Knight Boat:Design of an Autonomous, Homing Surface Vessel

2.017, Spring 2006

Design of Systems Operating in Random EnvironmentsSeth Clark, Evan Karlik, Harry Lichter, Mitul Luhar, Cha-Ling O’Connell,

Roberto Rangel, James Sannino, Nina Young

Diagram of Layout with Components Specified

Boat Layout with Weight and Balance

Compass

Trolling, Steering Motor,

Hydrophone #1

GPS

Large Battery #1

Small Battery #1

Small Battery #2

Board

Transducer Motor

Controller Box

SBC

Large Battery #2

Amplifier

Hydrophone #2 Hydrofoil #2

Hydrophone #3 Hydrofoil #1

And Mount

Acoustics

Wireless

The Team

Mission Objectives

1. Demonstrate homing to subsurface acoustic beacon

2. Sea State 3 conditions3. Navigation in global frame: GPS, compass4. Waypoint autopilot capability

Application

•

• system

AUV tracking

Short-baseline

Subsystem Ranking

1. Floats upright, stable, survivable2. Power system3. Wireless communication4. Propulsion and steering5. Acoustic sensing and ranging6. Navigation (GPS, compass)

Hardware: 2005 vs. 2006• Inherited:

– vessel hull (3.66m Pungo 120 kayak)– wireless modems, GPS, compass – thruster, steering motor – hydrophones, transducer

• New to 2006: – single-board computer (SBC), software – motor controller – long-range wireless antenna – circuitry for acoustics and powering

Flotationand

Stability

Design Decision

Primary Objective: Ability to float and remain in an upright position at Sea State 3

• Trimaran design – 3.66m Pungo 120 kayak hull – Two foam outriggers, mounting with 80/20

aluminum extrusion • Outriggers:

– Better overall stability – Larger and more stable base for mounting

hydrophones

Diagrams of Outrigger Design

Rendered Image

Diagrams of Outrigger Design

Two 0.15m x 0.20m x 0.89m foam blocks sculpted and Side Viewtapered for better streamlining, coated with fiberglass.

Diagrams of Outrigger Design

Rear View

Diagrams of Outrigger Design

Top View

Hydrophone Mounting

• Hydrofoil-shaped fin will be vertically inserted through outriggers

• Hydrophones vertically mounted within the hydrofoil fins. – hydrophones are toroidal – grill carved into the lower portion of the fin

Kayak with Outriggers Mounted

Stability Tests

• Simulated version of the final hull/outrigger system

• Inclining experiment– hull/outrigger design much more stable than the

monohull version

• Initial condition response experiment– displayed the outriggers’ ability to quickly stabilize

the kayak

Mock-up Hull/Outrigger System used in Stability Tests

Mock-up Design in Tow Tank Mock-up Outrigger Design

Inclining Experiment• Determine magnitude of the righting moment at

different angles • 1.5m aluminum bar was attached to the kayak 1.6m

forward of the stern • 72 kg of ballast added • Digital level • Vessel inclined with weights

– up to 89Nm.

Weights were added at a known distance to create an applied moment. The angle of heel

was then measured.

Inclining Experiment: Data

No. Weights Weight (N) Moment (NM) Roll Trial 1 (Degrees)

Roll Trial 2 (Degrees)

0 0 0 0.2 -0.7

1 23.422 17.00 1.4 0

2 46.84 35.60 2.9 0.8

3 70.262 53.40 4.75 1.8

4 93.684 71.20 6.8 2.7

5 117.106 89.00 8.8 3.6

Inclining Experiment: Monohull

Inclining Experiment: TrimaranResults of Inclining Experiment for Hull With

Outriggers

010

2030

405060

7080

90100

-2 0 2 4 6 8 10

Roll (Degrees)

Mom

ent A

rm (N

m)

Trial 1Trial 2

Comparison of Inclining Experiment Results for Monohull and Multihull Options

0

10

20

30

40

50

60

70

80

90

100

-2 0 2 4 6 8 10 12 14 16

Roll (Degrees)

Mom

ent A

rm (N

m)

Multihull 72kgBallast Trial 1

Multihull 72kgBallast Trial 2Monohull 65kgBallast

Monohull 89 kgBallast

We compared the Monohull and Multihull Designs to pick the more stable option

Inclining Experiment: Conclusions

•Trimaran design superior in terms of stability.

