591
1 INTRODUCTION
The autonomous underwater vehicles perform
locomotion and manipulation tasks that certainly
requireahighprecisionpositioning.Themainaimof
thecurrentresearchistoworkoutapreciseposition
stabilization system PPSS that ensures the
stabilization of the position and the correct
orientation of the vehicle. The PPSS system should
operate independently of the ma
in drive. The main
drive system is responsible for a good navigation.
The PPSS system has a separate electric executive
motors.Anelectricmadedriveallowsthevehicleto
work in conditions of immersion and to charge
unattended.Inthe paperthe functionalstructureof
PPSS system, some elements of operation of the
overall algorit
hm, a simulation model written in
Matlab software and sample simulation results are
presented.Havingthesimulationmodeltheresearch
of the vehicle movements during the planned
missionmaybecarriedout.Thesimulationprogram
alsoallowstocheckhowthecodedalgorit
hmswork
at each step of operation. The vehicle motion may
determined due to the influence of interferences as
well.Thedesignerswouldbeabletousethemodelto
determinethepossibilitiesoffurtherdevelopmentof
the vehicle including the energy usage during the
mission.
2 THERESEARCH
The contemporary tasks of navy ships require to
apply more and more advanced multi‐task ships.
Despite of the size the multi‐task ships are the
platforms for the flying drones and unmanned
waterborne vehicles. The unmanned maritime
vehicles may be the remote operated vehicles and
An Integrated Model of Motion, Steering, Positioning
and Stabilization of an Unmanned Autonomous
Maritime Vehicle
M.K.Gerigk
GdańskUniversityofTechnology,Poland
S.Wójtowicz
ElectrotechnicalInstituteinWarsaw,Poland
ABSTRACT: In the paper the aim of an interdisciplinary research is presented. The research method is
introduced. An object the unmanned autonomous maritime vehicle is briefly described. The key research
problemconcernsacombinedmodelofthevehiclemotionincludingtheloadsofliftandhydrodynamicnature.
Themodelta
kesintoaccountthegravityanddisplacementforces,resistanceandthrustforces,liftandother
hydrodynamicforces.Oneofthemajorresearchtasksistopreciselypredictthepositionofthevehicle.Todo
thatanintegratedmodelofacquiring,analyzingandprocessingthesignalsisnecessary.Theprocessedsignals
ma
ythenbeusedfortheprecisesteeringofthevehicle.Thevehicleshouldbeequippedwithastabilization
system. Some information on an integrated steering, positioning and stabilization system of the vehicle is
brieflypresentedinthepaper.Suchthesystemenablestoobtainafullyautonomousvehicle.Someinformat
ion
onthepropulsionandunderwaterenergysupplysystemsarepresentedinthepaper,too.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 4
December 2015
DOI:10.12716/1001.09.04.18
592
unmanned autonomous vehicles. The latest may be
calledasthemaritimeorunderwaterdrones.
Inthepaperthemaritimeandunderwaterdrones
willbecalledastheunmannedmaritimeobjects.The
reason is that the unmanned waterborne drones
sometimesmaynotbeautonomous.
The primary task of an object should be ab
le to
conductamissioninsuchawaythattheinformation
acquired by the object would directly be sent to,
processedandusedbythecommandcentre.
The main objective of the current research is to
workoutafunctionalmodeloftheadvancedobject
whichshould beable tomove onthe watersurface
with a different range of speed. The same object
could move ab
ove the water surface for a short
period of time but the flight height should be less
than 5 meters. The object should have a special
powersupplysystemenablingtoworkforatleast30
minutes up to a few hours before the new set of
energysupplyisdelivered.
Themethodologyofthecurrentresearchisba
sed
ontheholisticapproach.Theimplementationofthis
approachtothedesign,constructionandoperationof
the object is novel. The research method combines
the performa
nce‐oriented approach with the risk‐
based approach. The research problems associated
withdevelopmentofaconceptoftheobjectmoving
in two specific operational conditions is associated
with the following tasks to be performed: object
definition,assessmentofobjectperformance,steering
andcontrol,safety.
