速度时滞反馈控制下磁浮系统的稳定性与Hopf分岔

The problem of time delay speed feedback in the control loop is considered here.Its effects on the linear stability and dynamic behavior of the maglev system are investigated.It is found that a Hopf bifurcation can take place when the time delay exceeds certain values.The stability condition of the maglev system with the time delay is acquired.The direction and stability of the Hopf bifurcation are determined by constructing a center manifold and by applying the normal form method.Finally,numerical simulations are performed to verify the analytical result.     

Chaos Control and Bifurcation Behavior for a Sprott E System with Distributed Delay Feedback

In this paper, the problem of controlling chaos in a Sprott E system with distributed delay feedback is considered. By analyzing the associated characteristic transcendental equation, we focus on the local stability and Hopf bifurcation nature of the Sprott E system with distributed delay feedback. Some explicit formulae for determining the stability and the direction of the Hopf bifurcation periodic solutions are derived by using the normal form theory and center manifold theory. Numerical simulations for justifying the theoretical analysis are provided.     

预测PI控制系统的时滞稳定裕度

The variation of plant dead-time deeply affects the stability of the predictive PI control system. It is important for designing and applying the PPI controller to calculate the delay margin. A criterion of stability for the PPI system and the quantitive relationship among the delay margin, the time constant of the closed-loop system, and the dead-time of the model are given. A graphic algorithm to compute the delay margin is also developed. The phenomenon that there exist more than one stability delay zones is discussed. The algorithm is shown to be precise by some simulations.     

Robust stability criteria for uncertain linear systems with interval time-varying delay

This paper considers the robust delay-dependent stability problem of a class of linear uncertain system with interval time-varying delay and proposes less conservative stability criteria for computing the maximum allowable bound of the delay range. Less conservatism of the proposed stability criteria is attributed to the delay-central point method of stability analysis, wherein the delay interval is partitioned into two subintervals of equal length, and the time derivative of a candidate Lyapunov-Krasovskii functional based on delay decomposition technique is evaluated in each of these delay segments. In deriving the stability conditions in LMI framework, neither model transformations nor bounding techniques using free-weighting matrix variables are employed for dealing the cross-terms that emerge from the time derivative of the Lyapunov-Krasovskii functional; instead, they are dealt using tighter integral inequalities. The proposed analysis subsequently yields a stability condition in convex LMI framework that can be solved using standard numerical packages. For deriving robust stability conditions, two categories of system uncertainties, namely, time-varying structured and polytopic-type uncertainties, are considered. The effectiveness of the proposed stability criteria is validated through standard numerical examples.     

Complex instabilities near codimension-2 bifurcation and torus breakdown in a uk converter with an inductive impedance load

Power switching converters exhibit a wide range of nonlinear behavior,such as bifurcation and chaos.Complex instabilities near the codimension-2 bifurcation point are shown in some nonlinear higher order systems.In this study,codimension-2 bifurcation and complex instabilities in a single inner current loop controlled uk converter with an inductive impedance load are analyzed by studying the Floquet multipliers and switching modes of the system.The period1 orbit loses its stability by period-doubling and subcritical NeimarkSacker bifurcations.The period2 orbit enters a two-loop torus orbit via border collision and Neimark-Sacker bifurcations.The dynamic behavior of the system near the codimension-2 bifurcation points is clearly studied.The mechanism of the coexisting phenomenon from the subcritical Neimark-Sacker bifurcation is explained.Finally,chaos from torus breakdown is detected in this higher order switching converter with an inductive impedance load and its phase shift characteristics to diferent initial conditions are investigated.     

Complex instabilities near codimension-2 bifurcation and torus breakdown in a Cuk converter with an inductive impedance load

Power switching converters exhibit a wide range of nonlinear behavior, such as bifurcation and chaos. Complex instabilities near the codimension-2 bifurcation point are shown in some nonlinear higher order systems. In this study, codimension-2 bifurcation and complex instabilities in a single inner current loop controlled Cuk converter with an inductive impedance load are analyzed by studying the Floquet multipliers and switching modes of the system. The periodl orbit loses its stability by period-doubling and subcritical Neimark- Sacker bifurcations. The period2 orbit enters a two-loop torus orbit via border collision and Neimark-Saeker bifurcations. The dynamic behavior of the system near the eodimension-2 bifurcation points is clearly studied. The mechanism of the coexisting phenomenon from the subcritical Neimark-Sacker bifurcation is explained. Finally, chaos from torus breakdown is detected in this higher order switching converter with an inductive impedance load and its phase shift characteristics to different initial conditions are investigated.     

变时滞不确定Lurie系统的时滞分布依赖鲁棒稳定性分析

In this paper, the problem of robust absolute stability of Lurie system with probabilistic time-varying delay and normbounded parametric uncertainty is considered. The time delay variation range is divided into two sub-intervals. By considering the probability distribution of the time-varying delay between the two sub-intervals and the knowledge of the delay variation range, a novel linear matrix inequalities (LMIs) based stability condition is derived by defining a Lyapunov Krasovskii functional. It is illustrated with the help of numerical examples that the derived stability criteria can lead to less conservative results as compared to the results obtained by the traditional method of using the delay variation range information only.     

Variable structure control for three-variable autocatalytic reaction

In this paper, two irreversible exothermic autocatalytic reactions which carry out in continuous stirred tank reactor (CSTR) are considered. A differential-algebraic system is applied to model these chemical reactions. The stability and the dynamic behavior are studied for the differential-algebraic system. The Hopf bifurcation appears when the parameter exceeds a critical value. In order to eliminate this complex behavior, the differential-algebraic system is described by a single-input and single-output system with parameter varying within definite intervals, and then variable structure control with sliding mode based on a special power reaching law is designed to stabilize this chemical system. Numerical simulations are given to illustrate the effectiveness of the method.     

