Secure Control And Network Simulation Of Cyber-physical Systems

Cyber-Physical System(CPS)integrates physical process into the computing process.The computing process controls the physical process through network monitoring and computing,and the physical process affects the computing process through feedfack to complete the interaction between them.Cyber-physical systems have become the main symbol of the fourth industrial revolution.The next generation industry will be built on the CPS.With the development and popularization of CPS technology,the physical equipments that use the computer and network to realize the function expansion are everywhere,and will promote the upgrading of the industrial products and technology.CPS is becoming more complex,open and more vulnerable to security threats.Therefore,security has become a key factor to be considered.The main contents of this thesis include the following aspects:(1)As CPS is a dynamic hybrid system,the safety verification method of hybrid system—reachability analysis is studied.The reachability calculation means that all possible behaviors covered by finite number of simulation steps to ensure that the system trajectories stay in safe sets.In this thesis,the dynamical model of a pair of satellites formation flying is studied.Using the reachability analysis,the following satellite can safely reach the target set through a finite number of simulation steps.With the increasement of the number of simulation steps,the computation complexity increases dramatically.In order to simplify the computation of the reachable set,a general diamond method is proposed to carry out the internal approximation of the convex set.Simulations show that a good control performance is obtained,which makes the following satellite to reach the target set smoothly.(2)A game theory approach is adopted to the secure control of physical plant of CPS.A minimax controller is designed and applied on the simulation of a two tank system.This controller is resilient to the system under attacks especially to the time-varying delay attacks.At the same time,a LQG controller is designed for comparison.When the LQG controller is attacked by time-varying delay,the system tends to diverge and is not stable.The advantages of the designed controllers are demonstrated by comparison.(3)For the complete cyber-physical system,there is not a perfect simulation tool combining network,communication and control functions.The GISOO virtual testbed developed by José Araújo of the Royal Institute of Technology can be used to combine with the simulation platform of wireless sensor nodes(Cooja),and the common control system simulation platform(Simulink).This thesis uses this platform to carry out a virtual CPS system simulation experiment,and further studies the communication mechanism and control principle of CPS,which provides a basis for the in-depth study of CPS.