Investigations On Some Issues Of Event-triggered Networked Systems Subject To Cyber Attacks

Networked systems introduce a communication network to implement the communication between control components,which have the advantages of low cost,easy maintenance,convenient extension,etc.,and then have been applied in a broad range of areas.However,it can be noticed that the limitation of network bandwidth resources brings about such problems as time delay,packet dropout and so on,which influence the stable operation of networked systems.In order to decrease the times of data transmission and save the resources of limited bandwidth,much attention from scholars has been attached to event-triggered scheme when investigating the stability analysis,control and filtering problems for networked systems,and a rich body of research results are available.Meanwhile,it is worth noting that due to the openness of network,data transmission for networked systems are prone to be threatened by cyber attacks.Upon networked systems are controlled by malicious attackers,the aftereffect may not be estimated.In recent years,the research on the security problem of data transmission has not been fully investigated for networked systems.Therefore,it is of great theoretical and practical significance to study the impact of cyber attacks on networked systems.Moreover,owing to the physical constraints and technological restrictions,saturation phenomenon,as one of the factors affecting control system performance,commonly exists in components of networked systems.Based on the previous observations,the main research contents of this thesis are as follows:(1)For networked cascade control systems(NCCSs)subject to actuator saturations,hybrid-triggered scheme is introduced to reduce network load while improving system performance.Furthermore,taking stochastic deception attacks into consideration,a delay system model for NCCSs is firstly constructed.Based on the new model,the sufficient conditions guaranteeing the asymptotically mean-square stability for NCCSs are obtained with an H? norm bound by using Lyapunov stability theory.What's more,the gains of both primary and secondary controllers in NCCS are achieved by applying linear matrix inequality(LMI)techniques.Finally,a power plant gas-turbine system is presented to illustrate the usefulness of the designed state feedback controllers.(2)Distributed event-triggered filtering over sensor networks with sensor saturations and stochastic deception attacks is investigated,and then a new model of filtering error system is established.On the basis of the novel model,criteria for asymptotically stability with performance for filtering error system are obtained by means of Lyapunov stability theory.Moreover,the explicit expressions of distributed filters are achieved by solving a set of LMIs.Finally,an example of a stirred tank reactor and a numerical example are simulated to verify the usefulness of the designed distributed filters.(3)The problems concerning the restriction of limited bandwidth resources and the security of data transmission are discussed when a communication network is introduced into multi-area power systems.To be more specific,the issue of event-triggered load frequency control(LFC)for multi-area power systems is studied by considering the threat of denial-of-service(DoS)attacks and stochastic deception attacks,and then a new mathematical model is established.In view of the new model and by adopting Lyapunov stability theory,sufficient conditions ensuring multi-area power systems exponentially mean-square stable are acquired and the H?performance is analyzed.Moreover,criterion for designing the controller gain matrix is derived by utilizing LMI technique.Finally,the usefulness of the designed controller is demonstrated based on the simulation of a three-area LFC power system.