DoS攻击下基于多率采样的多智能体系统安全一致性

本 文 研 究 了 一 类 带 有 多 率 采 样 的 线 性 多 智 能 体 系 统(Multiagent Systems, MASs)在 拒 绝 服务(Denial-of-Service, DoS)攻击下的安全一致性控制问题, 其中DoS攻击通常阻断智能体之间的信息传输. 本文将多率采样在网络化控制系统中的结果推广到了多智能体系统, 并考虑了非理想通信网络环境. 首先, 通过引入一个匹配机制来同步由多率采样引起的智能体不同状态分量的采样数据. 然后, 在DoS攻击下, 针对带有多率采样的线性MAS提出了一个基于多率采样的安全一致性控制器. 通过使用李雅普诺夫稳定性理论和切换系统方法, 获得了包含DoS 攻击持续时间以及攻击频率的安全一致性充分条件. 最后, 给出了一个仿真例子来验证所提方法的有效性, 并给出了多率采样与单率采样机制的性能对比分析.     

拒绝服务攻击下直流微电网的事件触发控制

本文研究受拒绝服务攻击下直流微电网的事件触发控制问题. 考虑到直流微电网的状态并不总是可获得, 设计了一个观测器来估计直流微电网的状态. 基于观测器的估计状态, 对于受拒绝服务攻击的直流微电网设计了一种新颖的弹性攻击的事件触发控制器. 所提出的控制器设计方法可以通过分离方法转化成一个凸问题. 此外, 在所设计的事件触发机制中, Zeno行为也被讨论并且通过矛盾法被排除. 最后, 一个实际的电网例子被用来验证所提出的控制方案的有效性.     

Consensus Control of Multi-Agent Systems Using Fault-Estimation-in-the-Loop: Dynamic Event-Triggered Case

The paper develops a novel framework of consensus control with fault-estimation-in-the-loop for multi-agent systems(MASs) in the presence of faults. A dynamic event-triggered protocol(DETP) by adding an auxiliary variable is utilized to improve the utilization of communication resources. First, a novel estimator with a noise bias is put forward to estimate the existed fault and then a consensus controller with fault compensation(FC) is adopted to realize the demand of reliability and safety of a...     

Sliding Mode Control for Nonlinear Markovian Jump Systems Under Denial-of-Service Attacks

This paper investigates the sliding mode control (SMC) problem for a class of discrete-time nonlinear networked Markovian jump systems (MJSs) in the presence of probabilistic denial-of-service (DoS) attacks. The communication network via which the data is propagated is unsafe and the malicious adversary can attack the system during state feedback. By considering random Denial-of-Service attacks, a new sliding mode variable is designed, which takes into account the distribution information of the probabilistic attacks. Then, by resorting to Lyapunov theory and stochastic analysis methods, sufficient conditions are established for the existence of the desired sliding mode controller, guaranteeing both reachability of the designed sliding surface and stability of the resulting sliding motion. Finally, a simulation example is given to demonstrate the effectiveness of the proposed sliding mode control algorithm.      

Secure Impulsive Synchronization in Lipschitz-Type Multi-Agent Systems Subject to Deception Attacks

Cyber attacks pose severe threats on synchronization of multi-agent systems. Deception attack, as a typical type of cyber attack, can bypass the surveillance of the attack detection mechanism silently, resulting in a heavy loss. Therefore, the problem of mean-square bounded synchronization in multi-agent systems subject to deception attacks is investigated in this paper. The control signals can be replaced with false data from controller-to-actuator channels or the controller. The success of the attack is measured through a stochastic variable. A distributed impulsive controller using a pinning strategy is redesigned, which ensures that mean-square bounded synchronization is achieved in the presence of deception attacks. Some sufficient conditions are derived, in which upper bounds of the synchronization error are given. Finally, two numerical simulations with symmetric and asymmetric network topologies are given to illustrate the theoretical results.      

Distributed Fault-Tolerant Containment Control for Nonlinear Multi-Agent Systems Under Directed Network Topology via Hierarchical Approach

This paper investigates the distributed fault-tolerant containment control(FTCC)problem of nonlinear multi-agent systems(MASs)under a directed network topology.The proposed control framework which is independent on the global information about the communication topology consists of two layers.Different from most existing distributed fault-tolerant control(FTC)protocols where the fault in one agent may propagate over network,the developed control method can eliminate the phenomenon of fault propagation.Based on the hierarchical control strategy,the FTCC problem with a directed graph can be simplified to the distributed containment control of the upper layer and the fault-tolerant tracking control of the lower layer.Finally,simulation results are given to demonstrate the effectiveness of the proposed control protocol.     

