Modal optimization of doubly clamped base-excited multilayer broadband vibration energy harvesters

Piezoelectric vibration energy harvesters with doubly clamped base-excited multilayer structures have been developed. The vibration energy harvesters consist of stacked H-shaped configurations including up to three beams and two extra masses. One beam is doubly clamped as a base layer. The extra masses are attached between the base layer and the other two beams to connect them together. By altering mass positions and the thickness of the base layer, the vibration energy harvesters can generate considerable power output in up to five modes of vibrations. An optimization strategy is established for multi-resonance broadband vibration energy harvesters designs. The strategy is based on a modal approach, which can determine the modal performance of vibration energy harvesters using mass ratio and electromechanical coupling coefficient. In particular, mass ratio is used to represent the influence of modal mechanical behaviour on the power density. The design strategy is executed by selecting the multilayer configurations with close resonances and preferred values of mass ratios in multiple modes. These configurations have optimal or near-optimal structural performance for broadband power output. The finite element method and a distributed electromechanical parameter model are used to derive the required modal parameters and power output with resistive loads.