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SIMPLIFIED METHOD FOR OBTAINING NAVIGATIONAL INFORMATION
FROM HYDROPHONE ARRAYS
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
I dedicate this work to my family.
I would like to thank my family for their support throughout my college ca-
reer. I would also like thank all the members of the Machine Intelligence Lab at the
University of Florida. They have provided me with the motivation and knowledge
to make this all possible. I would especially like to show my appreciation to the
professors of the Machine Intelligence Lab, for giving me an opportunity to attain
this degree of education.
TABLE OF CONTENTS
ACKNOWLEDGMENTS ................... ...... iv
LIST OF TABLES ...................... ......... vii
LIST OF FIGURES ................... ......... viii
ABSTRACT ...................... ............. ix
1 INTRODUCTION .................... ....... 1
1.1 Underwater Acoustic Pinger ......... ........ .... 1
1.2 Subjugator 2000 ............................ 2
1.3 Cornell University AUV .. ...... ............... 2
1.4 Orca ............................ .... 3
1.5 Hydrophones ............................ 3
2 AMPLIFIER CIRCUIT ........................... 5
2.1 Differential Signal ........................... 5
2.2 Circuit Design .................. ... 5
2.2.1 Instrumentation Amplifier ................ 6
2.2.2 Schmitt-trigger Buffer ................ .. 8
2.3 Board Design .................. ... 8
3 SIGNAL PROCESSING BOARD .................. ..... 10
3.1 Atmel Mega 128 .................. ......... .. 10
3.2 Altera Flex 10K70 .................. ........ .. 11
4 SIGNAL PROCESSING .................. ........ .. 12
4.1 Frequency Filter .................. ......... .. 12
4.2 Hydrophone Time of Arrival ................ .. .. 15
5 TRIANGULATION .................. .......... .. 17
6 RESULTS AND CONCLUSION .................. ..... 19
6.1 Data Acquisition Results .................. .. 19
6.1.1 Data Set 1 .................. ........ .. 20
6.1.2 D ata Set 2 . . . . . . .. 21
6.2 Triangulation Results .................. ...... .. 22
6.3 Conclusion .................. ............ .. 23
APPENDIX ADDITIONAL FIGURES .............. .. .. 24
REFERENCES ................... ............... 27
BIOGRAPHICAL SKETCH .................. ......... .. 29
LIST OF TABLES
1-1 ALP-;:' .. Pinger Specifications .................. ..... 1
2-1 INA331 Specifications .................. .... 6
2-2 Threshold Voltages .................. ..... 8
3-1 Flex 10K70 Specifications .................. ..... .. 11
LIST OF FIGURES
1-1 Subjugator 2000 Hydrophone Array Layout . .
1-2 Cornell AUV 2003's Hydrophone Sensor Placement
1-3 Subjugator 2004 Hydrophone Placement . .
2-1 Amplifier Output . ..............
2-2 PSPICE Circuit Layout . ..........
2-3 PSPICE Transient Simulation . .......
2-4 Amplifier Board Layout.(Not to Scale) . ..
3-1 Signal Processing Board Block Diagram . .
4-1 Target Pinger Filter Simulation . ......
4-2 Filter Simulation High Frequency Noise . .
4-3 Filter Simulation Low Frequency Noise . ..
4-4 Time of Arrival ASM Flow C(! .it: First Two Cases
4-5 Simulation of Time of Arrival Calculator . .
5-1 Hydrophone Array on 2-D Coordinate Plane .
6-1 Dataset 1: Hydrophone 3 0 . ......
6-2 Dataset 1: Hydrophone 1 0 . .......
6-3 Dataset 1: Hydrophone 2 0 . .......
6-4 Dataset 2: Hydrophone 3 0 . ......
6-5 Dataset 2: Hydrophone 3 0 . ......
6-6 Dataset 2: Hydrophone 3 0 . ......
6-7 Triangulation Results of Dataset 1 . ....
