Class Of Linear Multi-agent Systems Research Articles

Event-triggered robust cooperative output regulation for a class of linear multi-agent systems with an unknown exosystem

This paper investigates the robust cooperative output regulation problem for a class of heterogeneous uncertain linear multi-agent systems with an unknown exosystem via event-triggered control (ETC). By utilizing the internal model approach and the adaptive control technique, a distributed adaptive internal model is constructed for each agent. Then, based on this internal model, a fully distributed ETC strategy composed of a distributed event-triggered adaptive output feedback control law and a distributed dynamic event-triggering mechanism is proposed, in which each agent updates its control input at its own triggering time instants. It is shown that under the proposed ETC strategy, the robust cooperative output regulation problem can be solved without requiring either the global information associated with the communication topology or the bounds of the uncertain or unknown parameters in each agent and the exosystem. A numerical example is provided to illustrate the effectiveness of the proposed control strategy.

Consensus of switched multi-agents system with cooperative and competitive relationship

In this paper, the consensus problem of a class of linear multi-agent systems is analysed. In our model, switching between subnetworks and competition between agents is considered simultaneously. We suppose that all subnetworks cannot achieve a consensus and switching signal has a minimum dwell time. By using the time-dependent quadratic Lyapunov function and the average dwell time method, a consensus condition of switched networks is obtained. By using the sum of squares (SOS) programming in the software package SOSTOOLS of Matlab, these resulting conditions can be implemented. The results obtained are also extended to uncertain linear multi-agent systems. Finally, a simulation example is given to illustrate the validity of our results.

Leader-Follower Asymptotic Consensus Control of Multiagent Systems: An Observer-Based Disturbance Reconstruction Approach.

In this article, a leader-follower asymptotic consensus control strategy is developed for a class of linear multiagent systems (MASs) with unknown external disturbances and measurement noises. First, the preconditions, the minimum phase condition (MPC) and observer matching condition (OMC), are discussed in detail, and an equivalent result under these two preconditions is given. In this way, the corresponding results from Corless and Tu (1998) are improved. Meanwhile, a reduced-order observer is designed for a constructed augmented system to estimate the system states and noises of each agent. Next, with the help of a traditional interval observer, a novel unknown disturbance reconstruction method is developed, and the reconstruction can converge to the unknown disturbance asymptotically and decouple from the control input. The subsequent asymptotic consensus is accomplished by utilizing an observer-based control scheme, with its design satisfying the so-called separation principle. Finally, two simulation examples are given to verify the effectiveness and show the advantages of the proposed methods.

Event-triggered secure consensus for MASs based on a multi-sensor multi-rate sampling mechanism

This paper is concerned with event-triggered secure consensus for a class of linear multi-agent systems (MASs) under denial-of-service (DoS) attacks. Different from some existing methods, a multi-sensor multi-rate (MSMR) sampling mechanism is introduced to sample system states of agents. A class of multi-rate observer is devised to deal with some problems involved, such as the asynchrony and the incompleteness of several state sub-vectors, caused by the MSMR sampling mechanism. By using the partially updated state information of each agent, a novel multi-rate event-triggered mechanism is proposed, in which the continuous monitoring of the combined measurement information is avoided. Then, an event-based distributed secure consensus control protocol is presented against DoS attacks for the MAS under a directed communication topology. By taking into account the information on the duration and frequency of the DoS attacks, a sufficient condition is established to design suitable control protocols such that consensus can be achieved. Finally, a numerical example is provided to show the effectiveness of the proposed method.

Dynamic Event-Triggered Consensus Control for Multi-Agent Systems Using Adaptive Dynamic Programming

The consensus optimal control problem for a class of linear multi-agent systems with directed communication networks is studied in this paper using adaptive dynamic programming. To overcome the restrictions of the agent’s low processing capability and to extend the actuator’s lifetime, consider the event-triggered. In the beginning, a dynamic event-triggered is provided, with several existing static event-triggered serving as special examples. When using the dynamic event-triggered, a longer interval can be shown between any two consecutive event-triggered. Designing a dynamic event-triggered control law becomes more challenging when implemented in directed networks. In addition, on the basis of dynamic event-triggered, a novel adaptive dynamic programming is used to construct a suitable dynamic event-triggered control law, which employs just the interaction information between agents and does not need model dynamics, overcoming the difficulty of solving the algebraic Riccati equation. Finally, the effectiveness of the proposed method is verified by simulation results, and no agent exhibits Zeno behavior.

