On a hyperbolic Duffing oscillator with linear damping and periodic forcing

Abstract

The Duffing oscillator describes the dynamics of a mass suspended on a spring with position-dependent stiffness. The mass is assumed to experience a linear damping and a time-dependent external forcing. The model has been instrumental in theoretical investigations of dynamical properties of systems with parity-conserving symmetry, where a double-well substrate connects two metastable states separated by a barrier. Physical systems of interest include nonlinear feedback-controlled mass-spring-damper oscillators, active hysteresis circuits (e.g. memristors), protein chains prone to hydrogen bond-mediated conformational transitions, centro-symmetric crystals and so on. In this work we consider a Duffing-type oscillator with a double-well potential represented by a hyperbolic function of mass position. The hyperbolic double-well potential has two degenerate minima that can be smoothly tuned by varying a deformability parameter, leaving unchanged the barrier height. We investigate solutions of the equation of motion in the absence and presence of damping and forcing. In the absence of perturbations numerical solutions lead to a periodic train of anharmonic oscillations featuring a crystal of pulse solitons of sech types. However, when the hyperbolic double-well potential is inverted, analytical solutions can be obtained which turn out to be kink-soliton crystals described by Jacobi elliptic functions. When damping and forcing are taken into consideration, the system dynamics can transit from periodic to chaotic phases or vice-versa via period-doubling or period-halving bifurcations, by simply varying the deformability parameter. The Poincaré map of the proposed model carries the well-known characteristic signatures of chaos presursors of the standard Duffing model, which happens to be just a particular case of the bistable oscillator model with the hyperbolic double-well potential.