A-i Time of Arrival ASM . ...........
A-2 Signal Processing Board . ..........
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
SIMPLIFIED METHOD FOR OBTAINING NAVIGATIONAL INFORMATION
FROM HYDROPHONE ARRAYS
C'!h Ii: A. Antonio Arroyo
Major Department: Electrical and Computer Engineering
This thesis describes a simplified method of acquiring acoustic information
from a hydrophone array. The hardware consists of an amplifier circuit and
a custom designed signal processing board. The hydrophone signal is directly
converted to digital form by saturating the signal in the amplifier circuit. The
result is a digital pulse waveform that can be analyzed by digital non-DSP devices.
The signal processing board consists of a Flex 10k FPGA and an Atmel Mega 128
8-bit microcontroller. Using state machines in the FPGA, the digital waveform
outputs of the amplifier circuit are filtered and cross-correlated. The time of arrival
values between the hydrophones is used in the triangulation calculations in the
Hydrophones are often used on autonomous submarines for navigational pur-
poses. This particular system is part of Subjugator, an autonomous submarine
designed by students of the Machine Intelligence Lab at the University of Florida.
The mission of this robot varies yearly. It is set by the rules of the annual AUVSI
underwater competition. In the past three years, the mission has required the robot
to navigate to an acoustic pinger. Future competitions will likely involve a similar
task. Therefore the goal of this system involves gathering accurate data from they
hydrophone sensor array and processing the data to obtain navigational infor-
mation. This chapter describes similar systems designed in previous Subjugator
projects as well as systems designed by other competing schools.
1.1 Underwater Acoustic Pinger
The underwater acoustic locator pinger is used to mark an underwater target
or site. They are typically used in offshore environments. In the case of the AUVSI
2004 Underwater Competition it was used to identity the recovery zone, which was
the final task of the mission [ ]. For testing purposes, prior to the competition,
an ALP-;:,,, I pinger was purchased and will be used in all testing of the system
described in this thesis. The pinger specifications, which are similar to those of the
competition pingers, are listed in table 1-1.
Table 1-1: ALP-;:i.. Pinger Specifications
Frequency 27 kHz
Acoustic Output 162 dB (re 1 pPa)
Pulse Length 5 ms.
Pulse Repetition 1 pulse/sec.
1.2 Subjugator 2000
Subjugator 2000 was the first of our submarines to use an acoustic positioning
system. The array used in this submarine consists of five hydrophones sensors in
an ultra short baseline configuration as shown in figure 1-1 [ ]. The value of d
in figure 1-1 is equal to one wavelength of the pinger signal. Therefore the phase
difference between the hydrophone outputs is used in the bearing calculation. The
output of the hydrophones are sent to a preamplifier circuit. The output of the
preamplifer is filtered using an analog bandpass filter. The filtered signal is passed
through a zero-crossing detector and fed into a DSP. The DSP then cross-correlates
the signals and forwards the timing information to an embedded linux computer
[ ]. Finally, the linux computer computes the bearing to the pinger source [ ].
HQ I H2
[ir J 'I H4
Figure 1-1: Subjugator 2000 Hydrophone Array Layout
1.3 Cornell University AUV
The Cornell AUV 2003 entry used a different array configuration from that
used on Subjugator 2000. This configuration, known as short baseline [ ], places
four hydrophones at the extremities of the sub as shown in 1-2. The timing
information obtained is the time of arrival between the hydrophones. This only
allows one sample per ping to be used to calculate the bearing to the source. The
data acquisition in this system involves a preamplifier circuit connected to an A/D
converter. The A/D values are processed by a DSP. The signal information from
the four hydrophones are processed in an embedded linux computer to compute the
bearing to the pinger source [ ].
.. ... .. .....,
Figure 1-2: Cornell AUV 2003's Hydrophone Sensor Placement
The MIT 2004 AUVSI entry, ORCA VII, uses an ultra short baseline hy-
drophone array. The array consists of four sensors in a pyramidal formation. The
data acquisition method is similar to that used on the Cornell University entry.
