Michael Robinson Thesis Defense

09:00 AM - 11:00 AM
Workman 117
Michael Robinson

The defense will be held in person at Workman 117 at 9:00 AM on December 2nd, 2022. There will also be virtual attendance on Zoom
Implementing Frequency Control of Ultrasonic Energy Transfer Through a Metal Barrier for Practical Applications
Ultrasonic energy transfer (UET) is a prominent area of research for sending signals through a metal barrier without penetration of the barrier. UET is a method of wireless power transfer using piezoelectric materials to transduce electrical signals into vibrations to propagate through an elastic medium, such as a metal barrier, and be transduced back to electrical signals. This allows communication and or power into and out of completely sealed metal enclosures. Piezoelectric UET through a metal barrier is a recent technology that began attracting research attention in the early 2000's, and although the mechanical transduction of signals for piezoelectric UET has been simulated and validation tests performed within the laboratory, there has been little to no focus on the integration of the technology into an operational environment. This is important because piezoelectric materials are sensitive to small changes in frequency, load, and temperature, in addition to other factors. Variations in these parameters can drastically decrease system efficiency, which is detrimental for systems transmitting power through a metal barrier.

This thesis aims to test these dependencies and investigate the method of using frequency control of a piezoelectric ultrasonic through barrier system under varying load conditions to increase system efficiency. First, the characteristics of the system are examined, primarily the operation of the piezoelectric system under dynamic driving and loading conditions. Next, tests are designed and performed to validate the operation of the UET through a metal barrier system and measure the efficiency of the system to provide a baseline efficiency for an uncontrolled system with a dynamic load. Finally, a method of Maximum Efficiency Point Tracking (MEPT) is proposed to increase system efficiency under dynamic load conditions by controlling the frequency of operation. The implemented MEPT algorithm demonstrates an increase in efficiency of 2.0-7.5% for a load varying from 25Ω to 100Ω. This demonstrates that an implemented frequency control scheme in response to a dynamic load can increase system efficiency in a UET through a metal barrier system. This finding highlights the need for greater electrical design of piezoelectric UET systems to ensure operability in dynamic operational environments.