Research On Robust Security Control Of Cyber-physical Systems Under Periodic DoS Attacks

In recent years,with the deep integration of informatization and industrialization and the development of digital economy,cyber-physical systems(CPSs)have received extensive attention and research as a new generation of intelligent systems.While the CPSs realizes remote real-time sensing and dynamic control,it also causes security threat.With the increasing openness of computer control networks,problems such as the occupation of network bandwidth resources caused by denial-of-service(DoS)attacks by blocking data transmission cannot be ignored.In addition,CPSs are in various complex environments,and there are often uncertainties and external disturbances in the actual operation process.In order to solve these existing system problems,this thesis adopts sliding mode control method and event-triggering mechanism,the robust security control issues of CPSs under periodic DoS attacks are studied.The main work scope is as follows:(1)Using the method of state feedback control,the security control of CPSs under periodic DoS attacks is studied.First,assuming that the periodicity of DoS attacks is known,and modeling it as a piecewise function,a time-triggered state feedback controller is designed.Second,the sufficient conditions that the controller parameters,time trigger period and periodic DoS attacks period need to be satisfied when the system is stable are given.Finally,the effectiveness of algorithm has been verified and validated through simulation examples.(2)Based on the research done from work(1),the sliding-mode control(SMC)method is used to achieve robust stabilization of the CPSs under periodic DoS attacks subject to bounded external disturbances.First,it is also assumed that the periodicity of DoS attacks is known and modeled as a piecewise function.Second,a new type of segmented SMC law is designed,and the sufficient condition respect to the controller parameters,the attack period and the upper bound of external disturbances need to satisfied are also given.Under this sufficient condition,the sliding surface is reachable,thereby achieving the stability of the closed-loop system.Finally,the effectiveness of algorithm has been verified and validated through simulation examples.(3)Based on the control algorithm of work(2),the event-triggering technology is combined with SMC,which can effectively save communication and computing resources while achieving robust stabilization of the system.First,based on the linear sliding surface designed in work(2),the event-triggering mechanism based on the linear sliding surface parameters and state measurement errors is designed.Second,an event-triggered sliding-mode controller is designed.Under a sufficient condition related to the event-triggered threshold,the siliding surface is reachable.At the same time,through the theoretical calculation of the lower bound of the event-triggering interval,it is proved that the Zeno phenomenon does not appear in the system.Finally,two simulation examples are compared in order to verify the effectiveness of algorithm.