•Monohull design (ballasted with 89 kg) rolled to an angle of 10 degrees after 4.3Nm moment

•Modified outrigger design rolled only 8.8 degrees when a 89.0Nm moment was applied!

Initial Condition Response Experiment

• Accelerometers at two different positions on the kayak

• Outriggers pushed down until the entire foam section submerged

• Kayak springs back from buoyancy• Outriggers provides more stable roll condition

than the monohull design – Rights itself from disturbances of 30 degrees

within 1 sec –Remains stable when forced in opposite directions

Initial Condition Response Experiment

ONE IMPULSE ON IMPULSES ON OUTRIGGER OPPOSITE SIDES

Virtually no ringing - 30˚ Impulses die out within 2 seconds

Trim Table

(Meters) Item x- y- z­# Component Name Mass (Kg) position position position

1 *Kayak 22.5 1.83 0 0.15 2 *Motor - Trolling 10.43 1 0 -0.33

3 *Motor -Steering(azumuth) 2 1 0

4 *Large Battery #1 22.68 1.48 0 0.2 5 *Large Battery #2 22.68 2.22 0 0.2 6 *Small Battery #1 2.27 1.67 0.02 7 *Small Battery #2 2.27 1.67 -0.02 8 Wireless 1 2.37 0 9 *Transducer 1.81 1.83 0

10 *Hydrophone #1 1.25 1 0 11 *Amplifier 4.76 2.75 0 12 *GPS 0.45 1.3 0 13 *Compass 0.45 0.48 0

119.67Total Displacement

0.11.921ll28 -0.141.92127

01.830.9126 01.830.91*Waterproofing25 01.830.91it24 01.670.9123 013.1822

-0.92.80.5Outrigger #221 0.92.80.5Outrigger #120

02.810.880/20 rack19 -0.92.81Hydrofoil #218 0.92.81Hydrofoil #117

-0.92.81.25Hydrophone #316 0.92.81.25Hydrophone #215

0.402.816.314 z-position y-position x- position Mass (Kg) Component Name Item #

(Meters)

Motor Contro er Box SBC in waterproof box *Electronics (wires, etc)

*Travel Cover for Cockp*Acoustics Board *Trolling Motor Mount

Outrigger System

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Moment Arm*Mass

Item # x y z

41.175 0 3.375

10.43 0 -3.4419

2 0 0

33.5664 0 4.536

50.3496 0 4.536

3.7909 0.0454 0

3.7909 -0.0454 0

2.37 0 0

3.3123 0 0

1.25 0 0

13.09 0 0

0.585 0 0

0.216 0 0

45.64 0 6.52

3.18 0 0

1.5197 0 0

1.6653 0 0

1.6653 0 0

1.6653 0 0

1.92 -0.14 0

1.92 0.1 0

15.525 1-0.04225.1017

Weighted Sum

zyx

LCG 1.88102

TCG -0.000334

VCG 0.129733

Diagram of Layout with Components Specified

Boat Layout with Weight and Balance

Compass

Trolling, Steering Motor,

Hydrophone #1

GPS

Large Battery #1

Small Battery #1

Small Battery #2

Board

Transducer Motor

Controller Box

SBC

Large Battery #2

Amplifier

Hydrophone #2 Hydrofoil #2

Hydrophone #3 Hydrofoil #1

And Mount

Acoustics

Wireless

Trim Table: Hull Characteristics

Area of Waterplane (m^2) 1.45 I_x_kayak (m^4) 0.04 I_x_pontoon (m^4) 0.10 Displacement (kg) 117.67 Volume of Displacement

(m^3) 0.12

BM (m) 1.96 KM (m) 2.00 KG (m) 0.13

KM = KB + BM GM = KM - KG BM = I_x_pontoon/Volume of Displacement KG = VCG KB ~ 0.04m

1.87GM (m) (Metacentric Height)

