Development of an Underwater Glidejkghr Equipped With an Auxiliary Propulsion Module

8/12/2019 Development of an Underwater Glidejkghr Equipped With an Auxiliary Propulsion Module

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EVELOPMENT OF N UN ERW TER GLI ER EQUIPPEWITH N UXILI RY PROPULSIO MO ULE

by

Brian ClausBachelor of Engineering

A thesis submitted to theSchool Gradufit c St udiesin partial fulfillment of th e

requirements for the degree ofJ\lfaster of EllginC { ring

Faculty of Engineering and Applied Sciencer lemorial Universit y of Newfoundland

September 5 2 1I W F O U N D I ~ A N D


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Contents

A bstract

cknow IcdgclHcnts

List o f Tables

Nomcnclalure

1IIl I oductioll1 1 Litel f1lllrc Review

1. .1 Ull(lerwater Gliders1.1.2 Long Range AUVs1 1 : Under-Ice AUVs1 1 4 The AutonomOliS Ocean Systems Lab

1.2 ivation and Scope of Work

Vchicle Modelling2 I Hydrodynamic .\Iodelling .2.2 Ballast Pump t\lodelling

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2 3 Glider Efficiency ~ l l o l l i n g

Propulsion Module Design3 Design Const raints3 2 Design3 3 Propeller Selection and Testing

tI Sysl ern Int egration and Modification4 1 Mechanical4 2 Electrical4 3 Software

5 System Evaluation a nd Tes ting5 Tow Tallk Self Propulsion Experiments5 2 Plume Tank Drag and Propulsion Test s5 3 Drift at Dept h Test s5 4 Drive at Dept h Tests5 5 Range Estimates

Summary

References

Appendix A Propeller Comparison Script

Appendix B Power Monit or Schematic

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AbstractA low power propeller based propulsion module has been developed to complementthe b uoy an cy engine of a 200 m Slocum electric glider. This device is introduced toallow new be hav io urs such as ho riz onta l Hight and faster overall speeds to expandthe existing operational envelope of underwater gliders. The design goal is to tllatchtypical horizontal glider speeds of 0.3 m s wbile minimising the impact of the moduleOi l the performance of the unmodified glider. After careful selection of the propellera nd mot or candidates the stand alonc propulsion module has been tested in a smallflume tank to verify the system s performance. Since the desired flight trajectory isrestricted to the horizontal plane the validity of a previously publishcd hydrodynamicmodcl of t.hc glidcr at zero angle of at t Hck was vcrificd by conducting drag l1lCc1SUfC-mcnt.s at various flow velocit.ics at full scale in a larger flumc tank Self propulsiont.ests were also performed t o establish the performance of t he glidcr with t he newpropulsion module in a larger flume t.ank and in a t.owing t.ank. Open wat.er t es tswere performed in a large test. t.ank to show the stability of t he plat.form for horizontalflight. The results frOl l these tesls show t ha t t he new propulsion modulc is capable ofdriving t.he vehiclc horizontally while Illat


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Acknowledgements[ would like to thank my supervisor, Dr. lr Bachmayer, Paul Winger, George Leggeand Tara Perry from th e l\ larine Institute, Jack Foley allel Craig J\ litchell from rvlcmo-rial Universit.y of Newfoundland MUN , Chris Williams, Jeswin Jeyasuyra and Moqine of the National Research Council Canada, Paul Lacroix and the Canadian Centrefor Ocean G li de rs for lise of the glider and th e Physical Oceallography Department.at rvlU for providing additional instrumentation and xperimcntal suppo rt. Thisproject is supported through f un di ng p ro vi de d by Natural Sciences and EngineeringResearch Coullcil, Memorial Universit.y of Newfoundland and SUIl Of Pctro Canada.


