Consensus Of Networked Multi-agent Systems Research Articles

Predictive Consensus for Networked Multi-Agent Systems With Switching Topology, Input Delay and Time-Varying Communication Delays

This brief investigates the consensus for networked delayed multi-agent systems with switching topologies and time-varying communication delays. Novel consensus protocol that uses (pseudo) predictive scheme is proposed to synchronize the states of agents. Sufficient consensus conditions are derived, and the results show that the state consensus can be guaranteed if the graphs contain a joint spanning tree as frequently as the system evolves and no eigenvalues of system matrix exist outside the unit circle. Numerical examples illustrate the theoretic results.

Sampled-position states based consensus of networked multi-agent systems with second-order dynamics subject to communication delays

This paper is concerned with the sampled-position states based consensus of networked multi-agent systems with second-order dynamics, where agents are connected through communication channels subject to time-varying communication delays. Note that consensus in such systems cannot be reached if using only the current sampled-position states. This paper investigates the positive effects of time-varying communication delays on the consensus. For two cases, where a directed graph has a fixed or switching topology, several sufficient conditions on consensus are derived by using a discretized Lyapunov-Krasovskii functional method. Based on the obtained conditions, suitable control protocols can be devised through tuning two parameters. Finally, simulation shows that consensus can be achieved using sampled-position states if the time-varying communication delays are within a certain time interval with its lower bound strictly greater than zero.

A class of robust consensus algorithms with predefined‐time convergence under switching topologies

SummaryThis paper addresses the robust consensus problem under switching topologies. Contrary to existing methods, the proposed approach provides decentralized protocols that achieve consensus for networked multiagent systems in a predefined time. Namely, the protocol design provides a tuning parameter that allows setting the convergence time of the agents to a consensus state. An appropriate Lyapunov analysis exposes the capability of the current proposal to achieve predefined‐time consensus over switching topologies despite the presence of bounded perturbations. Finally, this paper presents a comparison showing that the suggested approach subsumes existing fixed‐time consensus algorithms, which allows to provide extra degrees of freedom to obtain predefined‐time consensus protocols with improved convergence characteristics, for instance, to reduce the slack between the true convergence time and the predefined upper bound. Numerical results are given to illustrate the effectiveness and advantages of the proposed method.

Improved leaderless consenus criteria of networked multi-agent systems based on the sampled data

ABSTRACTThis paper is concerned with leaderless consensus of networked multi-agent systems with Lipschitz-type nonlinear dynamics based on the sampled data. By introducing a weighted average state of all nodes as the virtual leader, the error variables are defined as the distance between agents and the virtual leader. The improvements are done in two directions. First, several consensus conditions are derived by linear matrix inequalities based on Finsler's lemma instead of algebraic criteria based on the general algebraic connectivity. Finsler's lemma is utilised to deal with the linear dependence of the error variables. Second, a distributed event-triggered transmission strategy under the periodic sampling scheme is proposed to reduce the communication between agents and the control updates, which only need to check the event condition at each sampling instant, avoiding the continuous monitor. With the improved strategies, one theorem and two corollaries are derived and a co-design approach of the feedback gain and the event-triggered matrix is also presented. Finally, an example is provided to validate the effectiveness of the theoretical results.

Impulsive Consensus of Networked Multi-Agent Systems With Distributed Delays in Agent Dynamics and Impulsive Protocols

This paper studies the consensus problem of networked multi-agent systems (NMASs). Distributed delays are considered in the agent dynamics, and we propose a new type of impulsive consensus protocols that also takes into account of distributed delays. A novel method is developed to estimate the relation between the agent states at the impulsive instants and the distributed-delayed agent states, which helps to use the Razumikhin-type stability result to investigate the consensus of NMASs with distributed-delayed impulses. Sufficient conditions are established to guarantee that the network consensus can be reached via the proposed consensus protocols with fixed and switching topologies, respectively. Numerical simulations are also provided to demonstrate our theoretical results.

