P14251: Underwater Acoustic Communication

MotivationIn an attempt to foster student engineers in aquatic engineering problems, Boeing has supported several underwater-robotics related projects. The objective of this project was to send an acoustic signal underwater to achieve a specific data transfer rate out to a certain distance. The primary application would be to send information between two robots or a robot and a surface vessel.

DesignA 4-FSK modulation scheme was used to transmit the signal over the acoustic channel, using a speaker to output the signal and a hydrophone to read it in. Due to budget constraints, an optimal speaker for this application could not be selected, but the communication scheme was designed to work around this. For the microcontroller, the BeagleBone Black was chosen for its numerous GPIO ports, fast processor, and expansion potential. The underwater housing was made of sheet metal with the front and back plates mounted with screws, nuts and pems.

Design FeaturesMechanical Engineering8”x6”x6” Watertight Housing

Cable Glands for speaker and hydrophone Santoprene Gasket for face plates

Parabolic Dish Design Anticipated gain of 15 dB

Power Amplifier Heat Sink

Electrical EngineeringPCB Design

4 LayersModulation

Timer Chip & Pulse ShapingPower System

Computer EngineeringDemodulation

FFTData Compression

2:1Error Correction & Detection

Reed SolomonController ModuleCommunication Protocol

CSMA/CAUser Interface

CustomerDr. Andres Kwasinski

GuideLes Moore

Team MembersChristopher Monfredo (EE)Scott Hambleton (ME)Greg Davis (ME)Christopher Johnson (EE)Jon Holton (CE)

System Diagram

Engr. Requirement Unit of Measure Nominal Value

Signal Range m 30Signal Rate kb/s 15Probability of error in signal % <10Bit error detection %Bit error correction %Water resistant/sealed Y/N YSystem must be pressure resistant kPa 98Housing resists corrosion g/hrNon-naturally occurring underwater frequency Y/N YEach module must have receiver and transmitter Y/N YLow power requirement Watt 15

Engineering Requirements

Final Design vs Initial CAD

Printed Circuit Board Layout