Operation of energy harvesting devices in different vibration modes

In the past, most of the operating strategies of energy harvesting devices focus only on the resonant frequency of its first mode. The resonant frequency in this mode is fine tuned with an attached proof mass. This paper presents a new approach of operating energy harvesting devices in different vibration modes. With this operation strategy, the harvested power can be increased. The resonant frequencies of adopted piezoelectric devices in different modes can be fine tuned with the same mechanism. A mathematical model that estimates resonant frequencies of piezoelectric cantilevers is proposed for various scenarios. The theoretical results have also been validated by experiments with different mass moving along the experimental cantilever. Other important factors, such as resistive loads, that affect output power are discussed as well.