Frequency response of an energy harvester to harmonic noise: Towards stochastic frequency response of nonlinear systems

Energy harvesting of ambient energy of different forms has attracted considerable attention of researchers from both theoretical and applied fields. Whereas a typical design of energy harvester is based on a resonant structure - a linear oscillator - aimed at a harmonic excitation, in practice the behaviour of a harvester deviates from linear, and ambient excitations have a much more complex structure than a simple sine-wave. Therefore, it is important to develop a framework for a nonlinear harvester design that would target the stochastic nature of vibrations for effective energy harvesting. In this paper such framework is based on stochastic frequency response. Using the suggested framework the performance of a harvester model for soft and hard nonlinearities in stiffness was compared with the linear harvester. The comparison indicates the presence of a novel phenomena linked to stochastic bifurcations observed by varying characteristics of harmonic noise.