The only exception being that a single DSP is used to filter and cross-correlate the
hydrophone signals. The DSP also calculates the bearing and elevation angle to the
pinger source and sends the information to eh embedded linux computer [ ].
The hydrophones used in this application are designed for navigational use.
The array hydrophones are custom-designed International Transducers part ITC-
4155. They are omnidirectional in their horizontal plane [ ]. The sensitivity for
the frequency range of 20-40 kHz is -196 through -205 dBV referenced to 1pPa.
The output from the hydrophone is a differential sinusoidal signal corresponding to
the acoustic signal in the water. The hydrophones will be used in a short baseline
configuration as discussed in chapter 5 and as shown in figure 1-3.
Figure 1-3: Subjugator 2004
The amplifier circuit used in this application is designed to amplify a given
signal to saturation. The information of interest from the hydrophone signals are
the zero-crossings. By amplifying the signal to saturation the pertinent information
is maintained. This chapter explains how the differential signal of the hydrophones
are accessed and amplified.
/ p \ > -Amplifier
Figure 2-1: Amplifier Output
2.1 Differential Signal
The output of the ITC-4155 consists of two wires. One wire carries the signal
of the sensor output. The other carries a signal that is equal and opposite. Like a
single-ended signal, a differential signal requires a return path [ ]. In the case
of the ITC-4155 hydrophones, the two signal wires are surrounded by a shielding,
which is the return path. To properly connect the sensor, the signal wires are
attached to the differential amplifier inputs and the shielding should be connected
to ground. The instrumentation amplifier amplifies the difference of two signal
wires. In this manner, any common voltage on the signals, usually noise, is not
2.2 Circuit Design
The amplifier circuit consists of two main components: an instrumentation
amplifier and a schmitt trigger buffer. The instrumentation amplifier is used to
amplify the differential signal to saturation. The amplifier's output is fed to the
schmitt tri .-c --r buffer to convert the signal into a digital waveform.
2.2.1 Instrumentation Amplifier
Since the output of the hydrophone is a differential signal, an instrumentation
amplifier is used. The Burr-Brown INA331 instrumentational amplifier was chosen
based on the specifications listed in table 2-1.
Table 2-1: INA331 Specifications
High gain 5 to 1000 V\V
Bandwidth 2 MHz
Slew Rate 5 V\/s
Low bias current 0.5pA
The INA331 is then incorporated into the amplifier circuit with the following
Gain 300 V \ V
Input Common Mode Voltage = 2.5V
Single Supply Configuration
VREF = Ov
Figure 2-2: PSPICE Circuit Layout
GAIN = 5 + 5(R2/R1) (2.1)
The behavior of the instrumentation amplifier portion of the amplifier circuit
is simulated in PSPICE using two small-signal sources with a phase difference of
1800, see figure 2-2. This figure also shows the connections required for proper
use of the instrumentation amplifier. Resistors R1 and R2 determine the gain of
the amplifier as defined by equation 2.1. The simulated input is equivalent to a
differential signal with an amplitude of 50 mVp_p. The output of the simulation is
a rectified, saturated 5 Vp_p signal as shown in figure 2-3. The simulation results,
figure 2-3, show an input signal of 50 mVp_p and an output signal saturated to 5 V
that still contains the zero-crossing information of the input signal.
Figure 2-3: PSPICE Transient Simulation
2.2.2 Schmitt-tri- 1-_ r Buffer
The Schmitt-trigger buffer is used to condition the amplified hydrophone
signal. When input voltage exceeds the positive goin threshold, VT+, the output
voltage equals 5 V. The output voltage remains at 5 V until the input voltage is
below the negative goin threshold, VT-. With the following threshold specifications,
the buffer device converts a sinusoidal signal to a digital waveform.
