Hopf bifurcation analysis of asymmetrical rotating shafts

The Hopf and double Hopf bifurcations analysis of asymmetrical rotating shafts with stretching nonlinearity are investigated. The shaft is simply supported and is composed of viscoelastic material. The rotary inertia and gyroscopic effect are considered, but, shear deformation is neglected. To consider the viscoelastic behavior of the shaft, the Kelvin–Voigt model is used. Hopf bifurcations occur due to instability caused by internal damping. To analyze the dynamics of the system in the vicinity of Hopf bifurcations, the center manifold theory is utilized. The standard normal forms of Hopf bifurcations for symmetrical and asymmetrical shafts are obtained. It is shown that the symmetrical shafts have double zero eigenvalues in the absence of external damping, but asymmetrical shafts do not have. The asymmetrical shaft in the absence of external damping has a saddle point, therefore the system is unstable. Also, for symmetrical and asymmetrical shafts, in the presence of external damping at the critical speeds, supercritical Hopf bifurcations occur. The amplitude of periodic solution due to supercritical Hopf bifurcations for symmetrical and asymmetrical shafts for the higher modes would be different, due to shaft asymmetry. Consequently, the effect of shaft asymmetry in the higher modes is considerable. Also, the amplitude of periodic solutions for symmetrical shafts with rotary inertia effect is higher than those of without one. In addition, the dynamic behavior of the system in the vicinity of double Hopf bifurcation is investigated. It is seen that in this case depending on the damping and rotational speed, the sink, source, or saddle equilibrium points occur in the system.     

Hopf bifurcation analysis in a Lorenz-type system

In this technical note, the Hopf bifurcation in a new Lorenz-type system is studied. By analyzing the characteristic equations, the existence of a Hopf bifurcation is established. Some corresponding dynamics are also discussed briefly. Numerical simulations are carried out to illustrate the main theoretical results.     

四维超混沌系统Hopf分岔分析与反控制

对超混沌系统进行分岔反控制的研究已成为当前一个重要研究方向,常采用线性控制器实现反控制。首先,对一个四维超混沌系统的Hopf分岔特性进行了分析,利用高维分岔理论推导出分岔特性与参数之间的关系式,以此判断系统的分岔类型。然后,设计一个由线性与非线性组合成的混合控制器对系统进行分岔反控制,控制参数取值不同时,系统会呈现出不同的分岔特性。通过分析得出,调控线性控制器参数可以使系统Hopf分岔提前或延迟发生;同时,调控混合控制器的两个控制参数,可以改变系统Hopf分岔特性,实现分岔反控制。     

时滞Rucklidge系统Hopf分岔分析与电路实现

以一类新的单时滞Rucklidge系统为分析对象,通过计算时滞系统的平衡点,分析该系统在各平衡点的稳定性和Hopf分岔的存在性,得到其发生Hopf分岔的条件。Matlab多组数值仿真验证了理论分析的正确性。基于此设计了一种可切换时滞与非时滞的混沌电路,并运用Multisim14.0进行仿真,实验结果表明,该电路可行且有效。     

Hopf bifurcation analysis of a new commensurate fractional-order hyperchaotic system

In this paper, a new fractional-order hyperchaotic system based on the Lorenz system is presented. The chaotic behaviors are validated by the positive Lyapunov exponents. Furthermore, the fractional Hopf bifurcation is investigated. It is found that the system admits Hopf bifurcations with varying fractional order and parameters, respectively. Under different bifurcation parameters, some conditions ensuring the Hopf bifurcations are proposed. Numerical simulations are given to illustrate and verify the results.     

