5,069 research outputs found
A New Encounter Between Leader-Follower Tracking and Observer-Based Control: Towards Enhancing Robustness against Disturbances
This paper studies robust tracking control for a leader-follower multi-agent
system (MAS) subject to disturbances. A challenging problem is considered here,
which differs from those in the literature in two aspects. First, we consider
the case when all the leader and follower agents are affected by disturbances,
while the existing studies assume only the followers to suffer disturbances.
Second, we assume the disturbances to be bounded only in rates of change rather
than magnitude as in the literature. To address this new problem, we propose a
novel observer-based distributed tracking control design. As a distinguishing
feature, the followers can cooperatively estimate the disturbance affecting the
leader to adjust their maneuvers accordingly, which is enabled by the design of
the first-of-its-kind distributed disturbance observers. We build specific
tracking control approaches for both first- and second-order MASs and prove
that they can lead to bounded-error tracking, despite the challenges due to the
relaxed assumptions about disturbances. We further perform simulation to
validate the proposed approaches
A unified framework of fully distributed adaptive output time-varying formation control for linear multi-agent systems: an observer viewpoint
This paper presents a unified framework of time-varying formation (TVF)
design for general linear multi-agent systems (MAS) based on an observer
viewpoint from undirected to directed topology, from stabilization to tracking
and from a leader without input to a one with bounded input. The followers can
form a TVF shape which is specified by piecewise continuously differential
vectors. The leader's trajectory, which is available to only a subset of
followers, is also time-varying. For the undirected formation tracking and
directed formation stabilization cases, only the relative output measurements
of neighbors are required to design control protocols; for the directed
formation tracking case, the agents need to be introspective (i.e. agents have
partial knowledge of their own states) and the output measurements are
required. Furthermore, considering the real applications, the leader with
bounded input case is studied. One main contribution of this paper is that
fully distributed adaptive output protocols, which require no global
information of communication topology and do not need the absolute or relative
state information, are proposed to solve the TVF control problem. Numerical
simulations including an application to nonholonomic mobile vehicles are
provided to verify the theoretical results.Comment: 21 page
Distributed Observers Design for Leader-Following Control of Multi-Agent Networks (Extended Version)
This paper is concerned with a leader-follower problem for a multi-agent
system with a switching interconnection topology. Distributed observers are
designed for the second-order follower-agents, under the common assumption that
the velocity of the active leader cannot be measured in real time. Some dynamic
neighbor-based rules, consisting of distributed controllers and observers for
the autonomous agents, are developed to keep updating the information of the
leader. With the help of an explicitly constructed common Lyapunov function
(CLF), it is proved that each agent can follow the active leader. Moreover, the
tracking error is estimated even in a noisy environment. Finally, a numerical
example is given for illustration.Comment: Automatica 200
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
Consensus tracking in multi agent system with nonlinear and non identical dynamics via event driven sliding modes
In this work, leader follower consensus objective has been addressed with the
synthesis of an event based controller utilizing sliding mode robust control.
The schema has been partitioned into two parts viz. finite time consensus
problem and event triggered control mechanism. A nonlinear multi agent system
with non identical dynamics has been put forward to illustrate the robust
capabilities of the proposed control. The first part incorporates matching of
states of the followers with those of the leader via consensus tracking
algorithm. In the subsequent part, an event triggered rule is devised to save
computational power and restrict periodic updating of the controller involved
while ensuring desired closed loop performance of the system. Switching of the
event based controller is achieved via sliding mode control. Advantage of using
switched controller like sliding mode is that it retains its inherent
robustness as well as event triggering approach aids in saving energy
expenditure. Efficacy of the proposed scheme is confirmed via numerical
simulations.Comment: preprint, "IEEE Transactions on Automatic Control
Guaranteed Cost Tracking for Uncertain Coupled Multi-agent Systems Using Consensus over a Directed Graph
This paper considers the leader-follower control problem for a linear
multi-agent system with directed communication topology and linear nonidentical
uncertain coupling subject to integral quadratic constraints (IQCs). A
consensus-type control protocol is proposed based on each agent's states
relative to its neighbors and leader's state relative to agents which observe
the leader. A sufficient condition is obtained by overbounding the cost
function. Based on this sufficient condition, a computational algorithm is
introduced to minimize the proposed guaranteed bound on tracking performance,
which yields a suboptimal bound on the system consensus control and tracking
performance. The effectiveness of the proposed method is demonstrated using a
simulation example.Comment: Accepted for presentation at the 2013 Australian Control conferenc
Fixed-Time Cooperative Tracking Control for Double-Integrator Multi-Agent Systems: A Time-Based Generator Approach
In this paper, both the fixed-time distributed consensus tracking and the
fixed-time distributed average tracking problems for double-integrator-type
multi-agent systems with bounded input disturbances are studied, respectively.
