Researches On Networked Control Systems Based On Event-triggered Mechanism Under Cyber-attacks

Since the 1980s,computer networks have been widely used in the field of automatic control.With the rapid development of computer,communication technologies,and the increasing scale of control systems,networked control systems(NCSs)based on fieldbus or other communication networks have been widely proposed and applied.However,the insertion of communication network leads to many problems,such as limited resources,communication delay,packet loss and disorder,and cyber-attacks.Aiming at the issue of resource constraints,though the event-trigger scheme to reduce the cost of data transmission and controller calculations were widely studied for the NCSs,it's regretful that the triggering mechanisms cannot fully utilize the real-time information of the controlled system.Especially,the effects of accumulated cyber-attacks and intermittent deception attacks have not been fully considered when studying the cyber-attacks,and the research on dissipativity for networked control systems based on event-triggered technique has not appeared yet.Based on the deficiencies of existing works,this dissertation aims to investigate the event-triggered mechanism,cyber-attacks and dissipative control for the NCSs,which can present some meaningful results.The main contributions and contents are as the following points.Firstly,a distributed adaptive event-triggered mechanism is initially designed for the NCSs under stochastic cyber-attacks.Supposing that the network is subject to normal cyber-attacks and accumulated cyber-attacks together such that a closed-loop system model is achieved considering the statistical characteristics,then a mixed delay-dependent functional is constructed after taking the communication delay and cyber-attacks delay into consideration,and a co-design scheme of the event trigger and controller with less conservatism and easy verification is established with the help of the new integral inequality and reciprocal convex technique.Secondly,for the NCSs subject to both intermittent cyber-attacks and exogenous disturbance,a disturbance-sensitive adaptive event-triggered mechanism is designed,a corresponding intermittent cyber-attacks model is established,and a switching controller is designed based on the attack features.Then two augmented exponential functionals based on mixed delay-dependence are constructed to derive some sufficient conditions on global exponential stability for the closed-loop system.Furthermore,a co-design scheme of the event-trigger and controller gain based on linear matrix inequality(LMI)is established with the help of matrix transformation and variable substitution techniques.Especially,the exponential decay rate is employed to give an algorithm which can be used to calculate the minimum intermittent interval of the cyber-attacks.Finally,for the NCSs under the exogenous disturbance and parameter uncertainties,an improved disturbance-sensitive adaptive event-triggered mechanism is proposed.Based on state feedback controller,the closed-loop system model is established.Then an augmented exponential functional is constructed,which can make full use of the information on communication delay and time-varying triggering threshold.Thus,some sufficient conditions are obtained which can ensure the stability and dissipativity of the closed-loop system.Moreover,the co-design of the event-trigger and controller is presented.In the end,the controller gain and event-triggering parameters for the performance on dissipativity,_?control,passivity,and the combined_?control with passivity can be respectively obtained by selecting the appropriate dissipative parameters.