H-infinity bipartite consensus of multi-agent systems with external disturbance and probabilistic actuator faults in signed networks

<abstract><p>The H-infinity bipartite consensus problem is addressed for a class of linear multi-agent systems with external disturbance, where the positive and negative links are allowed in communication topology. A novel event-triggered communication scheme is presented to save limited network resources, which dependents on information from neighboring agents at event-triggered instants, the given event-triggered condition is detected only at discrete sampling times, thus Zeno behavior can be excluded, two types of event-triggered matrices have been introduced in our event-triggered communication scheme, which can further reduce the sampled-data transmission compared with some existed results. Considering the probabilistic actuator faults, the reliable controller is designed based on sampled-data, then a new distribution-based fault model is constructed by using coordinate transform. Some H-infinity bipartite consensus criteria can be derived by the Lyapunov stability theory and algebraic graph theory, at the same time, the feedback matrices and event-triggered matrices can be obtained by solving some linear matrix inequalities. Finally, a numerical example is employed to show the validity and advantage of the proposed transmission scheme.</p></abstract>

Consensus control for a class of linear multiagent systems using a distributed integral sliding mode strategy

In this paper, a consensus framework is proposed for a class of linear multiagent systems subject to matched and unmatched uncertainties in an undirected topology. A linear coordinate transformation is derived so that the consensus protocol design can be conveniently performed. The distributed consensus protocol is developed by using an integral sliding mode strategy. Consensus is achieved asymptotically and all subsystem states are bounded. By using an integral sliding mode control, the subsystems lie on the sliding surface from the initial time, which avoids any sensitivity to uncertainties during the reaching phase. By use of an appropriate projection matrix, the size of the equivalent control required to maintain sliding is reduced which reduces the conservatism of the design. MATLAB simulations validate the effectiveness and superiority of the proposed method.

Consensus Control of Linear Multiagent Systems Under Actuator Imperfection: When Saturation Meets Fault

This article is concerned with the consensus control problem for a general class of linear multiagent systems (MASs) subject to actuator imperfection consisting of both actuator saturations and actuator faults. A novel two-step saturation-resistant approach is proposed to attenuate the side effects resulting from the actuator imperfection. In the first step of controller design, the state information received from the neighboring agents is used to design a consensus controller capable of tolerating the actuator fault. Then, in the second step of controller optimization, the domain of attraction (DOA) is introduced for MASs to evaluate the performance of the controller and, subsequently, optimize the controller parameters to enlarge the DOA in terms of solutions to a certain set of matrix inequalities. Finally, simulation examples are provided to demonstrate the effectiveness of the developed saturation-resistant approach.

Stochastic faulty estimator-based non-fragile tracking controller for multi-agent systems with communication delay

A robust tracking control design problem for a class of linear multi-agent systems with fault signals is addressed in this study, where it is assumed that input signal of the leader is non-zero and unknown to the follower agents. An intermediate estimator, which bears stochastic failures, is designed to achieve the desired tracking performance and to estimate the combined unknown input signal of the leader input and the fault terms simultaneously. Assisted by the estimated terms, a robust non-fragile tracking control protocol that takes into account communication delays is proposed to eliminate the influence of the combined input signal. With the help of the Lyapunov-Krasovskii functional approach, a delay-dependent sufficient criterion is established to ensure that the resulting tracking error system states are uniformly bounded. On the basis of this criterion, the design procedure of the considered non-fragile control gain and the intermediate estimator gain matrices are presented. Two numerical examples, including a practical example, are used to reflect the validity and usefulness of the designed tracking control protocol.

