Horizontal fast excitation in delayed van der Pol oscillator

This paper investigates the interaction effect of horizontal fast harmonic parametric excitation and time delay on self-excited vibration in van der Pol oscillator. We apply the method of direct partition of motion to derive the main autonomous equation governing the slow dynamic of the oscillator. The method of averaging is then performed on the slow dynamic to obtain a slow flow which is analyzed for equilibria and periodic motion. This analysis provides analytical approximations of regions in parameter space where periodic self-excited vibrations can be eliminated. A numerical study is performed on the original oscillator and compared to analytical approximations. It was shown that in the delayed case, horizontal fast harmonic excitation can eliminate undesirable self-excited vibrations for moderate values of the excitation frequency. In contrast, the case without delay requires large excitation frequency to eliminate such motions. This work has application to regenerative behavior in high-speed milling.     

On the motion of a generalized van der Pol oscillator

A generalized van der Pol oscillator is considered, with positive real power nonlinearities in the restoring and damping force, including fractional powers. An analytical approach based on the Krylov–Bogoliubov method is adjusted to derive analytical expressions for the amplitude of a limit cycle for small values of the damping coefficient. These expressions are also derived for some integer power nonlinearities in the equation of motion and the results obtained compared with the existing results from the literature. Relaxation oscillations are studied for larger values of the damping coefficient. Matched asymptotic expansions are used and the influence of the powers of the restoring and damping force on the period of these oscillations is investigated. It is shown that not only can the period increase with the damping power, but it can also have a decreasing trend for some cases and the condition for this to hold is obtained.     

Van der Pol oscillator under parametric and forced excitations

We study a van der Pol oscillator under parametric and forced excitations. The case where a system contains a small parameter and is quasilinear and the general case (without the assumption of the smallness of nonlinear terms and perturbations) are studied. In the first case, equations of the first approximation are obtained by the Krylov-Bogolyubov-Mitropol’skii technique, their averaging is performed, frequency-amplitude and resonance curves are studied, and the stability of the given system is considered. In the second case, the possibility of chaotic behavior in a deterministic system of oscillator type is shown. Published in Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 2, pp. 206–216, February, 2007.     

On limit cycle approximations in the van der Pol oscillator

This paper applies bifurcation analysis to the well-known van der Pol oscillator to obtain approximations of its periodic solutions in the nearly sinusoidal regime. A frequency domain method based on harmonic balance approximations is used for small values of the bifurcation parameter. Moreover, a comparison with some other frequency domain approaches is also given. Finally, a total harmonic distortion is computed using the information provided by the frequency domain approach.     

Effect of bounded noise on chaotic motion of duffing oscillator under parametric excitation

A harmonic function with constant amplitude and random frequency and phase is called bounded noise. In this paper, the effect of bounded noise on the chaotic behavior of the Duffing oscillator under parametric excitation is studied in detail. The random Melnikov process is derived and a mean-square criterion is used to detect the chaotic dynamics in the system. It is found that the threshold of bounded noise amplitude for the onset of chaos in the system increases as the intensity of the noise in frequency increases. The threshold of bounded noise amplitude for the onset of chaos is also determined by the numerical calculation of the largest Lyapunov exponents. The effect of bounded noise on the Poincaré map and power spectra is also investigated. The numerical results qualitatively confirm the conclusion drawn by using the random Melnikov process with mean-square criterion for larger noise intensity.     

Construction of approximate periodic solutions to a modified van der Pol oscillator

A new iteration scheme is proposed and applied for the modified van der Pol oscillator. A simple and effective iteration procedure to search for the periodic solutions of the equation is given. This procedure is a powerful tool for the determination of the approximate frequencies and periodic solutions of the nonlinear differential equations. The solutions obtained using the present iteration procedure are in good agreement with the numerical integration obtained by a fourth order Runge–Kutta method, which shows the applicability of the procedure.     

A homotopy analysis method for limit cycle of the van der Pol oscillator with delayed amplitude limiting

In this work, a powerful analytical method, called Liao’s homotopy analysis method is used to study the limit cycle of a two-dimensional nonlinear dynamical system, namely the van der Pol oscillator with delayed amplitude limiting. It is shown that the solutions are valid for a wide range of variation of the system parameters. Comparison of the obtained solutions with those achieved by numerical solutions and by other perturbation techniques shows that the utilized method is effective and convenient to solve this type of problems with the desired order of approximation.     

Invariant manifolds of the Bonhoeffer–van der Pol oscillator

The stable and unstable manifolds of a saddle fixed point (SFP) of the Bonhoeffer–van der Pol oscillator are numerically studied. A correspondence between the existence of homoclinic tangencies (which are related to the creation or destruction of Smale horseshoes) and the chaos observed in the bifurcation diagram is described. It is observed that in the non-chaotic zones of the bifurcation diagram, there may or may not be Smale horseshoes, but there are no homoclinic tangencies.     

