Study On Control And Synchronization In Chaotic And Hyperchaotic Circuits

In this paper,we mainly studied on control and synchronization in chaotic and hyperchaotic circuits as well as on secure communication based on hyperchaos synchronization. Five pieces of research results are finished. Better results are obtained.At first,a method for controlling chaos is studied,which is based on phase switching modulation. The N-scroll Chua's circuit is controlled to its fixed point as well as periodic orbits by using switching modulation on one its phase. Its mechanism of control is analysed using the change of the max Lyapunov exponent when the system is controlled.In the second place,controlling using strategy of system parameter switching modulation in two hyperchaotic circuits is studied. The hyperchaotic circuits are controlled to their stable equilibriums as well as nP periodic orbits by change the external controlling parameter,such as the magnitude of modulation. It is possible that hyperchaotic circuits are controlled to special signal producer and signal exchanger by using this method of hyperchaos control.The third,Synchronization in unidirectionally coupled 4-order hyperchaotic Chua's circuits is studied. Synchronization of hyperchaotic systems can be achieved using only one variable unidirectionally coupled at discrete times. We obtain the threshold of couple coefficient based on Lyapunov stability theory. The theoretical analysis and numerical simulations show that this method is correct and efficient.The fourth,Synchronization in coupled hyperchaotic oscillator is studied. Synchronization of hyperchaotic oscillators can be achieved using only one variable unidirectionally coupled. The main advantage of this method is that it can be realized easily in engineer. The numerical studies and circuit experimental simulations show that this method is correct and efficient. In our circuit experimental simulations,the other variables of hyperchaotic systems synchronize precisely when a variable synchronizes generally.Finally,a general methodology for designing hyperchaotic cryptosystems is developed. The basic idea is to make the decrypter a nonlinear observer for the state of the encrypter. The utilization of hyperchaotic cryptosystems,as well as the increased complexity of the transmitted signal,seems to make a further contribution to the development of the communication systems with higher security.