Periodic event-triggered output regulation for linear multi-agent systems

This study considers the problem of periodic event-triggered (PET) cooperative output regulation for a class of linear multi-agent systems. The advantage of the PET output regulation is that the data transmission and triggered condition are only needed to be monitored at discrete sampling instants. It is assumed that only a small number of agents can have access to the system matrix and states of the leader. Meanwhile, the PET mechanism is considered not only in the communication between various agents, but also in the sensor-to-controller and controller-to-actuator transmission channels for each agent. The above problem set-up will bring some challenges to the controller design and stability analysis. Based on a novel PET distributed observer, a PET dynamic output feedback control method is developed for each follower. Compared with the existing works, our method can naturally exclude the Zeno behavior, and the inter-event time becomes multiples of the sampling period. Furthermore, for every follower, the minimum inter-event time can be determined a prior, and computed directly without the knowledge of the leader information. An example is given to verify and illustrate the effectiveness of the new design scheme.

Loop transfer recovery design for synchronization of homogeneous linear multi-agent systems

In this paper we propose the use of loop transfer recovery procedure in the context of cooperative control to aid the design of output feedback synchronization controllers with desirable performance characteristics. It is shown that, for a certain class of linear multi-agent systems, an upper bound on the singular values of the sensitivity matrix for the global networked system can be related to the dynamics of a classical single-system Kalman filter. A numerical example is presented to illustrate the main conclusions of this paper.

Convex synthesis for optimal ℋ∞ consensus of input-delayed multi-agent systems via dynamic relative output feedback

In this paper, we address the leaderless consensus control problem for a class of linear multi-agent systems (MASs) subject to nonlinear time-varying input delays and unknown external disturbances. The MAS is considered to be non-introspective, meaning that each individual agent is not able to measure the absolute plant state/output of its own but can sense relative information from its neighbours. A novel dynamic relative output-feedback (DROF) controller structure is proposed by leveraging the integral quadratic constraints (IQCs) from robust control theory. This new DROF controller is compelling in the sense that it utilises not only the relative plant outputs, but also the relative controller states and relative IQC-induced dynamics states for distributed feedback control. Based on this, the associated consensus control synthesis conditions that guarantee optimal disturbance attenuation performance in the presence of time-varying input delays are derived and formulated as linear matrix inequalities (LMIs), which can be solved efficiently via convex optimisation. Effectiveness of the proposed theoretical results is demonstrated through simulation studies.

Distributed global actuator fault-detection scheme for a class of linear multi-agent systems with disturbances

Abstract This paper proposes a distributed methodology for the detection of actuator faults in a class of linear multi-agent systems in the presence of disturbances. A cascade of fixed-time observers is introduced to give an exact estimate of the global system state for each agent whereby the convergence time is estimated regardless of the initial conditions. Distributed observers are then designed using Linear Matrix Inequalities (LMI), by employing the ℌ and ℌ∞ norms. The proposed method ensures global actuator fault detection, where each agent is capable of detecting not only its faults but also those that occur at any other part of the system. Numerical simulation results are carried out to show the effectiveness of the proposed approach.

Self-triggered consensus control for linear multi-agent systems with input saturation

In this paper, we study the consensus problem for a class of linear multi-agent systems &#x0028 MASs &#x0029 with consideration of input saturation under the self-triggered mechanism. In the context of discrete-time systems, a self-triggered strategy is developed to determine the time interval between the adjacent triggers. The triggering condition is designed by using the current sampled consensus error. Furthermore, the consensus control protocol is designed by means of a state feedback approach. It is shown that the considered multi-agent systems can reach consensus with the presented algorithm. Some sufficient conditions are proposed in the form of linear matrix inequalities &#x0028 LMIs &#x0029 to show the positively invariant property of the domain of attraction &#x0028 DOA &#x0029 . Moreover, some sufficient conditions of controller synthesis are provided to enlarge the volume of the DOA and obtain the control gain matrix. A numerical example is simulated to demonstrate the effectiveness of the theoretical analysis results.

Consensus of Higher Order Agents: Robustness and Heterogeneity

This paper explores the use of Kharitonov's Theorem on a class of linear multiagent systems. First, we study a network of the mth order (m ≥ 2) linear uncertain interval plants and provide conditions for achieving fullstate consensus, which relate the stability margins of each agent to the spectrum of the graph Laplacian. Then, a robustness analysis for such systems is presented when an edge weight in the underlying graph is perturbed. The same Kharitonov-based analysis proves useful in a related problem, where heterogeneous higher order linear models of agents are considered in a setup similar to pinning control, and conditions for consensus among the follower agents are derived. Numerous simulation examples validate the results.