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List of igures

2.1 Schema.tic of an autonomous underwater glider in tlte vertical planedefining the angles r ele va nt to the glider s path during ste[l ly stateglides. 12

2.2 Ballast. pump power monitoring from a mission out. of Bonavista, New-foundland on une 17t h, 2009 where t he left is a s l l ~ t of the datashowing the depth, bal la st purnp power a nd m ea sure d ballast pumpedan d tlte right is a close up of a dee p inflection point where the ballastpump is on 15

2.3 I tl st anta ne ous ball as t pump power at given depth z The o n t l i r ~ liredue to the motor startup current. 16

2.4 Ballast pump volumetric rate for a given dept,h comp uted from theBonavista 2009 mission while at depth where t he volume is increasing. 17

2.5 Balla.st pnmp volumetric rate for a given depth computed from theBotlilvista 2009 mission while at depth where the volume is decreasing. 19

2.0 Depth rate for a given d ep th w ith the pitch shown as l he mnrkercolour gradient for five profiles to 150 taken from the Bonavista 2009lnission

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2.7 Line connecting the ascending and descending steady state depth rateas a function of the b allast pu mpe d showing the ballast adjust.mentrequired. 22

2.8 Time averaged electrical input power to the ballast pump for a givendepth of profile. 23

2.9 Dallast pump power and efficiency for Graver s Slocum glider hydrodynamic model [ ] 25

2.10 Ballast pump power and efficiency for the William s Slocum gliderhydrodynamic model [2] 27

3.1 Energy flow diagram showing the inputs and out.puts for each stage ofenergy conversion 30

3.2 Motor and propeller efllciencies plot showing motors 1 8 combined withgearbox 34

3.3 Mot.or and propeller efficiencies plot showing mot.ors 1 8 combined withgearbox 2 35

3.4 Motor and propeller efficiellcies plot showing motors 1 8 combined withgearbox 3 36

3.5 Motor and propeller efficiencies plot showing motors 1 8 cOlnbined withgearbox 4 37

3.6 Ideal propeller efficiency for different. propeller diameters wit h a propeller located at the renr of a Slocum 200m glider. 4

3.7 Input ratio of cord length t o diamet.er for the propeller designed usingthe Open Prop MATLAB code 42

3.8 Selection of propellers tested in the Memorial University of Newfoundland flume tank 43

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3.9 Memorial University of Newfoundland flume tank test schematic forpropulsion system characterisation. 44

3.10 Calibration of the load cell ill the ?vlemorial University of Newfoundland flume tank experiment 45

3.11 Efficiencies of propellers for a given thrust for a flume tank water velocity of 0.3 m/s the drag force for a glider with an advance velocityof 0.3 m/s is shown as a vertical line 47

3.12 Efficiencies of propellers for a given thrust for a flume tank water velocity of 0.4 m/s the drag force for a glider with an advance velocityof 0.4 m/s is shown as a vertical line 48

3.13 Efficiencies of propellers for a given thrust for a fiume tank water velocity of 0.5 m/s the drag force for a glider with an advance velocityof 0.5 m/s is shown as a vertical line 49

3.14 Pixed propeller and folding propeller comparison for a propeller witha diameter of 0.2 III and a pitch of 0.15111 at flow sp . Cds of 0.3 lll/SandO 5mh 00

3.15 Image showing the differences between the fixed and folding propellerswith a diamet.er of 0.2 m and l pit.ch of 0.15 m. 51

3.16 Velocity cont.ours for a Slocum glider CPD model shown at. the locat.ionof t.he propeller with a 0.2 and 0.225 m circle overlaid to show thepropeller disk area where the advance velocit.y is 0.5 nt/so 52

3.17 I-lull efficiency from a comput.ational fiuid dynamic model for 0.2 mand 0.225 diameter propellers. 53

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3.18 Propulsion module efficiencies for a propeller with 0.2 m diameter and0.15 pitch at advance velocities of 0.3, 4 and 0.5 m/s The vehicledrag force is overlaid as vertical lines increasing from left to right fora given advance velocity. 54

5 Glider 49 showing the standard testing configuration of a taped sensorhole and power plug inside of tail-cone 62

5 Power requirements for a given velocity for different propellers in theMemorial University of Newfoundland tow t.ank 63

5.3 Motor duty cycle at a given advance velocity for different propellerswhere the battery voltage is 3 3 V 64

5 4 Power requirements at a given advance velocity for different externalcomponent configurations in the rVlemorial University of Newfoundlandtow lank 65

5.5 t\ arine Institute 4 m x 8 x 22 m flume tank experimental setup forfull scale glider hydrodynamic and propulsion testing 67

5.6 Expanded view of the Marine Institute Hume tank experiment.al setup 685.7 Marine Institute flume tank glider hydrodynnmic drag force measure

ment calibration and test.ing. 7

5.8 Self propulsion test results showing the force difference between theupstrealll and downstream load cell forces for a given electrical inputpower. The self propulsion condition for each curve is marked by an x 7

