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The Ap plication of Advanced Robotics and Sensor Techn ologies to the

Preservation of the USS Constitution

Jeffrey Cole*

Steven Du bowsky**

Nathan Rutman*

Craig Sun ada *

Departm ent of Mechanical Engineering

Massachusetts Institu te of Technology

Cambrid ge, MA O2139 USA

ABSTRACT

The application of robotics and advanced sensor technology to solve important

problems in the fields of architectural, archaeological and art conservation andpreservation is d iscussed . The USS Constitution is considered as a d emonstration

project of this work. Three important applications of this technology to the

preservation of the ship are discussed. A design is presented for one of these

ap plications -- a keel deflection m easur emen t system. It is conclud ed th at robotics

and ad vanced sensor technology offers substantial prom ise of hav ing imp ortan t

benefits for the restoration and pr eservation of imp ortant h istoric and architectur al

sites and m oments.

INTRODUCTION

This pap er reports on a research progr am in w hich we are exploring the app lication

of recently d eveloped technologies in robotics, sensors and real-time comp uters to

solve imp ortan t pr oblems faced by th e architectur al, archaeological and a rt conser-

vation and p reservation commu nities.

Over the p ast decade, significant ad vancement has been m ade in the technology of

robotics, sensors and comp uters, at su bstantial costs to governm ent agencies such a s

N ASA, the Dep artm ent of Defense, and the Dep artm ent of Energy [1-7]. This tech-

nology has imp ortant p otential app lication in the area of preservation and conser-

vation of historic and artistic treasures, and in par ticular m onu ments an d field sites.

Amon g the tasks that the conservation commu nity is called on to perform, there ex-

ist a num ber that could g reatly benefit from the ap plication of advan ced robotics and

*Gradu ate Research Assistant** Professor

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sensor technologies. Some traditional conservation

w ork has resulted, unavoid ably, in the deterioration of

the site. For examp le, conservation w ork on some large

mon um ents has used scaffoldin g anchors installed in

holes drilled into the monument itself. Some

conservation tasks, such as detailed site mappings,

require a great deal of tedious work. Many tasks are

limited d ue to safety considerat ions. Indeed , some tasks

that are of interest to the conservation community

sim p ly ar e no w imp ossible or im pr actical to execute d ue to safety concerns and

access limitations. Finally, many highly desirable conservation procedures are

simply too expensive using current techniques. Advanced robotics and sensor

technologies may be able to solve some of these pr oblems.

Working w ith researchers and practi t ioners in the conservation and preservation

fields has mad e it clear to u s, that w hile techn ical capabilities are very imp ortant,

the acceptance of robotics and sen sor technology to th ese fields will requ ire a highly

successful and v isible demon stration p roject. From ou r stud ies, w e have ident ified

the USS Consti tution as the id eal site for such a dem onstration p roject . Ou r p re-

l iminary w ork has shown that there are a nu mber of potential tasks, important to

the pr eservation of the ship, that ad vanced technology could p erform mor e effec-

tively tha n curr ent m ethods. In some cases the technology could offer greater safety

or is potentially more cost effective. In th is pap er w e describe three of these poten-tial app lications and their p ossible solutions. The first is an autom ated in -situ h og

measur ement sensor system to continuou sly monitor the shap e of the ships keel

w hile she in th e wat er. The second is a robotic system to d etect rot in the ship s in-

terna l structu re beneath its rock and chain ballast. The final is a robotic d evice to in-

spect the ships mast an d rigging for d eterioration.

It should be recognized th at a d emonstration on the USS Constitution w ould also

benefit the gr owth of robotics. It wou ld p rovide a challenging and exciting test-bed

for the techn ology und er actual field cond itions.

HO G MEASUREMENT SYSTEM

The keel of the ship changes shape over time du e to the effects of water an d loading.

In ord er to red uce this hog an d t hereby extend the life of the keel, it is necessary to

know the shap e of the curve accura tely. Presently, hog m easurem ent meth ods in-

clud e using d ivers wh o man ually measur e the d isplacement of the keel from a fixed

reference line, or ind irect meth ods from in side the ship s hu ll. We have d eveloped

Figure 1. The USS Constitu tion

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a system based on d istributed sensor technology for quickly, accur ately, and inexpen-

sively determ ining the keel shap e. Simply p ut, the system m easures the w ater pres-

sur e at a sma ll set of locations (seven) on the keel . From these measu remen ts a

comp ut er accur ately infers the shape of the keel, in real-time.

