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

Launch Platform

Practice Side

Competition Side

BridgeRooftopRooftop

Technical Objectives

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

Frequency: 20-30kHz

2s

1.3ms

t1

t2Pinger

t1<t2

Measure Time Delay

t1

t2Pinger

t1 = t2

Adjust Direction

Physical Constraints

Length 5”

Width 5”

Depth 2”

Voltage 24VDC

Current 2A

Pic of BOX & mcu6”

5.5”

Sonar System Block Diagram

Hydrophones

Pinger

Variable Gain Amplifier

ADC

Measure Time Delay

RS232

MCU

Amplifiers

Hydrophones

Pinger

Variable Gain Amplifier

ADC

RS232

MCU

Measure Time Delay

LMC6484IN-ND

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

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

Hydrophones

Pinger

Variable Gain Amplifier

ADC

RS232

MCU

Measure Time Delay

Sonar System Controller

Samples at 1 Msps Determines time delay in samples

ADC

RS232

MCU

Measure Time Delay

Determining Time Delay

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

Eliminates error from submarine design changes.

t1 > t2 t1 = t2

t1

t2

Demonstration

Hydrophones Pinger

Pool

Laptop

Serial Cable

Electronics

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