Table 2-2: Threshold Voltages
VT+ 2.65 V
VT- 1.88 V
2.3 Board Design
The design of the amplifier board is constrained by the space available in
the given application, Subjugator 2004. In this submarine, the amplifier board is
installed inline between the hydrophones and the wet pli'-' i. L hull connections.
The board is made water-proof by using a mold to seal it with epoxy. The shape of
the mold requires the board to be less than 4 inch long and less than 1 inch wide.
The amplifier board needs to be placed as close as possible to the hydrophone
to retain most of the signal integrity. The instrumentation amplifier and the
schmitt tri--.- v-r are available in small surface mount packages. The additional
passive components used in the amplifier circuit are also available as surface mount
components. The board layout is shown in figure 2-4.
Since a suitable connector for the hydrophone wire is not readily available,
the board was designed to connect directly to it. The three pads on the left hand
side of the board are arranged specifically for the hydrophone sensor wire. When
assembling the board, the two signal wires are soldered to the smaller pads. By
pulling the back over the insulation, it can be soldered to the larger pad.
Figure 2-4: Amplifier Board Layout. (Not to Scale)
SIGNAL PROCESSING BOARD
The signal processing board consists of an Atmel Mega 128 and an Altera
Flex 10K70 FPGA. The Mega 128 is the main control unit of the autonomous
submarine. All sensors are interfaced to the microcontroller as shown in figure
3-1. The microcontroller makes control decisions for its current task based on its
partially processed sensor data. The FPGA is currently used solely for processing
the hydrophone signals. In the future, the FPGA can be used to interface more
sensors and/or provide a fast parallel processing environment. The processing
board includes additional hardware to interface a digital compass, communicate to
a an embedded linux PC, and allow in-system programming of the Mega 128 and
Flex 10k70. This chapter describes the functionality of the Mega 128 and the Flex
3.1 Atmel Mega 128
The Atmel Mega 128 is an eight-bit microcontroller unit with flexible and
powerful on-chip peripheral capabilities. The functionality of this microcontroller
include an eight-channel analog-to-digital converter (ADC) with ten bits of
resolution, two universal .i- vinchronous serial transever (UART), and eight high-
precision timing output lines. The architecture of the code onboard the Atmel
is designed as an interrupt-driven sensor data acquision (ISDA) and interrupt-
driven accutuator control (IAC). The incorporation of the ISDA/IAC philosophy
eliminates wasteful polling routines freeing processor time to make high level
decisions and perform complex calculations [ ].
UART Mega 128
Figure 3-1: Signal Processing Board Block Diagram
3.2 Altera Flex 10K70
An Altera Flex 10K70 serves as a flexible hardware expansion device. Cur-
rently, logic cells are utilized for debug registers, additional I/O pins, and hy-
drophone logic [ ]. The hydrophone logic only occupies 15' of the logic elements
of the Flex 10k70. This leaves a 3200 logic elements for future expandability. The
Flex 10K70 features are shown in table 3-1.
Typical Gates 70,000
Logic Elements 3,744
Logic Array Blocks 468
Embedded Array Blocks 9
Total RAM Bits 18,432
Table 3-1: Flex 10K70 Specifications
The amplified signal is processed in the FPGA as a digital waveform. The
three hydrophone signals are processed simultaneously to determine the time of
arrival of the pinger signal to each hydrophone. First, each signal is filtered for
a pinger frequency of 27 kHz. The output of each filter block is then processed
to determine the time each hydrophone sensed the ping relative to the first
hydrophone that senses the ping. The state machines developed for filtering the
signals and timing the arrival of the pings are described in this chapter [ ].
