Energy harvesters are a promising technology for capturing useful energy from the environment or a device's operation. This research will develop and implement a novel energy harvester design for capturing vibrational energy in environments with a broad ambient vibration frequency spectrum. The design uses flexible ceramic piezoelectric elements that produce electricity when mechanically strained, which are in a buckled state at equilibrium. Preliminary experimental results show that a harvester with this design can output appreciable power over a broad range of forcing frequencies, unlike harvesters of vibrational energy based on linear mechanical principles which only give appreciable response if the dominant ambient vibration frequency is close to the resonance frequency of the harvester. The proposed work includes the experimental characterization of this device for periodic and stochastic forcing, plus the development of low- and high-dimensional models that will be analyzed theoretically and computationally. Particular attention will be paid to parameter and forcing regimes for which there is chaotic response, since the preliminary experimental results suggest that this is where the energy harvesting could be maximized. The dependence of the response on parameters will be determined, and multiparameter optimization will be used to identify parameter values for the device for which the energy harvesting is optimized.
Vibrational energy harvesters have potential application in a variety of environments which produce considerable vibrational energy, such as automobiles, trains, aircraft, watercraft, machinery, and buildings. Energy harvesters could power auxiliary functions for such systems, for example the wireless transmission of data for system monitoring. Furthermore, many mechanical and electronic systems such as autonomous vehicles and sensor networks require bulky batteries and/or power supplies for their operation. If energy harvesters could be used to provide complete or supplementary power for such systems, they could function with reduced cost and inconvenience of replacing their batteries. This work will also develop a rigorous modeling framework for piezoelectric vibrational energy harvesters which will be beneficial for other researchers working in this and other areas for which both piezoelectric and mechanical effects are important.