A double Hopf bifurcation phenomenon

Summary A degenerate dynamic bifurcation phenomenon exhibited by autonomous systems is analyzed in detail. The situation arises when a key coefficient vanishes at a critical point where Hopf's transversality condition is also violated simultaneously. It is demostrated analytically that, unlike the phenomenon of Hopf bifurcation, in this case the existence of bifurcating family of limit cycles cannot be guaranteed. Indeed, an existence condition emerges as an integral part of the analysis. Under this existence condition, several topologically distinct phenomena may arise, and the conditions giving rise to such cases are discussed. the asymptotic equations of the bifurcating paths, the family of limit cycles and frequency-amplitude relationships are given in general, explicitforms which can be used in the analyses of specific problems directly.

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Sommario Il lavoro analizza in dettaglio un fenomeno di biforcazione dinamica degenere che si presenta in sistemi autonomi. La situazione sorge quando un coefficiente si annulla in un punto critico dove viene anche simultaneamente violata la condizione di trasversalità di Hopf. Si dimostra analiticamente che, a differenza del fenomeno di biforcazione alla Hopf, in questo caso l'esistenza di una famiglia biforcante di cicli-limite non può essere assicurata; infatti una condizione di esistenza emerge come parte integrante dell'analisi. Sotto tale condizione possono sorgere diversi fenomeni topologicamente distinti; si discutono le condizioni che danno luogo a questi casi. Le equazioni asintotiche degli itinerari di biforcazione, la famiglia di ciclilimite e le relazioni frequenza-ampiezza vengono fornite in forme generalied espliciteche possono essere usate direttamente nelle analisi di problemi specifici.

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The financial support of NSERC of Canada is acknowledged. A part of this paper was presented at 1984 IEEE Int. Sym. on Circuits and Systems, Montreal, Canada [1].     

Stability and Hopf bifurcation analysis for an energy resource system

This paper investigates the dynamical behaviors for a four-dimensional energy resource system with time delay, especially in terms of equilibria analyses and Hopf bifurcation analysis. By setting the time delay as a bifurcation parameter, it is shown that Hopf bifurcation would occur when the time delay exceeds a sequence of critical values. Furthermore, the stability and direction of the Hopf bifurcation are determined via the normal form theory and the center manifold reduction theorem. Numerical examples are given in the end of the paper to verify the theoretical results.     

Stochastic Hopf bifurcation of quasi-nonintegrable-Hamiltonian systems

A new procedure for analyzing the stochastic Hopf bifurcation of quasi-non-integrable-Hamiltonian systems is proposed. A quasi-non-integrable-Hamiltonian system is first reduced to an one-dimensional Itô stochastic differential equation for the averaged Hamiltonian by using the stochastic averaging method for quasi-non-integrable-Hamiltonian systems. Then the relationship between the qualitative behavior of the stationary probability density of the averaged Hamiltonian and the sample behaviors of the one-dimensional diffusion process of the averaged Hamiltonian near the two boundaries is established. Thus, the stochastic Hopf bifurcation of the original system is determined approximately by examining the sample behaviors of the averaged Hamiltonian near the two boundaries. Two examples are given to illustrate and test the proposed procedure.     

Global Hopf bifurcation of two-parameter flows

The behavior of center-indices, as introduced by J. Mallet-Paret & J. Yorke, is analyzed for two-parameter flows. The integer sum of center-indices along a one-dimensional curve in parameter space is called the H-index. A nonzero H-index implies global Hopf bifurcation. The index H is not a homotopy invariant. This fact is due to the occurrence of stationary points with an algebraically double eigenvalue zero, which we call B-points. To each B-point we assign an integer B-index, such that the H-index relates to the B-indices by a formula such as occurs in the calculus of residues.This formula is easily applied to study global bifurcation of periodic solutions in diffusively coupled two-cells of chemical oscillators and to treat spatially heterogeneous time-periodic oscillations in porous catalysts.Dedicated to the memory of Charlie Conley     

Hopf bifurcation phenomenon in catalytic reaction

In this paper, we intend to discuss Hopf bifurcation phenomenon under the effect of the periodic small perturbation on local temperature fluctuations (flikering) phenomenon of catalytic reaction. With the obtained results, we expect to provide basis for selecting reaction parameters.     