The object is defined as a hybrid mono‐hull
including the hull form, arrangement of int
ernal
spaces, propulsion subsystem, ballast system and
otherfunctionalsubsystems
The problem of estimating the object mass
requires to estimate the weight of the following
items:
weight of all the ma terials used concerning the
weightofskinplates,mainframes,etc.,
weightofthepropulsionsystem,
weightofallthesub‐systemsandequipment,
pa
yload.
Then the object performance may be assessed.
This is connected with estimation the floatability,
stability, resistance and propulsion characteristics
first of all. After the steering and control
characteristicsareestimatedthemaneuverabilityand
seakeeping of the object ma
y be assessed. The
assessment of the object performance and risk
assessment may be done for the data operational
conditions and sequence of events under
consideration.
Theconceptoftheobject hasbeendevelopedby
Mirosław K. Gerigk, Profesor of Gdańsk University
of Technology. He is responsible for the furt
her
research and design where the object hull form,
choice of materials, construction and strength,
propulsion, energy supply, sea loads and object
hydrodynamicsaretheresearchanddesigndrivers.
Dr.StefanWójtowiczisgenerallyresponsibleforthe
development of the vehicle steering and control
systems. The entire research tea
m consists of the
specialistsfromafewPolishresearchinstitutions.
3 THEMETHOD
The research method is a kind of performance‐
oriented risk‐based method which enables to assess
theobjectsafetyatthedesignstageandinoperation,
Gerigk (2010). The method takes into account the
influenceofdesignandoperationalfactorsonsafety
including the safety management related factors as
well. The holist
ic approach to assessment of the
object safety is applied. The method is based on
implementationofthesystemapproachtosafety.
For the object performance evaluation the
investigations using the physical models and
numerical simulation techniques may be applied.
The object performance estimation enables to take
intoaccounttheinfluenceoftheint
ermediateevents,
additionalevents(releases)andconsequencesonthe
object behavior. This may be done for the data
sequence of events for a scenario under
consideration.
Theriskassessmentisbasedonapplicationofthe
matrixtyperisk modelwhichisprepared insucha
way tha
t it enables to consider almost all the
scenariosofevents.Thecriteriawithinthemethodis
to achieve an adequate level of risk using the risk
acceptance criteria, risk matrix, Gerigk (2010).
Providingasufficientlevel ofsafetybasedontherisk
assessment is the main objective. It is either the
design,operationalororganizationalobjective.Safety
isthe designobjective between theother objectives.
Themea
sureofsafetyoftheobjectistherisk(levelof
risk).
The structure of the method is presented in
Figure1,Gerigk(2010).
Themethodisbasedonthefollowingmainsteps:
setti
ng the requirements, criteria, limitations,
safetyobjectives;
definingtheobjectandenvironment;
identifying the hazards and identifying the
sequencesofevents(scenarios);
assessingtheobjectperformance;
estimatingthe risk according to the event tree
analysisETAandmatrixtyperiskmodel(riskis
estimatedseparatelyforeachscenarioseparately);
assessingtheriskaccordingtotheriskacceptance
crit
eria(riskmatrix)andsafetyobjectives;
managing the risk according to the risk control
options;
selecting the design (or operational procedure)
that meet the requirements, criteria, limitations,
safetyobjectives;
optimizingthedesign(oroperationalprocedure);
ma
kingthedecisionsonsafety.
593
Shi
p
/aircraft
Natural
environment
Hull form
Arrangement of
internal spaces
Loadin
g
conditions
Start
Safety objectives
Standard design objectives
Design requirements, criteria, limitations
Risk acceptance criteria
Limitations concerning the costs and benefits
Design/operation
Aircraft/ship and environment
definition
Hazard identification
Identification of accident scenarios
Estimation of the
probability of hazard
occurence P
i
Assessment of aircraft/ship
performance in:
- undamaged conditions
- damaged conditions
Risk estimation
R
i
= P
i
* C
i
Risk assessment:
Is risk tolerable?
