Modeling and experimental investigation of a bistable vibration energy harvester based on polyvinylidene fluoride (PVDF) film

Through a snap-through process, the bistable vibration energy harvester (EH) could undergo large amplitude motion and yield a large energy output. But realizing the transitions between the stable states is a prerequisite for high power output of the bistable piezoelectric EH. To explore the conditions under which the harvester could switch from one stable state to the other, a bistable vibration EH based on PVDF film and its analytical model are investigated. The mechanisms responsible and the transitions of the harvester between the stable states are derived. The relationship between the PVDF axial compression distance, the mass of the proof mass, the excitation frequency and the critical switching force is obtained. The numerical simulation analysis of the bistable vibration EH is conducted. The effects of the different design parameters on the output performance of the EH are analyzed. The boundary conditions for the PVDF beam to realize the transitions between the stable states are obtained. A prototype of a bistable vibration EH was fabricated and measured. When the excitation frequency is 14 Hz, the mass of the proof mass is 12 g, the axial compression distance of the PVDF beam is 0.2 mm, the EH's RMS output voltage value is 4.2 V with the load resistance of 1 M omega. The maximum output power of 22.85 mu W is obtained at the load resistance of 0.7 M omega. It is found that the excitation frequency of implementing the transitions between the stable states increases with increasing the axial compression distance of the PVDF beam. The characteristic experimental results are contrasted with the simulation analysis results, which prove the validity of the presented model.