Asynchronous decentralised event-triggered control of multi-agent systems

In this paper, the consensus problem of first-order multi-agent systems under linear asynchronous decentralised event-triggered control is investigated. Both undirected and directed topologies are considered. In the analysis, the closed-loop multi-agent systems with the event-triggered control are modelled as switched systems. After proposing the decentralised event-triggered consensus protocols, decentralised state-dependent event conditions are derived, which act as switching signals. The consensus analyses are performed based on graph theory and stability results of switched systems. Under the event-triggered control schemes presented, consensus is reached with enlarged sampling periods and no Zeno behaviour. Simulation examples are given to illustrate the effectiveness of the proposed theoretical results.     

Distributed event-triggered consensus for multi-agent systems with quantisation

This paper studies the consensus problem for multi-agent systems with quantised information communication via event-triggered control. First, the asynchronous event-triggered control for multi-agent systems is considered based on distributed uniform-quantised protocols. It is shown that practical consensus among agents is guaranteed and occurrence of Zeno behaviour is prevented under the designed event-triggering mechanisms. Second, under the proposed protocols using logarithmic quantised information, both synchronous and asynchronous event-triggered control algorithms are given to solve the practical consensus problem. Meanwhile, Zeno behaviour of the closed-loop systems can be excluded under the proposed event-triggered algorithms. Finally, numerical simulations are given to illustrate the effectiveness of the derived results.     

Decentralised consensus for multiple Lagrangian systems based on event-triggered strategy

This paper considers the decentralised event-triggered consensus problem for multi-agent systems with Lagrangian dynamics under undirected graphs. First, a distributed, leaderless, and event-triggered consensus control algorithm is presented based on the definition of generalised positions and velocities for all agents. There is only one triggering function for both the generalised positions and velocities and no Zeno behaviour exhibited under the proposed consensus strategy. Second, an adaptive event-triggered consensus control algorithm is proposed for such multi-agent systems with unknown constant parameters. Third, based on sliding-mode method, an event-triggered consensus control algorithm is considered for the case with external disturbance. Finally, simulation results are given to illustrate the theoretical results.     

事件触发机制下的多智能体领导跟随一致性

研究了一类具有动态领导者的一阶多智能体系统的一致性问题。基于事件触发机制给出两种一致性协议,即集中式触发控制协议和分散式触发控制协议。利用李雅普诺夫稳定性理论和模型转化方法分别给出多智能体系统在两种协议作用下达到领导跟随一致的充分条件。同时,理论计算表明,系统在两种控制协议下均不存在Zeno行为。实例仿真结果验证了理论方案的有效性。     

Edge event-triggered control for multi-agent systems under directed communication topologies

The edge event-triggered consensus control for multi-agent systems with single- or double-integrator dynamics under directed communication topologies is investigated in this paper. With the edge event-triggered sampling strategies, a class of novel consensus protocols is proposed to reduce control update frequency. The main features of the proposed edge event-triggered control include three aspects: (i) measurement errors are defined based on directed information flow and thus they allow that the communication topology is directed, (ii) each individual controller updates its output only when the associated edge event occurs and the control actions are independent of other agents, and (iii) the proposed edge event-triggered control does not exhibit Zeno behaviour and it is shown that the inter-event intervals are lower bounded by a positive constant. In the consensus analysis, matrix transformation techniques are used to convert the high-dimensional system into a low-dimensional system, and some sufficient consensus conditions are derived for the multi-agent systems with single- or double-integrator dynamics. Finally, the effectiveness of the edge event-triggered sampling strategies is illustrated by simulations.     

事件触发控制下二阶多智能体的量化一致性

针对多智能体系统网络通信过程中信息需要量化的情况,研究了二阶多智能体系统在事件触发控制下的量化一致性。基于事件触发控制策略,提出一致性协议,并采用对数量化器对控制输入进行量化处理。利用Lyapunov稳定性理论,对系统进行一致性分析,得到了多智能体系统渐近趋于一致的充分条件。仿真结果说明了理论分析的有效性。     

网络攻击下多智能体系统动态事件触发一致性

研究网络攻击下一般线性多智能体系统的动态事件触发一致性问题.考虑多智能体系统在受到网络攻击后,被攻击节点的状态会改变,导致与其相应的连接无法工作,设计修复策略恢复被攻击节点及其相应的连接,给出网络攻击下分布式事件触发控制协议.在静态事件触发机制基础上,通过引入动态阈值参数,提出动态事件触发机制.进一步,利用图论、线性矩阵不等式和李雅普诺夫函数方法,给出网络攻击下实现多智能体系统一致性的充分条件,并证明在所提出的动态事件触发条件下,能够有效避免芝诺行为.最后,通过仿真例子来验证理论结果的有效性.     