Event-Triggered Asymmetric Bipartite Consensus Tracking for Nonlinear Multi-Agent Systems Based on Model-Free Adaptive Control

In this paper, an asymmetric bipartite consensus problem for the nonlinear multi-agent systems with cooperative and antagonistic interactions is studied under the event-triggered mechanism. For the agents described by a structurally balanced signed digraph, the asymmetric bipartite consensus objective is firstly defined, assigning the agents’ output to different signs and module values. Considering with the completely unknown dynamics of the agents, a novel event-triggered model-free adaptive bipartite control protocol is designed based on the agents’ triggered outputs and an equivalent compact form data model. By utilizing the Lyapunov analysis method, the threshold of the triggering condition is obtained. Subsequently, the asymptotic convergence of the tracking error is deduced and a sufficient condition is obtained based on the contraction mapping principle. Finally, the simulation example further demonstrates the effectiveness of the protocol.      

Human-in-the-Loop Consensus Control for Nonlinear Multi-Agent Systems With Actuator Faults

This paper considers the human-in-the-loop leader-following consensus control problem of multi-agent systems(MASs)with unknown matched nonlinear functions and actuator faults.It is assumed that a human operator controls the MASs via sending the command signal to a non-autonomous leader which generates the desired trajectory.Moreover,the leader’s input is nonzero and not available to all followers.By using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults,respectively,the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed.It is proved that the state of each follower can synchronize with the leader’s state under a directed graph and all signals in the closed-loop system are guaranteed to be cooperatively uniformly ultimately bounded.Finally,simulation results are presented for verifying the effectiveness of the proposed control method.     

DoS攻击下网络控制系统的记忆型事件触发控制

针对一类网络化控制系统，当考虑网络控制系统遭受PWM （Pulsewidth-Modulated）型DoS （Denial-of-Service， DoS）攻击时，提出一种基于缓存机制的记忆型事件触发机制策略.本文考虑的DoS攻击可检测，并且攻击的周期时长以及每周期内的最短休眠时间已知.为了减少网络控制系统中数据包的发送频次，本文设计了基于相对误差的新型事件触发策略，与传统事件触发策略相比，通过增加缓存器来有效利用已经发送的历史采样数据，最终达到改善系统动态过程的目的.接下来，综合考虑网络攻击和事件触发方案，建立了网络化切换系统模型，构造分段李雅普诺夫泛函，推导出系统指数稳定的结论并且对控制器增益及事件触发参数进行协同设计.最后，通过仿真案例，验证了所提出方法的有效性.     

Distributed Adaptive Fault-Tolerant Output Regulation of Heterogeneous Multi-Agent Systems With Coupling Uncertainties and Actuator Faults

In this paper, we consider the distributed adaptive fault-tolerant output regulation problem for heterogeneous multiagent systems with matched system uncertainties and mismatched coupling uncertainties among subsystems under the influence of actuator faults. First, distributed finite-time observers are proposed for all subsystems to observe the state of the exosystem. Then, a novel fault-tolerant controller is designed to compensate for the influence of matched system uncertainties and actuator faults. By using the linear matrix inequality technique, a sufficient condition is provided to guarantee the solvability of the considered problem in the presence of mismatched coupling uncertainties. Moreover, it is shown that the system in closed-loop with the developed controller can achieve output regulation by using the Lyapunov stability theory and cyclic-small-gain theory. Finally, a numerical example is given to illustrate the effectiveness of the obtained result.      

具有指定性能和全状态约束的多智能体系统事件触发控制

针对一类非严格反馈的非线性多智能体系统一致性跟踪问题,在考虑全状态约束和指定性能的基础上提出了一种事件触发自适应控制算法.首先,通过设计性能函数,使跟踪误差在规定时间内收敛于指定范围.然后,在反步法中引入Barrier Lyapunov函数使所有状态满足约束条件,结合动态面技术解决传统反步法产生的"计算爆炸"问题,并利用径向基函数神经网络（Radial basis function neural networks,RBF NNs）处理系统中的未知非线性函数.最后基于Lyapunov稳定性理论证明系统中所有信号都是半全局一致最终有界的,跟踪误差收敛于原点的有界邻域内且满足指定性能.仿真结果验证了该控制算法的有效性.     

欺骗攻击下网络化系统事件触发安全控制

针对网络控制系统受欺骗攻击问题,提出了事件触发器与安全控制器协同设计策略。提出了离散事件触发机制,克服了连续事件触发机制需要新增专用硬件且需要复杂计算避免芝诺现象局限。建立了有机融合欺骗攻击、事件触发机制、网络诱导延时及外部扰动多约束参数的闭环系统时滞模型,推导出了欺骗攻击下事件触发控制系统渐近稳定的充分条件,得到了事件触发器与安全控制器的协同设计条件。仿真验证了方法的有效性。     

含执行器故障的切换非线性系统的事件触发自适应模糊容错控制

本文研究在平均驻留时间约束下,一类含有执行器故障的切换非线性系统输出反馈自适应模糊事件触发容错控制问题.首先,建立了一个模态依赖的状态观测器估计不可测量状态.利用模糊逻辑系统来逼近未知项.其次,构建自适应模糊容错事件触发控制方案能够节省网络资源和数据传输.然后,通过构造多Lyapunov函数和平均驻留时间法,证明闭环系统所有状态半全局一致最终有界的同时排除了Zeno现象.最后,通过数值仿真验证该方法的有效性.     

