Event-triggered Consensus For Multi-agent Systems Research Articles

Secure Fully Distributed Event-Triggered Consensus of Multi-Agent Systems Against Distributed Sequential Scaling Attacks

This article is concerned with the secure fully distributed event-triggered consensus problem of general linear multi-agent systems subject to distributed sequential scaling (DSS) attacks. First, a generic DSS attack model is proposed, which enables different attack strategies in terms of scaling factors, attack frequency and duration to be incorporated in various communication channels. Different from existing attack models, the DSS attack is a kind of scaling attacks in which attack sequences are characterized by the sequential attacks and with distributed attack strategies for different attack objectives. To resist the adverse effects of such DSS attacks and further reduce the unnecessary communication consumption of each communication channel, a channel-based dynamic event-triggered mechanism is next presented. Moreover, a fully distributed event-triggered consensus control protocol is developed such that the dependence of any global information of the network topology can be eliminated. Formal analysis criteria on the asymptotic convergence of the resultant consensus errors and Zeno-freeness are then derived, where the relationship of the triggering parameters, distributed scaling factors and attack constraints is explicitly expressed. Furthermore, an offline algorithm without any global information is provided to determine both the adaptive consensus protocol gain matrices and the triggering parameters. Therefore, the parameters calculated by this algorithm are applicable to multi-agent systems of different scales, which also confirms the flexibility and scalability of the proposed fully distributed event-triggered consensus control protocol. Finally, two simulation examples involving different scales of intelligent vehicles are given to validate the efficacy of the obtained theoretical results.

Adaptive Event-Triggered Consensus of Multi-Agent Systems in Sense of Asymptotic Convergence.

In this paper, the asymptotic consensus control of multi-agent systems with general linear agent dynamics is investigated. A neighbor-based adaptive event-triggering strategy with a dynamic triggering threshold is proposed, which leads to a fully distributed control of the multi-agent system, depending only on the states of the neighboring agents at triggering moments. By using the Lyapunov method, we prove that the states of the agents converge asymptotically. In addition, the proposed event-triggering strategy is proven to exclude Zeno behavior. The numerical simulation results illustrate that the agent states achieve consensus in sense of asymptotic convergence. Furthermore, the proposed strategy is shown to be scalable in case of variable agent numbers.

Event-Triggered Consensus of Multi-Agent Systems with Prescribed Performance

Event-Triggered Consensus of Multi-Agent Systems with Prescribed Performance

Improved Adaptive Dynamic Event-Triggered Consensus of Multi-Agent Systems

This brief exploits the adaptive dynamic event-triggered (ADET) consensus problem for multi-agent systems (MASs). Firstly, we propose a novel ADET protocol which improves the existing dynamic event triggered (DET) protocol and adaptive event-triggered (AET) protocol based on sampling control. The possibility that linear matrix inequalities (LMIs) has no feasible solution is reduced by presetting an adaptive maximum threshold. The asymptotic stability criterion is obtained. Subsequently, the controller gain and ADET parameters are obtained. Finally, the validity of the theoretical results in this brif is verified by a numerical simulation.

Dynamic Event-Triggered Consensus for Multiagent Systems Under DoS Attacks: A Hybrid System Approach

Dynamic Event-Triggered Consensus for Multiagent Systems Under DoS Attacks: A Hybrid System Approach

Matrix measure-based event-triggered consensus of multi-agent systems with hybrid time delays

Considering that there are many systems with limited energy resources in reality, this paper mainly concentrates on researching the leader-following consensus issue for an array of nonlinear multi-agent systems with hybrid time delays. The purpose of this article is to reduce the load of communication and controller updates for multi-agent systems on the basis of consensus achieving, a novel distributed event-triggered impulsive control strategy is therefore proposed to realize the global and exponential leader-following consensus. By jointly utilizing the matrix measure protocol, the comparison principle and the parameter variation formula method, sufficient conditions for the realization of leader-following consensus are successfully obtained. Moreover, the convergence rate is precisely estimated and the Zeno behavior is proved not exist in closed-loop systems. Eventually, a numerical example is given to demonstrate the effectiveness of proposed control strategy and the rightness of theoretical analysis.

Adaptive event-triggered consensus of multi-agent systems with spherical polar coordinate quantization mechanism

Adaptive event-triggered consensus of multi-agent systems with spherical polar coordinate quantization mechanism

Finite-time dynamic event-triggered consensus of multi-agent systems with mismatched disturbances based on disturbance observer

In this paper, the finite-time dynamic event-triggered consensus of second-order multi-agent systems with mismatched disturbances is studied. First, a nonlinear finite-time disturbance observer is designed to estimate the mismatched and matched disturbance of each follower. Second, the nonlinear dynamic integral sliding surface is developed through the mismatched and matched disturbance estimated by the observer. Then, combined with the dynamic event trigger strategy and the designed integral sliding surface, a new distributed control protocol is proposed, ensuring the finite-time consensus of the system. An analysis of Zeno behavior has found that the event-triggered interval has a positive lower bound. Finally, the effectiveness of the proposed control algorithm is verified by numerical simulation.

