Kinetic energy harvesting with bistable oscillators

The goal of powering small-scale electronic mobile devices with energy harvested from the ambient has been in recent years the subject of a great research effort. It has been observed that the harvesting of kinetic energy present in the form of random vibrations (from non-equilibrium thermal noise up to machine vibrations) is an interesting option due to the almost universal presence of this kind of motion. Present working solutions for vibration energy harvesting are based on oscillating mechanical elements that convert kinetic energy via capacitive, inductive or piezoelectric methods. These oscillators are usually designed to be resonantly tuned to the ambient dominant frequency. However, in most cases the ambient random vibrations have their energy distributed over a wide spectrum of frequencies, being rich especially at low frequency, and frequency tuning is not always possible due to geometrical/dynamical constraints. In this paper we discuss a different method based on the exploitation of the dynamical features of stochastic bistable oscillators employed to model nonlinear piezoelectric harvesters. Such a method is shown to outperform standard linear oscillators and to overcome some of the most severe limitations of present approaches. The digitally simulated output response of a bistable piezoelectric energy harvester to real measured environmental vibrations is presented. The results of the simulations confirm the superior performances of this approach.