Ranking the
hazards,
Risk acceptance
criteria
No Yes
Risk
control
options:
-prevention
-reduction
-mitigation
Modification of design or
operational procedure
Choice of optimal design or
operational procedure
System of making the decisions on the object
safet
y
in undama
g
ed/dama
g
ed conditions
End
Estimation of
accident
consequences C
i
Are costs too hi
g
h ? NoYes
Costs/benefits analysis
Models of risk
Accident categories
Wind
Waves
Another
Stranding
Collision
P
i
, C
i
, R
i
– concerns the
iterations in respect to
all the possible events
accident scenarios
Hazard assessment
Figure1.Structureofthemethodofriskandsafetyassessmentofshipsandmaritimeobjects,(M.K.Gerigk,2010).
4 THEUNMANNEDAUTONOMOUSMARITIME
VEHICLE
The primary aim of the research is to work out a
functionalmodeloftheobjectmovingintwospecific
operationalconditions.Theoperationalconditionsare
relatedtothetaskstheobjectisdesignedfor.
The novel solutions have been applied regarding
the hull form, arrangement of internal spaces,
materials
andpropulsionsystem.Thefinalhullform
isacombinedʺplanning‐wingingroundʺhullform.
The basic arrangement of internal spaces has been
designed according to functional requirements. The
arrangement of the object internal spaces is very
much affected by the sub‐systems predicted to be
installed. The sub‐
systems which have been taken
intoaccountareasfollows:
air‐jetpropulsionsub‐system,
water‐jetpropulsionsub‐system,
powersupplysub‐system,
ballastsub‐system,
airsupplysub‐system,
hydraulicsub‐system,
steeringsub‐system,
communicationandnavigationsub‐system
multi‐task patrol sub‐system or combat sub‐
system.
The stealth technology achievements have been
appliedtoobtaintheuniquehydrodynamicandother
characteristics. The major factors enabling obtaining
the object stealth features are: hull form, hull skin
594
cover,modifiedboundarylayer,modifiedemissionof
vibrationsandacoustic(hydro‐acoustic)space.
Ithasbeenanticipatedthattheobjectmayhavea
possibility to move on the water surface and for a
short period of time above the water surface. The
flightheightissmallanditisassumed
tobelessthan
5meters.
The second version of the object has the main
parametersasfollows:
overalllengthL‐isequalto5.8meters,
operationalbreadthB‐isequalto5.2metersor6.0
meters,dependingonthewingsystemapplied,
breadthduringtransportB
t‐isequalto2.4meters,
heightH‐isequalto1.1meters,
mass is equal to from 1.8 tons to 2.4 tons,
dependingontheweightofequipmentinstalled,
maximumobjectspeedonthewatersurfacev
ws‐is
equalto15meters/seconds,
maximum object speed above the water surface
v
aws‐is equal to from 15 meters/seconds to 45
meters/seconds, depending on the air‐jet
propulsionandwingsystemapplied.
A visualization of the first, second and third
versionoftheobjectunderconsiderationispresented
inFigure2.
Figure2.Avisualizationofthreeversionsoftheunmanned
autonomousmaritimevehicle,(M.K. Gerigk,2011‐2015).
5 THEAIMOFCURRENTRESEARCH
Oneofthemainresearchanddesignissuesistowork
outa precisepositionstabilizationsystemPPSSforan
unmanned autonomous maritime vehicle. This
system is independent from the main propulsion
system which is responsible for the vehicle motion
controlled by the navigation system. Both the main
propulsion and PPSS systems have the acting
electricalengines.Theelectricpropulsionenablesthe
vehicle to work during the submersible mode and
automaticenergyuploading.
Itshouldbepossibletouploadthebatteriesusing
the installed photovoltaic batteries. The underwater
mobile uploading stands perhaps cause that the
vehicleisabletostaysubmergedwithoutlimitations.
The PPSS systemshould be treated as a separate
module because the activity of the vehicle which is
connected with collecting the species, detecting the
objects, scanning the sea bottom, geometry
measurementsofthesurroundingenvironmentusing
the tools installed onboard the vehicle. All these
activitiesrequireaprecisedeterminationandkeeping
thevehiclepositionandorientation.
Currently,theresearchisperformedforavehicle
modelpresentedinFigure3.