4.1 Frequency Filter
Two registers containing the time values of the desired frequency band are
accessed by the Mega 128 microcontroller at reset. A state machine uses a counter
to calculate the elapsed time between rising edges. When the time between rising
edges falls between the desired frequency band values, the frequency filter module
outputs a high signal. The state machine operates and samples the hydrophone
signal with a 4 MHz clock. A 27 kHz hydrophone signal is t 148 samples of a
4 MHz clock. To use a 1 kHz frequency band centered at 27 kHz in the state
machine, the microcontroller writes frequency band values of 145 and 151 to
their corresponding registers. The sampling frequency can be increased for more
S r.-- Pin- mil
Figure 4 : Target Pinger Filter Simulation --
Figure 4-1: Target Pinger Filter Simulation
Figure 4-2: Filter Simulation High Frequency Noise
accuracy, but it is not necessary since the competition pinger frequencies will be at
least 1 kHz apart.
Module Testing.This module is tested using the test vector for a 27 kHz signal
as shown in figure 4-1. The input,labeled i/,;./ includes simulated noise identified
by the circled regions. The resulting output, labeled freq, is high when the time
between rising edges of the input is 37 us. The simulated noise creates edges that
falsely trigger the state machine and causes the output to go low.
The high frequency noise is di-ph i' i t in more detail in figure 4-2. The period
of the 27 kHz is a 37/s. The the first time bar, at 203.455 ps, is the first rising
edge. The next time bar is at the next rising edge and is equal to +37.13 ps. This
causes the output signal freq to go high. The noise edge occurs at +44.215 ps,
resulting in a period of 44.215 37.13 7 7/s, which causes the state machine to
ti .- -r freq to low.
The low frequency noise causes the same result on the 'freq' output as shown
in figure 4-3. The time from the first time bar, at 55.59/s, to the second time bar
is ,37ss. During this time, the output value of 'freq' is high. The time from the
second time bar to the third time bar is 40/ps, which is -25 kHz. The frequency
range lies outside the desired range, causing the output of 'freq' to go low.
SI I I -
Figure 4-3: Filter Simulation Low Frequency Noise
-------- I ------
ia %a m
;| a | a i
| A ^A 2
; A A i r
I I ir
0 <1- f
SnC 4A ^
: k I ;
II ^^' ^
8~ D:D ___ ;S _____^
4.2 Hydrophone Time of Arrival
The flow chart on page 25 describes the state machine used to calculate the
time of arrival of the pinger signal to the hydrophones. The flow chart includes all
the different combinations in which the hydrophones can recieve the pinger signal.
Figure 4-4 refers to the initial states, SO and S1, in which all the output values are
reset and the input signals HI, H2 and H3 are all low. Figure 4-4 further describes
the first set of combinations where the hydrophone H1 recieves the pinger signal
first. State S'?_I. 1r;/ starts a counter used to measure the time of arrival of the
pinger signal to the hydrophones. Also in state S'?_I. l.;, the output WE1 is set
high for one clock cycle. All the states labeled .qX_-.. .r; pulse a write enable signal
that trigger a register to latch the current count value. When an edge has been
detected in each of the hydrophone inputs, an interrupt signal is generated in state
Interrupt which is interfaced to the Mega 128. The Mega 128 will read the three
values from the hydrophone registers in the interrupt service routine.
[ count ,:
E delay_cnt I 'IIIII'I"I" ':"
Figure 4-5: Simulation of Time of Arrival Calculator
Module Testing. The test vector for this module simulated the output from the
filter modules. An edge is generated on each of the three input lines. Figure 4-5
shows an instance of the simulation, where the write enable signals are generated
after each edge is detected in any of the inputs. The simulation also shows the
interrupt occurring after an edge is detected on each of the inputs. The state
machine returns to its initial state after a delay a .5s.
The angle to the pinger source is determined by using simple geometry. A
system of linear equations is derived from the dimensions of the sensor array and
the angles of the hydrophones to the pinger. Figure 5-1 shows how the array is
represented on a coordinate system with respect to the pinger source.