Analysis of the effects of communication delays for consensus of networked multi-agent systems

Achieving cooperation and coordination in a network of multi-agent systems is key to solving the consensus problem. Synchronization of such systems requires consistent communication between agents to reach a consensus, which is not feasible in the presence of delays, data loss, disturbances, and other unpredictable factors. Communication delays combined with environmental uncertainties can cause adverse effects and negatively change the behavior of the networked system preventing synchronization. In this paper, the stability of the delayed networked systems is analyzed using delay differential equations. Solving these equations has not been feasible, because of the infinite number of characteristic roots. The approach based on the LambertWfunction has the capability of analytically solving delay differential equations. The approach is used to quantify and analyze the stability of the delayed networked systems. The communication between the agents is modeled using the graph theory and the Laplacian matrix. The stability is analyzed by incorporating the Laplacian matrix into the Lambert W function based approach which provides the locus of the eigenvalues of the system as delay changes. Sensitivities and convergence speed with respect to delay for various topologies of the network are presented for comparison. The numerical results and implementation using MATLAB/Simulink are presented for illustration.

Consensus in Networked Multiagent Systems With Stochastic Sampling

This brief addresses the consensus problem in networks with stochastic sampling, assuming that the sampling intervals are independently and identically distributed. Necessary and sufficient conditions to guarantee mean square consensus of both first-order and second-order multiagent systems are derived in terms of statistical properties of the sampling intervals. Numerical examples are also given to verify the theoretical results, revealing that the conditions on the sampling intervals are significantly relaxed in contrast to the previous sufficient conditions. By applying the first-order model to opinion consensus problems with intermittent interactions, it is finally found that the temporal heterogeneity of human activities impedes the opinion consensus forming.

Consensus for networked multi-agent systems with unknown communication delays

The problem of consensus for linear discrete-time networked multi-agent systems with directed topologies and communication delays is investigated in this paper. The communication delays are assumed to be constant but unknown. A consensus protocol is designed to compensate for the unknown delays based on the networked predictive control scheme. A sufficient condition for the consensus of multi-agent systems is derived. Finally, a numerical example is given to illustrate that the consensus protocol proposed in this paper is effective.

Output consensus of networked multi-agent systems with time-delay compensation scheme

The output consensus problem of linear discrete-time multi-agent systems (DTMASs) with heterogeneous dynamics and a communication delay is investigated in this paper. In order to remove the negative effects of the communication delay, the networked predictive control scheme is introduced to compensate for the network delay actively. A novel distributed protocol is proposed with the predictions of agents׳ outputs at current time, instead of available outdated data. For DTMASs with heterogeneous agents and a constant communication delay, the sufficient conditions of output consensus are obtained while agents׳ states are not measurable. Simulation results are further presented to demonstrate the effectiveness of the theoretical results.

Bipartite output consensus in networked multi-agent systems of high-order power integrators with signed digraph and input noises

ABSTRACTIn this paper, we concentrate on investigating bipartite output consensus in networked multi-agent systems of high-order power integrators. Systems with power integrator are ubiquitous among weakly coupled, unstable and underactuated mechanical systems. In the presence of input noises, an adaptive disturbance compensator and a technique of adding power integrator are introduced to the complex nonlinear multi-agent systems to reduce the deterioration of system performance. Additionally, due to the existence of negative communication weights among agents, whether bipartite output consensus of high-order power integrators can be achieved remains unknown. Therefore, it is of great importance to study this issue. The underlying idea of designing the distributed controller is to combine the output information of each agent itself and its neighbours, the state feedback within its internal system and input adaptive noise compensator all together. When the signed digraph is structurally balanced, bipartite output consensus can be reached. Finally, numerical simulations are provided to verify the validity of the developed criteria.

Consensus of networked multi-agent systems with diverse time-varying communication delays

In this paper, the problem of consensus for discrete-time networked multi-agent systems (NMASs) with a directed topology and diverse time-varying communication delays is investigated. By introducing the networked predictive control scheme, the predictions of states at current time, instead of available outdated states, are exploited to design a distributed consensus protocol, which compensates for communication delays actively. For NMASs with identical linear agents and bounded time-varying communication delays, necessary and sufficient conditions of the consensus are provided. Numerical simulations are given to compare the proposed networked predictive control method with the standard non-predictive way, and demonstrate the effectiveness of theoretical results.

Joining consensus of networked multi-agent systems with nonlinear couplings and weighting constraints

This paper studies the joining consensus of networked multi-agent systems subject to nonlinear couplings and weighted directed graphs via pinning control. A weighted-average consensus protocol is proposed to achieve the collective decision by interacting with the local information of some pinned agents. By proposing a novel joining consensus protocol, average consensus and general consensus strategies are joined to achieve an agreement for the weighting networked system. Furthermore, by calculating a proper consensus gain and using finite control Lyapunov controllers, an efficient joining consensus protocol is presented to improve the consensus speed. Sufficient conditions for achieving the consensuses asymptotically are proved. Finally, theoretical results are validated via simulations.

