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Access Type

WSU Access

Date of Award

January 2022

Degree Type


Degree Name



Mechanical Engineering

First Advisor

Chin-An Tan


Rapid technological advances in low-power and large-scale integrated electronics such as IoT wireless sensors have created immense opportunities for piezoelectric vibration energy harvesters (PVEHs) to become a viable alternative to costly and environmentally hazardous conventional batteries. These harvesters are designed to exploit the resonance phenomenon of a vibrating medium; therefore, their harvesting effectiveness suffers from an inherent narrow frequency bandwidth. To address this issue, this dissertation focuses on three main objectives: (i) introducing a novel tool for systematic modeling and efficient design of linear PVEHs (ii) investigating the effect of support boundary uncertainty on the efficiency of narrow bandwidth harvesters and (iii) modeling and optimized design of tunable wide bandwidth harvesters. In this research, issues in the existing distributed parameter models are first addressed and frequency solution response for PVEH beam systems by the distributed transfer function method (DTFM) is provided. The DTFM results are validated against modal analysis results. It is shown that the modal analysis solution converges to the DTFM solution as the number of modes used in the eigenfunction expansion increases. Next, the impact of support flexibility on the harvesting efficiency of PVEH beam systems is investigated. A novel analytical function relating the boundary stiffness parameters and the power harvesting efficiency is determined by nonlinear curve fitting of the calculated data. This novel formula enables quantification of the boundary rigidity in terms of harvesting power efficiency target. Applicability of this analytical function for end-of-line quality check of the boundary of PVEH is brought forth as well. The last objective of this dissertation is to investigate two mechanical tuning strategies for widening the harvesting bandwidth of PVEH beam systems. First, a framework for designing artificially created flexible boundaries to tune the resonance frequency of a PVEH beam system is introduced. Using nonlinear curve fitting, an analytical formula relating the boundary stiffness parameters and the tuned frequency of the harvester is presented. Next, resonance frequency tuning using an intermediate proof mass is explored. Using DTFM, the resonance frequencies of the tuned system is mapped to the mass and location of the proof mass. Finally, the mass is assumed to be constant during the operation of the PVEH and the minimum mass required to track a frequency-varying vibration source while meeting the power requirement is estimated.

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