Observer-Based Distributed Secure Consensus Control of a Class of Linear Multi-Agent Systems Subject to Random Attacks

This paper is concerned with an observer-based distributed secure consensus control strategy for a class of linear multi-agent systems (MASs) with random attacks. Due to the fact that not all state information is available, observers are employed to estimate the internal states. The communication topology is randomly switching under the attacks, and a distributed secure consensus strategy is proposed using the output information. The feedback gains are calculated via solving the Riccati equation and Riccati inequality, and stability analysis is proven that the MAS achieves secure consensus tracking in the mean square sense. Finally, two examples are provided to verify the effectiveness of the observer-based control strategy.

Robust cooperative output regulation of uncertain linear multi-agent systems not detectable by regulated output

This paper considers the robust cooperative output regulation problem via measurement feedback for a class of linear multi-agent systems, which is not detectable by regulated output. To solve it, necessarily additional measurement is assumed to be available, and the normal form defined on the additional measurement is utilized. Under mild assumptions on the communication network and the zero dynamics, a novel distributed measurement feedback controller can be established, consisting of the distributed dynamical compensator, internal model and possibly asymptotic observer, such that all regulated errors can globally exponentially converge to zero. Only regulated output of each agent needs to be transmitted to its neighbors, while neither the plant state nor the controller state is required to be exchanged with its neighbors.

A Distributed Dynamic Event-Triggered Control Approach to Consensus of Linear Multiagent Systems With Directed Networks.

In this paper, we study the consensus problem for a class of linear multiagent systems, where the communication networks are directed. First, a dynamic event-triggering mechanism is introduced, including some existing static event-triggering mechanisms as its special cases. Second, based on the dynamic event-triggering mechanism, a distributed control protocol is developed, which ensures that all agents can reach consensus with an exponential convergence rate. Third, it is shown that, with the dynamic event-triggering mechanism, the minimum interevent time between any two consecutive triggering instants can be prolonged and no agent exhibits Zeno behavior. Finally, an algorithm is provided to avoid continuous communication when the dynamic event-triggering mechanism is implemented. The effectiveness of the results is confirmed through a numerical example.

Dynamic event-triggered leader-following consensus control of a class of linear multi-agent systems

We address the leader-following tracking consensus issue for a class of linear multi-agent systems (MASs) via dynamic event-triggered (DET) approaches in this paper. The DET communication mechanism is introduced by an additional internal dynamic variable, and is developed to schedule agents’ data transmission. State observers are also employed to tackle the scenario wherein inner information of follower agents are not available for measurement. And then, state-based and observer-based distributed control proposals are proposed on the basis of dynamic event-triggered mechanism (DETM), respectively. To avoid continuous measurement information monitor, we present a technical approach for generation of the combinational information from their own neighboring agents only at event instants. The stabilities of the resulting closed-loop systems, both state-feedback one and output-feedback one, are rigorously analyzed in theory, and it is proven that all signals in the closed-loop system are bounded and Zeno behavior is also excluded. Simulation examples are presented to illustrate the theoretical claims.

Observer-based event-triggered leader-following control of a class of linear multi-agent systems

ABSTRACTThis paper addresses an observer-based consensus problem for leader-following control of a class of linear multi-agent systems (MASs) under a directed communication topology via event-triggered approaches. State observers are employed to tackle the scenario wherein inner information of the follower agents are not available for measurement. And then, an observer-based distributed leader-following control scheme is developed on the basis of event-triggered mechanisms. Further, to avoid continuous measurement information monitor, we present a technical approach for generation of the combinational information from their own neighbouring agents only at triggered instants. In theory, the stability of the resulting closed-loop system is rigorously investigated, and it is proven that all signals in the closed-loop system are bounded and Zeno behaviour is also excluded. Finally, simulation examples are presented for illustration of the theoretical claims.