2010219022_ Control and Driving of a Robot For

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CADSM*2001 Proceedings 179Control and Driving of a Robot forUnderwater Ship Hull Operation

Grzegorz Roznowski, Zdzislaw Kowalczuk, Pawel Raczynski11.GENERALDEAbs/rnc/ - The paper describes a robot system for underwater

cleaning and maintenance of ship hulls, drilling platforms orfloating docks. It works under water an d it is gripped to the steelsurface of a hull using the power of magnetic attraction. Itscontrol and hydraulic drives systems are presented in this paper.

Fig. 1 shows the s t ructural scheme of the moving cleaningtool of the robot. Th e numbers indicate the following blocks:

Keywords - Control and Driving, Robot System, Undenvater bristle bnlshes head ( I ) , dr i v i nggear of arms (21, drive wheelOperations. (3), driving gear (4), lectrohydraulic rotary joint (9 , rame

(6) and ballast tanks (7 & 8).I. INTRODUCTION The tool shown at Fig.2 consists of two wheels connected

with a driving axle, which is propelled by a hydraulic engine.On e of the main for dry docking is to a The wheels are controlled by two electromagnetic clutchesand they are gripped to the cleaned iron flat surface on the

principle Of magnetic ower attractionmarine growth accumulated on sides and a flat bottom of aship. Such growth brings about great resistance to the passageof the hull thorough the water, reducing the speed of thevessel and imposing requirements as to extra power of mainengines in order to maintain a reasonable schedule, which inturn results in conseq uent increase in fuel consumption.

Th e two rotating brushes (cleaning heads) driving byhydraul ic engines are m ounted on two swinging arm s whichare propelled by hydraulic servo motor. The brushes scratch

There are underwater cleaning systems controlled either bydivers or electronic equipment . The second one we c an nameas underwater robots. When a submarine body is unlesspartially m ade of steel and these parts .need sometimes to becleaned, for example as a flat bottom and hull of a ship, adrilling platform or floating dock, we offer a new design ofunderwater robot for brushing maintenance.

. Grzegorz Roznowski - Faculty of Mechanical Eng ineering Technical. University of Gdansk, Narutowicza 11/22, 809-52 Gdansk,

~ POLAND, Email: [email protected]. Zdzislaw Kowalczuk - Faculty of Electronics, Telecommunication &

Computer Science, Technical University of Gdansk, NarutowiczaI 1/22 ,80 952 G dansk, POLAND, E-mail: [email protected] Raczynski - Faculty of Electronics, Te lecomm uni- cation &Computer Science, Technical University of Gdansk, Narutowicza11/22,80 95 2 Gdansk, POLAND,E-mail: [email protected]

. ,

I!--

Fig.] Structural scheme of the moving cleaning tool.

out the marine growth. The bristles lie flat and smooth on thecleaned surface making a shaving effect in such a way as toomit injuring of the paint coat of the base. The system mayalso be used in underwater inspection providing that adva ncedhigh - sensitive television equipment any appropriate, for thepurpose, photo camera, is suppl ied. The working movement o fthe arms of the cle aning heads is synchronised with the rate of

Lviv-Slavsko , Ukraine, VI-th Intcmational Conferen ce the Experience c,f Designing and Ap plication ofCAD Systems i n hlicroelectronics

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180 CADSM*2001 Proceedingsthe robots tool movement. Clutching and breaking obtainveering of the tool the left or right wheel respectively. Thereis also an electromagnetic distributor electrically controlled,the purpose of which is to control the mechanical moment ofthe hydraulic engine and switch on and off the cleaning heads.

__ _ .. . . .. . . - . .!.. . . . . ... .- . ./,/ 4. L I~- - - -

Fig 2 The drivewheel with magnetic clutch

111.ROBOTIZATIONIt is assumed, that cleaning is to be carried out irrespective

of the weather conditions, place of mooring Shelf area or anope n sea) as well as of underwater visibility and d rifts (up to 4knots). It is a multi-task system for small and large vessels,

drilling platforms and floating docks as well as it shouldwork as a moving supply station for manual cleaning of smallsurfaces (a rudder for instance). As example of the generalconcept of the robot system for underwater brushingmaintenance let us use the cleaning of the ships hull. It isshow n in Fig.3.

Fig.3. General concept of the system

The robot tool equipped with heads and driv e is moving on theunderwater surface of the sh ip hull (1). The cleaning tool (5) of thesystem is supplied with all necessary sensors , actuators as well as alocal microprocessor controller. Electro-hydraulic turning joint andset of electrical and hydraulic leads (4) serve as a central system

(da t a and pow er-supply ing) base connecting the working tool w i th ahost computer (3 ) placed on a n assistant vessel (2). A hydroacusticsubsystem is applied to localise a current position of th e tool inrelation to the cleaned surface. Markers (6) of th e localisation.subsystem are hanging down on both sides of th e ship. The mannerin which the robot system is to be exploited is as follows:

At the beginning the robot tool is put into the water using thesmall crane which is placed on the assistant boat together withthe electro-hydraulic generator. The two ballast tanks of thetool are designed in order to make i t unsinkable. When thecleaning brushes start to work, at the moment the tool beginsto move towards the cleaned surface providing the tool hashad appropriate orientation. When the tool is close to thesurface being cleaned, electromagnets are switched on as tocling the tool to the underwater objec t.