Hopf bifurcation analysis and numerical simulation in a 4D-hyoerchaotic system

This paper investigates the Hopf bifurcation of a four-dimensional hyperchaotic system with only one equilibrium. A detailed set of conditions is derived which guarantees the existence of the Hopf bifurcation. Furthermore, the standard normal form theory is applied to determine the direction and type of the Hopf bifurcation, and the approximate expressions of bifurcating periodic solutions and their periods. In addition, numerical simulations are used to justify theoretical results.     

Stochastic Hopf bifurcation in quasi-integrable-Hamiltonian systems

A new procedure is developed to study the stochastic Hopf bifurcation in quasiintegrable-Hamiltonian systems under the Gaussian white noise excitation. Firstly, the singular boundaries of the first-class and their asymptotic stable conditions in probability are given for the averaged Ito differential equations about all the sub-system‘s energy levels with respect to the stochastic averaging method. Secondly, the stochastic Hopf bifurcation for the coupled sub-systems are discussed by defining a suitable bounded torus region in the space of the energy levels and employing the theory of the torus region when the singular boundaries turn into the unstable ones. Lastly, a quasi-integrable-Hamiltonian system with two degrees of freedom is studied in detail to illustrate the above procedure.Moreover, simulations by the Monte-Carlo method are performed for the illustrative example to verify the proposed procedure. It is shown that the attenuation motions and the stochastic Hopf bifurcation of two oscillators and the stochastic Hopf bifurcation of a single oscillator may occur in the system for some system‘s parameters. Therefore, one can see that the numerical results are consistent with the theoretical predictions.     

Hopf bifurcation in a three-dimensional system

In this paper,Liapunor-Schmidl reduction and singularity theory are employed to discuss Hopf and degenerate Hopf bifureations in global parametric region in a three-dimensional system x=-βx+y, y=-x-βy(1-kz), z=β[α(1-z)-ky²], The conditions on existence and stability are given.     

Measuring the criticality of a Hopf bifurcation

Nonlinear Dynamics - This work is based on the observation that the first Poincaré–Lyapunov constant is a quadratic function of the coefficients of the two-dimensional vector field at a...     

Hopf bifurcation analysis of a four-neuron network with multiple time delays

This paper reveals the dynamics of a neural network of four neurons with multiple time delays and a short-cut connection through a combined study of theoretical analysis, numerical simulations, and experiments. The first step of the study is to derive the sufficient conditions for the stability and instability of the network equilibrium, and the second step is to determine the properties of the periodic response bifurcating from a Hopf bifurcation of the network equilibrium on the basis of the normal form and the center manifold reduction. Afterwards, the study turns to the validation of theoretical results through numerical simulations and a circuit experiment. The case studies show that both numerical simulations and circuit experiment get a nice agreement with theoretical results.     

Hopf bifurcation analysis in synaptically coupled HR neurons with two time delays

This paper presents an investigation of stability and Hopf bifurcation of a synaptically coupled nonidentical HR model with two time delays. By regarding the half of the sum of two delays as a parameter, we first consider the existence of local Hopf bifurcations, and then derive explicit formulas for determining the direction of the Hopf bifurcations and the stability of bifurcating periodic solutions, using the normal form method and center manifold theory. Finally, numerical simulations are carried out for supporting theoretical analysis results.     

Hopf bifurcation analysis in a delayed oncolytic virus dynamics with continuous control

A delayed oncolytic virus dynamics with continuous control is investigated. The local stability of the infected equilibrium is discussed by analyzing the associated characteristic transcendental equation. By choosing the delay ?? as a bifurcation parameter, we show that Hopf bifurcation can occur as the delay ?? crosses some critical values. Using the normal form theory and the center manifold reduction, explicit formulae are derived to determine the direction of bifurcations and the stability and other properties of bifurcating periodic solutions. Numerical simulations are carried out to support the theoretical results.