Direction-Finding Sonar System for Autonomous Submarine

Estee Amana, Nicole Rennalls, Mitcham Costley, Frederick Ealick

ECE Department

Georgia Institute of Technology

ECE4007 L01

October 22, 2008

Project Overview

Submarine

Autonomous Underwater Vehicle

Georgia Tech Marine Robotics Group

Navy SEAL Practice Pool

Navy Competition 2009

Launch Platform

Practice Side

Competition Side

BridgeRooftopRooftop

Mission

To build sonar system under $400 to complete “Rooftop” task for competition

Design Objectives

Detect Ping

Frequency: 20-30kHz

2s

1.3ms

60°

Determine Direction

Top View

Direction of Motion

MRG GroupSonar Group RS-232

Communication

Physical Constraints

Length 5”

Width 5”

Depth 2”

Voltage 24VDC

Current 2A

t1

t2

t1< t2

Time Delay

Receiver #1

Receiver #2

Technical Approach

Sonar System Block Diagram

Hydrophones

Pinger

Variable Gain Amplifier

ADC

Measure Time Delay

RS232

Linux SBC

Hydrophones

Hydrophones

Pinger

Variable Gain Amplifier ADC

RS232

Linux SBC

Measure Time Delay

Hydrophone Construction

Transducer

Metal Casing

Metallic Membrane

Coaxial Cable

Cost: $150

Amplifiers

Hydrophones

Pinger

Variable Gain Amplifier

ADC

RS232

Linux SBC

Measure Time Delay

Filtering Amplifier Design and Testing

Four stage amplifier circuit Band pass filter to remove noise

μV V

Cost: $50

Amplification

Incoming Hydrophone Signal

Outgoing Amplified Signal

Linux SBC

Hydrophones

Pinger

Variable Gain Amplifier

ADC

RS232

Linux SBC

Measure Time Delay

Sonar System Controller

Receives 1000 samples/channel Averages 10 highest & 10 lowest samples Determines time delay

Cost: $150

Cross-correlation

0 0.2 0.4 0.6 0.8-5

0

5

0 0.2 0.4 0.6 0.8-5

0

5

0 0.1 0.2 0.3 0.4 0.5-5000

0

5000

V

Time (sec)

V2

Auto-calibration

Goal: Eliminate error from submarine design changes, trace lengths, etc.

Hydrophone

Submarine

Pinger

Direction of motion

Demonstration

Hydrophones

Waterproof PVC Pipe

Pinger

GT Pool

Laptop

Serial Cable

Electronics

Current Status

Construct and test amplifier prototype Implement existing embedded code Build hydrophones Construct amplifier on solder board Test automatic gain control

Dec

Project Schedule

Oct Nov

Test amplifier with pinger

Control gain

Demonstration

Competition Date: June 2009

Mount hydrophones

Assemble circuit solder

board

Complete hydrophones

Integrate system

Design PCB