Studies of acoustic-electric feed-throughs for power transmission through structures

Abstract

There are numerous engineering design problems where the use of wires to transfer power and communicate data thru the walls of a structure is prohibitive or significantly difficult that it may require a complex design. Using physical feedthroughs in such systems may make them susceptible to leakage of chemicals or gasses, loss of pressure or vacuum, as well as difficulties in providing adequate thermal or electrical insulation. Moreover, feeding wires thru a wall of a structure reduces the strength of the structure and makes the structure prone to cracking due to fatigue that can result from cyclic loading and stress concentrations. One area that has already been identified to require a wireless alternative to electrical feedthroughs would be the container of any Mars Sample Return Mission, which would need wireless sensors to sense a pressure leak and to avoid potential contamination. The idea of using elastic or acoustic waves to transfer power was suggested recently by [Y. Hu, et al., July 2003]. This system allows for the avoidance of cabling or wiring. The technology is applicable to the transfer of power for actuation, sensing and other tasks inside any sealed container or vacuum/pressure vessel. An alternative approach to the modeling presented previously [Sherrit et al., 2005] used network analysis to solve the same problem in a clear and expandable manner. Experimental tests on three different designs of these devices were performed. The three designs used different methods of coupling the piezoelectric element to the wall. In the first test the piezoelectric material was bolted using a backing structure. In the second test the piezoelectric was clamped after the application of grease. Finally the piezoelectric element was attached using a conductive epoxy. The mechanical clamp with grease produced the highest measured efficiency of 53% however this design was the least practical from a fabrication viewpoint. The power transfer efficiency of conductive epoxy joint was 40% and the stress bolts (12%). The experimental results on a variety of designs will be presented and the thermal and non-linear issues will be discussed.

Study on energy focusing synthesis on pipe using time reversal technique

“…After sampling with sampling frequency Fs, the discrete time version of the received signal is y=XJ +v (2) where{= [10 1, ... J M-lt and x = [ xo X l transmitting signal is divided into a reference length of Nand guard period of M bits, and M is the channel memory.…”

“…A sinusoidal voltage was applied to the transducer at a known frequency generating a stress wave that travels through the armor into the receiver. Recently, a wireless acoustic electric feed-through network model was investigated by building and testing prototype devices at the Jet Propulsion Laboratory [2]. Three designs used different methods of coupling the piezoelectric element to the wall.…”

Wireless energy transmission through a sealed wall using the acoustic-electric interaction of piezoelectric ceramics

“…After receiving the vibrations from the outer shell, the inner transducer is able to convert the mechanical energy into electric one again through the converse piezoelectric effect. Sherrit et al [8,9] and Bao et al [1,10] investigated the energy loss of this transmission method by experiments and finite element computations, and demonstrated experimentally 110W power through the wall at 88% efficiency. Saulnier et al [11] and Primerano et al [12] have studied wireless communication through a steel wall by using ultrasound piezoelectric transducers, where conventional radio-frequency communications cannot be applied due to shielding of the steel.…”

Electrical optimization of power delivery through thick steel barriers using piezoelectric transducers

“…Alternatively, many approaches have been presented that utilize piezoelectric transducers to transmit power and/or data through metallic barriers using ultrasound. [2][3][4][5][6][7][8][9][10][11] This work presents a practical methodology for electrically characterizing and optimizing the power transfer efficiency through an acoustic-electric channel. The channel is formed by coaxially aligning and acoustically coupling a pair of piezoelectric disk transducers to opposite sides of a thick metallic barrier.…”