Low Energy, Passive Acoustic Sensing
for Wireless Underwater Monitoring
Networks
Gavin Lowes
Jeff Neasham, Richie Burnett, Charalampos Tsimenidis
INTRODUCTION TO PROJECT
• EPSRC sponsored £1.3m three year project in
collaboration with Newcastle University, Heriot-Watt
University and the University of York
• Development of affordable technology for large
scale, smart wireless sensing networks to be
deployed in the oceans.
PROJECT DATA COMMUNICATION ENABLER
Low power, low cost miniature underwater
acoustic modem developed by Newcastle
University Sensors, Electromagnetics and
Acoustics Laboratory (SEALab)
Supply Voltage 3 – 6.5V
Supply Current Listening: 2.5mA
Receiving: 5mA
Transmitting: max 300mA
Standby/sleep: < 100uA
Acoustic
directivity
Near omnidirectional
Acoustic data
rate
640 bits/s, unicast and broadcast
data messages up to 64 bytes
Max range 3.6 km
Addressing Up to 256 units
Range variance ~10 cm
RS232
interface
9600 Baud, 8-bit, no parity, 1
stop bit, no flow control
AIMS AND OBJECTIVES
Research and develop the SENSOR PAYLOAD for the USMART project
• Detect acoustic signals of interest reliably and at low-power
• Classify successfully detected signals of interest
• Transmit compressed data through an underwater network of nodes
• Maintain a low-power, low-cost development approach
Signals of Interest include… Cetaceans, VESSEL DETECTION, Underwater Threats, Subsea Assets, Noise Pollution
LOW POWER VESSEL DETECTION
DETECTION SOURCE MOTIVATION
(1)Propeller Cavitation - Formation and
collapse of bubbles in water at or on the
surface of a rotating propeller, occurring
when the pressure falls below the
vapour pressure of water.
(1) https://www.maritime-executive.com/article/us-japan-and-germany-join-australian-stealth-research
(2) https://www.bbc.co.uk/news/uk-england-kent-46679414
(2)
• Detection of vessels which are being used
to carry out dangerous and illegal functions.
• Examples include – Drug trafficking,
defence related threat detection, border
control.
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwi2g46EgpTlAhVCzoUKHVDxCuMQjRx6BAgBEAQ&url=https://www.logolynx.com/topic/bbc%2Bnews%2B24&psig=AOvVaw3opsn5rZbkf2CQIvW8BYV3&ust=1570876739478845https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwi2g46EgpTlAhVCzoUKHVDxCuMQjRx6BAgBEAQ&url=https://www.logolynx.com/topic/bbc%2Bnews%2B24&psig=AOvVaw3opsn5rZbkf2CQIvW8BYV3&ust=1570876739478845
SIGNAL DETECTION METHOD
Cavitation Signal
Band Pass Filter
Rectifier
Envelope Tracker
Fast Fourier Transform
DEMON Spectrum
Detection of Envelope Modulation on Noise (DEMON)
VESSEL DETECTION CRITERIA
• The vessel detection algorithm searches for consistent DEMON spectral peaks.
• A linear fit is applied to the frequency peak history over a user defined time frame.
• Standard Error Of the Estimate (SEOE) is calculated to determine how well the actual recorded samples 𝑦 relate to the estimated samples ො𝑦.
• 𝑆𝐸𝑂𝐸 = σ( ෝ𝑦 −𝑦)2
𝑛 −2
• The acceptable SEOE value is one of a variety of user defined system thresholds to tune the algorithm to specific applications.
RECEIVE AND TRANSMIT SYSTEM DIAGRAM
VESSEL SIGNAL
DATA TRANSMITTED
DETECTION
ALGORITHM
DESIGN CHARACTERISTICS
• Integrated with existing acoustic
communication device via add-on signal
processing PCB
• Shared Transducer for Receive and Transmit
• Power consumption - 11.4mW using a 6V
supply.
• Cost - less than £40 in quantities of 200 units.
• Cable Connection to Depth Rated Battery
Pack
• Encapsulated in Acoustically Favourable
Polyurethane for Underwater Applications
DATA TRANSMISSION
RECEIVED SIGNALDATA TRANSMISSION
• Once the algorithm decides a vessel has been
detected, data is sent acoustically through the water
using the acoustic communication device developed by
Newcastle University.
FIELD TRIAL – BIOGRAD NA MORU, CROATIA
Positive detection
of RHIB at approx.
1.6km.
Detection data
transmitted
acoustically over a
200m range back
to the receiver
station.
DECODED DETECTION DATA
NORTH SEA DEPLOYMENT – NOVEMBER 2019
WIFI LINK University Marine Station Newcastle University CampusDATA BUOY
HYDROPHONE 1
HYDROPHONE 2
ACOUSTIC MODEM 1
ACOUSTIC MODEM 2
Newcastle University - Acoustic Network GatewaY (ANGY)
1km (potential for up to 3.6km in single hop)10m from
sea floor
Battery Pack
Vessel Detector/
Acoustic Modem
30
m d
ep
th
Acoustic Data Transmission
NORTH SEA DEPLOYMENT – NOVEMBER 2019
CONCLUSIONS
This presentation had demonstrated the following:
• Ability to detect propeller cavitation signals using DEMON methodology.
• Implementation of DEMON methodology using analogue electronics.
• The vessel detection criteria to decide whether a vessel is present.
• Low-power, low-cost project ethos has been maintained.
• Data communication using integrated underwater acoustic modem.
• Field trial results proving the system for vessel detection and communication.
FUTURE WORK
• Use Low-Power vessel detector to wake-up a higher power classification mode.
• Classification mode will perform time-frequency analysis on full spectrum signal.
• Spectral feature extraction will be used to classify specific vessels based on their
acoustic signature.
• Expand the current system to also detect divers.
• Explore other applications such as cetacean whistle detection/classification and
subsea asset monitoring.
• Research the feasibility of adding other sensors to the system (magnetometer,
temperature etc) to offer more data to the end user application.
• Test the system as part of the USMART underwater network.
THANK YOUhttps://research.ncl.ac.uk/usmart/ [email protected]