Periodic Event-triggered Consensus of Multiagent Systems Under Random Packet Dropouts

Periodic Event-triggered Consensus of Multiagent Systems Under Random Packet Dropouts

Quantization-Based Event-Triggered Consensus of Multiagent Systems Against Aperiodic DoS Attacks

This article focuses on the secure consensus problem of linear multiagent systems (MASs) with quantized event-triggered control (ETC) against denial-of-service (DoS) attacks. DoS attacks with constrains on frequency and duration are discussed, which intend to block the communication links between agents to destroy the consensus. Due to the limited transmission capacity and communication resources, a uniform quantizer and an event-triggered mechanism (ETM) are considered to economize energy consumption. An ETC protocol based on the quantized relative state is designed to resist malicious DoS attacks. Then, sufficient conditions to guarantee the practical consensus of MASs are derived with finite data transmission rates, and the tolerance of DoS attack frequency and duration are given. The Zeno behavior does not exhibit by proving that lower positive bounds exist for all agents, indicating the feasibility of the proposed ETM. Finally, two simulation examples are given to verify the validity and superiority of the theoretical results.

A Novel Event-Triggered Consensus Approach for Generic Linear Multi-Agents Under Heterogeneous Sector-Restricted Input Nonlinearities

This paper deals with the event-triggered (ET) consensus of generic linear multi-agent systems (MASs) subject to heterogeneous sector-restricted input nonlinearities over directed graphs. A new multiplicative input uncertainty-based model is derived to contemplate each agents' sector-restricted input nonlinearity. The proposed approach has been considered for an ET consensus of MASs under input nonlinearities to achieve an efficient control bandwidth by decreasing the sampling frequency. A consensus controller design condition with non-identical control gains is developed to ensure exponential stability with the ET mechanism for generic linear MASs with heterogeneous actuators. To the best of our knowledge, this is the first investigation of the consensus of linear MASs with heterogeneous sector-restricted nonlinearties at the control input, representing any continuous-time function bounded between two linear functions. The addition of the ET mechanism has further strengthened our contribution. This study also demonstrates that the designed ET condition under heterogeneous nonlinear inputs for a strongly connected topology can effectively exclude the Zeno behavior. Finally, a simulation example employing six spacecrafts is provided to illustrate the efficacy of the suggested consensus controller.

Dynamic asynchronous edge-based event-triggered consensus of multi-agent systems

This paper studies the asynchronous edge-based dynamic event-triggered consensus problems for multi-agent systems (MASs) with general linear dynamics. First, the static-gain edge-based protocol is proposed to assure that the agents achieve consensus asymptotically and that a uniformly positive minimum inter-event time (MIET) exists under the corresponding dynamic triggering mechanism. Then, to remove the requirement for the global information associated with the graph, an asynchronous edge-based event-triggered consensus control law that involves a dynamic gain is developed. A novel triggering mechanism that includes two dynamic parameters and a class of positive L1 functions under no Zeno behavior is further proposed to determine triggering instants of each edge in the graph. In addition, the continuous communication link is avoided. Finally, the application in a group of fixed-wing aircraft illustrates the validity of the theoretical results.

A Hybrid Systems Approach to Event-Triggered Consensus of Multiagent Systems With Packet Losses

This article addresses the event-triggered consensus problem of multiagent systems (MASs) with packet losses. The packet losses are not restricted to be identical, and a hybrid systems framework is proposed to handle the considered problem with or without leader in a unified framework. Distributed control law is constructed based on an estimator, whose dynamics are related to whether packet losses occur. A novel hybrid event-triggering mechanism (ETM) is proposed, and a lower bound of the interevent times is enforced to guarantee Zeno-freeness. For stability analysis, a unified hybrid model is constructed to describe the dynamics of MAS with or without leader. In accordance to this model, how to design the hybrid ETM and consensus analysis are formally developed, and the maximum allowable successive packet losses can be explicitly computed. Moreover, even if there exist nonlinearities and disturbances in system dynamics, and the leader has nonzero input, the proposed method can still be applied. Finally, examples are provided to illustrate the superiority of the proposed method.

Switched observer-based dynamic event-triggered consensus of multi-agent systems under DoS attacks

This paper investigates the observer-based consensus control for high-order nonlinear multi-agent systems (MASs) under denial-of-service (DoS) attacks. When the DoS attacks appear, the communication channels are destroyed, and the blocked information may ruin the consensus of MASs. A switched state observer is designed for the followers to observe the leader’s state whether the DoS attacks occur or not. Then, a dynamic event-triggered condition is proposed to reduce the consumption of communication resources. Moreover, an observer-based and dynamic event-triggered controller is formulated to achieve leader-following consensus through the back-stepping method. Additionally, the boundedness of all closed-loop signals is obtained based on the Lyapunov stability theory. Finally, the simulation results demonstrate the effectiveness of the presented control strategy under DoS attacks.

