncertain agent parameters.
The last topic discusses cooperative stabilization control of
rigid formations via an event-triggered approach. We first design
a centralized event-triggered formation control system, in which
a central event controller determines the next triggering time
and broadcasts the event signal to all the agents for control
input update. We then build on this approach to propose a
distributed event control strategy, in which each agent can use
its local event trigger and local information to update the
control input at its own event time. For both cases, the trigger
condition, event function and trigger behaviour are discussed in
detail, and the exponential convergence of the formation system
is guaranteed
- …