15,790 research outputs found
Reduced-order Distributed Consensus Controller Design via Edge Dynamics
This paper proposes a novel approach to design reduced-order distributed
consensus controllers for multi-agent systems (MASs) with identical linear
dynamics of agents. A new model namely edge dynamics representing the
differences on agents' states is first presented. Then the distributed
consensus controller design is shown to be equivalent to the synthesis of a
distributed stabilizing controller for this edge dynamics. Consequently, based
on LQR approach, the globally optimal and locally optimal distributed
stabilizing controller designs are proposed, of which the locally distributed
stabilizing controller for the edge dynamics results in a distributed consensus
controller for the MAS with no conservative bound on the coupling strength.
This approach is next further developed to obtain reduced-order distributed
consensus controllers for linear MASs. Several numerical examples are
introduced to illustrate the theoretical results.Comment: submitted to IEEE Transactions on Automatic Contro
Robust Consensus Analysis and Design under Relative State Constraints or Uncertainties
This paper proposes a new approach to analyze and design distributed robust
consensus control protocols for general linear leaderless multi-agent systems
(MASs) in presence of relative-state constraints or uncertainties. First, we
show that the MAS robust consensus under relative-state constraints or
uncertainties is equivalent to the robust stability under state constraints or
uncertainties of a transformed MAS. Next, the transformed MAS under state
constraints or uncertainties is reformulated as a network of Lur'e systems. By
employing S-procedure, Lyapunov theory, and Lasalle's invariance principle, a
sufficient condition for robust consensus and the design of robust consensus
controller gain are derived from solutions of a distributed LMI convex problem.
Finally, numerical examples are introduced to illustrate the effectiveness of
the proposed theoretical approach.Comment: submitted to IEEE Transactions on Automatic Contro
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
Optimal Output Consensus of High-Order Multi-Agent Systems with Embedded Technique
In this paper, we study an optimal output consensus problem for a multi-agent
network with agents in the form of multi-input multi-output minimum-phase
dynamics. Optimal output consensus can be taken as an extended version of the
existing output consensus problem for higher-order agents with an optimization
requirement, where the output variables of agents are driven to achieve a
consensus on the optimal solution of a global cost function. To solve this
problem, we first construct an optimal signal generator, and then propose an
embedded control scheme by embedding the generator in the feedback loop. We
give two kinds of algorithms based on different available information along
with both state feedback and output feedback, and prove that these algorithms
with the embedded technique can guarantee the solvability of the problem for
high-order multi-agent systems under standard assumptions.Comment: 23 page, 5 figures, accepted by IEEE Transactions on Cybernetic
Robust Consensus of Linear Multi-Agent Systems under Input Constraints or Uncertainties
This paper proposes a new approach to analyze and synthesize robust consensus
control laws for general linear leaderless multi-agent systems (MASs) subjected
to input constraints or uncertainties. First, the MAS under input constraints
or uncertainties is reformulated as a network of Lur'e systems. Next, two
scenarios of communication topology are considered, namely undirected and
directed cyclic structures. In each case, a sufficient condition for consensus
and the design of consensus controller gain are derived from solutions of a
distributed LMI convex problem. Finally, a numerical example is introduced to
illustrate the effectiveness of the proposed theoretical approach.Comment: submitted to Automatica. arXiv admin note: text overlap with
arXiv:1605.0364
Distributed Average Tracking for Lipschitz-Type Nonlinear Dynamical Systems
In this paper, a distributed average tracking problem is studied for
Lipschitz-type nonlinear dynamical systems. The objective is to design
distributed average tracking algorithms for locally interactive agents to track
the average of multiple reference signals. Here, in both the agents' and the
reference signals' dynamics, there is a nonlinear term satisfying the
Lipschitz-type condition. Three types of distributed average tracking
algorithms are designed. First, based on state-dependent-gain designing
approaches, a robust distributed average tracking algorithm is developed to
solve distributed average tracking problems without requiring the same initial
condition. Second, by using a gain adaption scheme, an adaptive distributed
average tracking algorithm is proposed in this paper to remove the requirement
that the Lipschitz constant is known for agents. Third, to reduce chattering
