The Algorithm Designs For The Networked Control System Under The Network Attacks

With the rapid development of computer technology,control technology and communication technology,the Networked Control System(NCS)has gradually become a research hotspot in the field of control.NCS has the advantages of low system wiring cost,strong system scalability,convenient information sharing,as well as convenient remote control,maintenance and diagnosis.However,while the convenience is brought into NCS by the communication networks,so did its disadvantages,such as packet loss,time delay,and out-of-order data packets.At the same time,it also faces network attacks.Aiming at the network attacks in NCS,the work of this dissertation is as follows:(1)For the detection of replay attacks in NCS,a method of real-time detection of replay attacks using active packets loss technology is designed.The replay attacks discussed in this article occurs in the feedback loop network,and the active packets loss used for detection happens in the forward path.The effectiveness of the detection method is firstly proved at the theoretical level.Taking a four-wheeled vehicle as the controlled object,the effectiveness of the method is further verified by the simulation results.In order to determine the optimal active packets loss rate,the vehicle's detection results for replay attacks and speed tracking results are taking into consideration,and the range of the optimal active packet loss rate of the vehicle is determined to be 12% to16%,which can ensure that the replay attacks is detected accurately and that the vehicle is drived smoothly.(2)Based on the detection method of replay attacks proposed in this dissertation,a dual channel and dual LQG control redundancy method is designed to defend against the replay attacks.When one of the channels is attacked by replay attacks,the control signal sent from the other channel will be sent to the actuator by the selection unit,so as to alleviate the adverse impact on NCS when one of the channels is attacked by the replay attacks.With four-wheeled vehicles is used as the controlled object,the harm of the replay attacks and the effectiveness of the defense method are verified by the simulation results.(3)Aiming at the problem of DoS attacks in NCS,the DoS attacks and the network packet loss is distinguished from theoretical point,and according to the difference between which,the detection of DoS attacks based on channel power snooping is proposed.On the basis of detection,a multi-step predictive control algorithm is used to mitigate the impact of DoS attacks on NCS,and to give enough time to the artificial elimination of the attack source to ensure that the system can operate stably during this period.Finally,the effectiveness of the detection method and defense method is verified by simulation results.Finally,the work of this dissertation is summarized,and the future work is prospected.