5.9 Self propulsion test results showing the power required for a givenadvance velocity at steady sta te

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5.10 Self propulsion test results showing the force difference between theupstream and downstream load cell forces for a given m ot or duty cycle.The self propulsion condition for each curve is mar ked by an x 74

U Self propulsion test results showing the motor duty cycle required fora given advance velocity at steady state 75

5.12 Depth controller structure 765 3 Depth controller ballast pump delta bbJ tuning tests 785.14 Depth controller maximum hovering depth rate Zin tuning tests 795 5 Depth controller initial ballast pump volume Vo tuning tests 85.16 Depth measurements during the drift-at-dept.h t.est missions in the deep

water test tank at lvlemorial University of Newfoundland 825.17 Pitch measurement s during the drift-at -depth test missions in t he deep

wat.er tes t tank at f\lemorial University of Newfoundland 835.18 Fast Fourier transform of the pitch measurements during the drift -at.

dept.h test missions ill the deep water test t ilnk at Memorial Universityof Newfoundland 8

S.19 Depth results for the hybrid glider flying 30 t l horizolltally at 1.6 int.he Ocean Engineering Basin shown in blue. From top t o bottom t headvanl.:e velocit.y of the vehicle is 0.2 mis 0.3 mis 0.4 mis 0.5 Illis andO G Ill/s The dept.h reSlllts from the deep wat.er test tank at MemorialUniversit.y of Newfoundland arc overlayed in red and adjusted to theSDtl1e depth setpoim 86

S.20 Pitch r es ul ts for t he hybri d glider flying 30 set to a pitch angle ofzero degrees. From top to bottom the advance velocity of the vehicleis 0.2 mis 0.3 mis 0 4 mis O S Illis and 0.6 m/s


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88

5 21 Fast Fourier transform results of the pitch data from the Ocean En-gineering Basin tank tests From top to botlom the advance velocityof the vehicle is 2mis 0 3 mis 4 mis 0 5 mls and 0 6 m/s Theblack vertical lines indicate the minimum frequency corresponding 1 0a period equal to half of the t otal sample tillle

5 22 Roll results for t he hybrid glidcr flying 30 m in the O test tankFrom top to bottom the advance velocity of the vehicle is 0 2 mis 3

m / s 0 4 m / s 0 5 m ~ a n d O 6 m / s

5 23 Righting moment result s for the hybrid glider flying 30 m in the Otest tank From top to bottom the advance velocity of t he vehicle is 2mis 0 3 mis 0 4 mis 0 5 m/s and Gm/s 90

5 24 Estimated range for a glider operating in hybrid propeller only andballast pump only modes where the top is for full 200 m depth divesand the bottmn is for 10 m average depth dives 93


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ist of ables2 Hydrodynamic lift and drag coefficients for t he model t.akcn from Gra.vcr

et al. [2.2 Instant.aneous ballast. pump powcr coefl1cients2.3 Posit.ivc volumetric rat.e coefficients2 4 Negative volnmel,ric rate coefficients2.5 Hydrodynamic drag coefHcients for the model taken from Williams et

t

t

t8

8

3.1 Motor coefficients for motors considered during selection. he selcctcdmotor is shown in bold. 38

3.2 Gearbox coeOlcients for gearboxcs considered during se ccl,iotl. TIllselected gearbox is shown in bold.

5 Coefficients for the electrical power to the propeller

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omenclature Ang c of attack l J bp Ratio of lime ballast. pump is acti C to total profile time bbp Ballast. pump delta value Icc/s]l: J.prop Ratio of time propeller is active to total profile time [ Ii; Horizontal glider velocit.y lm/sl

Steady slate d epth rate [m/sl Nominal depth rate [m/sl Hovering depth rate [m/s] [nput. maximum hovering depth rat.e [ ll sli Propulsive efficiency [ 1

'Ill lIull crlidcllcy [ ]If Ideal act.uator disk efficicilcy [ 1lbJlh lydrodynamicefficiency of the buoyancy driven glider lbpt Mechanical efficiency of the b lIla iL pump [ 1

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Gear box efficiency [

tIme Magnetic coupling efficiency [ ]

