In this paper uncertainty-based design optimization of a micro energy reclamation device is presented. The goal is to optimally design a Microelectromechanical Systems based device to extract maximum power from externally introduced vibrations. This microstructure consists of an array of piezoelectric composite cantilever beams connected to a free standing mass. Each cantilever beam undergoes deformation when subjected to external base vibrations. This deformation induces a mechanical strain in the beam resulting in the conversion to electric voltage due to the piezoelectric effect. In case of microstructures, uncertainties in geometry as well as material properties are large and therefore may have significant effects on the mechanical behavior. In the present paper uncertainties in geometry and material properties are considered. A description of uncertainties via bounds on the uncertainty variables is adopted. Uncertainty-based design optimization is carried out using the anti-optimization technique.

In this paper, an accurate physical model of a piezoelectric cantilever beam that is suitable for multi domain simulations of the transducer for energy harvesting is presented. In a composite piezoelectric cantilever beam with a proof mass that is subjected to a base acceleration, a strain is developed in the structure that produces a voltage due to the piezoelectric effect. Subsequently, the piezoelectric composite is connected to an energy reclamation circuit that uses a flyback converter topology, to maximize power transfer via an impedance match with the structure. Hence, an accurate model of the device is required to characterize its overall electromechanical behavior, to theoretically predict the power generation, and to optimize the device and power converter circuit. The Lumped Element Model (LEM) thus developed was validated within 10% experimentally on meso-scale piezoelectric cantilever composite beams.

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NOMENCLATURE ABSTRACTIn this paper, the development of a first generation MEMS-based piezoelectric energy harvester capable of converting ambient vibrations into storable electrical energy is presented. The energy harvester is designed using a validated analytical electromechanical Lumped Element Model (LEM) that accurately predicts the behavior of a piezoelectric composite structure. The MEMS device is fabricated using standard sol gel PZT and conventional surface and bulk micro processing techniques. It consists of a piezoelectric composite cantilever beam (Si/SiO 2 /Ti/Pt/PZT/Pt/Au) with a proof mass at one end. A prototype device packaged in a 5 mm 2 area produces 0.98 W rms power into an optimal resistive load when excited with an acceleration of 1 m/s 2 at its resonant frequency of 129 Hz. Although the model predicts the general behavior of the device accurately, knowledge of the overall system damping is critical to accurately predict the power output, and therefore individual dissipation mechanisms in the system must be investigated. This effort lays the foundation for future development of MEMS piezoelectric energy harvester arrays as a potential power solution for self sustaining wireless embedded systems. The electromechanical model further enables intelligent and optimal design of these energy harvesters for specific applications minimizing prototype test runs.

This paper discusses the performance of an acoustic energy harvester employing an electromechanical Helmholtz resonator with a piezoelectric composite backplate. Sufficient energy is available in fluid/acoustic systems to potentially power elements of active flow control systems. Acoustic energy reclamation has been demonstrated using an electromechanical Helmholtz resonator excited by an incident acoustic field, successfully self-powering an electret microphone. The selfpowered microphone calibration shows good agreement with a conventionally powered case. The proof-of-concept demonstration in this paper employed a linear regulator circuit to convert the ac piezoelectric generator voltage into a constant dc voltage.