【作者】 刘丹；

【导师】 叶丹；

【作者基本信息】 东北大学 ， 控制理论与控制工程， 2022， 博士

【摘要】 复杂动态网络(Complex Dynamical Network,CDN)广泛存在于自然界、社会生活和工程领域中,因其在工程、生物、数学、医药卫生、交通运输、物理、军事等领域有巨大的潜在应用而备受关注。同步行为是CDN最具代表性的研究课题之一,它不仅能帮助我们理解网络结构对同步能力的影响,从而指导我们高效地构造网络,而且还能通过对其进行有效控制来提高同步效益或降低有害同步的影响。随着网络技术的迅猛发展,CDN不再是单纯的物理系统,而是一个信息与物理高度融合的信息物理系统。毫无疑问,在信息物理系统框架下的CDN必然会面临恶意攻击的威胁。因此,当CDN遭受恶意攻击时,如何设计有效的安全策略来降低攻击对网络同步性能的影响,进而减少损失,是亟待解决的问题。目前,CDN的安全同步控制研究仍处于起步阶段,许多新的挑战有待解决。例如,现存大多结果仅考虑了连接边受到恶意攻击的情况,而忽略了测量通道和控制通道遭受网络攻击的情况。另外,现有结果所提出的安全同步策略大多依赖网络通讯拓扑等全局信息,然而在实际应用中很难,甚至不能获取这样的全局信息。本文在现有工作的基础上,以一类遭受恶意攻击的CDN为研究对象,利用Lyapunov稳定性理论、比较理论、图论、线性矩阵不等式等理论方法,并结合自适应技术和切换技术,研究了CDN的安全同步控制问题。本文的主要内容归纳如下:第一、二章系统地介绍了CDN的研究背景与意义、CDN及其同步控制研究现状、现存研究的不足与挑战,并给出了与本文相关的预备知识。在信息物理系统框架下,第三章研究了拒绝服务(Denial-of-Service,DoS)攻击下CDN的安全同步控制问题。首先,仅利用牵制节点的测量输出,设计一个基于牵制节点的观测器估计系统中所有节点状态。与现有仅考虑系统在绝对安全的网络环境下所得的结果不同,本章考虑了测量通道(传感器——估计器)和控制通道(控制器——执行器)同时遭受DoS攻击的情况。当攻击者处于激活状态时,这两个通道被堵塞,导致信息不可用。通过Lyapunov稳定性理论和比较理论,给出DoS攻击下的CDN安全同步控制方案。最后,对一个由蔡氏电路组成的CDN进行仿真,验证所得理论结果的有效性。第四章研究了异步恶意攻击下的CDN安全同步控制问题。现存工作主要考虑节点之间的连接边遭受攻击或者控制通道(控制器——执行器)遭受DoS攻击的情况。本章考虑更一般的情况,即这两种类型的攻击同时存在,且异步发生的情况。此外,为了克服系统状态不可用带来的困难,仅利用牵制节点的测量输出设计观测器估计系统状态,进而用于设计牵制控制器。对于现实中的大规模复杂动态系统,这样的观测器更具实用性。通过构造一个分段Lyapunov函数,给出确保CDN在异步攻击下的安全同步标准。最后,将设计的安全同步方案应用于由蔡氏电路构成的CDN中,验证所得理论结果的有效性。第五章研究了连接攻击下基于边的分布式自适应安全牵制同步控制问题。这里所考虑的连接攻击是一类以破坏邻居节点之间的连接为目的的恶意攻击。在这种不安全的网络环境下,针对耦合强度和耦合增益设计两种基于边的分布式自适应更新策略(即同步更新策略和异步更新策略),进而实现CDN的安全同步控制。然后,利用边牵制技术,把相应的安全同步分析推广到仅更新部分耦合强度和耦合增益的情况。值得注意的是,这些安全策略是在完全分布式框架下获得的,不需要任何全局信息。最后,通过一个例子验证所得理论结果的有效性。第六章针对控制通道遭受DoS攻击的情况,在第五章的基础上研究了 CDN的安全群集同步控制问题。首先,设计一个自适应策略更新耦合权值和耦合增益。该策略是在完全分布式框架下提出的,即不利用网络拓扑或网络节点数量等任何全局信息。然后,进一步把DoS攻击下的安全群集同步分析推广到仅更新部分边耦合权值和增益的情况。通过构造带指数项的Lyapunov函数,给出相应的安全群集同步条件,同时也给出系统所能容忍的DoS攻击持续时间占比条件。最后,所提出的理论结果通过对一个由蔡氏电路构成的CDN进行仿真得到验证。第七章针对一类事件触发耦合CDN,研究了其在连接攻击下的安全同步控制问题。这里所考虑的连接攻击是一类针对每条连接边的攻击都是相互独立的恶意攻击,这就意味着存在多种针对通讯拓的连接攻击模式。然后,通过构建多模式连接攻击的相关模型,分析多模式连接攻击对同步误差系统的影响。与此同时,为了减少通讯负担和节约耦合资源,建立了一个基于数据采样的事件触发耦合机制。在这种情况下,仅需要在离散的采样时刻监视触发条件。通过利用Lyapunov理论和一些不等式技术,给出确保CDN在多模式连接攻击下的安全同步条件。最后,将设计的安全同步控制方案应用于由蔡氏电路构成的CDN中,验证所得理论结果的有效性。第八章总结了全文的成果与不足并对未来研究方向进行了探讨。更多还原

