This paper presents the development of an acoustic energy harvester using an electromechanical Helmholtz resonator (EMHR). The EMHR consists of an orifice, cavity, and a piezoelectric diaphragm. Acoustic energy is converted to mechanical energy when sound incident on the orifice generates an oscillatory pressure in the cavity, which in turns causes the vibration of the diaphragm. The conversion of acoustic energy to electrical energy is achieved via piezoelectric transduction in the diaphragm of the EMHR. Moreover, the diaphragm is coupled with energy reclamation circuitry to increase the efficiency of the energy conversion. Lumped element modeling of the EMHR is used to provide physical insight into the coupled energy domain dynamics governing the energy reclamation process. The feasibility of acoustic energy reclamation using an EMHR is demonstrated in a plane wave tube for two power converter topologies. The first is comprised of only a rectifier, and the second uses a rectifier connected to a flyback converter to improve load matching. Experimental results indicate that approximately 30 mW of output power is harvested for an incident sound pressure level of 160 dB with a flyback converter. Such power level is sufficient to power a variety of low power electronic devices.
This paper presents the development and implementation of an inductive, underwater wireless power transfer system for use with unmanned underwater vehicles (UUVs). Specifically, the design and fabrication of power transfer coils and power electronics is provided for a system capable of providing 75W to a load. At small standoff distances (<2 inches) and frequencies below 300kHz, it is shown that there is little difference between inductive power transfer in air and seawater. Measured data shows that at power levels of 75W, the system efficiency from the transmitter to a rectifier and resistive load is above 85%.
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.
This paper demonstrates the system operation of a self-powered active liner for the suppression of aircraft engine noise. The fundamental element of the active liner system is an electromechanical Helmholtz resonator (EMHR), which consists of a Helmholtz resonator with one of its rigid walls replaced with a circular piezoceramic composite plate. For this system demonstration, two EMHR elements are used, one for acoustic impedance tuning and one for energy harvesting. The EMHR used for acoustic impedance tuning is shunted with a variable resistive load, while the EMHR used for energy harvesting is shunted to a flyback power converter and storage element. The desired acoustic impedance conditions are determined externally, and wirelessly transmitted to the liner system. The power for the receiver and the impedance tuning circuitry in the liner are supplied by the harvested energy. Tuning of the active liner is demonstrated at three different sound pressure levels (148, 151, and 153 dB) in order to show the robustness of the energy harvesting and storage system. An acoustic tuning range of approximately 200 Hz is demonstrated for each of the three available power levels.
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