Xiaoqun Wu

Synchronization of a unified chaotic system and the application in secure communication

This Letter further investigates the synchronization of a unified chaotic system via different methods. Several sufficient theorems for the synchronization of the unified chaotic system are deduced. A scheme of secure communication based on the synchronization of the unified chaotic system is presented. Numerical simulation shows its feasibility.

Generalized outer synchronization between complex dynamical networks

In this paper, the problem of generalized outer synchronization between two completely different complex dynamical networks is investigated. With a nonlinear control scheme, a sufficient criterion for this generalized outer synchronization is derived based on Barbalats lemma. Two corollaries are also obtained, which contains the situations studied in two lately published papers as special cases. Numerical simulations further demonstrate the feasibility and effectiveness of the theoretical results.

Pinning synchronization of delayed neural networks

This paper investigates adaptive pinning synchronization of a general weighted neural network with coupling delay. Unlike recent works on pinning synchronization which proposed the possibility that synchronization can be reached by controlling only a small fraction of neurons, this paper aims to answer the following question: Which neurons should be controlled to synchronize a neural network? By using Schur complement and Lyapunov function methods, it is proved that under a mild topology-based condition, some simple adaptive feedback controllers are sufficient to globally synchronize a general delayed neural network. Moreover, for a concrete neurobiological network consisting of identical Hindmarsh-Rose neurons, a specific pinning control technique is introduced and some numerical examples are presented to verify our theoretical results.

Fast‐scale bifurcation in single‐stage PFC power supplies operating with DCM boost stage and CCM forward stage

This paper describes the fast-scale bifurcation phenomena of a single-stage single-switch power-factor-correction (PFC) regulator comprising a boost stage operating in discontinuous conduction mode (DCM) and a forward stage operating in continuous conduction mode (CCM). The two stages combine into a single stage by sharing one main switch and one control loop. Using ‘exact’ cycle-by-cycle computer simulations, the effects of various circuit parameters on fast-scale instabilities are studied. The results are qualitatively verified by experimental measurements. This work provides a clear picture of how the variation of certain practical parameters can render such a circuit fast-scale unstable. Copyright

ULTIMATE BOUND ESTIMATION OF A CLASS OF HIGH DIMENSIONAL QUADRATIC AUTONOMOUS DYNAMICAL SYSTEMS

This paper aims to propose a unified approach for the ultimate bound estimation of a class of High Dimensional Quadratic Autonomous Dynamical Systems (HDQADS). Using the proposed method and the optimization idea, a sufficient condition is then given for estimating the ultimate bounds of a class of HDQADS. To validate the above sufficient condition, this paper further investigates the ultimate bound estimation of a hyperchaotic system, a 6D and a 9D chaotic system, separately. Moreover, the ultimate bounds for a general Lorenz system, a low-order atmospheric circulation model, and a new 3D chaotic system are also discussed in detail. In particular, it should be pointed out that a unified and accurate ultimate bound estimation is attained for the generalized Lorenz system and it includes several well-known results as its special cases. Some numerical simulations are also given to verify and visualize the corresponding theoretical results.

Flocking of multi-agent dynamical systems based on pseudo-leader mechanism

Abstract Flocking behavior of multiple agents can be widely observed in nature such as schooling fish and flocking birds. Recent literature has proposed the possibility that flocking can be achieved even with only a small fraction of informed agents with the desired position and velocity. However, it is still a challenging problem to determine which agents should be informed or have the ability to detect the desired information. This paper aims to address this problem. By combining the ideas of virtual force and pseudo-leader mechanism, where a pseudo-leader represents an informed agent who can detect the desired information, we propose a scheme for choosing pseudo-leaders in a multi-agent group, which can be applied to an unconnected or switching neighbor graph. Numerical examples are given to show the effectiveness of the methods presented in this paper.

SYNCHRONIZATION OF IMPULSIVELY COUPLED SYSTEMS

In the past years, impulsive control for a single system and impulsive synchronization between two systems have been extensively studied. However, investigation on impulsive control and synchronization of complex networks has just started. In these studies, a network is continuously coupled, and then is synchronized by using impulsive control strategy. In this paper, a new and different coupled model is proposed, where the systems are coupled only at discrete instants through impulsive connections. Several criteria for synchronizing such kind of impulsively coupled complex dynamical systems are established. Two examples are also worked through for illustrating the main results.

Sustained Slow-Scale Oscillation in Higher Order Current-Mode Controlled Converter

DC-DC converters under current-mode control have been known to exhibit slow-scale oscillation as a result of a Hopf-type bifurcation as one or more of the parameters of the outer voltage loop are varied. In the absence of the outer voltage loop (i.e., open loop), slow-scale oscillation was generally not observed in simple low-order dc-dc converters, i.e., buck, buck-boost, and boost converters. In this paper, slow-scale bifurcation in a higher order current-mode controlled converter is studied. It has been found experimentally that, even in the absence of a closed outer voltage loop, a current-mode controlled Cuk converter can exhibit a slow-scale Hopf-type bifurcation. The phenomenon was observed in a commercial low-ripple dc-dc converter which has been designed using the Cuk converter and the LM2611 controller. Such slow-scale oscillation of the inner current loop can also be observed in full-circuit SPICE simulations. An averaged model has been developed and implemented in SPICE to find the Hopf bifurcation boundaries. With this averaged model, the Hopf bifurcation can be explained conveniently using the traditional loop gain analysis. Specifically, the extra degrees of freedom in higher order dc-dc converters have opened up a new possible mode of instability which has not been found in simple low-order dc-dc converters.

Second-order consensus of multi-agent systems with nonlinear dynamics via impulsive control

In many real-world multi-agent systems, the intrinsic dynamics of velocity for each agent is usually nonlinear dynamic rather than static. Moreover, it is often difficult to obtain the continuous velocity information of multi-agent systems. To overcome the above essential difficulties, this paper aims at investigating the second-order consensus problem of multi-agents systems with nonlinear dynamics by using impulsive control signal protocol. In detail, by using the impulsive signals from agents and virtual leaders, several impulsive control protocols are designed for reaching the second-order consensus of multi-agent systems with fixed or switching topologies. The theoretical analysis is also given to guarantee the second-order consensus based on algebraic graph theory and stability theory of impulsive differential equations. Finally, two typical examples are used to validate the above developed theoretical results.

Synchronizability of Duplex Networks

This brief presents some rules and properties about synchronizability of duplex networks composed of two networks interconnected by two links. For a specific duplex network composed of two star networks, analytical expressions containing the largest and smallest nonzero eigenvalues of the (weighted) Laplacian matrix, the interlink weight, and the network size are given for three different interlayer connection patterns. It is shown that connection patterns have great influence on the ability of the duplex system to synchronize, and connecting high-degree nodes is the most effective way to achieve synchronization, while connecting low-degree nodes is the least. Numerical examples are also provided to verify the effectiveness of theoretical analysis. This work sheds new light on understanding synchronizability of groups of interconnected networks or networks of networks (NONs). Particularly, in the design of circuit networks such as power grids, the findings can facilitate engineers with optimal selections of interconnection patterns and parameter assignments, in terms of optimizing the stability of desired synchronous states and minimizing control cost.