A SHALLOW DRAFT VEHICLE FOR INTERDISCIPLINARY
RESEARCH AND EDUCATION
Carl Steidley, Ray Bachnak, Wien Lohatchit, Alex Sadovski, Cody Ross
Department of Computing and Mathematical Sciences
Texas A&M University-Corpus Christi
6300 Ocean Blvd.
Corpus Christi, TX 78412, USA
Keywords: Human augmentation and shared control, Control and supervision systems
Abstract: Water quality data collection in shallow water areas can be a challenging task. Obstacles encountered in
s
uch environments include difficulty in covering large territories and the presence of inaccessible areas
due to a variety of reasons such as a soft bottom or contamination. There is also a high probability of
disturbing the test area while placing the sensors. This paper describes a NASA-funded project, which
has had a great deal of student involvement and is currently in the test phase, to develop a remote-
controlled, shallow-draft vehicle designed as a supplemental tool for our studies of the South Texas
Coastal waters. The system transmits environmental data wirelessly via a radio to a docking and control
station in real-time.
1 INTRODUCTION
Data collection in shallow water areas normally
requires setting up sensors in several places. In
addition to being redundant and time consuming,
this task when performed manually has a high
chance of disturbing the test area. Investigators in
the Department of Computing and Mathematical
Sciences (CAMS) in conjunction with the Center
for Coastal Studies (CCS) of Texas A&M
University-Corpus Christi (A&M-CC) currently
collect water quality data in areas with water 3 ft.
or deeper by a man-controlled boat. A number of
research centers have been developing
autonomous boats (Hall, et al, 2002, Ross, 2002,
Rocca, 2000, Woods Hole, 2002). These boats,
however, require course planning prior to
deployment. As a result, the pre-planned course
is not easily changed once the boat is in the water.
This paper describes a project undertaken by an
interdisciplinary team of CAMS computer
science, engineering technology, geographic
information sciences, and mathematics professors
and students along with environmental
investigators at CCS to design and develop a
remotely controlled boat that
continuously and
efficiently collects water quality in shallow water
areas (6
in-3 ft), rather than using fixed position
sensors to make the water quality collections.
Our boat is small in size (7ft in length and 3 ft
i
n width), has a shallow draft, and can be easily
steered to collect data in real-time. The prototype
is designed to collect salinity and other
environmental data and is equipped with onboard
computers, water quality instruments
(Hydrolab®), GPS, digital compass, a remote
control receiver, and a receiver/transmitter radio
(Freewave). It also has sensors to detect objects
from all directions (front, sides, back, and bottom)
and will eventually have the ability to
intelligently maneuver around obstacles.
Acquired data is transmitted wirelessly via a radio
to a remote control station in real-time and ata is
logged to a PC for later processing.
2 SYSTEM DESIGN
Designing the boat took into consideration the
following operational requirements: (a) The boat
was to be remotely controlled within the
operator’s line of sight, (b) It was to be small and
easy to transport in the back of a truck without
extra towing equipment, (c) It was to be stable
326
Steidley C., Bachnak R., Lohatchit W., Sadovski A. and Ross C. (2004).
A SHALLOW DRAFT VEHICLE FOR INTERDISCIPLINARY RESEARCH AND EDUCATION.
In Proceedings of the First International Conference on Informatics in Control, Automation and Robotics, pages 326-329
DOI: 10.5220/0001126003260329
Copyright
c
SciTePress
enough to resist waves and wind, (d) It had to
have the ability to travel through areas with a
draft as small as 6 inches, (e) It had to have
sensors to detect objects from all directions (front,
sides, back, and bottom), and (f) It had to transmit
data wirelessly to a docking and control station in
real-time. The following paragraphs describe the
major components of the system.
3 REMOTE CONTROL
STATION
This station is located onshore and consists of a
remote controller and a PC. The remote controller
transmits data to steer the boat and select its
speed. The PC is used to store and process the
received data and to display the status of major
systems and onboard sensors. The PC display
serves as a guide to assist the operator with
navigation when objects around or under the boat
are detected. The operator is able to direct
the
boat to investigate areas of interest.
4 HULL DESIGN ISSUES
Issues considered in selecting a hull shape
included onboard weight, type of power,
condition of the water in which the boat is used,
means of transportation to the launch site, and the
desired draft (Handerson, 1972).
Since the draft of the boat is one of the most
important criteria, a flat bottom was selected.
After considering a variety of hull materials, it
was determined that most materials are too heavy
to meet our shallow draft requirement, thus, we
selected polyurethane. Polyurethane has two
major advantages: (1) It floats with the least draft,
and (2) It can be easily modified and customized
by carving it before adding a protective coating of
fiberglass. The boat deck is carved to fit the
battery and electronic components, which are
encased in a waterproof container. Total weight of
the prototype is approximately 150 lb.
The transom is strengthened, in order to secure
the motor, with 3/16” aluminum sheets. All pieces
are configured with reusability in mind and for
easy replacement of damaged parts.
The motor was chosen to propel the prototype
boat. This motor is rated for salt water operations
and can propel a boat as heavy as 1500 lb. It has
hand-controlled steering and 5-speeds forward
and 2-speeds reverse.The motor was easily
modified for remote control. The remote control
function was accomplished via a Futaba® 6-
channel FM radio. Currently only two channels
are used. One channel controls the steering via a
high torque servo and pushrod that connects to the
shaft of the motor and the other channel controls
forward and reverse speed via a remote control
switch. The control switch consists of two relays
that open and close according to the pulse signal
of the Receiver (Rx).