An operator using the host computer console controls all thetools operations. A set of working mo veme nts of the cleaningtool over a chosen piece of a cleaned surface, which are up tothe system operator, composes a working cycle.

Taking into account the above considerations, the followingissues have to be de termined:- current tool position,--

local control o f the cleaning tool,central compu ter aided robot control.

Iv.ROBOT C O N T R O L SYSTEM

Robo t contro l system consists of four ma in functional parts:local microcomputer under w ater robot controller,local microcomputer navigation sy stem controller,host comp uter and operator console,integrated power and communication system.

Th e configuration of control system has been sh own at Fig. 4.The working head controller has been placed in a waterproofdisplacem ent container. Its main tasks a re:

command interpretation and execution,receiving commands from the host computer,

direct digital control of workin g head mo vem ents,based on onboard sensors (mec hanica l indicators,hull curvature sensors and cleanin g quality sen sors),

Lviv-Slavsko. Ukraine, VI-th International Conference the Experience otDesigning and Application of CAD Systems in Microelectronics



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CADSM"200 Proceedings

Mcontrol &navigatio

Fig.4 Robot controller architecturemonitoring system status and sending messages tothe host

The onboard microcomputer controlsworking head movements (start/stop, going forward,turning Iefi and right),cleaning movements (swinging motion of cleaningarms, rotational motion of cleanin g brushes),hold down to the hull (turning on an d offelectromagnets placed in road wheels)

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The onboard controller has been prepared for additionaltasks, which might be, implemented in the future robotversions. It has got some spare digital and analogue inputswhich allow to serve

* additional sensors increasing operational safcty(ultrasonic sensors and i angc-finders),quality of cleaning process sensors

Extra outputs may be used for controlhng motion andcleaning speed

Navigation system has been composed as a set of' fouihydroacustic range finders It is placed in a waterproofdisplacement container of the woiking head of robot I t iscontrolled by a microcomputer system, which is connectcd tohost via a serial interface and mode m Its m a i n task:, are

reccivmg commands fioin host.

0 consecutive measurements of the distance betweenfront and rare of the robot and four base pointsmarked with hydroacustic transponders,calculation of the working head position andorientation based on measured distances fi om basepoints,sendin g position co-ordinates and navigation systemstatus to the host

Architecture of the positioning system has been shown atFig 5 Robot working area is bordered by four transpondersRobot onboard navigation system consists of range finder co-operating with two transducers placed one at the front part ofworking head and the second at the rear Having measureddistances from the front transducer to the base transpondersan d distances from rear transducer to thc transponders it ispossible to calculate working head position and orientationeven if some measurements failedThe host computer is installed 011 board of a service ship it

IS connected to working hcad controller? via m odem and awatei proof wire An industri'il standard PC compatiblecomputer has bcen used a5 a host Its main tasks arc

sendingheceiving niesrages froin working headcontlollcl9,intei'ictivc cu-opeiation w i t h Operdtoi.



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I x2 CADSM*2001 Proceedings

0 presentation of the cleaning process status and effectsat the computer console,supervis ing working head movements and cleaningprocess .

A map o f robot working area is presented to operator onthe screen o f thehost computer . T wo different colourshave been u sed to represent cleaned and not cleanedareas. Working.head move ments arc a lso visualised onthe screen

Three robot control algor i thms has been implemented:manual ,teach-in,fully automatic (working head scans the area until itisnt cleaned in accordance to working head onboardsensor).::

Working head power supply and data transmission systemhas been integrated. Only one pair of wire i s used to supplyelectric components of workin,? head and to transfer messages

between host and onbo ard control lers . The special ised modemhas developed to separate vol tage supply f rom data s t ream.R E F E R E N C E S

[ I ] Bublick T.J., Robot App l icat ions , Wiley andSons, 1985.[2 ] Faulkner D., Int. Shipbuilding Progress, No367, 1985.[3] Kitowski Z., Moreck.i A., Ostachowicz W., Underwaterrobotics in Poland, Proceedings of the 24-thInternational Symposium on Industrial Robots, Tokyo,Japan, 1993, pp. 51 5 - 522.[4] Morecki A., Knapczyk J . , Fundamental Robot ics ,Wydawnictwo Nairkowo Trchniczne, Warszawa, 1993.

V. CONCLUSIONIt has been described a model of the underwater robot forcleaning maintenance on the ships hul l , dr i l l ing plat form o rfloating dock. It is shown on the photography in a s impli f iedrepresentation. Experiments in a wet dock have been carried

out. Conclusions resulting from them will hopefully aHow usto el iminate all drawbacks as wel l as the elements of thesystcm. which were indispensable in the research model ofthe underwater model .


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2010219022_ Control and Driving of a Robot For