Dynamics of excited piecewise linear oscillators

Abstract

The current work is devoted to the analytical study of the dynamics of piecewise linear (PWL) oscillators subjected to various types of excitations. Straightforward analytical study of the response of this class of strongly nonlinear oscillators is rather complex, as it requires the computation of time instants of transitions from one linear state to another. This difficulty is commonly overcome by using the averaging procedure. In the present study, we devise an averaging method which naturally fits to the analysis of a general class of resonantly forced PWL systems with zero offset. This method is based on introduction of non-analytic PWL basis functions with corresponding algebra thereby enabling the application of direct averaging method to the resonantly forced, strongly nonlinear PWL oscillators (PWLOs). We demonstrate the efficiency of the considered averaging method for the three different cases of forced PWLOs. We first consider the PWL Mathieu equation and asymptotically obtain the relatively simple analytical expressions for the transition curves corresponding to the most significant family of m:1 sub-harmonic resonances for both damped and undamped cases. The second dynamical system considered herein is a PWL Van der Pol oscillator. In this example, we use the derived averaged model to explore the effect of asymmetry parameter on the limit cycle oscillations. As a final example, we consider an externally forced PWL Duffing oscillator to illustrate the effect of stiffness asymmetry parameter on its resonance curves. Results of the analysis for all the three considered models show a fairly good correspondence with the numerical simulations of the model within the limit of asymptotic validity.