积分事件触发策略下的线性多智能体系统领导跟随一致性

研究有向切换拓扑下线性多智能体系统的事件触发一致跟踪问题.大多数已有的工作研究了固定拓扑下的事件触发控制,然而,当智能体间联系随时间发生改变或通信拓扑随时间发生变化时,该控制策略失效.鉴于此,在考虑切换拓扑的基础上提出一种基于积分型事件触发的控制策略.首先,当拓扑图包含一棵生成树且领导者是根节点时,利用Lyapunov稳定性理论、代数图论和矩阵变换,基于积分型事件触发控制协议,在切换拓扑下多智能体系统达到领导跟随一致性;然后,当存在多个领导者时,基于设计的触发机制在切换拓扑下多智能体系统实现包含控制,上述两种情况下闭环系统均不存在Zeno现象;最后,通过仿真结果验证控制策略的有效性.     

Bipartite Byzantine-resilient event-triggered consensus control of heterogeneous multi-agent systems

This article studies the bipartite resilient event-triggered consensus control for a class of the heterogeneous multi-agent systems. Due to the external cyberattacks, some agents may become the Byzantine agents and will affect the behavior of the other agents. To improve the security of the multi-agent systems against the Byzantine agents, a novel bipartite event-triggered heterogeneous mean-subsequence-reduced algorithm is designed. First, to handle the heterogeneous multi-agent systems, a state transformation is carefully designed, to facilitate the design and analysis of the bipartite resilient consensus algorithm. Based upon the designed state transformation, the bipartite resilient control inputs are constructed, where the structural balance analysis shows that the resulting effective signed graph and the equivalent signed graph are both structurally balanced, if the signed graph of the multi-agent systems is structurally balanced. In addition, a dynamic event-triggered mechanism is proposed, where a set of dynamic factors are introduced into the event-triggered functions to prevent the usage of the global topology information. By virtue of the designed algorithm, it is guaranteed that the heterogeneous multi-agent systems can achieve the bipartite consensus in the presence of the Byzantine agents, and the communication burden among the agents can be reduced. The numerical simulations are conducted to verify the effectiveness of the proposed algorithm.     

Dynamic Event-Triggered Fixed-Time Consensus Control and Its Applications to Magnetic Map Construction

This article deals with the consensus problem of multi-agent systems by developing a fixed-time consensus control approach with a dynamic event-triggered rule. First, a new fixed-time stability condition is obtained where the less conservative settling time is given such that the theoretical settling time can well reflect the real consensus time. Second, a dynamic event-triggered rule is designed to decrease the use of chip and network resources where Zeno behaviors can be avoided after consensus is achieved, especially for finite/fixed-time consensus control approaches. Third, in terms of the developed dynamic event-triggered rule, a fixed-time consensus control approach by introducing a new item is proposed to coordinate the multi-agent system to reach consensus. The corresponding stability of the multi-agent system with the proposed control approach and dynamic event-triggered rule is analyzed based on Lyapunov theory and the fixed-time stability theorem. At last, the effectiveness of the dynamic event-triggered fixed-time consensus control approach is verified by simulations and experiments for the problem of magnetic map construction based on multiple mobile robots.

     

Generalised exponential consensus of the fractional-order nonlinear multi-agent systems via event-triggered control

In this paper, the leader-following consensus problem of the fractional-order nonlinear multi-agent systems via event-triggered control is considered. An effective event-triggered controller is designed and then generalised exponential consensus of the controlled multi-agent systems is studied in the sense of Mittag-Leffler stability of fractional-order systems. The event-triggering function design is dependent on the parameter of the system structure and the minimum inter-event interval can be flexibly adjusted with different fractional-order α. With the event-triggered control scheme, the consensus condition is obtained and the convergence rate of the system is estimated. Numerical simulation indicates the effectiveness of the theoretical results.     

Agent-based time delay margin in consensus of multi-agent systems by an event-triggered control method: Concept and computation

This paper deals with defining the concept of agent-based time delay margin and computing its value in multi-agent systems controlled by event-triggered based controllers. The agent-based time delay margin specifying the time delay tolerance of each agent for ensuring consensus in event-triggered controlled multi-agent systems can be considered as complementary for the concept of (network) time delay margin, which has been previously introduced in some literature. In this paper, an event-triggered control method for achieving consensus in multi-agent systems with time delay is considered. It is shown that the Zeno behavior is excluded by applying this method. Then, in a multi-agent system controlled by the considered event-triggered method, the concept of agent-based time delay margin in the presence of a fixed network delay is defined. Moreover, an algorithm for computing the value of the time delay margin for each agent is proposed. Numerical simulation results are also provided to verify the obtained theoretical results.     

基于事件触发的离散多智能体二分一致性

针对一阶离散多智能体系统,研究了事件触发控制下的二分一致性问题.首先考虑智能体间通信拓扑结构为无向连通结构平衡图的情形,针对各智能体设计事件触发控制,包括仅依赖于自身及邻居智能体采样状态的控制输入,以及仅依赖自身状态的事件触发条件,实现了对通信资源的节约利用.基于图论、离散系统稳定性理论,证明系统能够实现二分一致性.同时,合理设置控制输入及事件触发条件中参数,保证系统不存在Zeno现象.之后,进一步分析设计了包含有向生成树的结构平衡图下,多智能体系统的事件触发控制.最后利用仿真实例验证了理论结果的有效性.     

