Controller Design For Nonlinear Networked System Under Cyber-attacks

In networked control systems,which are dependent on the computer networks,the nodes enable to exchange the information with their neighbors via the communication networks.For decades,the rapid advances of computer communication technologies bring about consider-able conveniences on industrial systems,and thus highly facilitate the production efficiency.The network-induced phenomena,owing primarily to the inherent limit of networks,are easi-ly encountered during data transmissions,such as the transmission delay,the packet loss,and the channel fading.On the other hand,the networked systems might suffer from the malicious cyber-attacks due mainly to their openness and sharing characteristics,including but not limited to the denial-of-service attacks,the replay attacks,and the deception attacks.In many cases,in order to achieve the purpose of destruction,attackers will not launch a single form of attack,but launch a complex form of mixed attack with stronger destructive power.Moreover,in practical applications,the target plants tend to be nonlinear,and thus it is of importance to take the non-linearity into account when investigating the control problems for networked control systems.Based on the aforementioned discussions,it is meaningful to study the control issues for the nonlinear systems undergoing cyber-attacks.In this thesis,we are interested in designing suitable controllers for the nonlinear systems with multiple cyber-attacks to guarantee the stability/boundedness on the closed-loop control systems.The organization of this thesis is arranged as follows:（1）The static output feedback control problem is addressed for a class of nonlinear delayed systems with cyber-attacks and packet losses.With the aid of the Lyapunov analysis technique,sufficient conditions are first developed to guarantee both the mean-square exponential stability and the prescribed H_∞performance index on the closed-loop control systems,and then the con-trol gains are calculated by linear matrix inequalities method and Singular Value Decomposition（SVD）method.（2）The observer-based l₂-l_∞control issue is investigated for the switched Lurie systems undergoing hybrid attacks.A hybrid attack model is presented,which is made up of the denial-of-service attack and the replay attack occurring in the communication channel.By means of the mean residence time and Singular Value Decomposition techniques,sufficient conditions are first provided to guarantee the particular l₂-l_∞performance constraints,and then the desired controller parameters are derived in terms of the solutions to some linear matrix inequalities and the use of SVD method.（3）A novel observer-based control scheme is proposed for an array of nonlinear stochastic systems with multi-attacks.To save limited network resources,the event-triggered strategy is employed in communication channel to cut down the data transmission qualities.With the aid of stochastic analysis and Singular Value Decomposition methods,a sufficient condition is first established such that the closed-loop control system is exponentially bounded in mean square.Then,the gain matrix of the observer-based controller is computed by SVD method and resorting to the solution to the linear matrix inequality.In this thesis,the effects of various forms of network attacks and network-induced phe-nomena are considered in networked control systems,the corresponding control schemes are designed and the simulation cases with actual background are used to verify their effectiveness.Therefore,the study of this thesis is not only of great theoretical value but also of great practical significance.