Motor efficiency [

1/1 Propeller efficiency ] sy s System efficiency [

Measured system efficiency ]11 , Moto speed [RPM]

11 Propeller speed [B.P] vl]

Vehicle roll ]

luid densit.y [kg/Ill:

T Motor torque [Nm]

T Propeller torque [Nm]Pitch angle [oJ

Glide-path angle [0J

A ross sectional area [m: ]

Propeller disk area [1021

Co Graver lift coefficient Iincar term [dey-II

c Graver lift coefficient. square term [dcg

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C Graver drag coefficient constant term [Craver drag coefficient square term [deg 1

Williams drag coefficient constant term Hs Williams drag coefficient square tcrm [deg 2

D Drag coefficient [ ]

Lift coefficient lip Propeller diameter mJdu Vehicle hull diameter [mlp r p Distance propeller is active during profile [ ll]

Energy available Pbpc Ele< triclll energy consumed per up and down profile [

Pu Buoyant force [N]PD Drag force [NFg Cravitational force [N]

F Lift forceForce llleasure


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Gravitat.ional onst nt [m/s

J Righting moment arm mElectrical current.IA]

10 No-load electrical current [A]

k l for


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bp nstantaneous ballast pump power IW]

bprr ~ e s u r c d ballast pump power [WIPhyd Hydrodynamic power [WIprop Elcctrical power to the propeller IW] Volumetric rate [m 3 /s] Volumetric rate when volume is incn a ling m 3/s]

Volumetric rate when volume is decrcasing [cc/s]flo Positivc \ olulIletric rate constant term m 3 js]fit Positivc \ ohllnetric rate linear term m2 jsl Negative volumetric rate constant terlll [mJjs]

qJ Negative volumetric rate linear term [m 2 js]J? I BlllIge for buoyancy driven glidN [Ill]

J?hyl>rul Hauge for hybrid glider [m]

? U Bange for propeller driven glider [m]

hrustdeduction factor [ ]tbp otal profile tim for ballast driven glider s

t r im propeller is active during profile[s]

Electrical voltage IVI

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V Volume ] dvance velocity m slV Total balla. it j lJmp \ olume change Im 3 jV Initial x-hover-ballast ll j

Wake fraelion Vehicle depth ml

oo rag cocfficient for zero pilch [D rag coefficient from Williams et. 8oo rag force for zero pitch [

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C ha pt e r 1Introduction

1 1 Literature Review1 1 1 Underwater GlidersTh e conception of underwater gliders was initially lIlolivalro by th e scientific drivet.o bet.tcr under st and t he subsurface layers of th e world s ocealls. This desire wasShOWll through initial development of ocean floals by StommC l and Swallow [4] [5].These floats, through ll ny iterations, developed into th e Autollomous Lnp;rangianCirculation Explorer (A LACE) floats fl < a part of th e world ocean circulation project[61, [71. Slightly before this , Douglas Webb, wlto had bC Cll heavily involved in th efloat development, conceived the origilll:ll COIlCCpt. for fill tllldt>fwalt r glider as a typeof controllable> profiling floal. Discussiolls of this COIlCC Pt. with lIenry SfollllllC llc \ lOt heir vision of th e glider s role ill oceanographic research as portrayal of a futureworld outrol centre for gliders [8].

Several years later th e first rcvisioll of what later b( ( alllC th e SI()( lIIl1 glider wasdcveloped as a variation of a profileI with controllable fins which allowed for gliding


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ll PTEft 1. INTIlODU TION

mot.ions and t.herefore, a horizontal motion component. in addition to t.he verticalmotion component. [9J. Webb s original plan was to develop a glider wit.h a thermalengine, capable of harnessing the sharp temperat.ure gradient. found in much of t.heoceans to cause buoyancy differences large enough to sustain gliding motion POJ;however, due to the complicated nature of the thermal engine, electric vcrsions ofthe Slocum gliders were developed to expedite product dc\ clopmcnt II I], [121, [131Concurrent to this development, other notable glidcrs wcre developed including theSpray glider at the Scripps Institute for Oceanography and the Sea Glider at theUniversity of Washington [14], 115]. The Spray glider was originally developed as anautonomous profiling float. and the Seaglider as a virtual mooring capable of long termmonitoring of critical locations. These three gliders were the first commercially avail-able underwater gliders and scveral articles can b(' found Ihat, outline and comparethei abilities \16]' [171. [18], [191. 1201

