On Sampled-data Fault-tolerance Synchronization Control Method For Chaotic Secure Communication Systems

Chaos is a seemingly random irregular movement, which can be described by deterministic nonlinear systems, without adding any random factors, it can appear random behavior. Since 1990s, chaotic synchronization phenomena have been found in more and more fields. Chaotic synchronization received extensive attention of the researchers. Because of its extreme sensitivity to initial value, unpredictability, it thus is suitable for secure communication. The faults on sensors, actuators and components occur inevitably in the secure communication based on chaotic system, therefore it would cause chaos circuit performance dramatically down or even cause the failure of entire communication system and bring huge economic loss. Therefore, fault tolerant synchronization for chaotic system has attracted greater attention and became one of the advanced objectives in chaos control field. The main contents of this dissertation contain the synchronization of chaotic system based on sampled-data and fault-tolerance and its application in secure communication system, the main contributions are as follows:Firstly, when some actuator failures occur in chaotic systems, the synchronization based on sampled-data control between the master and slave chaotic systems is investigated. With the Euler approximate discretization method, the sample-data chaos system is converted into discrete-time system. Based on the Lyapunov stability theory and the LMI optimization technique, the fault tolerant control is proposed to guarantee synchronization for the master and slave systems. Furthermore, the proposed synchronization control method is applied to the chaos secure communication system and is the validity confirmed by simulation results.Secondly, considering a class of chaotic system with parameter uncertainties and actuator failures, the state feedback control theory is used to design a sampled-data fault-tolerant synchronization control strategy. With the Euler approximate discretization method, the sampled-data chaos system is converted into discrete-time system. Based on Lyapunov stability theory, the theorem for chaotic systems synchronization is obtained, and guaranteed cost performance is satisfied. Based on chaos synchronization, a chaotic secure communication system is built using chaotic masking technique, which is very useful.Thirdly, for a class of chaotic system with random uncertainty and actuator failures, a fault-tolerant sampled-data synchronous controller is studied. The input time delay method is adopted to convert the sampling control system into a continuous-time system with control input delays. The synchronization of the chaotic system is proved by Lyapunov theory for both normal and fault case. Numerical simulation results show the effectiveness of this method, which is established by the Chua's circuit. The synchronization method is applied to chaotic secure communication system at last.Finally, the main work of this dissertation is summarized and some future research directions are put forward.