Chaotic Control,Synchronization And Its Application To Secure Communication

There are lots of chaotic phenomena in the real world, such as orenz system in the meteorology, Chua circuit system and so on. Because chaotic system is extremely sensitive to the initial* condition which make the chaotic output not meet people's demand, we always need to restrain the chaos in many practical systems. On the other hand, the chaotic system is benefitial to other systems due to its hard prediction and inner randomicity, such as, the application to the secure communications. So it is very important to chaos control and application about how to restrain chaos when it is harmful and how to make use of it when it is useful. And the research on it will have theoretical significance and real applied value.In this thesis, the problem of the chaos control, synchronization and application to secure communication is studied deeply and widely. The detail is clarified as follows:First of all, the paper discussed the adaptive control and backstepping control methods of chaotic system. The main results are: 1) based on the simply linear feedback method, we discussed the chaos system control of Chen's chaotic system. When the parameters are known, we give the range of feedback gain which make the chaotic system exponentially stable. When the parameters are unknown, the chaotic system is asymptotically stable by designing an adaptive controller, which can solve the incontinuity problem in ordinary adaptive controller; 2) based on backstepping method, we addressed the control of a class of chaos system in the case of the existence of external disturbance. Finally the parameter expression of system's controller is obtained by gradually iteration. The designed system controller get over the external disturbance's effect on system and make the system asymptotically stable.Secondly, the paper discussed the problem of chaos synchronization. The main results are: 1) 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 synchronize well. In addition, the method don't need the Lyapunov's exponent of system synchronization, and we can adjust theobserver parameters properly to satisfy with the better performance index demand; 2) based on the approximation performance of neural network, by making use of RBF neural network and selecting proper online adjustment of the network weight, we realize the self-structure synchronization and the different-structure synchronization of two chaotic system, respectively, in the case of disturbance of systemmatic parameters.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 synchronization of superchaos system and apply it to chaotic secure communication in the disturbance. The designed secure communication system overcomed the disturbance effect on chaotic synchronization. The obtained results developed the results of existed papers. 2) to improve the communicative secrecy, we use multi-step superchaos secure communication system to realize the secure communication. The system of secure communication is very complicate, and this method remarkably improved the secrecy of chaos communication.