Parametric resonance exploitation due to periodic damping in an electromechanical energy harvester

Recent years have witnessed an increasing interest in energy harvesting in order to improve the overall power efficiency and making sensors self-sufficient and durable. One major potential source of energy is related to vibrations, ubiquitous in every mechanical system. In order to increase net harvested power and absorption frequency bandwidth, nonlinearities inducing instability may be exploited: this paper considers periodic variations of the damping term of the power take-off system, which creates conditions for parametric resonance. The stability transition curves of the system are studied according to the Floquet theory, computed by harmonic balance. Numerical simulations are performed in order to study the performance of active and passive parametric control, as well as constant-coefficient passive control. Active control requires a more complex power take-off system able to feed energy into the system in order to increase the overall net harvested power. The increase in complexity should be justified by the marginal gain in power extraction performance. A fundamental role is played by the level of internal dissipation of the system, which is found to make the active parametric control strategy best for applications with low internal damping, while less attractive for more dissipative systems.