Greg DavisScott HambletonJon HoltonChris JohnsonChris Monfredo

5/13/14 Rochester Institute of Technology 1

P14251Underwater Acoustic Communication

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 2

Project BackgroundBoeing wants to improve it’s relationship with RIT through sponsoring projects that involve students in aquatic engineering challenges. This project is to design a limited bandwidth communication system. The system is to be able to send and receive information as well as have communication protocols that allow for multiple systems to be able to communicate in a swarm.

This system is acoustic based. Using a speaker and hydrophone, high frequency signals are to be sent between two watertight modules that are housing the electronics necessary to send and receive meaningful data.

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 3

Project GoalsTo be able to send a signal 30 meters with high accuracy as quickly as possible. The system should be able to withstand pressures caused by 10 meters of water and should be able to resist corrosion and leaking. The system needs to be easily modified for the purposes of future expansion. The housing should be easily retrofitted to hold either future optical signal systems.

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 4

Customer NeedsCustomer Rqmt. #

Importance Description

CR1 9 Send signalCR2 9 Send signal at a rate in kb/sCR3 9 System must function underwaterCR4 9 Reliable communication schemeCR5 9 Communications must resist frequency contaminationCR6 9 Must have 2-way communication capabilitiesCR7 3 Low power consumptionCR8 3 System must be function in seawaterCR9 3 System must be pressure resistantCR10 3 System must be able to operate in ambient water temp.CR11 3 System must be easy to integrate into larger systemCR12 3 Power integrationCR13 3 Thermal integrationCR14 3 Internal communicationCR15 3 System size should be small (Height, width, length)CR16 3 The signal should have as much encryption as possibleCR17 1 Light system weightCC1 N/A Acoustic communication schemeCC2 N/A Max power consumption of 15 wattsCC3 N/A Total project budget of $1750

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 5

Engineering Specifications

Rqmt. # Priority Source Engr. Requirement (metric)Unit of

MeasureTolerance Value (+/-)

Nominal Value

Comments/Status

S1 9 CR1 Signal Range m 5/5 30S2 9 CR2 Signal Rate kb/s 5 15S3 9 CR4 Probability of error in signal % 0/10 <10S4 9 CR4 Bit error detection %S5 9 CR4 Bit error correction %S6 9 CR3,CR9 Water resistant/sealed Y/N YS7 3 CR3,CR10 System must be pressure resistant kPa 0/0 98S8 3 CR9 Housing resists corrosion g/hr As per ASTM B117-11S9 3 CR5,CR7 Non-naturally occurring underwater frequency Y/N YS10 3 CR6 Each module must have receiver and transmitter Y/N YS11 3 CR8 Low power requirement Watt 0/5 15S12 1 CR16 System Length m - Unspecified by customerS13 1 CR16 System Width m - Unspecified by customerS14 1 CR16 System Height m - Unspecified by customerS15 3 CR11,CR12,CR14 System heat sink capability Watt 5 to 15S16 3 CR12,CR13 System power integration Y/N YS17 3 CR12,CR15 System internal communication capability Y/N YS18 3 CR11 Operating Temperatures deg. F 25/25 55S19 1 CR17 Signal Encryption bits - As strong as possible, given timeS20 1 CR17 Signal Compression ratio - As much as possible, given timeS21 1 CR12 Low weight kg -

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 6

System Diagram

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 7

Risk AnalysisID Problem Likelyhood Damage Importance Mitigation Owners

1 The housing isn't watertight 2 3 6 Test waterproofing and test the empty housing SH, GD2 Short circuit 1 3 3 CJ, CM3 Damage due to mis-handling parts 1 2 2 Team must be c areful with components All4 Loss of carrier frequency 1 3 3 Have a robust communication scheme in place CJ, CM5 Power loss 1 1 1 CM6 Power Surge 1 3 3 Surge Protection CM7 Data loss 2 3 6 Have tested error correction/detection JH8 Overheat microprocessor 1 3 3 Use effi cient code and have thermal management JH, GD9 Corrosion breach 1 3 3 Galvanize or use corrosion resistant materials SH, GD

