Thruster Communication for Subsurface Environments; Turning Waste Noise into Useful Data
Acoustic communication serves as one of the primary means of wirelessly communicating underwater. Whereas much of the developments in the field of wireless communication have focused on radio frequency technology, water highly absorbs radio waves rendering the link not feasible for most all subsurface operations. While acoustic links have enabled new capabilities for systems operating in this challenging environment, it has yet to reach the commodity availability of radio systems, meaning that an entire class of small, low-cost systems have been unable to make use of these links. The systems in question are primarily autonomous underwater vehicles (AUVs), as they typically operate untethered as compared to remotely operated vehicles (ROVs). To address this gap in capability, a prototype system was constructed leveraging the ambient noise produced by brushless electric thrusters to transmit data. This research aims to build on this work and answer some key questions about the technology. The primary research question is how the operation of a thruster as a propulsor impacts the transmission of data. A characterization of the system will be presented, isolating the behavior of the thruster. From this, it will be shown that a thruster behaves in a manner nearly identically to a purpose-built transducer solution. From this finding, an analysis into the optimization of the link is presented, analyzing protocol improvements, inter symbol interference, and approaches to leveraging signal harmonics of the data link to increase bandwidth. From this work, a transmitter implementation was demonstrated utilizing frequency shift keying to send data at a rate of 2000 bits per second. Beyond the specifics of this work, this transmission system was demonstrated on a low-cost, open-source motor controller, enabling a system to easy integrate or enable this capability. This demonstrates that most any system can leverage this technology to add additional operational capability.
Acoustic communication, wireless, subsurface, waste noise, Data Science, Electrical and Computer Engineering
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