The Research On Security Control Of Cyber-physical Systems Under Denial-of-service Attacks

Cyber-Physical System(CPS)is a large-scale complex system with deep integration and collaborative design of cyber layer and physical layer.CPS has been widely used in various fields due to its highly integrated and highly networked characteristics different from traditional control systems.The open sharing of cyber layer brings more efficiency to the practical application of CPS,at the same time,it also increases the risk faced by CPS.Among these potential risks,network attacks have become the primary security problem to be solved by CPS because of its great destructive power.Among them,Denial-of-Service(DoS)attack is the most common and easy to implement type of network attack.It can cause the system to reject the normal data receiving and sending requests by occupying the network resources of the communication channel.From the control point of view,this paper studies the CPS security control under DoS attack.The specific contents are as follows:First of all,considering the diversity of CPS packet loss,it is assumed that the probability characteristics of the evolution of the total number of packet loss have an upper limit,and the inherent packet loss Markov process and DoS attack Markov process satisfying this constraint are analyzed respectively.On this basis,the independent description of the two packet loss factors is given.In order to save the bandwidth resource of CPS network layer,the event triggering mechanism is introduced,and the asymptotic stability of CPS with Markov packet loss process under the action of event triggering control rate is studied.According to the obtained stability conditions,the calculation method of the state feedback controller is given.The simulation results show that the proposed method can not only save network resources but also ensure system stability.Secondly,further consider the diversity of DoS attack in attack channel selection.On the one hand,the attacker can attack in the output channel or feedback channel,thus modeling the CPS under attack as a switching system with three types of situations;on the other hand,the DoS attack is random and continuous,and the CPS under attack can be modeled as a nested switching system on the basis of three types of subsystems,and the number of subsystems of the switching system is dynamically variable.For the uncertain switching system which is affected by DoS attack and changes in real time,the controller will continuously calculate a series of control quantities during DoS attack and send them together when the data can be transmitted to compensate for the lost information at the device end.Then,the exponential stability condition of CPS is given,and the dynamic output feedback controller satisfying the condition is designed.The validity of the proposed method is verified by a networked inverted pendulum model.Finally,from the more practical situation,the influence of intelligent DoS attack on CPS is studied,and the hierarchical design of security control method is carried out.The socalled intelligent DoS attack means that the attacker will consider the attack cost under energy constraints and choose the most favorable strategy for himself.Therefore,this paper analyzes the optimal strategy of attack and defense in the game process,and the optimal packet transfer rate of CPS cyber layer under this strategy pair is obtained.The exponential stability of the physical layer is analyzed,and the sliding mode control method is proposed according to the obtained CPS exponential stability condition.Numerical simulation shows that the game strategy and control method can ensure the stability and security of CPS.