Research On Event-triggered Security Control Of Networked Control System Under Denial Of Service Attacks

With the development of automatic control technology and communication technology,traditional point-to-point control systems are gradually being replaced,and the Networked Control System(NCS)has emerged at the historic moment.The introduction of shared communication networks has also accelerated the popularity of networked control system,making networked control system not only involve military,political,social life and other aspects,but also show its value and importance in more and more fields,but with the increase of cyber attacks methods,the networked control system also faces many security problems.Among the many forms of cyber attacks,the most commonly encountered cyber attacks is the Denial of Service(DoS)attack.Due to its simple operation and obvious effects,DoS attacks are favored by attackers.DoS attacks send a large amount of useless data information to the communication channel,occupying or even exhausting the system's communication resources,so that communication data cannot be transmitted timely and efficiently,and the closed-loop networked control system has real-time requirements.If a DoS attack is encountered,the performance of the control system will be seriously affected,and in extreme cases,the system will be unstable.Therefore,in this thesis,in response to DoS attacks on networked control system,event-triggered control is combined with switching systems theory method and linear matrix inequality technology to analyze and study the networked control system,in order to achieve the goal of system stability control.The main tasks as follows:(1)The purpose and significance of the topic are described,and the research works of communication constraints inherent in the networked control system are introduced.The research results of DoS attacks that often occur in the networked control system are summarized by classification.At the same time,combined with the research direction,the security control research work of the networked control system based on the event triggering mechanism under DoS attacks is described.Finally,an overview of the basic theory related to this article is given.(2)Aiming at the situation where the measurement channel of a linear networked control system is subjected to a DoS attack,the design of the output feedback controller of the networked control system is studied.Considering the delay,packet loss and other factors caused by DoS attacks,a closed-loop networked time-delay system model is established based on the elastic event triggering mechanism.Based on this,the system stability analysis is performed,and based on the new Lyapunov functional,the maximum duration of the DoS attack allowed by the system is derived,and the flexible event triggering mechanism and the output feedback controller are collaboratively designed.(3)Aiming at the situation that the measurement channel and the control channel are subject to DoS attacks at the same time,the design of the guaranteed performance controller of the networked control system is studied.By analyzing the DoS attack time and data transmission characteristics,combi ning the event triggering detection rules and the strength of the DoS attack,the networked control system is modeled as a type of non-uniformly sampled discrete switching system.Based on the established networked system model,sufficient conditions for t he exponential stability of the closed-loop system are given using the average dwell time method,and a state feedback controller is designed to achieve the stabilization control of the networked control system.(4)The security control of networked control system with uncertainty in DoS attacks environment is studied.Based on the elastic event triggering mechanism,a robust control method is used to transform the uncertain system into a type of virtual system with the best performance function,and the du ration and frequency of DoS attacks are characterized;at the same time,based on the established networked system model,A robust controller is designed to ensure the input to state stability(ISS)of the networked control system.Finally,the full thesis work is summarized,and the future research direction of this subject is analyzed and prospected.