15,766 research outputs found
Multi-Agent Distributed Coordination Control: Developments and Directions
In this paper, the recent developments on distributed coordination control,
especially the consensus and formation control, are summarized with the graph
theory playing a central role, in order to present a cohesive overview of the
multi-agent distributed coordination control, together with brief reviews of
some closely related issues including rendezvous/alignment, swarming/flocking
and containment control.In terms of the consensus problem, the recent results
on consensus for the agents with different dynamics from first-order,
second-order to high-order linear and nonlinear dynamics, under different
communication conditions, such as cases with/without switching communication
topology and varying time-delays, are reviewed, in which the algebraic graph
theory is very useful in the protocol designs, stability proofs and converging
analysis. In terms of the formation control problem, after reviewing the
results of the algebraic graph theory employed in the formation control, we
mainly pay attention to the developments of the rigid and persistent graphs.
With the notions of rigidity and persistence, the formation transformation,
splitting and reconstruction can be completed, and consequently the range-based
formation control laws are designed with the least required information in
order to maintain a formation rigid/persistent. Afterwards, the recent results
on rendezvous/alignment, swarming/flocking and containment control, which are
very closely related to consensus and formation control, are briefly
introduced, in order to present an integrated view of the graph theory used in
the coordination control problem. Finally, towards the practical applications,
some directions possibly deserving investigation in coordination control are
raised as well.Comment: 28 pages, 8 figure
Containment Control of Second-order Multi-agent Systems Under Directed Graphs and Communication Constraints
The distributed coordination problem of multi-agent systems is addressed in
this paper under the assumption of intermittent communication between agents in
the presence of time-varying communication delays. Specifically, we consider
the containment control problem of second-order multi-agent systems with
multiple dynamic leaders under a directed interconnection graph topology. Also,
communication between agents is performed only at some discrete instants of
time in the presence of irregular communication delays and packet dropout.
First, we present distributed control algorithms for double integrator dynamics
in the full and partial state feedback cases. Then, we propose a method to
extend our results to second-order systems with locally Lipschitz nonlinear
dynamics. In both cases, we show that the proposed approach leads to our
control objectives under sufficient conditions relating the characteristics of
the communication process and the control gains. We also show that our approach
can be applied to solve various similar coordination problems in multi-agent
systems under the same communication constraints. The effectiveness of the
proposed control schemes is illustrated through some examples and numerical
simulations.Comment: Modified version. Paper submitted for publicatio
Designing Distributed Fixed-Time Consensus Protocols for Linear Multi-Agent Systems Over Directed Graphs
This technical note addresses the distributed fixed-time consensus protocol
design problem for multi-agent systems with general linear dynamics over
directed communication graphs. By using motion planning approaches, a class of
distributed fixed-time consensus algorithms are developed, which rely only on
the sampling information at some sampling instants. For linear multi-agent
systems, the proposed algorithms solve the fixed-time consensus problem for any
directed graph containing a directed spanning tree. In particular, the settling
time can be off-line pre-assigned according to task requirements. Compared with
the existing results for multi-agent systems, to our best knowledge, it is the
first-time to solve fixed-time consensus problems for general linear
multi-agent systems over directed graphs having a directed spanning tree.
Extensions to the fixed-time formation flying are further studied for multiple
satellites described by Hill equations
Fixed-time consensus of multiple double-integrator systems under directed topologies: A motion-planning approach
This paper investigates the fixed-time consensus problem under directed
topologies. By using a motion-planning approach, a class of distributed
fixed-time algorithms are developed for a multi-agent system with
double-integrator dynamics. In the context of the fixed-time consensus, we
focus on both directed fixed and switching topologies. Under the directed fixed
topology, a novel class of distributed algorithms are designed, which guarantee
the consensus of the multi-agent system with a fixed settling time if the
topology has a directed spanning tree. Under the directed periodically
switching topologies, the fixedtime consensus is solved via the proposed
algorithms if the topologies jointly have a directed spanning tree. In
particular, the fixed settling time can be off-line pre-assigned according to
task requirements. Compared with the existing results, to our best knowledge,
it is the first time to solve the fixed-time consensus problem for
double-integrator systems under directed topologies. Finally, a numerical
example is given to illustrate the effectiveness of the analytical results
Distributed Control of Networked Dynamical Systems: Static Feedback, Integral Action and Consensus
This paper analyzes distributed control protocols for first- and second-order
networked dynamical systems. We propose a class of nonlinear consensus
controllers where the input of each agent can be written as a product of a
nonlinear gain, and a sum of nonlinear interaction functions. By using integral
Lyapunov functions, we prove the stability of the proposed control protocols,
and explicitly characterize the equilibrium set. We also propose a distributed
proportional-integral (PI) controller for networked dynamical systems. The PI
controllers successfully attenuate constant disturbances in the network. We
prove that agents with single-integrator dynamics are stable for any integral
gain, and give an explicit tight upper bound on the integral gain for when the
system is stable for agents with double-integrator dynamics. Throughout the
paper we highlight some possible applications of the proposed controllers by