A number of other underwater gliders have been deve op


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I I M T l m L INTIlO U TION

feedback control method was developed and tested [28]. Dynamic, stabilisation andcoordination mathematical models were also developed using the ROGUE glider 1291,[30j. This simulated dynamic model was later extended to the Slocum vehicle usingfield data to generate a hydrodynamic model [3]. Bachmayer et aI., using this modeland some recorded data from field trials with the Slocum glider, tUlled several of t hecontrol loops wi thi n t he vehicle [31]. A summary of th e dynamic modelling work011 th e Slocum an d ROGUE gliders may be found in raver sthesis t] Additionalstability and non-linear control methods for underwater glidcrs from th e PrincetonUniversity Dynamics and Control Systems grOlIl> may be found in 1321, [331

A larger hybrid gliding vehicle named STERNE was devcloped at ~ S I T inl:rance [3 1]. Th e lans detailed a vehicle substantially larger than the Slocum gliders,around 1000 kg, capable of travelling faster than Inany of the 1her underwater glidersto date and having both ballast control and a propeller. For testing. II 1/3 scalel abor at or y version of t he vehide was built which was arollnd t he same size as th eSlocum gliders.

Several other hybrid glider developments include th e AUV-glider and the Folagaglider [35J, [36J, [37J. The AUV-glider was developed at the Plorida Illst it lite for Tech-llology as hybrid lWl,Wf f tl the long endmanc blloyanty drivf ll glidprs and propellerbased Autonomous Underwater Vehicles AUVs). This vchicle w


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C II P TE ll I INTRODUCTION

A more recent commercial glider development is the Sea Explorer by ACSA Underwater CPS. The Sea Explorer is an underwater glider with acoustic navigation thathas an optional propeller sed propulsion module to make a hybrid ype glider [41].The vehide is still in development and expected to have an endurance on the orderof months and weigh about 60 kg.

The Libcrdade/X-ray is another glider configuration that is in development. Thisvchide is a blended wing/body type glider that makes lISC of the flying wing concept1421 1431 To generate sufficient lift for this configuration the wing must be larger thanthat of vehides mentioned previously making this glider the largest at a wingspan of6 m. The vehicle is to be capable of speeds of lip to 3 knots with an endurance of1Il0lllhs and a range of over 1000 km.

Another variation on a gliding vehicle is the Wn\ e Glider by Liquid Robotics.The \WlV glider uses a surface buoy couplrd to a large gliding submerged body toharvest wave motion and propel itself forwards. In this way the vehicle has no electricpropulsive load and maintains a speed relative to t he mean wave height [44]. A recentnpplicllt ion of this technology in the form of a buoy replacement was met wit.h successwhere the Wavc Glider was able to stay 011 station at all t imes with the exception of( xtrC lIle winds. In this situation the vehicle wns still able to recover its position afterthe weal her evcnt [45].

Throughout the development cycle of these first underwater gliders there hasbt t ll significant interest by the Navies in various coulllries. In 2003 dirccl.ly after theIhn C Office of Naval Research (ONR) funded Sloculll, Sea Clider and Spray gliderprograms finished, a glider systems study was perform( (l and compiled for ONR 120]Shorlly after the completion of this study, ONR announced a contract for over ahlilldr( (1 gliders prompting iRobot to exclusively licenS< the Sea Glider, Teledyne topurchase \\ cbb Research and Bluefln Robotics to license the Spray 146]. In early


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CIIAI:>TER INTRODUCfION

2009 Teledyne \Vebb Research announced that it h ad been successful in its bid forthe contract 147]. This contra.ct has lead to significant developments with the Slocumglider to harden the system to military specifications leading to he second generationof Slocum gliders, the Slocum C2.

Another primary motiwltor for development of gliders and glider related technologies hfL i been the scientific community [ 8 The lIlost prevalcnt uses in scicnce havebcn ill Physical Ocean og raph y where t hey havc been used as pro61ers, gatheringS3linity, density and temperature information through conductivity, temperature an ddensity CTO SC nsors. publications ha\ e ix en dedicf\ted to the correctionand interprctation of this data as the vehicles use a non-pumped eTO sensor whichprCSC nts tillle-lag errors and challenges with dynamic mcasllrClllcnls which vary insp,wc and timc [19]. Additional popular SC nsors indudc dissolved oxygcn sensors.backscaltcr sensors, turbulence meters, Acoustic Ooppkr Current Profilers, varioussonar devices and hydrophones to name a few.