This simple configuration worked well for
tests of concept in the lab. However, another
arrangement was needed prior to sea trials. Since
the original equipment servo harness was made of
plastic and could easily break. Additionally, the
RC switch did not allow us to control variable
speed. It could only provide one speed forward
and one speed reverse. The first of these
problems was corrected by replacing the servo
harness with a 12 VDC steering motor that drives
a built-in worm gear in combination with an RC
switch to control the direction, left or right. The
second problem, that of varying the speed of the
motor, was solved using electronic control, which
would allow varying the speed in forward and
reverse. The speed of the motor is simply a
function of the position of the radio controller
joystick (Steidley, 2003).
5 STEERING MOTOR
PROTECTION
Since the steering motor is exposed to water, it
had to be waterproofed. Two nested boxes are
used to keep water from reaching the motor. The
outside box prevents splashing water from
reaching the motor, and the inside box is an
electronic waterproof box that prevents the water
that escapes from the first box from reaching the
steering motor. The boxes are attached to the
transom mount of the trolling motor.
6 MOTOR AND STEERING
A MotorGuide model GWT36 electric trolling
presents the most recently collected GPS,
Hydrolab, and depth finder information.
Additionally, system power constraints in terms
of battery voltage and computed estimated
running time are displayed on the GUI.
A SHALLOW DRAFT VEHICLE FOR INTERDISCIPLINARY RESEARCH AND EDUCATION
327
In addition, the depth and GPS navigational data
are displayed graphically in a separate window to
visually aid the researcher/operator. The GUIs
are written in Visual Basic and Gnuplot is used to
plot the depth and navigational data in the
separate window.
7 SYSTEM POWER
Two batteries are used to power the system. A
marine battery for the motor and another small
battery to operate the other onboard electronic
components, including; radio, embedded PC,
sensors, and GPS. The system operates at medium
speed with the 98Ah marine battery for about 4.8
hrs without recharging.
8 EMBEDDED SYSTEM PC AND
SENSORS
The onboard PC consists of a stack of PC/104
modules, called the “Cube,” with analog-to-
digital conversion capabilities and serial port
interfaces. The cube acts as a central control unit
and interfaces with the radio and all onboard
sensors, including the GPS and digital compass.
The water quality sensor is a Hydrolab® designed
to be used in fresh, salt, or polluted water. This
instrument measures several parameters,
including temperature, pH, dissolved O
2
, and
salinity. Our Hydrolab® model includes a pump
via a tube to take the water through the process
onboard. This device is useful in shallow water
areas since the Hydrolab® does not have to be
immersed in water (Steidley, 2003).
9 SYSTEM SOFTWARE
We have developed our system on a Linux-based
platform. The footprint version of Linux runs the
Cube PC/104 data collection and control
computer. Generally, Linux shell scripts that
operate from the Cron utility can be used to
execute data collection from a sensor at a
specified time or date, once configuration file
parameters are set in the shell scripts. However,
Cron is limited to execution intervals of a minute
or more. Since we require data collection at
shorter intervals, we have written a serial task
scheduler to collect data. For example, data is
collected from the GPS receiver and Hydrolab at
15 second intervals and written directly to
compact flash disk memory. The data is
wirelessly transmitted by radio from the serial
port of the Linux based platform on the boat to
the laptop control computer on shore. After error
checking the incoming data, the control computer
processes the received data for display on a
graphical user interface.
To provide the researcher/operator with
navigational and current data collection
information we have designed the GUI, which.
10 TESTING THE PROTOTYPE
Our first “sea test” was performed primarily to
determine that the boat draft met the design goal
of a six-inch or less draft. We also wanted to
gather experimental data to determine the optimal
locations of the compartments where the
waterproof case and the battery were to be
permanently placed. The test was completed on
December 17, 2002. The draft was measured at
two different places: 1) the bow of the boat and 2)
the transom of the boat. The test was conducted
first without any load and again with all
components expected to be present during
operation (trolling motor, marine battery, and
waterproof case filled with the electronic
component used for propulsion control and data
collection). Table 1 summarizes the results of the
draft test.
The test revealed some major
accomplishments: the boat met the draft design-
specification and remained stable in rough water
conditions with and without the load.
Selecting the material used to construct the
hull and determining the size of the boat were two
important decisions. Increased stability of the
boat may yet be achieved by slight modifications
of the hull. Stability was also improved when the
waterproof case was permanently installed. This
lowered the center of gravity and reduced friction
from the wind. This was necessary due to the
strength, durability, and reliability needed in
Corpus Christi's windy conditions.
11 SECOND SEA TRIAL
A second sea trial was performed in February
2003. The purpose of this test was to check the
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Table 1: First Test Results
BOAT CONDITION DRAFT AT BOW (IN) DRAFT AT TRANSOM (IN)
EMPTY 1 1.5
LOADED 2 3
test results met all expectations. We are currently
installing the instrumentation and preparing for a
third test of the Hydrolab and depth finding
systems.
12 CONCLUSION
This paper presents the design and development
of a remotely-operated shallow-water boat for
wireless data logging. The boat was designed to
help CCS researchers monitor water quality and
pave the way for more sophisticated data
collection systems in shallow water areas. The
design and development of the boat has had a
great deal of student, both graduate and
undergraduate, involvement. Initial test results
show that the system has the desired features and
satisfies the design criteria. This project provides
a valuable contribution to research in a number of
fields, including oceanography, studies of
contaminated environments, and hazardous areas.
ACKNOWLEDGEMENT
This project is partially supported by a NASA-
IRA grant, contract # NCC5-517.
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