Alex Phipps

Underwater wireless power transfer for maritime applications

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%.

Thermal and biofouling effects on underwater wireless power transfer

This paper presents a characterization of the thermal effects and marine fouling on an undersea wireless power transfer system. The coils used in wireless power transfer experience elevated temperatures due to the resistive losses in the wire. Several different coating strategies to both protect the coils against seawater and dissipate the generated heat are investigated. In addition, the rise in temperature can increase the likelihood of marine bio-fouling on the exposed surfaces of the coils. A study of bio-fouling on the wireless power transfer coils and whether there might be increased microbial growth as a result of the power transfer is also explored.

Development of kinetic energy harvesting systems for vehicle applications

This work demonstrates the implementation of a functional kinetic energy harvester designed to power wireless sensor electronics used in vehicular applications. The design, fabrication, and experimental characterization of a complete electrodynamic (magnetic) energy harvesting system capable of delivering in excess of 10 mW from 100 milli-gs of acceleration is presented. Unlike previous energy harvesting research, which typically focuses on individual components for proof-of-concept testing, the system implemented for this work includes the integration of a low-frequency transducer, power electronics circuitry, and a rechargeable storage element, all of which are required for a functional system. The design trade-offs, which result from the integration of these system components are examined and design rules for maximizing efficiency are given. Finally, field testing is presented, which demonstrates the ability of the system to operate over a range of different vehicle speeds.

Standards and methods of power control for variable power bidirectional wireless power transfer

Unmanned and autonomous systems are used extensively for Navy missions. While most of these systems are able to operate without human interaction, limitations in power capacity place a fundamental limit on overall system autonomy. Inductive wireless power transfer provides an effective way to enhance unmanned systems (vehicles, sensors, etc.). This report examines different methods for efficiently controlling power modulation and determining which side, transmitter or receiver, commands power needs. The need for charging a wide array of systems and bidirectional power capabilities are considered, which point toward a need of underwater wireless power standards, a framework of which is proposed.

Design considerations for an active rectifier circuit for bidirectional wireless power transfer

The capability of bi-directional, underwater power transfer (both sending and receiving power) increases the functionality of underwater vehicles by allowing them to be charged and provide charge wirelessly to other systems without leaving the water. To minimize the footprint of the charging circuitry, a single transistor-based full-bridge circuit can be used to either send or receive power. This work focuses on the operation of the circuit in power receive mode, as an active rectifier. An algorithm common for active rectification is presented, and the effects of non-idealities on the timing control and efficiency is presented through experimental results.