1.1.2 Long Range AUVs is interesting to not.e that. Autonomous Underwater Vehicles AUVs) and glidersdeveloped to llIeet difrerent needs and markets while still being 1l1l Ierwater vehicles.Ollly reeelll,ly havc some of the rotes of AUVs and Undt fwater gliders begun to merge.Olle notahle eXllmple of this is the Long Range Autosub LBA) 6000 AUV whichC xtC llds the AlIlosub 6000 architecture to a version with a fallgc of 6000 klll [50], [51]Previously, vehicles with a range of over I X) ) kill were exclusively the d omai n ofunderwater gliders. This transition is motivated by th > dcsire to push the boundariesof the typcs of missions possible with ulldcrwater vchicles. The LRA is scheduledfor field tesling in January 2 11 with some possible missions including travcrsing


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CIIAPTJ R 1 INTRODUCTION

beneath the arct.ic ice cap and in the strong current. region of the


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CIIAPTER INTRODUCTION

have on t he climate. This program has collected the most data to date on under-icepropert ies in arcti c waters 159j [60]. The use of the Autosub platform for undericc missions also prompted significant investigation into under-icc AUV risk of lossassessment after the loss of olle of the Autosub , chicles [61].

1.1.4 The Autonomous Ocean Systems LabThe Autonomous Ocean Systems Lab AOSL) at lemorial University of ewfoundland ~ I U N focuses on the development of occantechnologies related to scientific andindustrial needs. Current research projects include a highly maneuverable yet stableAUV platform for high resolution sonar bathometry being developed in conjunctionwith f\larport Canada and the r\ational Research Council Instit lite for Occan T hnology [62]: the hybrid glider and t he subject of this thesis [63] [6 j; lh integrationand data corre


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I I P T I ~ l t l INTRODUCTION

like pattern through the water column 115]. 4 [1 ] The endurance of these un-derwater vehicles varies from weeks t.o several mOllths and even longer in t.he case ofthe thermal glider 110]. In contrast currently available propeller driven autonomousunderwater vehicles (AUVs) achieve an endurance fIluging from hours to days. Thisstark contrast can mostly be attributed to a purpose bui lt system and to the lowspeed at. which the gliders move [671 and [68]. Cliders typically move at horizontalspeeds of about 0.3 m/s compared to propeller dri\ Cll Vs which typically move ataverage speeds greater than l 0 m/s The low speed capability can create significantproblems when operating in areas of strong water currcnts which exceed the glider smaximum forward speed. If the direction of the current.s is known pnol l or mea-sured m s tu [69] the missions can be designed to either avoid these areas or to t.akeadvantage of them. In this case the operator must. nxlir< Ct the glider to better dealwit h th( current by moving away from that regioll or. in lh( case of significant verticalstratification, try to operate below/above t.he expected layer of high( sl, lateral veloc-ities. However, in the case of unknown Clll J ClitS Illey can pose a significant risk tothe successful execut.ion of t.he mission plan. Thesc iSSII s have given riS lO the ideaof the hybrid glider which combines the glidillg beh1:lviolll s of tradit.iollalundcrwat.ergliders wit.h \..hc propeller driven behaviours of AUVs.

This thesis addresses the design and t.esting of auxiliary propulsion module forthe Slocum e1ass of underwater gliders. The objectives of the project are to enablethe glider to move horizontally at the lIolninal glider 51) 1 of 3 lIl/s alld. for shortpcriods of time, to double its horizontal sp( { d to approximately 0.6 Ill s To thisend a simplified malhematical model of underwater gliders as well as a model for theSioculll 200 m glider ballast pump power consumption based on experimental dataarc described. These two models arc used to de dol) design constraints and initialcomponellt selection. The design and tcsting process for the propeller and motor


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CII PTER l INTRO U TION

are presented during which the final configuration is shown. Following this, themechanical, electrical and software integration of the module into the existing glideris discussed. The system testing and evaluation including experimental results fromfull-scale tests in the ~ r i n e Institute MI) of ),Iemorial University of Newfoundland MUN), tow tank self-propulsion tests in the Ocean Engineering Research Centre tMU T and open water flight tests in the Ocean Engineering Basin OEB) t NationalBcscarch Council s Institute for Ocean Technology are presented. A range model fora hybrid glider is developed sed on the combination of an AUV range model andthe hydrodynamic model for the glider. he last section summarises the results ofthe design and evaluation phase of the hybrid glider and gives n overview of the nextst ps in the development of the hybrid glider towards a fully operational system.