An Overview of Recent Advances in the Event-Triggered Consensus of Multi-Agent Systems with Actuator Saturations

The event-triggered consensus of multi-agent systems received extensive attention in academia and industry perspectives since it ensures all agents eventually converge to a stable state while reducing the utilization of network communication resources effectively. However, the practical limitation of the actuator could lead to a saturation phenomenon, which may degrade the systems or even induce instability. This paper plans to offer a detailed review of some recent results in the event-triggered consensus of multi-agent systems subject to actuator saturation. First, the multi-agent system model with actuator saturation constraints is given, and the basic framework of the event-triggering mechanism is introduced. Second, representative results reported in recent valuable papers are reviewed based on methods for dealing with saturated terms, including low-gain feedback, sector-bounded conditions, and convex hull representations. Finally, some challenging topics worthy of research efforts are dicussed for future research.

An asymmetric Lyapunov-Krasovskii functional approach for event-triggered consensus of multi-agent systems with deception attacks

This study provides an asymmetric Lyapunov–Krasovskii functional (LKF) to address the leader-following consensus of multi-agent systems (MASs) subject to deception attacks. To reduce unwanted signal transmissions between agents, we employ an event-triggering scheme. Also, a stochastic variable following a Bernoulli distribution is used to describe whether the communication among agents are affected by deception attack signals. A connected interaction graph is presented to describe the flow of information among neighboring agents. The considered problem is first modified into a stabilization problem by using the properties of algebraic graph theory. Then, we design a novel asymmetric LKF to show the desired stability conditions in the form of linear matrix inequalities (LMIs), which lead us the consensus of the chosen MAS. The efficacy of the obtained results is validated via illustrative examples.

Resilient finite-time distributed event-triggered consensus of multi-agent systems with multiple cyber-attacks

This study addresses the resilient finite-time distributed event-triggered (ET) consensus control of multi-agent systems (MASs) with multiple cyber-attacks, such as replay, deception, and denial-of-service (DoS) attacks. For the first attempt, a model is proposed for multiple cyber-attacks on MASs under DoS, deception, and replay attacks, that occur stochastically in a unified framework. Furthermore, an appropriate distributed ET consensus control mechanism is proposed to handle the unwanted traffic in the network communication channel. This scheme determines whether or not the signal can be transmitted to each agent in MASs. Sufficient conditions for the consensus of MASs are derived using Lyapunov stability theory and linear matrix inequalities (LMIs), which ensure the exponentially mean-square finite-time stability. On the basis of the obtained conditions, the explicit expressions of the consensus control gain matrix and trigger parameter matrices are given. Eventually, simulation results are provided to verify the proposed theoretical results.

Completely Event-Triggered Consensus for Multiagent Systems With Directed Switching Topologies.

This article studies the leader-following consensus of multiagent systems (MASs) with completely event-triggered mechanisms (CETMs) and directed switching topologies. When most event-triggered schemes in MASs only reduce each agent's data transmissions to neighbor agents, CETMs further reduce data transmissions to actuators with one triggered function in each agent. To guarantee the switching links utilized by CETMs contain a directed spanning tree at any time, triggered decisions are improved to include the instants at which each agent's output links or leader link change. Furthermore, a less conservative method based on matrix inequalities is combined to minimize the allowable average dwell time (ADT) of switching topologies under the design conditions of CETMs. Based on multiple Lyapunov functions (MLFs), the sufficient conditions for controller gains that guarantee the leader-following consensus of MASs are proposed when the ADT of switching topologies is larger than the allowable value. Finally, an example of autonomous underwater vehicles (AUVs) is given to illustrate the effectiveness of CETMs.

Event-Triggered Consensus of Multiagent Systems With Time-Varying Communication Delay

In this article, the consensus problem of linear multiagent systems (MASs) is investigated, where an event-triggered mechanism combined with sampler is introduced to rationally utilize the network bandwidth and the communication energy. Different from most existing results on the event-triggered consensus of MASs, a time-varying communication delay (CD) with a more general form is constructed in this article. With the help of a new class of Lyapunov functional and advanced inequalities, some novel criteria for achieving the asymptotic consensus of the considered MASs under different CD cases are obtained. For demonstrating the superiority of the proposed method from the conservatism and the practicability, a compared example and an application of spacecraft formation flying are proposed, respectively.

On Topology Optimization for Event-Triggered Consensus With Triggered Events Reducing and Convergence Rate Improving

This brief considers the network topology optimization problem for event-triggered consensus of multi-agent systems (MASs) to reduce the triggered events and improve the convergence rate. For a MAS with an undirected graph as its communication network, edge swapping operations are applied to optimize its network topology, which keep the number of links incident to each agent unchanged. Based on the theory of graph spectra, a necessary condition is provided to determine an effective edge swapping operation which leads to less event triggered times and faster convergence rate. An iterative algorithm is developed to optimize the network topology for MASs under the first-order event-triggered consensus protocol. Finally, some numerical simulations are given to illustrate the effectiveness of the approach.