realistic simulations of autonomous satellites, power systems and building
temperature control.Comment: Automatic Control, IEEE Transactions on, July 201
On the Synchronization of Second-Order Nonlinear Systems with Communication Constraints
This paper studies the synchronization problem of second-order nonlinear
multi-agent systems with intermittent communication in the presence of
irregular communication delays and possible information loss. The control
objective is to steer all systems' positions to a common position with a
prescribed desired velocity available to only some leaders. Based on the
small-gain framework, we propose a synchronization scheme relying on an
intermittent information exchange protocol in the presence of time delays and
possible packet dropout. We show that our control objectives are achieved with
a simple selection of the control gains provided that the directed graph,
describing the interconnection between all systems (or agents), contains a
spanning tree. The example of Euler-Lagrange systems is considered to
illustrate the application and effectiveness of the proposed approach.Comment: 21 pages, 8 figures. Submitted for journal publicatio
Fully Distributed Flocking with a Moving Leader for Lagrange Networks with Parametric Uncertainties
This paper addresses the leader-follower flocking problem with a moving
leader for networked Lagrange systems with parametric uncertainties under a
proximity graph. Here a group of followers move cohesively with the moving
leader to maintain connectivity and avoid collisions for all time and also
eventually achieve velocity matching. In the proximity graph, the neighbor
relationship is defined according to the relative distance between each pair of
agents. Each follower is able to obtain information from only the neighbors in
its proximity, involving only local interaction. We consider two cases: i) the
leader moves with a constant velocity, and ii) the leader moves with a varying
velocity. In the first case, a distributed continuous adaptive control
algorithm accounting for unknown parameters is proposed in combination with a
distributed continuous estimator for each follower. In the second case, a
distributed discontinuous adaptive control algorithm and estimator are
proposed. Then the algorithm is extended to be fully distributed with the
introduction of gain adaptation laws. In all proposed algorithms, only one-hop
neighbors' information (e.g., the relative position and velocity measurements
between the neighbors and the absolute position and velocity measurements) is
required, and flocking is achieved as long as the connectivity and collision
avoidance are ensured at the initial time and the control gains are designed
properly. Numerical simulations are presented to illustrate the theoretical
results
A Lyapunov redesign of coordination algorithms for cyberphysical systems
The objective is to design distributed coordination strategies for a network
of agents in a cyber-physical environment. In particular, we concentrate on the
rendez-vous of agents having double-integrator dynamics with the addition of a
damping term in the velocity dynamics. We start with distributed controllers
that solve the problem in continuous-time, and we then explain how to implement
these using event-based sampling. The idea is to define a triggering rule per
edge using a clock variable which only depends on the local variables. The
triggering laws are designed to compensate for the perturbative term introduced
by the sampling, a technique that reminds of Lyapunov-based control redesign.
We first present an event-triggered solution which requires continuous
measurement of the relative position and we then explain how to convert it to a
self-triggered policy. The latter only requires the measurements of the
relative position and velocity at the last transmission instants, which is
useful to reduce both the communication and the computation costs. The
strategies guarantee the existence of a uniform minimum amount of times between
any two edge events. The analysis is carried out using an invariance principle
for hybrid systems
Distributed model independent algorithm for spacecraft synchronization under relative measurement bias
This paper addresses the problem of distributed coordination control of
spacecraft formation. It is assumed that the agents measure relative positions
of each other with a non-zero, unknown constant sensor bias. The translational
dynamics of the spacecraft is expressed in Euler-Lagrangian form. We propose a
novel distributed, model independent control law for synchronization of
networked Euler Lagrange system with biased measurements. An adaptive control
law is derived based on Lyapunov analysis to estimate the bias. The proposed
algorithm ensures that the velocities converge to that of leader exponentially
while the positions converge to a bounded neighborhood of the leader positions.
We have assumed a connected leader-follower network of spacecraft. Simulation
results on a six spacecraft formation corroborate our theoretical findings.Comment: Submitted to 5th CEAS Conference on Guidance, Navigation and Contro
Observer-Based Distributed Leader-Follower Tracking Control: A New Perspective and Results
Leader-follower tracking control design has received significant attention in
recent years due to its important and wide applications. Considering a
multi-agent system composed of a leader and multiple followers, this paper
proposes and investigates a new perspective into this problem: can we enable a
follower to estimate the leader's driving input and leverage this idea to
develop new observer-based tracking control approaches? With this motivation,
we develop an input-observer-based leader-follower tracking control framework,
which features distributed input observers that allow a follower to locally
estimate the leader's input toward enhancing tracking control. This work first
studies the first-order tracking problem. It then extends to the more
sophisticated case of second-order tracking and considers a challenging
situation when the leader's and followers' velocities are not measured. The
proposed approaches exhibit interesting and useful advantages as revealed by a
comparison with the literature. Convergence properties of the proposed
approaches are rigorously analyzed. Simulation results further illustrate the
efficacy of the proposed perspective, framework and approaches.Comment: International Journal of Control 201
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