Design of networked control systems with bounded arbitrary time delays

This paper is mainly concerned with the model predictive control (MPC) of networked control systems (NCSs) with uncertain time delay and data packets disorder. The network-induced time delay is described as bounded and arbitrary process. For the usual state feedback controller, by considering all the possibilities of delays, an augmented state space model of the closed-loop system, which characterizes all the delay cases, is obtained. The stability conditions are given according to the Lyapunov method based on this augmented model. The stability property is inherited in MPC which explicitly considers the physical constraints. A numerical example is given to demonstrate the effectiveness of the proposed MPC.     

具有修正的Lelie-Gower项Holling-III类时滞捕食系统的Hopf分支

研究了一类具有修正的Leslie-Gower项与Holling-III类功能性反应函数的时滞捕食系统. 以时滞为分支参数, 讨论系统正平衡点的局部稳定性, 给出系统产生Hopf分支的时滞关键值. 进一步, 确定系统Hopf分支的方向与分支周期解稳定性, 并对系统全局分支周期解的存在性进行讨论. 最后, 利用仿真实例验证理论分析结果的正确性.     

具时滞的非线性纵向飞行模型稳定性和分支分析

研究一类具有时滞的非线性飞行模型的稳定性和分支问题。首先考虑数据测量的时间延迟,给出了含时滞的大迎角纵向多项式飞行模型;然后应用泛函微分方程Hopf分支理论和中心流形等非线性方法给出了该模型稳定性和分支的解析分析,得到了由时滞引起的Hopf分支存在条件、分支点计算公式以及分支周期解的稳定性判别准则;最后利用所得结论进行了飞行实例分析,分析结果表明,数据测量延时可能会引起飞行稳定性的改变,而且延时超过一定临界值时将产生Hopf分支,出现纵向周期振荡,其结论具有实际参考意义。     

分数阶时滞传染病模型的传播动力学

本文研究了一个具有时滞的分数阶SEIR传染病模型,并且着重研究了时滞的引入对模型的动力学行为的影响.首先,建立了分数阶SEIR传染病模型并给出了无时滞情况下地方病平衡点稳定的充分条件,以此来确保时滞的引入具有实际意义.其次,结合分岔理论求得了Hopf分岔发生的条件以及分岔阈值的表达式.研究发现,系统的动力学行为依赖于分岔的临界值.在此基础上,研究了分数阶阶次的变化对分岔阈值的影响,发现随着阶次的增加系统的Hopf分岔将会提前.最后用数值仿真结果来验证理论推导的正确性.     

Delay-induced Hopf bifurcation in a noise-driven excitable neuron model

A FitzHugh–Nagumo neuron model with cubic nonlinearity and discrete delay is considered, in which the time delay is regarded as a parameter. The effect of time delay on the linear stability and Hopf bifurcation of the model is studied. The existence, stability and direction of the local and global Hopf bifurcation are derived. Some numerical simulations are employed to validate the main results of this work.     

Bifurcation control of small‐world networks with delays VIA PID controller

In this paper, the problem of bifurcation control for a small‐world network model with time delay is studied. We first put forward a Proportional‐Integral‐Derivative (PID) feedback scheme to control the Hopf bifurcation of the network. The time delay is selected as the bifurcation parameter. The conditions of the stability and Hopf bifurcation are given for the controlled network. By using the center manifold theorem and the normal form theory, the direction and stability of bifurcating periodic solutions are confirmed. The feasible region of the parameters of the controller is determined. It is found that the bifurcation dynamics of the small‐world network are optimized by adjusting the parameters of the PID controller. Finally, a numerical example verifies the effectiveness of the designed PID controller, and the relationships between the onset of the Hopf bifurcation and the control parameters are obtained.     

时滞诱发的忆阻型Hopfield神经网络的复杂动力学

本文研究含时滞的忆阻型环状Hopfield神经网络的稳定性、Hopf分岔以及复杂振荡模式.根据特征方程根分布情况,获得了系统全时滞稳定条件和与时滞相关的稳定条件.通过数值计算揭示了丰富的动力学现象,如多种周期运动和混沌吸引子等,并给出了Poincaré截面上的分岔图.设计了电路实验平台,取得了与理论分析和数值计算高度吻合的实验结果.     

分数阶计算机病毒模型的稳定性与分岔分析

随着有线和无线通信网络的普及,计算机病毒已经成为当代信息社会的一大威胁,单纯依靠杀毒软件已经无法彻底清除病毒,而通过对其在互联网上的传播机制的分析,以及对其模型的研究,可以找到有效的防范计算机病毒的对策。因此,基于非线性动力学与分数阶系统理论,建立了一类具有饱和发生率的分数阶时滞SIQR计算机病毒模型。计算出模型的平衡点,并通过分析相应的特征方程研究了时滞对平衡点稳定性的影响。选择时滞作为分岔参数,得到了发生Hopf分岔的时滞临界值。研究发现,系统的动力学行为依赖于分岔的临界值,同时给出了系统局部稳定和产生Hopf分岔的条件。在此基础上,研究了分数阶阶次的变化对分岔阈值的影响。最后,通过数值模拟验证了理论分析的正确性。     

A delayed diffusive predator–prey system with predator cannibalism

A diffusive predator–prey system with cannibalism and maturation delay in predator subject to Neumann boundary condition is studied in this paper. Instability and Hopf bifurcation induced by time delay are investigated. By the theory of normal form and center manifold method, the conditions for determining the bifurcation direction and the stability of the bifurcating periodic solution are derived. Some numerical simulations are given to support our results.