10 Speaker doesn't work 1 1 1 Has been found to work, repeatably in a lab environment CJ, CM11 Ordered components do not match specs 2 3 6 Order from reputable sources with return policies All12 Demodulation Chip doesn't work 2 3 6 Do DSP on the R-Pi. CJ (JH)13 Bandpass Filter doesn't work 1 1 1 CJ14 Mode Choke doesn't work 1 1 1 CJ15 Sheet metal housing is too expensive 1 3 3 Highly unlikely given current financial status of the project GD, SH16 PCB is too expensive 1 2 2 Use a perf board and hand solder CM17 Speaker/Hydrophone dish doesn't work 2 2 4 We check functionality first, then prioritize the dish SH, GD18 Power Converteres can have too much ripple 1 2 2 Scale C and L components or use higher current capacity converter CM19 AGC doesn't work 2 1 2 There are plenty of AGC chips available CM20 Power amplifier doesn't work 2 2 4 TI has technical support for our power converter CM21 Noise on and/or electrically charged box 1 3 3 Ground the box CM22 Discharging the batteries too low 2 3 6 Implement a battery level indicator CM

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 8

Full System Build

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 9

Full System Build

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 10

System TestsMechanical•Watertight•Pressure resistance•Corrosion resistance

Electrical•Signal Path Tracing•Power Systems•PCB Verification

Computer•FFT Synchronization•Error Handling•Sending/Receiving Frames

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 11

Results vs SpecificationsPriority Source Engr. Requirement (metric)

Unit of Measure

Tolerance Value (+/-

)

Nominal Value

Final Status

9 CR1 Signal Range m 5/5 309 CR2 Signal Rate kb/s 5 159 CR4 Probability of error in signal % 0/10 <109 CR4 Bit error detection %9 CR4 Bit error correction %9 CR3,CR9 Water resistant/sealed Y/N Y Slight Leaking from screws - Can be fixed3 CR3,CR10 System must be pressure resistant kPa 0/0 98 Tested to 4.5 m3 CR9 Housing resists corrosion g/hr3 CR5,CR7 Non-naturally occurring underwater frequency Y/N Y3 CR6 Each module must have receiver and transmitter Y/N Y3 CR8 Low power requirement Watt 0/5 151 CR16 System Length m -1 CR16 System Width m -1 CR16 System Height m -3 CR11,CR12,CR14System heat sink capability Watt 5 to 15 Untested3 CR12,CR13System power integration Y/N Y3 CR12,CR15System internal communication capability Y/N Y3 CR11 Operating Temperatures deg. F 25/25 55 Untested1 CR17 Signal Encryption bits - Will not be implemented - optional spec1 CR17 Signal Compression ratio -1 CR12 Low weight kg -

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 12

State of the Project

The system is mostly functional. There are issues with the speaker and the fickle nature of this device has caused numerous problems. The software is functioning in one-way communication, but the code is in place to make it function in two-way. Messages can be sent reliably but at low speeds. The electronics are designed to support 4 FSK and should be easily integrated into future builds.The housing has a leak issue. After an overnight test there was a small amount of water inside the housing.

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 13

Lessons Learned

•BeagleBone Black vs. Raspberry Pi•Automatic Gain Control•Pulse Shaping•Power Amplifiers•PCB Design•Hydrophones•Power Converter Startup Current•3-D Printing•Parabolic Dish Design•malloc()•Bit Collisions

Underwater Acoustic Communication

5/13/14 Rochester Institute of Technology 14

Recommendations For Improvements

•Circuit Board Changes•New Acoustic Transmitter•Flyback Diodes•New FFT Package (FFTW)•Better Synchronization Algorithm•Fix ADC