and make the algorithms easier to implement, a continuous distributed average
tracking algorithm based on a time-varying boundary layer is further designed
as a continuous approximation of the previous discontinuous distributed average
tracking algorithms
Improving performance of droop-controlled microgrids through distributed PI-control
This paper investigates transient performance of inverter-based microgrids in
terms of the resistive power losses incurred in regulating frequency under
persistent stochastic disturbances. We model the inverters as second-order
oscillators and compare two algorithms for frequency regulation: the standard
frequency droop controller and a distributed proportional-integral (PI)
controller. The transient power losses can be quantified using an input-output
H2 norm. We show that the distributed PI-controller, which has previously been
proposed for secondary frequency control (the elimination of static errors),
also has the potential to significantly improve performance by reducing
transient power losses. This loss reduction is shown to be larger in a loosely
interconnected network than in a highly interconnected one, whereas losses do
not depend on connectivity if standard droop control is employed. Moreover, our
results indicate that there is an optimal tuning of the distributed
PI-controller for loss reduction. Overall, our results provide an additional
argument in favor of distributed algorithms for secondary frequency control in
microgrids.Comment: 2016 American Control Conference, Boston, July 201
On Existence of Equilibria, Voltage Balancing, and Current Sharing in Consensus-Based DC Microgrids
In this work, we present new secondary regulators for current sharing and
voltage balancing in DC microgrids, composed of distributed generation units,
dynamic RLC lines, and nonlinear ZIP (constant impedance, constant current, and
constant power) loads. The proposed controllers sit atop a primary voltage
control layer, and exchange information over a communication network to perform
secondary control actions. We deduce sufficient conditions for the existence
and uniqueness of an equilibrium point, and show that the desired objectives
are attained in steady state. Our control design requires only the knowledge of
local parameters of the generation units, facilitating plug-and-play
operations. We provide a voltage stability analysis, and illustrate the
performance and robustness of our designs via simulations. All results hold for
arbitrary, albeit connected, microgrid and communication network topologies
Minimum-Rank Dynamic Output Consensus Design for Heterogeneous Nonlinear Multi-Agent Systems
In this paper, we propose a new and systematic design framework for output
consensus in heterogeneous Multi-Input Multi-Output (MIMO) general nonlinear
Multi-Agent Systems (MASs) subjected to directed communication topology. First,
the input-output feedback linearization method is utilized assuming that the
internal dynamics is Input-to-State Stable (ISS) to obtain linearized
subsystems of agents. Consequently, we propose local dynamic controllers for
agents such that the linearized subsystems have an identical closed-loop
dynamics which has a single pole at the origin whereas other poles are on the
open left half complex plane. This allows us to deal with distinct agents
having arbitrarily vector relative degrees and to derive rank- cooperative
control inputs for those homogeneous linearized dynamics which results in a
minimum rank distributed dynamic consensus controller for the initial nonlinear
MAS. Moreover, we prove that the coupling strength in the consensus protocol
can be arbitrarily small but positive and hence our consensus design is
non-conservative. Next, our design approach is further strengthened by tackling
the problem of randomly switching communication topologies among agents where
we relax the assumption on the balance of each switched graph and derive a
distributed rank- dynamic consensus controller. Lastly, a numerical example
is introduced to illustrate the effectiveness of our proposed framework.Comment: Revised version submitted to IEEE Transactions on Control of Network
System
Coordination of Multi-Agent Systems under Switching Topologies via Disturbance Observer Based Approach
In this paper, a leader-following coordination problem of heterogeneous
multi-agent systems is considered under switching topologies where each agent
is subject to some local (unbounded) disturbances. While these unknown
disturbances may disrupt the performance of agents, a disturbance observer
based approach is employed to estimate and reject them. Varying communication
topologies are also taken into consideration, and their byproduct difficulties
are overcome by using common Lyapunov function techniques. According to the
available information in difference cases, two disturbance observer based
protocols are proposed to solve this problem. Their effectiveness is verified
by simulations.Comment: 12 pages, 4 figures, 2 table
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