(-L sin30,-L cos 30c ,
SL sin 30,-L cos 30)
Figure 5-1: Hydrophone Array on 2-D Coordinate Plane
The origin is set at the hydrophone that recieves the pinger signal first. The
coordinates of the other hydrophones are derived from the shape of the array, in
relation to the origin. The arcs represent the pinger signals as they arrive at each
hydrophone. The value of T1 is equal to the distance between the arcs divided
by the speed of sound in water. Similarly the value of T2 is equal to the distance
between the arc crossing the origin the an arc crossing the left hydrophone,
which is not shown. The value of L is the maximum time difference between two
hydrophones, assuming the array is in an equilateral triangle configuration. The
time of arrival values are converted to distance values by the relationship of the
speed of sound in water t 1500m/s. 5.1 is the distance equation between two
cartesian coordinate points (xl, y ) and (x2, Y2). Equations 5.2 and 5.3 are distance
equations for the right hydrophone to the pinger and the left hydrophone to the
d =V(x2 x)2 + (2 yy2) (5.1)
TD +1 T L(-L si3in30- Dsin )2 + (-Lcos 30- Dcos)2 (5.2)
TD + T2 (L sin 300 TD sin )2 + (-L cos 300 TD cos )2 (5.3)
Equations 5.2 and 5.3 are combined to generate two equations, 5.4 and 5.5.
This system of equations are solved for the angle 0 given the values T1, T2, and L.
T2(2TD + T2) + TDL sin 0 = L(L + /3TD cos ) (5.4)
T (2TD + T) = L(L + /3TD cos +TD sin ) (5.5)
RESULTS AND CONCLUSION
The system described in the previous chapters was integrated and tested in
a 2' x 5' x 1.5' container of water. The following figures are the results of =730
recorded data values for the first set and ,1030 data values for the second set.
Since phase difference is not being used, only one result can be recorded per ping.
In this test setup the pinger was placed 5 5 from the center line of the third
hydrophone. The array was placed at one end of the container, while the pinger
was at the other end. This chapter will described the results of the data acquisition
and the triangulation. The final section describes methods to improve this system.
6.1 Data Acquisition Results
Since the pinger and the array are both stationary, the time values of these
results are not expected to fluctuate more than 10 samples from a mean value.
The following three figures are histograms of the first set of results. The x axis
corresponds to time values, while the y axis corresponds to number of occurrences.
Time of arrir l dslinbution, OUTPUT7
I Hytoptlone 2
o 200 4oo 600 1000 1200
Figure 6-1: Dataset 1: Hydrophone 3= 0
Time of arrival dslinbutlon. OUTPUT7
Figure 6-2: Dataset 1: Hydrophone 1 0
6.1.1 Data Set 1
Figure 6-1 extracts all set of values whose time for hydrophone 3 is equal to
zero. This figure shows two very distinguishable peaks at ,425 for hydrophone 1
and 680 for hydrophone 2. This analysis concludes that hydrophone 3 is most
likely equal to zero.
Figure 6-2 is a histogram of all set of values whose time for hydrophone 1 is
equal to zero. The result is a more even distribution than that of figure 6-1.
Time of arrival dslinbutlon. OUTPUT7
200 400 600 800 1000
Figure 6-3: Dataset 1: Hydrophone 2
Figure 6-3 is a histogram of all set of values whose time for hydrophone 2 is
equal to zero. The result is similar to that of figure 6-2.
6.1.2 Data Set 2
Time of earrivl dslnbution. OUTPUT6
M HyDoptone 2
0 100 200 300 400 500 600 700 800 900 1000
Figure 6-4: Dataset 2: Hydrophone 3= 0
From this data set, figure 6-4 represents the distribution of the time values of
hydrophones 1 and 2, while the time value of hydrophone 3 is equal to zero. This
figure has a well defined peak for hydrophone 1 at ,50 which occurs nearly 700
times. The highest peak for hydrophone 2 occurs nearly 300 times at a time value
Figure 6-5, refers to the distribution of time values of hydrophones 2 and 3
with respect to hydrophone 1 being equal to zero. This figure shows a similar dis-
tribution as that of figure 6-4, where hydrophone 2 now contains =650 occurrences
of the approximate time value of 60. However, the peak for hydrophone 3 is lower
than that of hydrophone 2 in figure 6-4.