The system is able to use a sm allnum ber of sensors by app lying Chebyshev theory todeterm ine the op timal locations for the pressure measur ements. These locations

are selected to m inimize the maximu m m easurement error. The water pressure on

the keel is converted to an air pressure signal by fixed keel pr essure transd ucers, see

Figur e 2. Pressure sensors then m easure the p ressure at th e keel, wh ich is a d irect

function of the d epth. These pressure sensors are exposed only to air p ressure and

are located at an on-board measu rement compu ter within the ship. This design

pu ts all electronic hard w are elements in a shirt sleeve environm ent. It perm its

the use of inexpensive commercial components and makes maintenance and

calibration o f the system easy.

d i f f e r en t i a l

p r e s s u r e

Senso rs

a i r

hoses

com put e rre f e rencep r e s s u r e

Wa t e r P ressu re / A i r

Pr e s s u r e T r a n s d u c e r s

k e e l

D a t a Acq u i s i t i on

In t e r f ace

Figure 2. The Hog measu remen t system overview. Sensors on the keel report pressure at specific loca-

tions, from w hich the compu ter calculates the k eel shape.

The keel pressures are compared to a reference pressure at one end of the ship using

these differential pr essure sensors. This allow s accurate measu rements over the

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small range of transd ucer dep ths. From th ese finite dep th m easurements the com-

pu ter calculates the shap e of the keel, see Figure 3.

Keel p osi t ion ( f t )- 4

- 2

0

2

4

6

8

1 0

1 2

1 4

Figure 3. Keel shap e inferred from seven measurem ents. The bars are sensor readings, the solid line is

diver-measured d ata, and the dashed line is the curve shape in ferred from the sen sors.

SUB-BALLAST IN SPECTION

The area und erneath th e ballast in the hold of the ship is subject to d amp , rot-indu c-

ing cond itions, see Figu re 4. It is imp ossible for w orkers to inspect this area except

du ring d ry-dock, w hen th e ballast is removed. In order to facilitate more frequent

inspection, the u se of a small autonom ous field robot to p erform this inspection is

being considered, see Figure 5. The robot w ould carry a video camera and sensors

designed to detect and measure rot.

Keelson

Sister Keel

Proposed Ballast Support

B a l l a s tInspect ion Surfaces

D r a i n

Keel Hu l l

L imber s t rake

Figure 4. Sub -ballast area. The area is only exposed d uring d ry dock. An autom ated inspection system

that can work u nd erneath the ballast wou ld be very useful.

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The inspection task is fur ther comp licated by the presence of diagonal riders, w hich

period ically cut off sections of the su b-ballast area. The robot w ould have t o climb

out of the area, over the rider, and then back dow n into the next section.

Figure 5. A concept for a sub-ballast inspection robot.

Various asp ects of this problem are being stud ied, includ e rapid mechanical robotic

design, robust plann ing algorithm s, adv anced sensor techn ology, and control sys-tems. The resu lts of this wor k w ould be useful in a wid e variety of field ap plica-

tions, includ ing other conservation tasks.

MAST AND RIGG ING IN SPECTION

Finally, the masts of the ship are also subject to rot an d n eed p eriodic insp ection.

The cur rent insp ection m ethod has a w orker climb to extreme heights, and / or ex-

pen sive (and un sightly) cranes to inspect the up per sections, see Figure 6. The top -

most sections are never insp ected. A robotic solution m ight again be u seful.

We are examining tw o ap pr oaches to this pr oblem, see Figure 7. First is a climbing

robot concept to navigate the comp lex rigging and climb the m asts. This ap pr oach

challenges present technology. However, we have developed a simple climbing

robot and are stud ying its potential extension to such tasks as mast inspection. The

second app roach is long reach m anip ulators, see Figure 7. Problems relating to the

control of long reach flexible ma nipu lator systems are similarly un d er stud y in our

laborator y in connection with NASAs Sp ace Station Freed om .

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mast inspec t ion

Figure 6. The complexity of the Constitu tions rigging and h eight of her masts (220) mak e inspection

difficult.

Tranporter/Control Unit

IntelligentInspectionDevice

ArticulatedDeployableElements

CompositeMaterials

AutonomousClimbingInspectionRobot

CCD camera

Ultrasonic Sensor

RF Transmitter/Receiver Control

Figure 7. Two mast inspection robot concepts

CONCLUSIONS

This pap er reports on a research p rogram to explore the ap plication of robotics, sen-

sors and r eal-time compu ter techn ologies to solve imp ortan t problem s faced by the

architectural, archaeological and art conservation and preservation communities.

The USS Constitution id entified h as been iden tified as the id eal site for a dem on-

stration project of this w ork. This pap er d escribes three potentially imp ortant ap pli-

cations of this technology to the p reservation of the ship .

We believe that su ch adv anced techn ology cou ld p erform th ese tasks more effec-

tively, safely, and w ith less total cost than cu rren t meth od s. A conclusion of our

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