On The Robust Synchronization Control Methods For Chaotic Secure Communication Systems Based On Sampled Data

Because of the unique charm, chaos has become a hot research focus of both domestic and foreign scholars. In recent years, chaos synchronization and its application in secure communication have aroused of wide attention. However, most of the research results focus on continuous-time controller for the synchronization problem of chaotic system. With the popularity of digital circuit, digital circuit in the communication system gradually takes the place of the analog circuit and becomes a hot research topic. In this dissertation, on the basis of a comprehensive and systematic research of related literature, the robustness synchronization control of the chaotic secure communication system based on sample data is studied, the main contributions are as follows:Firstly, considering a class of data-sampled chaotic system with uncertainties and external interferences, a robust H∞controller is designed. The sampling system is described by an input delay approach. The MLC (Murali-Lakshmanan-Chua) chaotic circuit is taken for an example. Numerical simulation results show that the designed controller can achieve synchronization of the two chaotic systems, and has a good suppression of external disturbances. Based on chaos synchronization, a chaotic secure communication system is built using chaotic masking technique, which achieves the secure communication of useful signals.Secondly, the synchronization controlling problem of chaotic systems with uncertainties and time-varying delay is investigated. For the master and slave systems with time-varying delay, a sufficient delay-dependent robust stability condition is given by applying linear matrix inequalities and Lyapunov stability theory. The synchronization method is applied to chaotic secure communication system, which is established by the Chua’s circuit. Numerical simulation results show the effectiveness of this method.Thirdly, for a class of chaotic system with disturbance based on sampled-data, a test function is constructed and the worse destroy case for the system which is caused by the disturbance is considered according to the system’s states. A synchronization controller is designed in that case which ensures the error system asymptotically stable. A stability theorem is given to achieve the synchronization of the two chaos systems. Based on the synchronization platform, communication signals can be masked completely by chaos signals. In the following, the Chua’s circuit is considered to illustrate the effectiveness of the controller designed.Finally, the main work of this dissertation is summarized and some future research directions are put forward.