组合连通拓扑下基于事件触发的多智能体快速一致性算法

针对组合连通拓扑下多智能体系统控制过程中存在通信和计算资源损耗大以及系统收敛速度慢等问题,提出一种新的具有状态预测器的事件触发一致性控制协议,通过设计状态预测器使每个智能体都能对其邻居智能体的未来状态作出预测;同时,对于智能个体给出了基于状态信息的事件触发条件,当状态误差满足该条件才触发事件.在该控制策略下多智能体系统可在节约通信和计算资源的同时具有更快的收敛速度.利用Lyapunov稳定性理论和代数图论,证明了所提事件触发控制策略能够有效实现组合连通拓扑结构下的平均一致性,且不存在Zeno行为.仿真实例进一步验证了理论结果的有效性.     

事件触发下多智能体系统固定时间二分一致性

针对具有符号有向图的一阶多智能体系统,研究了其固定时间二分一致性问题。为降低控制过程中多智能体系统的能量损耗,提出了一种基于事件触发机制的分布式控制协议。以图论和李雅普诺夫理论为主要研究工具,给出了多智能体系统在所设计控制协议作用下实现固定时间二分一致性的充分条件和与系统初始状态无关的收敛时间上界,并证明了使用该协议可以有效避免对智能体的连续控制和Zeno行为的发生。数值算例验证了所得理论结果的有效性。     

切换拓扑下多自主体系统的事件触发一致性控制

本文针对一阶非线性多自主体系统,考察了切换拓扑下的事件触发一致性控制问题.当切换拓扑子图的并图包含有向生成树时,基于一阶保持器提出了一种分布式事件触发一致性算法,用以降低网络的通信负载.运用迭代法和不等式法,得到了多自主体系统达到有界一致性的充分条件.此外,证明了所提事件触发机制不存在Zeno现象,并得到了触发间隔的正下界.最后,给出仿真实例,验证了所提事件触发一致性算法和理论分析结果的有效性.     

Distributed fuzzy adaptive event-triggered finite-time consensus tracking control for uncertain nonlinear multi-agent systems with asymmetric output constraint

This article investigates the consensus problem for uncertain nonlinear multi-agent systems (MASs) with asymmetric output constraint. Different from BLF-based constraint consensus tracking control, a novel approach based on nonlinear state-dependent function is proposed to solve the asymmetric output constraint, which need not convert output constraint into tracking error bound. First-order sliding mode differentiator is incorporated into each step of backstepping control design to reduce computation burden. Further, in combination of proposed event-triggered mechanism based on time-varying threshold, a distributed fuzzy adaptive event-triggered finite-time consensus method is developed. It can ensure that the consensus tracking error tends to a small neighbor in a finite time and the asymmetric output constraint of each subsystem is not violated. Two simulations are given to demonstrate the effectiveness of control method.     

多智能体系统的事件驱动控制

近年来事件驱动控制发展迅速,并引起了多智能体系统领域研究者的极大关注.本文对基于事件驱动控制的多智能体系统的研究现状进行综述.从智能体动力学角度,分别对这个领域的一些代表性成果和研究方法进行了归纳总结.进一步,论述了边事件驱动控制策略下的多智能体系统的研究成果.随后,利用一类新型事件驱动控制来探讨多智能体系统的一致性问题.最后,给出了尚未解决的问题和未来值得关注的研究方向.     

Connectivity-preserving consensus: An adaptive event-triggered strategy

The connectivity of communication graph is indispensable for consensus of multi-agent systems (MASs), which in many applications (e.g., wireless sensor) depends on the relative distances between agents. But, in the adaptive setting particularly with system nonlinearities and event-triggered communication, it is rather difficult to enforce the relative distances within the limited range for the connectivity. This paper focuses on developing an adaptive event-triggered control strategy with connectivity preservation in the context of nonidentical unknown control coefficients and heterogeneous nonlinearities coupling with parameter uncertainties. First, a group of potential functions are introduced acting as control barrier functions to constrain the relative distances between agents within the limited range for all time. Also, two dynamic gains are specialized for each agent to handle the system uncertainties, system nonlinearities and negative effect of the execution error. Then, an adaptive event-triggered protocol is designed for each agent such that the connectivity-preserving consensus of MASs is achieved and Zeno behavior is excluded. Moreover, an extended study is conducted on a leader-following scenario. Two simulation examples illustrate the effectiveness of the proposed event-triggered control strategy.     

Event-triggered adaptive consensus control of nonlinear multi-agent systems with unknown control directions and actuator saturation

This article addresses the event-triggered adaptive consensus control of nonlinear multi-agent systems with unknown control direction and actuator saturation. A new robust adaptive control algorithm based on an event-triggered mechanism is designed. The smooth Lipschitz function approximates the saturated nonlinear function, while the Nussbaum function handles unknown control directions and residual terms. The event-triggered mechanism is designed to determine the time of communication, significantly reducing the communication burden. An additional estimator is utilized to deal with unknown parameters involved in neighbor dynamics and prevent information exchange to consistency errors between connected subsystems. The results show that all the signals of the closed-loop system are uniformly bounded, and the consensus tracking error converges to a bounded set. Meanwhile, Zeno's behavior is eliminated. Simulation results confirm the superiority of the proposed method.