On Chaotic Secure Communication Systems Based On Sampled-data Synchronization Controller

Chaotic system is an extremely complex nonlinear system, and the chaotic signal with the feature of natural concealment, unpredictability, quite sensitivity to initial values, noise-similarity, is very suitable for the secure communication. With the rapid development of digital computer technology, the sampled-data control systems attract widespread attentions. However, there often exits several chaotic systems with asynchronous switching and inputs missing in sampled-data control systems, which will seriously reduce system performance or even destroy the stability of system. Therefore, in this dissertation, the sampled synchronization control issues in chaotic secure communication system are mainly studied, the main contents of the dissertation are as below:Firstly, a switched system is proposed to describe the chaotic systems with control inputs missing. And it is essentially a switched system with a stable subsystem and an unstable one. Here, control inputs missing means the zero control input. A sufficient condition is derived for the exponential stability of the system, and the obtained condition establishes the quantitative relation between the packet-dropout rate and the stability of the system. Simulation results illustrate the effectiveness of the chaotic secure communication systems based on chaotic masking techniques.Secondly, a synchronization problem is investigated for the chaotic systems with control inputs missing and delay. Based on the zero-input strategy, the switching model is established with stable and unstable subsystems, and Lyapunov-Krasovskii functional is used to prove the stability of the error system, which the designed controller can make the system achieve synchronization in a very short time. Sufficient conditions for the exponential stability of chaotic system are presented in terms of a set of LMIs, and the relation between the synchronization time and data loss rate is discussed. It is shown by simulation results that the chaotic masking technology can cover and recover the useful signal effectively.Furthermore, for the security communication system with multi-chaotic systems, the synchronization controllers cannot be switched synchronously when the chaotic systems are switched from one to another. The system is transformed into a continuous-time switched delay system. By applying the average dwell time method, a sufficient condition is derived witch guarantees the exponential stability of the whole systems with the asynchronously switched controllers. The unified chaotic system is applied as the numerical examples. It is shown by the simulation results that, the secure communication technology with multi-chaotic systems switch is more security and effect.Finally, a conclusion is given and some open areas are also proposed.