Design and modeling of a micro piezoelectric electric generating device with adjustable resonance frequency

Aiming at the inconvenience of energy supplying for microelectronic devices, a micro piezoelectric electric generating device working based on surrounding vibrations was designed in this paper. As the device may harvest a biggest energy when it is resonating with the surrounding vibrations, its resonance frequency was designed adjustable with the span of piezoelectric vibrators. What is more, the harvesting performance of the micro generating device was investigated by theoretical modeling and finite element analyzing methods. It is found that the resonance frequency rises with the span increasing and the variation can be 500Hz or more. The output voltage depends on the structure parameters of the piezoelectric vibrators. By contrast, it rises with the increasing of vibrator's length while decreases with the increasing of metal substrate's thickness and the linearity between them are all well. However, it rises first then falls with the increasing of both the vibrator's width and the piezoelectric ceramic piece's thickness. The optimal interval values of the width and the thickness are 4~5mm and 0.4~0.5mm, respectively. The theoretical calculations have similar variation trends with the finite element simulations. However, there are some differences between them as the joint points are not included when calculating the equivalent mass which should be noticed in actual applications. It is believed that this work may provide an effective technological way for energy supplying of low energy microelectronic products such as wireless sensor network nodes and so on.