Transcript Direction Finding Sonar System for Autonomous Submarine

Submarine Sonar Detection
Wura Bamgbose, Brian Fletcher,
Ryan LaFrance, Erin Walters
School of ECE
Georgia Institute of Technology
ECE4007 L01
April 20, 2009
Project Overview
Sonar detection system
 Marine Robotics Group
 Navy competition

Navy Competition 2009
Rooftop
Bridge
Practice
Side
Rooftop
Competition
Side
Launch Platform
Technical Objectives
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Amplify and detect a ping between 20-30 kHz
Determine the direction of origin of the ping
Communicate time delay with submarine’s
main control system
Detect Ping
2s
1.3ms
Frequency: 20-30kHz
Measure Time Delay
Pinger
t2
t1
t1<t2
Adjust Direction
Pinger
t2
t1
t1 = t2
Physical Constraints
6”
Pic of BOX &
mcu
5.5”
Length
Width
5”
5”
Depth
2”
Voltage 24VDC
Current
2A
Sonar System Block Diagram
Variable Gain
Amplifier
Hydrophones
ADC
Pinger
MCU
Measure
Time
Delay
R
S
2
3
2
Amplifiers
Variable Gain
Amplifier
Hydrophones
ADC
Pinger
MCU
Measure
Time
Delay
R
S
2
3
2
LMC6484IN-ND
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Rail-to-Rail Output Swing (within 20 mV of
supply rail 100 kW load)
Excellent CMRR and PSRR: 82 dB
Input impedance of 1 TΩ
Quad operational amplifier
Amplifier Design Performance


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Target gain of 100dB
Three stage amplifier circuit
Low gain first stage to limit noise of the
signal
Actual gain of 84dB
Amplifier Output With 50uV Input
Amplifier Output With 500uV Input
Amplifier Schematic
High-pass filter
Low-pass filter
Digital potentiometer
Band-pass Filter


Target -3dB frequencies of 18kHz & 42kHz
Actual -3dB frequencies of 18kHz & 52kHz
Microcontroller
Variable Gain
Hydrophones Amplifier
Pinger
MCU
ADC
Measure
Time
Delay
R
S
2
3
2
Sonar System Controller
MCU
ADC
Measure
Time
Delay


R
S
2
3
2
Samples at 1 Msps
Determines time delay in samples
Determining Time Delay
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Peak detection of signals on both channels
End detection of both signals
Cross correlation between start and end
points
Cross correlation has a max at the time delay
Signal Detection
Cross-correlation
V
V2
Auto-calibration
t1
t2
t1 > t2  t1 = t2
Eliminates error from submarine design changes.
Demonstration
Electronics
Laptop
Pool
Serial Cable
Hydrophones
Pinger
Remaining Tasks
Move cross-correlation code to MCU
 Design auto-calibration function
 Troubleshoot automatic gain control
 Test system in a pool

Overall Analysis

Done well:
Good noise filtering
 High gain
 Sufficient sampling rate


Improvements:
MCU with more memory
 Build circuit on one PCB to improve
performance and reduce size
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