The distribution in figure 6-6 corresponds to the scenario where hydrophone
2 is equal to zero. The results in this figure have a low number of occurences.
Therefore this scenario cannot be considered as the conclusive result. The results of
figure 6-4 are the best values to use in triangulating this data set.
Time of arrival dslnbutlon. OUTPUT6
Figure 6-5: Dataset 2: Hydrophone 3= 0
Time of arrival dslnbutlon, OUTPUTG
Figure 6-6: Dataset 2: Hydrophone 3= 0
6.2 Triangulation Results
Using the results from the previous section, the angles were calculated per
the method described in chapter 5. The angles, as shown in figure 6-7, show the
distrubition of values from the previous section as being mainly the reflections of
the pinger signal in the test environment. The correct angle, 5o, is within the
cluster of bearings close to the zero degree mark. The echoes of the test container
are visible in area centered at 220.
150/ \ 30
180 0 O
240 __- 300
Figure 6-7: Triangulation Results of Dataset 1
Similar tests were performed in a pool, that resulted in inconclusive data. The
acoustic noise of the pool pumps did not allow the signal filters to work properly.
Based on these results, the system described in this thesis is affected by noise.
Creating a reliable acoustic based positioning system, requires accurate signal
filtering. The passive hydrophone sensors used in this system are sensitive to most
frequencies of noise. With proper analog or digital filtering, the sensors can be
used with better results. The system described in this thesis can be made more
reliable may building more complex filtering entities in the FPGA. The FPGA can
parallel process all the filtering of the signals and cross-correlate at high speeds.
However, the development time for using the FPGA will take longer than using
a Digital Signal Processor. The best approach would likely invole developing a
tunable analog filter that feeds into an FPGA or DSP to cross-correlate the signals.
Sl V T S2a S3aa delay S3aa S4aa delay S4aa
WE1= 0 WE2=1 I WE2=0 a WE3 =1 WE3 =0
SWE1 WE31 WE31 WE2
VF S2b delay S3ba delay S3ba S4ba delay S4ba
WE2 = 1 WE1 = 1 WE1 = 0 WE3 = 1 WE3 0
> s tac hunter
S2b S3bb delay Sbb S4bb delay S4bb
F E2 =0 WE3 = 1 WE3 = 0 T WE1 1 WE1 0
S2cdelay S3ca delay Slca S4ca delay S4ca
W nE2= TWE1 1 TWE1=0 WE21 WE2 0
S2 V j S3cb delay | S3cb S4cb delay S4cb
WE3 = 0 T WE2= 1 WE2 = 0 T WE1 = 1 WE1 = 0
T T F
Figure A-1: Time of Arrival ASM
Figure A-2: Signal Processing Board
 AUVSI, "Official rules and mission 7th annual international autonomous un-
derwater vehicle competition," http://www.auvsi.org/competitions/water., b',
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Verlag New York, 2003.
My educational background includes a bachelor's degree in computer engineer-
ing from the University of Florida. After being involved in a successful robotics
competition team my last semester as an undergraduate. I designed a first place
autonomous PONG p1 icing robot for the 2002 IEEE Southeastern Conference
Hardware Competition. I was given the opportunity to continue my education,
in the focus of intelligent information systems, by the professors of the Machine
Intelligence Lab. Throughout my education as a graduate student, I participated in
many robotics projects. I was a member of the 2003 Subjugator Team that com-
peted at the AUVSI underwater competition and placed eighth out of 12 teams.
For the 2004 Subjugator Team, I was promoted to team leader. I went on to lead
a team of eight outstanding engineers to design a functional and competitive au-
tonomous submarine in three months time. We placed seventh out of 18 teams at
that year's AUVSI Underwater Competition. I went on to graduate with an excep-
tional engineering background, due to the participation in the Machine Intelligence
Lab at the University of Florida.