Motor Control

Thruster Control

• 24V trolling motor is boat’s only thruster• Trolling motor controller simply takes

analog signal of 0-3.1V to control power • The SBC produces analog signal of 0-10V

– voltage divider used to obtain the 0-3.1 volts

Thruster controlled wirelessly

Steering System

Servo Control • two circuit boards control 24V Servo Motor

• serial adaptor board • PICservo motor control board

• two digital control signals sent from SBC to the PICservo board – steady signal to indicate direction

– pulse of at least .2µs for each motor encoder step

• 33 steps/degree on servo motor• SBC counts each step sent to determine

the current motor position

SBC Buffer

NMCtest.exe

PICservo Box

Boat Hardware

Vessel Control

SBC serial ports

keyboard

to screen

digital I/O

on/off/reset

hard drive

fan

analog I/O

CommunicationsSBC

Compass

Antenna

Band Pass Filter

Thruster

Adapter

GPS Modem

Azimuth Motor

Laptop

Low Pass Filter

Sine Generator XR2206

Thruster Controller

Board

Transducer

Transformer

Audio Amplifier

Modulation AD630

Programmable Gain

Amplifier

Hydrophones

Smart Serial

Wireless

PICservo

Power Systems

laptop

USB

USB RF

antenna

SBC

RS-232 RF

12 V

9 V

12 V

modem

long-range

modem

Control Interface •

– SBC –

( ial I/O) – laptop –

MAIN

w

r

c

g

a

MENU

Wireless Test

Steer Straight-Line Course

GPS Waypoint

Acoustic Homing

Visual C++

serial modem • CrossCut ser

USB modem

Remote Control

Remote Control

* * * * *REMOTE CONTROL MODE:t - Enter new thrust (0 to 100)s - Enter new motor angle (-90 to 90)c - Jump to Steer Straight-Line Courseu - Updatex - Stop vehicle, return to Mode MenuEnter choice:

Acoustics and

Signal Processing

Acoustic System Overview •

100 m • Short-Baseline System

Objective: Track transponder moving at 1.5 m/s within

Acoustic System Overview

Hardware: • Transducer used to create source signal • Transponder responds • Hydrophones (H1, H2, H3) receive response

Signal Processing and Software • Autocorrelation used to calculate receiving time

differences • Triangulation used to locate transponder

TransducerMost transducers

incapable of <2 kHz

ITC 1001 • Piezo-Electric • Spherical Transducer• Peak TVR [18kHz]: 149 dB re µPa/V @ 1m

i.e. 10(149 - 120)/20 Pa per 1 V input @ 1 m

Figure by MIT OCW.

Directivity Pattern at 18.0 kHz

240

10dB/div

270

300

120

90

60

210 180 150

330 0 30

110

2 10

120

130

140

150

18Frequency in kHz

dB re

µPa

/V @

1m

26 34

Transmitting Voltage Response

Figure by MIT OCW.

Transponder and Hydrophones

• Receive Sensitivity: 100 dB re µPa @ 1m

• Transmit Source Level:

Sonardyne 7656 Transponder

Sonardyne type 7656 Transponder 188 dB re µPa @ 1m

STL SQ03 Hydrophone • Frequency Response:

1-65000 Hz • Receive Sensitivity:

-195 dB V re 1 µPa @ 1m • 40dB pre-amplifier STL SQ03 Hydrophone

Transducer Voltage

• Convenient Transponder Operating Frequency Channel:Source: 20.49 kHzResponse: 29.76 kHz• Can use conventional Audio Amplifiers to fire Transducer

Estimate voltage needed at transducer for 1 km range • Transducer TVR = 145 dB re µPa/V @ 1m • Transponder Sensitivity = 100 dB re µPa @ 1m • Transmission losses at 1 km = 20 log10(1000) = 60 dB • V = 100 + 60 – 145 = 15 dB re 1 V = 5.6 V

Amplification at HydrophoneResponse Signal Estimation: • Transponder Response = 188 dB re µPa @ 1m• Attenuation losses at 1 km= 60 dB • Hydrophone Sensitivity

