Recent Development of Piezoelectric Energy Harvesting Structures and the Technology of Frequency Up-converting Oscillators

Abstract

Piezoelectric material is a kind of excellent electromechanical conversion element, has the advantages of small volume, low cost, reliability and so on. But how to design piezoelectric oscillators and efficiently scavenge ambient vibration energy, is still a key technical problem needed to be solved in the corresponding field. Three kinds of typical piezoelectric oscillators based on the resonant frequency matching strategy, represented by constant resonant frequency, resonant frequency tuning and wideband operating frequency structures, are the partial solution to the problem mentioned above. However, the problems such as the low output power and the reliability of oscillating structures are still existing, while harvesting the ambient low or ultra-low frequency vibration energy. To up-convert the excitation frequency into high oscillation frequency of piezoelectric structures through mechanical frequency up-conversion technology, is a reasonable approach and can break through the low power density limitation of piezoelectric elements under the condition of ultra-low frequency. Several kinds of mechanical frequency up-conversion techniques are distinguished and introduced, especially for an internal resonance based frequency up-conversion approach in nonlinear vibration systems. Such approach has the advantages of low threshold of excited acceleration, less energy losses during the frequency conversion stage, etc., broadening the mechanical frequency up-conversion research in the field of piezoelectric oscillators.