Necessary and sufficient condition for average consensus of networked multi-agent systems with heterogeneous time delays

This paper deals with an average-consensus problem of networked multi-agent systems with heterogeneous time delays. First, a necessary and sufficient condition is derived for multi-agent systems to achieve average consensus. This condition is represented in the form of an algebraic condition by using the delay-transition and the delay-weighted Laplacians. Second, a performance criterion is introduced to evaluate multi-agent systems that do not achieve average consensus. The criterion is represented in terms of the norms with respect to the above Laplacians. These results imply that the introduced Laplacians play important roles in analysing multi-agent systems with heterogeneous time delays. The validity of the analysis results is demonstrated by simulations with six-agent systems.

Consensus of networked multi-agent systems with communication delays based on the networked predictive control scheme

The consensus problem of discrete-time networked multi-agent systems (NMASs) with a communication delay is investigated in this article, where the dynamics of agents described by discrete-time linear time-invariant systems can be either uniform or non-uniform. For the NMASs with a directed topology and constant delay, a novel protocol based on the networked predictive control scheme is proposed to compensate for communication delay actively. Using algebraic graph theories and matrix theories, necessary and/or sufficient conditions of achieving consensus are obtained, which indicates that, under the proposed protocol, the consensus is independent of the network delay and only dominated by agents' dynamics and communication topology. Meanwhile, the protocol design and consensus analysis are also presented in the case of no network delay. Simulation results are further presented to demonstrate the effectiveness of theoretical results.

Extended consensus analysis of multi-agent systems with switching topologies

Theoretical analysis of consensus for networked multi-agent systems with switching topologies was conducted. Supposing that information-exchange topologies of networked system are dynamic, a modified linear protocol is proffered which is more practical than existing ones. The definition of trajectory consensus is given and a new consensus protocol is exhibited such that multi-agent system achieves trajectory consensus. In addition, a formation control strategy is designed. A common Lyapunov function is proposed to analyze the consensus convergence of networked multi-agent systems with switching topologies. Simulations are provided to demonstrate the effectiveness of the theoretical results.

Consensus of networked multi-agent systems via the networked predictive control and relative outputs

This paper investigates the consensus problem of discrete-time networked multi-agent systems (DNMASs) with a directed topology and communication delay, where exact state and output of each agent are not measured, and yet output differences between agent and its neighboring ones (relative outputs for short) are available. Based on the networked predictive control scheme and relative output data, a novel protocol is proposed to overcome the effect of delay on the consensus actively. Moreover, for the DNMASs with a fixed topology and constant communication delay, delay-independent necessary and/or sufficient conditions of achieving consensus are obtained, which reveal that the essence of dominating the consensus is agents' dynamics and communication topology. Simulation results further demonstrate the effectiveness of theoretical results.

Group consensus of networked multi-agent systems with directed topology

AbstractGroup consensus problems of multi-agent systems in directed networks with fixed and switching topologies are addressed in this note. Under mild assumptions, necessary and/or sufficient conditions of group consensus are derived, based on algebraic graph theories and matrix theories. For the fixed topology case, the group consensus can be guaranteed by the Hurwitz stability of coefficient matrices. For the switching topology case, the group consensus is proved to be equivalent to the asymptotical stability of a class of switched linear systems under arbitrary switching signal. A simulation result is provided to demonstrate the effectiveness of the theoretical results.

Optimal Weights for Consensus of Networked Multi-Agent Systems

This paper presents an introduction about the Voice over Internet Protocol (VoIP) technology and some background infor-mation about fundamental frequency of Thai language and some different characteristics of fundamental frequency of child voice, male voices and female voices. Also, voice quality indicator and an overview of voice quality measurement methods have been presented. However, only subjective measurement methods were considered in detail. Moreover, brief information about voice codecs has been described. For the approach of this study, the data set from listening-opinion tests with G.711 and G.729 has been used and analyzed. Analyzed results from T-test and ANOVA show that G.711 and G.729 provide voice quality without difference significantly, although in cases of voices from children, female and male speakers. Therefore, this paper presents the evidence which is inconsistent with the general understanding of most engineers, who implement VoIP systems.