Chaotic Synchronization And Its Application In Secure Communication

There are lots of chaotic phenomena in real word. Knowledge on chaos is one of important achievements in nonlinear science. With the further research of chaos, chaos control becomes an advanced research field. In this thesis, the problem of the chaos synchronization and application to secure communication is studied deeply and widely. The detail is clarified as follows:First of all, the dissertation discusses systematically basic concepts; main feature, measure, research method, and theoretical foundations of utilizing chaos in communication system are investigated briefly, which establishes foundation to research it systematically and profoundly. Secondly, the paper discussed the problem of chaos synchronization. The main results are: (1) Make use of the Lyapunov stability theories, adopt to install the method that combine with pole placement control and adaptive control together to design the controller; and adjust the parameters according to adaptive theory. That method realized availably chaotic synchronization of the systems, and has strong robustness to parameters mismatching and noise. Opposite in pure adaptive control, the join of adaptive adjustment to parameters accelerates the speed of synchronization, and increases the robustness of the system. (2) Considering the existence of random disturbance, we realize the chaos synchronization based on the state observer. Even when the disturbance is very large, the system still synchronization well. In addition, the method don't need the Lyapunov's exponent of system synchronization, and we can adjust the observer parameters properly to satisfy with the better performance index demand; (3) A kind of synchronization technique is presented based on variable structure system control theory and above conclusion in the dissertation. Chaos synchronization problem is particular with two points, that is, both the thickness of sliding mode field at equilibrium point and output of controller at equilibrium point should be zero.Finally, the paper discussed the problem of chaos secure communication.The main results are: (1) based on the observer, which is wildly used in practical application, we realize the system of secure communication. The designed secure communication system overcomes some disturbance effects, such as channel noise. (2) Based on the adaptive controller, we realize the system of secure communication. The system has strong robustness to noise.