Firstly, a new practical robust fixed-time sliding mode control method based on
the time-based generator is proposed. Secondly, a fixed-time distributed
consensus tracking observer for double-integrator-type multi-agent systems is
designed to estimate the state disagreements between the leader and the
followers under undirected and directed communication, respectively. Thirdly, a
fixed-time distributed average tracking observer for double-integrator-type
multi-agent systems is designed to measure the average value of reference
signals under undirected communication. Note that both the observers for the
distributed consensus tracking and the distributed average tracking are devised
based on time-based generators and can be extended to that of high-order
multi-agent systems trivially. Furthermore, by combing the fixed-time sliding
mode control with the fixed-time observers, the fixed-time controllers are
designed to solve the distributed consensus tracking and the distributed
average tracking problems. Finally, a few numerical simulations are shown to
verify the results.Comment: 11 pages, 10 figure
Coordination Over Multi-Agent Networks With Unmeasurable States and Finite-Level Quantization
In this note, the coordination of linear discrete-time multi-agent systems
over digital networks is investigated with unmeasurable states in agents'
dynamics. The quantized-observer based communication protocols and Certainty
Equivalence principle based control protocols are proposed to characterize the
inter-agent communication and the cooperative control in an integrative
framework. By investigating the structural and asymptotic properties of the
equations of stabilization and estimation errors nonlinearly coupled by the
finite-level quantization scheme, some necessary conditions and sufficient
conditions are given for the existence of such communication and control
protocols to ensure the inter-agent state observation and cooperative
stabilization. It is shown that these conditions come down to the simultaneous
stabilizability and the detectability of the dynamics of agents and the
structure of the communication network.Comment: 10 pages, 2 figure
Coordinated Output Regulation of Heterogeneous Linear Systems under Switching Topologies
This paper constructs a framework to describe and study the coordinated
output regulation problem for multiple heterogeneous linear systems. Each agent
is modeled as a general linear multiple-input multiple-output system with an
autonomous exosystem which represents the individual offset from the group
reference for the agent. The multi-agent system as a whole has a group
exogenous state which represents the tracking reference for the whole group.
Under the constraints that the group exogenous output is only locally available
to each agent and that the agents have only access to their neighbors'
information, we propose observer-based feedback controllers to solve the
coordinated output regulation problem using output feedback information. A
high-gain approach is used and the information interactions are allowed to be
switched over a finite set of fixed networks containing both graphs that have a
directed spanning tree and graphs that do not. The fundamental relationship
between the information interactions, the dwell time, the non-identical
dynamics of different agents, and the high-gain parameters is given.
Simulations are shown to validate the theoretical results
Optimal mass transport and kernel density estimation for state-dependent networked dynamic systems
State-dependent networked dynamical systems are ones where the
interconnections between agents change as a function of the states of the
agents. Such systems are highly nonlinear, and a cohesive strategy for their
control is lacking in the literature. In this paper, we present two techniques
pertaining to the density control of such systems. Agent states are initially
distributed according to some density, and a feedback law is designed to move
the agents to a target density profile. We use optimal mass transport to design
a feedforward control law propelling the agents towards this target density.
Kernel density estimation, with constraints imposed by the state-dependent
dynamics, is then used to allow each agent to estimate the local density of the
agents.Comment: 6 pages, 6 figures, accepted to the 57th IEEE Conference on Decision
and Contro
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