Adaptive Networked Synchronization Of Uncertain Chaotic System And Consensus Of Chaotic Multi-agent System

As a typical nonlinear system,chaotic system has attracted much attention because of their special and complex dynamic characteristics.Further more,due to its wide application in secure communication,image processing and other fields,synchronization of chaotic systems has become a hot topic in the field of engineering.However,the existing synchronization methods and control techniques still need to be improved.In addition,in the practical synchronization problem,the system uncertainty will make the synchronization problem more complicated.Based on the background of secure communication and applying the theory of integer and fractional order Lyapunov stability,this dissertation focuses on the adaptive synchronization of several uncertain chaotic systems and the consensus control of uncertain chaotic multi-agent systems.The main contents are listed as follows:In order to enhance the security of chaotic secure communication scheme,the synchronization scheme is improved from three aspects.Firstly,an five-order memristor-based chaotic circuit systems with unknown disturbances is chosen as the drive system to improve the concealment of encryption signal,and the modified function projective lag synchronization is investigated via adaptive control technique to further to improve the anti-deciphering ability of the communication scheme.Secondly,based on the finite-time modified function projective lag synchronization,a novel chaotic synchronization scheme with definite attenuation rate is put forward by introducing an exponential attenuation rate.Applying adaptive control technology and sliding mode control technology,the adaptive finite-time modified function projective lag synchronization with definite attenuation rate for two chaotic systems with unknown parameters is investigated.Numerical simulations verified the exponential attenuation rate designed in this chapter can further shorten the synchronization time and improve synchronization accuracy.Thirdly,to further improve the security of secure communication scheme,a new synchronization scheme which called modified function projective multi-lag generalized compound synchronization is proposed for multiple different chaotic systems with unknown parameters.As an advantage of the new method,not only the addition and subtraction,but also the multiplication of multiple chaotic systems are taken into consideration.This make the signal hidden channels be more abundant and the signal hidden methods be more flexible.By virtue of the finite-time stability theory and the adaptive control technique,an adaptive finite-time control scheme is designed to realize the finite-time synchronization and to track the unknown parameters accurately.In order to reduce the burden of the limited communication network in the process of secure communication,two novel event-triggered mechanisms are proposed.On one hand,for the integer order system,the switching event-triggered mechanism,which can update the threshold parameters online,is designed.On the basis,combined with a reduced-dimension observer,the new event-triggered mechanism is applied to deal with the networked synchronization of the integer order chaotic systems with different dimensions.The study result shows this scheme can effectively improve the data filtering ability and reduce the network burden while ensuring desirable synchronization performance.On the other hand,for the fractional order system,a novel combined event triggered mechanism which depends both on the relative error and the absolute error of the sampled-data is designed.Next,combined with the adaptive control technology,the combined triggered mechanism is applied to the network synchronization control of nonlinear uncertain fractional chaotic systems and the consensus control of the fractional chaotic multi-agent systems respectively.