Design, modeling, and optimization of nonlinear piezoelectric energy harvesters

Over the past few years, structural health monitoring using wireless sensors has received significant emphasis to improve the safety, serviceability, and reliability of mechanical and civil structures. However, battery powered wireless sensors pose a critical issue of periodic replacement/recharge of the batteries which results in significant amount of maintenance cost. Moreover, the disposal of chemical batteries causes environmental hazard. With advancement in smart materials, low-power-consuming electronic devices, and integrated circuits, energy harvesting has emerged as a potential technology for powering wireless sensor nodes. Several ambient energy sources such as solar, wind, thermal gradient, and vibration are suitable for energy harvesting. However, the ubiquitous nature of vibration has encouraged researchers to opt it for energy harvesting through certain transduction mechanisms. Among various transduction mechanisms, energy harvesting from vibrations using piezoelectric materials has garnered a lot of academic focus because of its higher power density, high voltage output, and ease of application. Conventional cantilever-type linear piezoelectric energy harvesters suffer from narrow operational bandwidth. Various techniques have been employed to broaden the bandwidth of linear harvester, such as oscillator arrays, multi-modal oscillators, passive or active resonance tuning, and nonlinear techniques. Magnetic interaction has been largely utilized for broadband energy harvesting and various configurations with magnetic interaction have been proposed. However, accurate modeling techniques for analyzing the nonlinear piezoelectric harvesters are not developed so far. In this thesis, accurate theoretical and finite element models for predicting the performance of complex nonlinear piezoelectric energy harvesters are developed. The developed models are used for maximizing the power output and bandwidth of harvesters while ensuring the structural integrity. Furthermore, the influence of geometric, material, and damping nonlinearities on the dynamics of harvester are investigated. A nonlinear piezoelectric harvester array is proposed for broadband energy harvesting from low frequency and low amplitude vibrations. Finally, the reliability of piezoelectric energy harvester’s performance at different strain amplitudes over extended periods of time is investigated.Doctor of Philosophy (CEE