【Abstract】 Complex dynamical network(CDN)widely exists in nature,social life,and engineering fields,which has attracted much attention due to its huge potential applications in engineering,biology,mathematics,medicine and health,transportation,physics,military,and so on.The synchronization behavior of CDN is one of the most representative research topics.It is not only conducive to comprehending the influence of network structure for synchronization ability,so as to guide us to efficiently construct network,but also improves the synchronization efficiency or reduces the influence of harmful synchronization through effective control.With the rapid development of network technology,CDN is no longer a simple physical system,but a cyber-physical system with high integration of information and physics.There is no doubt that CDN under cyber-physical system framework is inevitable to face the threat of malicious attacks.Therefore,when CDN suffers from malicious attacks,how to design an effective security strategy to reduce the impact on attacks for synchronization performance and reduce losses is an urgent problem.At present,the study on the security synchronization control problem of CDN is still in its infancy and many new challenges remain to be solved.For example,most of the existing results only consider the case where link edges are attacked but ignore the case where the measurement and control channels suffer from cyber attacks.Moreover,most of the existing results on security synchronization strategies are dependent on communication topology,but it is difficult or even impossible to be acquired such global information in practical applications.Based on the existing works,a class of CDN subjected to malicious attacks is taken as the research object in this thesis,by employing the Lyapunov stability theory,comparison theory,graph theory,linear matrix inequality,and other theoretical methods,combing with adaptive technology and switching technology,the security synchronization problem of CDN is investigated.The main content of this thesis is summarized as follows.Under the framework of cyber-physical systems,Chapter 3 investigates the secure synchronization control problem of CDN subject to denial-of-service attacks.First,a pinning-nodes-based observer,which only utilizes the measurement outputs of pinning nodes,is designed to estimate the states of all nodes in system.Different from the existing results where the network environment is secure,denial-of-service(DoS)attacks are considered in the measurement(sensor-to-estimator)and control(controller-to-actuator)channels.These two channels will be blocked by DoS attacks when the attacker is active.By the theories of Lyapunov and comparison,the secure synchronization control scheme of CDN under DoS attacks is given.Finally,the availability of the obtained theoretical outcomes is confirmed by utilizing a CDN composed of Chua’s circuits.Chapter 4 studies the secure synchronization control problem of CDN against asynchronous attacks.Existing works mainly consider the case that the link edges between nodes suffer from attacks or the control channels(controller-to-actuator)suffer from DoS attacks.This Chapter considers a more general case where both types of attacks occur asynchronously.Besides,to overcome the difficulty caused by the unavailability of state system,only the measurements of pinning nodes are used to design the pinningnodes-based observer to estimate all system states,which is then used to design pinning controller.Such an observer is more realistic for large-scale complex systems.By establishing a piecewise Lyapunov function,the secure synchronization criteria of CDN under asynchronous attacks are obtained.Finally,the proposed security synchronization scheme is applied to a CDN composed of Chua’s circuits,and the availability of the developed theoretical results is verified.Chapter 5 investigates the edge-based distributed adaptive security pinning synchronization control problem under link attacks.The link attacks considered here are a class of malicious attacks aimed at breaking the links between neighboring nodes in CDN.In such an insecure network environment,two kinds of edge-based distributed adaptive update strategies(synchronous and asynchronous)for coupling strengths and gains are designed to realize the security synchronization control for CDN.Then,by virtue of the edge pinning technique,the corresponding security synchronization analysis is extended to the case where only partial coupling strengths and gains are updated.It is worth noting that these designed adaptive strategies are obtained in a fully distributed framework,and do not require any global information.Finally,the availability of the achieved theoretical outcomes is verified by a numerical example.In Chapter 6,for the case where control channel suffers from DoS attacks,the security cluster synchronization control for CDN is investigated based on Chapter 5.First,an adaptive strategy is designed to update coupling weights and gains.This security strategy is developed in a fully distributed framework,i.e.,it does not use any global information,such as network topology,the number of nodes,and so on.Then,the security cluster synchronization analysis under DoS attacks is extended to the case where only partial coupling weights on edges are updated.By constructing the Lyapunov functions with exponential terms,the corresponding security cluster synchronization conditions are presented,and the DoS attack duration ratio that system can tolerate is also obtained.Finally,the proposed theoretical results are validated by simulation of a CDN consisting of Chua’s circuits.In Chapter 7,the security synchronization problem of a class of event-triggered coupling CDN under distributed link attacks is studied.The link attack considered here is a class of malicious attack that attacks for link edges are independent of each other,which means that there are multiple attack patterns for communication topology.Then,the relevant model of link attacks with multiple patterns is constructed to analyze the effect on synchronization error system.Meanwhile,to reduce communication burden and save coupling resources,a sampled-data-based event-triggered coupling mechanism is established.In this situation,the triggering condition is supervised only at discrete sampling instants.By employing Lyapunov theory and some inequality techniques,sufficient conditions are given to guarantee synchronization against link attacks with multiple patterns.Finally,the proposed security synchronization scheme is applied to a CDN composed of Chua’s circuits,and the availability of the obtained results is verified.In Chapter 8,the achievements and deficiencies of the dissertation are summarized and the future research directions are discussed.更多还原