含执行器故障的切换非线性系统的事件触发自适应模糊容错控制

本文研究在平均驻留时间约束下,一类含有执行器故障的切换非线性系统输出反馈自适应模糊事件触发容错控制问题.首先,建立了一个模态依赖的状态观测器估计不可测量状态.利用模糊逻辑系统来逼近未知项.其次,构建自适应模糊容错事件触发控制方案能够节省网络资源和数据传输.然后,通过构造多Lyapunov函数和平均驻留时间法,证明闭环系统所有状态半全局一致最终有界的同时排除了Zeno现象.最后,通过数值仿真验证该方法的有效性.     

Adaptive Consensus of Non-Strict Feedback Switched Multi-Agent Systems With Input Saturations

This paper considers the leader-following consensus for a class of nonlinear switched multi-agent systems (MASs) with non-strict feedback forms and input saturations under unknown switching mechanisms. First, in virtue of Gaussian error functions, the saturation nonlinearities are represented by asymmetric saturation models. Second, neural networks are utilized to approximate some unknown packaged functions, and the structural property of Gaussian basis functions is introduced to handle the non-strict feedback terms. Third, by using the backstepping process, a common Lyapunov function is constructed for all the subsystems of the followers. At last, we propose an adaptive consensus protocol, under which the tracking error under arbitrary switching converges to a small neighborhood of the origin. The effectiveness of the proposed protocol is illustrated by a simulation example.      

DoS攻击下具备隐私保护的多智能体系统均值趋同控制

均值趋同是一种广泛应用于分布式计算和控制的算法, 旨在系统通过相邻节点间信息交互、更新, 最终促使系统中所有节点以它们初始值的均值达成一致. 研究拒绝服务(Denial-of-service, DoS)攻击下的分布式离散时间多智能体系统均值趋同问题. 首先, 给出一种基于状态分解思想的分布式网络节点状态信息处理机制, 可保证系统中所有节点输出值的隐私. 然后, 利用分解后的节点状态值及分析给出的网络通信拓扑条件, 提出一种适用于无向通信拓扑的多智能体系统均值趋同控制方法. 理论分析表明, 该方法能够有效抵御DoS攻击的影响, 且实现系统输出值均值趋同. 最后, 通过仿真实例验证了该方法的有效性.     

Fault Accommodation for a Class of Nonlinear Uncertain Systems With Event-Triggered Input

The event-triggered fault accommodation problem for a class of nonlinear uncertain systems is considered in this paper.The control signal transmission from the controller to the system is determined by an event-triggering scheme with relative and constant triggering thresholds.Considering the event-induced control input error and system fault threat,a novel eventtriggered active fault accommodation scheme is designed,which consists of an event-triggered nominal controller for the time period before detecting the occurrence of faults and an adaptive approximation based event-triggered fault accommodation scheme for handling the unknown faults after detecting the occurrence of faults.The closed-loop stability and inter-event time of the proposed fault accommodation scheme are rigorously analyzed.Special cases for the fault accommodation design under constant triggering threshold are also derived.An example is employed to illustrate the effectiveness of the proposed fault accommodation scheme.     

基于网络资源管理技术的SDN DoS攻击动态防御机制

软件定义网络(software defined networking, SDN)已经迅速成为一种新的网络通信管理模式,极大地改变了传统网络架构.SDN可以通过将控制层与数据层分离来实现更细粒度的网络控制与管理.但是,转控分离的SDN架构也使得控制器极易成为DoS攻击的目标.为解决这一问题,现对SDN中的DoS攻击进行全面的研究,并提出一种轻量有效的MinDoS防御机制,该机制主要由简化的DoS攻击探测模块和优先级管理模块这2个核心模块实现.该机制可以根据用户信任值将流请求分类并将其划分到具有不同优先级的多个缓冲队列,然后使用SDN控制器以双轮询机制来调度处理这些流请求,从而在DoS攻击下更好地保护控制器.另外,MinDoS还结合了多控制器动态调度策略来降低全局响应时间,提高用户服务质量.最后,分别在SDN单控制器和多控制器实验环境中对MinDoS防御性能进行综合评估,实验结果表明：MinDoS防御效果良好,系统设计满足预期目标.     

Input-to-State Stabilization of Nonlinear Impulsive Delayed Systems: An Observer-Based Control Approach

This paper addresses the problems of input-to-state stabilization and integral input-to-state stabilization for a class of nonlinear impulsive delayed systems subject to exogenous disturbances. Since the information of plant’s states, time delays, and exogenous disturbances is often hard to be obtained, the key design challenge, which we resolve, is the construction of a state observer-based controller. For this purpose, we firstly propose a corresponding observer which is independent of time de...     

Dynamic Event-Triggered Consensus Control for Input Constrained Multi-Agent Systems With a Designable Minimum Inter-Event Time

This paper investigates the consensus control of multi-agent systems(MASs) with constrained input using the dynamic event-triggered mechanism(ETM). Consider the MASs with small-scale networks where a centralized dynamic ETM with global information of the MASs is first designed. Then, a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale networks. It is shown that the semi-global consensus of the MASs can be achieved by the designed bounded control...