= -195 dB V re 1 µPa @ 1m + 40 dB (pre-amp) = -155 dB V re 1 µPa @ 1m

Voltage after hydrophone• V = 188 – 60 – 155 = -27 dB V Gain required for 1V signal • Gain = +27 dB V

Electronics: Transducer• SBC digital output is set high

• The XR2206 function generator chip creates a 20.49 kHz signal

• Amplifier transmits high current signal

• Transformer used to change into a high voltage signal

SBC/ TT8 (Digital output)

Sine Generator XR2206

Max 1V

Audio amplifier Sony XM2200

Transducer

(20.49 kHz)

Transformer

Transducer PCB

XR2206Amplitude Control

From SBC D/O

To Amplifer

Power

Frequency Control Input/Output Level Shifting

Frequency Modulation • SBC maximum sampling rate = 45 kHz

• sampling ≥ 2F)Modulation to avoid aliasing (F

Electronics: Hydrophones

• Input signals from hydrophone amplified

• Band Pass filter used to limit the signal to 29.76 kHz

• XR2206 function generator signal at (29.76 + δ) kHz

• Modulation

• 2-pole Butterworth low pass filter

• SBC samples signal

Hydrophones

Programmable Amplifier

Band Pass Filter

ADC on SBC

Function Generator XR2206

(29.76 + δ kHz)

Low Pass Filter (δ kHz)

AD630 Modulator

(Gain 60 dB)

(29.76 kHz)

Hydrophone PCB

Hydrophone

Power

Modulating signal from XR2206

AD630 Modulator

Programmable Amplifier

Output to SBC

Bandpass Filter 2 pole Low-pass Filter

Signal Processing: Autocorrelation

Time difference in the response signal reaching the hydrophones

Software: Triangulation

t1-tt = (1/c)(2R – r1cos (Θ1- Φ))

t2-tt = (1/c)(2R – r2cos (Θ2- Φ))

t3-tt = (1/c)(2R – r3cos (Θ3- Φ))

t1,t2,t3: total travel time to hydrophone

tt: transponder response time

Navigation

Compass – Block Diagram

Compass – Field TestCompass Data

Bea

ring

(deg

ree)

300

250

200

150

100

50

0

-50

-100

-1500 0.5 1 1.5 2 2.5

Time (ms) x 104

GPS

• •

positioning systems •

Determine vessel location Used in combination with acoustic

Map vessel’s traveling history

• (6-40 V DC)

GPS - Specifications

Garmin HVS GPS Unit

• 9 V battery

• 2 serial ports

GPS – Block Diagram

GPS – Field Test

Budget

Item Total Cost SBC $ 1,044.00

SBC LCD screen $ 447.00

LCD Cable $ 65.00

SBC Development Kit & Accessories $ 728.00

SBC Keyboard and Accessories $ 243.00

80GB HD for SBC $ 70.00

CD Drive for SBC $ 30.00

PIC Servo SC Board & Accessories $ 623.55

630JN Modulating Chips $ 59.00

Antenna & Cable $ 265.00

Power systems Hardware & Materials $ 220.95

Express PCB $ 59.00

Cables $ 102.24

80/20 Extrusion $ 300.00

TOTAL $ 4,256.74

Total Cost for Materials Purchased Spring 2006 = $4256.74 Lab consumables provided by OETL < $100.00

MATERIALS COST

Acoustics Materials $5,951.00

SBC and Related Materials $2,627

Navigation Materials $874.00

Wireless Materials $670.00

Power Systems $458.00

Assorted Electrical Components and Cables $161.00

Kayak and Outrigger Accessories $983.00

Motor and Accessories $1,224.00

TOTAL COST $12,948.00

Current State of Project• 22 of 25 milestones completed

• Functional C++ programs created for acoustics and wireless

• Compass interfaced with SBC • GPS interfaced with SBC • Motor control using PICservo and SBC

• SBC fires transducer, accepts hydrophone signals

Future Work• Assembled vessel has motor systems,

power, SBC, wireless • Achieve wireless control of steering motor• Read modulated hydrophone inputs to

SBC • Next term: Install acoustic system,

compass, GPS • Feedback control• Field testing!

Questions?

Comments?