Synchronization of van der Pol oscillator and Chen chaotic dynamical system

This paper addresses the synchronization problem of two different electronic circuits by using nonlinear control function. This technique is applied to achieve synchronization for the stable van der Pol oscillator and Chen chaotic dynamical system. Numerical simulations results are given to demonstrate the effectiveness of the proposed control method.     

Bifurcation analysis in van der Pol's oscillator with delayed feedback

In this paper, a classical van der Pol's equation with generally delayed feedback is considered. It is shown that there are Bogdanov–Takens bifurcation, triple zero and Hopf-zero singularities by analyzing the distribution of the roots of the associated characteristic equation. In the situation that the zero is as a simple eigenvalue, the normal forms of the reduced equations are obtained by the center manifold theory and normal form method for functional differential equation, and hence the stability of the fixed point is determined, and transcritical and pitchfork bifurcations are found.     

Hopf-pitchfork bifurcation in van der Pol's oscillator with nonlinear delayed feedback

First, we identify the critical values for Hopf-pitchfork bifurcation. Second, we derive the normal forms up to third order and their unfolding with original parameters in the system near the bifurcation point, by the normal form method and center manifold theory. Then we give a complete bifurcation diagram for original parameters of the system and obtain complete classifications of dynamics for the system. Furthermore, we find some interesting phenomena, such as the coexistence of two asymptotically stable states, two stable periodic orbits, and two attractive quasi-periodic motions, which are verified both theoretically and numerically.     

Vibration suppression of self-excited oscillations by parametric inertia excitation

The main objective of this contribution is to show the phenomenon of full vibration suppression of a simple two degrees of freedom rotary oscillator by interaction between self-excitation and parametric excitation. One disk is under the influence of self-excitation, modelled by a negative damping coefficient, while the moment of inertia of the second disk is periodically varied in time within an open-loop control with a fixed frequency. Both disks are coupled by a linear spring-element. Parametric excitation develops equations of motion with time-periodic coefficients. Using the averaging method for a firstorder approximation general conditions for full vibration suppression are analytically derived for the two degrees of freedom system with harmonic inertia variation. The approximated analytical stability predictions are verified and compared to results obtained from numerical time integration of the original equations of motion. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Boundedness for network of stochastic coupled van der Pol oscillators with time-varying delayed coupling

In this paper, network of stochastic van der Pol oscillators with time-varying delayed coupling is considered. By using graph theory and Lyapunov functional method, the asymptotic boundedness in pth moment of the network is investigated. Moreover, by constructing an appropriate Lyapunov function, sufficient principle in the form of coefficients of network which ensures the asymptotic boundedness is established. Finally, a numerical example is given to show the effectiveness of the proposed criteria.     

Comparative dynamics of chains of coupled van der Pol equations and coupled systems of van der Pol equations

Theoretical and Mathematical Physics - We consider chains of van der Pol equations closed into a ring and chains of systems of two first-order van der Pol equations. We assume that the couplings...     

Double Hopf bifurcation for van der Pol-Duffing oscillator with parametric delay feedback control

The stability and bifurcation of a van der Pol-Duffing oscillator with the delay feedback are investigated, in which the strength of feedback control is a nonlinear function of delay. A geometrical method in conjunction with an analytical method is developed to identify the critical values for stability switches and Hopf bifurcations. The Hopf bifurcation curves and multi-stable regions are obtained as two parameters vary. Some weak resonant and non-resonant double Hopf bifurcation phenomena are observed due to the vanishing of the real parts of two pairs of characteristic roots on the margins of the “death island” regions simultaneously. By applying the center manifold theory, the normal forms near the double Hopf bifurcation points, as well as classifications of local dynamics are analyzed. Furthermore, some quasi-periodic and chaotic motions are verified in both theoretical and numerical ways.     

Oscillatory region and asymptotic solution of fractional van der Pol oscillator via residue harmonic balance technique

In this paper, a powerfully analytical technique is proposed for predicting and generating the steady state solution of the fractional differential system based on the method of harmonic balance. The zeroth-order approximation using just one Fourier term is applied to predict the parametric function for the boundary between oscillatory and non-oscillatory regions of the fractional van der Pol oscillator. The unbalanced residues due to Fourier truncation are considered iteratively by solving linear algebraic equations to improve the accuracy of the solutions successively. The highly accurate solutions to the angular frequency and limit cycle of fractional van der Pol oscillator are obtained and compared. The results reveal that the technique described in this paper is very effective and simple for obtaining asymptotic solution of nonlinear system having fractional order derivative.