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Abstract: When seeking a solution in series form, the number of terms needed to satisfy some preset requirements is unknown in the beginning. An iterative formulation is proposed so that when an approximation is available, the number of effective terms can be doubled in one iteration by solving a set of linear equations. This is a new extension of the Newton iteration in solving nonlinear algebraic equations to solving nonlinear differential equations by series. When Fourier series is employed, the method is called the residue harmonic balance. In this paper, the fractional order van der Pol oscillator with fractional restoring and damping forces is considered. The residue harmonic balance method is used for generating the higher-order approximations to the angular frequency and the period solutions of above mentioned fractional oscillator. The highly accurate solutions to angular frequency and limit cycle of the fractional order van der Pol equations are obtained analytically. The results that are obtained reveal that the proposed method is very effective for obtaining asymptotic solutions of autonomous nonlinear oscillation systems containing fractional derivatives. The influence of the fractional order on the geometry of the limit cycle is investigated for the first time. [Copyright &y& Elsevier]

Abstract: The residue harmonic balance is developed for coupled systems exemplified by the damped Duffing resonator driven by a van der Pol oscillator. This technique combines the features of harmonic balance and parameter bookkeeping to obtain approximate solutions to any desired accuracy. For the two degrees of freedom system, the zeroth-order approximation uses just one Fourier term resulting in a set of two nonlinear algebraic equations that can be solved analytically. The unbalanced residue due to Fourier truncation is improved by solving linear equations that automatically increase the number of terms to balance the previous truncation completely. Highly accurate bifurcation frequencies for various parameters are obtained and are verified by numerical integration results. The effects of the coupling stiffness on the angular frequency and amplitude of steady state response are investigated. The effects of the nonlinear damping are also studied. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: A new approach that the iterative homotopy harmonic balancing is presented for charactering and predicting analytical approximations of conservative oscillator with strong odd-nonlinearity in the paper. The new technique does not depend upon small parameter assumption and incorporates the salient features of both methods of the parameter-expansion and the harmonic balance. The results of applying this procedure to the studied examples that the cubic–quintic Duffing equation and Duffing-harmonic equation show the high accurate, simplicity and efficiency of the approach. The approach can be easily extended to other nonlinear oscillators. [Copyright &y& Elsevier]

Abstract: In this paper, we predict the accurate bifurcating periodic solution for a general class of first-order nonlinear delay differential equation with reflectional symmetry by constructing an approximate technique, named residue harmonic balance. This technique combines the features of the homotopy concept with harmonic balance which leads to easy computation and gives accurate prediction on the periodic solution to the desired accuracy. The zeroth-order solution using just one Fourier term is applied by solving a set of nonlinear algebraic equations containing the delay term. The unbalanced residues due to Fourier truncation are considered iteratively by solving linear equations to improve the accuracy and increase the number of Fourier terms of the solutions successively. It is shown that the solutions are valid for a wide range of variation of the parameters by two examples. The second-order approximations of the periodic solutions are found to be in excellent agreement with those obtained by direct numerical integration. Moreover, the residue harmonic balance method works not only in determining the amplitude but also the frequency of the bifurcating periodic solution. The method can be easily extended to other delay differential equations. [Copyright &y& Elsevier]