Direction-Finding Sonar System for Autonomous Submarine

Nicole Rennalls, Estee Amana, Frederick Ealick, Mitcham Costley

ECE Department

Georgia Institute of Technology

ECE4007 L01

December 1, 2008

Project Overview

Georgia Tech Marine Robotics Group

Autonomous Underwater Vehicle

Navy SEAL Practice Pool

Navy Competition 2009

Launch Platform

Practice Side

Competition Side

BridgeRooftopRooftop

Mission

To build a sonar system under $400 to complete the “Rooftop” task, which improves upon previous design group efforts

Design Objectives

Detect Ping

Frequency: 20-30kHz

2s

1.3ms

60°

Determine Direction

Top View

Direction of Motion

MRG GroupSonar Group

RS-232Ethernet

Communication

Physical ConstraintsAvailable Actual

Length 5” 4”

Width 5” 4.5”

Depth 2” 2”

Voltage 24VDC 24VDC

Current 2A 0.2A

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

Copper Disc

Copper Tube

Teflon Cable

BNC Connector

Epoxy Filling

Hydrophone Construction

Cost: $87

Piezoelectric Crystal

Epoxy Filling

Aluminum Foil

Hydrophone Testing

PVC Pipe

Dr. T. Michaels’ Tank

Amplifiers

Hydrophones

Pinger

Variable Gain Amplifier

ADC

RS232

Linux SBC

Measure Time Delay

MAX4196

Single-supply Rail-to-rail output (within 200 mV) Drawbacks:

Inconsistent gain across frequency band Complexity associated with four stages Gain adjustment difficult

Present Amplifier Design

Cost: $20EL8171

Intersil EL8171

Single-supply Rail-to-rail output (within 0 mV) Advantages:

PMOS input Stable gain across frequency band Fewer stages

Amplification

Automatic Gain Control

Digital Potentiometer DS1802

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

Cross-correlation of Real Data

0 20 40 60 80 1000

2000

4000

0 20 40 60 80 1000

2000

4000

0 20 40 60 80 1001.5

2

2.5x 10

8

V

V2

Sample #

Auto-calibration

Goal: Eliminate error such as submarine design changes and trace lengths.

Hydrophone

Pinger

Direction of motion

Previous Demonstration Proposal

Hydrophones

Waterproof PVC Pipe

Pinger

GT Pool

Laptop

Serial Cable

Electronics

Current Test Configuration

Hydrophone #1

Hydrophone #2

Signal Source

Transducers in Tank

Received Signals at 45°

Received Signals at -45°

Remaining Work

Complete amplifier on solder board Complete power supply circuit Eliminate reflections for demonstration

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