6 THEFUNCTIONALITYANDPHYSICAL
MODELOFPPSSSYSTEM
Besidesofthemainpropulsionsystemthevehiclehas
asystemofprecisepositioning.Thesystemconsistsof
four thrusters as an example locatedhorizontally or
verticallytothevehiclebaseplane.ThePPSSsystem
needs to obtain the required position of the vehicle.
Thepositionin
3DspaceisdeterminedbytheNHiO
including point P
1 or by the plane H and points P1
and P
2. The position of the PPSS system thrusters
according to the vehicle base plane is presented in
Figure3.
Figure3.ThepositionofthePPSSthrustersaccordingtothe
vehiclebaseplane,(S.Wójtowicz,M.K.Gerigk,2015).
The physical model consists of the geometrical
position of the precise propulsion units, formal
description of the sensor system, AI (Artificial
Intelligence) system for analyzing the data and
systemofeffectors.
Fourthrusterslocatedsymmetricallyaccordingto
the vehicle centre plane are installed in such a way
that the thrust vectors
may be perpendicular to the
vehicle base plane if required. The vehicle motion
may be obtained using and steering the rotational
speedoffourthethrustersinthesametime.
For the modelling purposes in the case of small
valuesofvehiclespeedduringtheprecisepositioning
it seems that
the positions of the precise propulsion
units are very important. It is briefly presented in
Figures4and5.
595
Figure. 4. A standard model using 6DoF, (S. Wójtowicz,
M.K.Gerigk,2015).
Figure5.Thevectorsoftheprecisepropulsionunitsduring
thepositioningofthevehicle,(S.Wójtowicz,M.K. Gerigk,
2011‐2015).
The 6 DOF (degree‐of‐freedom) model including
thelinearu,v,w(surge,sway,heave)andangularp,
q, r ( roll, pitch, yaw) velocities is the base for
predicting the seakeeping characteristics of the
vehicle. The relative position to the sea bottom (or
GPScoordinates)isintheformthevector
ofposition
x,y,zandEulerangles,,.
7 ACOMPUTERSIMULATIONOFPPSSSYSTEM
Thecomputational model havebeen prepared using
the Matlab environment. There are six main
interrelatedmodulesofthecomputationalmodel.Itis
possibletoputinthepreliminaryandfinalposition
of
thevehicle,thrust ofthepropeller (rotationalspeed)
and expected impacts (current). Some preliminary
results of computer simulation of the PPSS system
work connected with the precise positioning of the
vehiclearebrieflypresentedinFigure6
596
Figure.6.Thepreliminaryresultsofcomputersimulationof
thePPSSsystemwork.
8 CONCLUSIONS
The autonomous underwater vehicles performs the
motionandmanipulationtasksthatrequirethehigh
precisionpositioning.Thesubjectofthearticlewasto
presentthepreliminaryresultsconcerningtheprecise
position stabilization system PPSS that ensures the
stabilizationofthepositionandthecorrectorientation
of the vehicle. The
paper covers the functional
structure of PPSS system, operation of overall the
algorithm, simulation model in Matlab environment
andsamplesimulationresults.
The PPSS system operates independently of the
mainpropulsionsystemwhichisresponsibleforthe
vehicle navigation. The PPSS system has a separate
electric executive motors form the
main propulsion
system.Generally,theelectricdriveallowstoworkin
conditions of immersion and to charge the vehicle
batteriesbeingunattended.
Usingthesimulationmodelitmaybecarriedout
theresearchofthevehiclemotionduringtheplanned
mission.Thesimulationprogramalsoallowstocheck
howthedeveloped
algorithmsareworkingateach
stage of operation. It is possible to analyze how the
vehicle motion is affected due to the different
interferenceslikethewatercurrent.Forthedesigners
itispossibletousethemodeltofurtherdevelopthe
vehicle including tracking the vehicle energy usage
during
themission.
Atthecurrentstageofresearchthefollowingta sks
havebeenperformed:
functionalityofPPSSsystem,
physicalmodelofPPSSsystem,
computersimulationofPPSSsystem.
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