Event-Triggered Security Control Of Cyber-Physical Systems Under Denial-of-Service Attacks

With the deep development of informatization and industrialization,cyberphysical system(CPS),which integrates computing,communication,and control technologies,has emerged and been widely used in critical infrastructures,such as industrial internet,smart power grid,intelligent transportation system,etc.The realtime interaction between the cyber world and the physical process realizes the autonomy and cooperation of the whole system.However,the mutual influence of information security threats and engineering safety issues brings great challenges to the security protection of CPS.In recent years,frequent network accidents have made CPS security control research a frontier hot issue in the field of automation.In essence,CPS is a complex networked control system with a feedback mechanism,and its ubiquitous interconnection characteristics make it increasingly open.At the same time,system developers often neglect the protection of the inherent security of CPS.Once the security defense mechanism deployed on the information side fails,malicious adversaries can invade the information system,leading to the chain propagation of CPS-induced failures,thereby causing serious non-contact damage to physical process.On the other hand,in the process of sensing and collecting the physical equipments,CPS can generate massive data based on time series,which undoubtedly aggravates the risk of useless data blocking communication networks with limited bandwidth.Therefore,from the perspective of resource-aware security control,this paper studies the event-triggered security control of CPS under denialof-service(DoS)attacks,so as to ensure that CPS can operate safely in an unreliable network environment under the premise of maximum protection of communication resources.The main research contents of this paper are as follows.(ⅰ)The event-triggered robust security control problem of continuous-time nonlinear CPS under DoS attacks is studied.Firstly,nonlinear CPS is approximated processed based on T-S fuzzy model.Secondly,a discrete event-triggered control strategy without Zeno behavior is proposed,and the assumption of the full state information availability is relaxed.Inspired by the maximum transmission interval,a robust fuzzy controller design strategy is proposed,which enables the closed-loop system to achieve input-to-state stability under DoS attacks.Finally,based on the average dwell time method and iterative method,the maximum tolerable duty cycle of the system is given.Under the robust security control strategy,the system shows strong robustness to external disturbances,measurement noise,and DoS attacks.(ⅱ)The event-triggered distributed security control problem of continuoustime linear interconnected CPS under DoS attacks is studied.Firstly,a distributed event-triggering rule with independent and asynchronous properties is developed,and neither Zeno behavior nor singular triggering behavior occurs.Secondly,the continuous Markov process is introduced to describe the numerous communication topologies generated by DoS attacks.On this basis,a switching distributed security controller design strategy is proposed,which can enable each follower to track the leader asymptotically under DoS attacks.Finally,the tolerance of the controller to DoS attacks is quantified by characterizing the attack duration and frequency.(ⅲ)The event-triggered fixed-time security control problem of continuoustime nonlinear interconnected CPS in the presence of DoS attacks is studied.Firstly,a distributed event-triggering rule with fractional power term is proposed,and neither Zeno behavior nor singular triggering behavior occurs.On this basis,a selftriggering rule that avoids continuous communication is designed to further reduce the conservatism of event-triggering rules.Secondly,a fixed-time distributed controller design based on symbolic function is proposed to ensure that the system achieves secure leader-following consensus in a fixed time.Finally,for the situation that the directed paths from the leader are interrupted by DoS attacks,a fixed-time distributed observer design strategy is proposed to ensure that all followers can accurately estimate the information of the leader state in a fixed time.(ⅳ)The event-triggered robust security control problem of continuous-time stochastic jump CPS in the presence of DoS attacks is studied.Firstly,based on a security-oriented resilient method,a stochastic event-triggering rule relying on DoS attacks is proposed.Secondly,the maximum tolerable downtime of the system is obtained by an iterative method.Finally,the delay-dependent Lyapunov-Krasovskii functional is constructed,and the related event-triggered robust security controllers are designed when the transition rate is exactly known and uncertain,thus achieving the co-design of feedback gains and trigger parameters.(ⅴ)The event-triggered dual-mode security control problem of continuoustime stochastic jump CPS under DoS attacks is studied.Firstly,a stochastic eventtriggering rule is proposed to characterize different data transmission behaviors under DoS attacks.Secondly,by analyzing the internal relationship between system modes and event-triggering instants,it is proved that Zeno behavior and singular triggering behavior do not occur.Finally,according to the current network service quality,an event-triggered dual-mode security controller is proposed to ensure the stable operation of the system under DoS attacks.The control strategy makes full use of the system information while ignoring data loss caused by intermittent DoS attacks,thus achieving higher control performance.