Chaotic Synchronization Via Variable Structure Methods And Its Application To Secure Communication

In the past decades,the security of information has attracted considerable attention due to the increasing popularity in computer and communication technology,which makes secure communication become one of the key technology in communication areas.Characteristics such as imperceptibility,aperiodicity and noise-like make the chaotic signal especially suitable for secure communication.Implementation of chaotic synchronization has provided the theoretical basis for the secure communication,making the chaotic synchronization and its application become a potential high-tech.This thesis investigates the following synchronization problems:Sliding-mode synchronization for nonidentical Markovian jump neural networks with partially unknown transition probabilities;Variable structure synchronization for switched time-delay neural networks subject to packet dropouts;Network-based synchronization via variable structure control with stochastic actuator activation and its application to secure communication.The main contents of this thesis are summarized as follows:1.An integral sliding mode control is designed for synchronization of two nonidentical Markovian jump neural networks with leakage delay,discrete time-varying delays and partially unknown transition probabilities.Based on a mode-dependent Lyapunov-Krasovskii functional combined with Finsler's lemma,delay-dependent conditions guaranteeing the mean-square exponential stability of the synchronization error dynamics in sliding mode are derived in terms of linear matrix inequalities.Then,a sliding mode synchronization controller is designedsuch that the synchronization error system's trajectories converge to predefined sliding surfaces in a finite time and remain there for all subsequent times.2.The problem of variable structure synchronization for switched time-delay neural networks subject to packet dropouts is concerned.A randomly switched variable structure control law is proposed to achieve the complete synchronization of the master system and the slave system in the sense that the trajectories of the error system are ultimately mean-square bounded for any switching signal with some average dwell time constraint.3.The problem of network-based synchronization via fuzzy variable structure control considering network-induced delay and stochastic actuator assignment.By means of an input-output method,sufficient conditions are proposed to ensure mean-square ultimate bounded stability of the synchronization error system.The controller gains can be obtained by solving a set of linear matrix inequalities.Simulation results are given to validate the effectiveness of the proposed criteria of variable structure synchronization and to present an application of the proposed variable structure synchronization method to secure communication.