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

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

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

 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

, 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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