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Chapter 2

Vehicle Modelling

A 1I\00 e of the vehicle is presented to facilital


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CIIAPTIm V ~ I I C L I : : MODELLINC 11

21)

where ; is the glide-path angle, Fl is the hydrodynamic lift, Po is the hydrodynamicdrag, Pg is the gravitational force and n is the buoyant force. The lift and dragforce may t hen be defined as [31

I 2pACda v;Po = ~ p A C o a v ~

2.2)

23)where a is the angle of attack, 0 is the pitch angle defined as 0 = ; 0 , P is fluiddensity, is the cross sectional area and V is the advance velocity. In [31 the authorspresent the hydrodynamic model parameters for a Slocum 200 II I ullderwa.ier glider.Prom 2.2) the lift coefficient Cda based on fr ontal a re a is det.ermined as

2.4)and similarly from 2.3) the drag coefficient Co 0 ) as

25)where the coefficients from 2.4) and 2.5) a re defined as in Tab 2

POl the purposes of the propulsion module design th e glider was assumed to beballasted lleutrally buoyant, t rillllllt, d for level Hight at pitch angle 0 = 0 and movingat a constant speed. These assumptions do not hold for regular glider operationsbnt. for t he initial design purpose they provide a start ing point while significantlysimplifying the later al plane h yd ro dyn am ic model of gliders as presented in [281.As a result of the a ssumed pitch a ngle = 00, the glide-path angle ,; = 0 and


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C I l I T I ~ l t 2 V lmlCLE I vlom:LLING 2

. .

Figure 2.1: Schematic of all utonomous uuderw ter glider in the \ l l tieal platle dcfillingthe lI11glt S H 1cvaut to the glider s p th during ste dy st.nl( glides.

Co 76 deg c 4 6 deg 2 0.214C 32 3 eg

Tnble 2.1: lydrodyn mic lifL nd dr g (;oefllcients for the model t ~ \ k 1 1 frolll Cnn t l CL aI. [3]


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C I I P T ~ l l 2. VEHI LE MO ELLING

t.herefore t.he angle of at.tack 0 = Cf as well. Under the assumplion of constantvelocit.y, t.here is no acceleration, therefore added mass effects can be neglected andt.he C


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C I I A P T ~ 2. VEHI LE M O ~ L L I N G 14

s ub se t of t he data recorded in this mission is shown in Fig. 2.2.During a mission the ballast pump turns on only at the inflection points of a profile,

at eit her t he deepest or shallowest point s of the profile. From t hese measurementsthe instantancous electrical power for a given depth may be ploued llS in Fig. 2.3,establishing the load line for the pump as a function of depth as in

2.7)where z is the glidcr depth and the coefficients for 2.7) are defined as il l Tab. 2.2

Table 2.2: Inst.a.ntaneous ballast. pump power codtlciellLs

The lI1C Chankal power output by the balla. 1 as ill

29)Tilc , )[lljllllNI Volullielric rate is plotted in Fig. 2.4 for tIle OIHlvbtl i 2009 Illission

whel c th{ VOhlll\ is illcreasing. The rate is shown to dC{ l { ase wil h depth whcn t hevolulllc is in l C Hsing. Le .. the glidcr is coming back to thc surfac .

jo jIZ 2.1O)


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CIiAPTEn 2 VEl leL f\IODELLING 15

f t s z S Z J ~1000 2000 3000 4000 5000 1140 1160 1180i ~ : : I

O - - 1 1 O O O - - - - ; : 2 0 0 0 - I I l . 3 0 0 0 - - - - - : 4 0 0 0 ~ - 1 I 5 0 0 0 1140 1160 1180

r k r _ j j d ~~ 5000 1000 2000 3000 4000 ~ 40 1160 1180Time [5] Time [Figure 2 2: Dallast pllmp power monitoring frOIllI\ mission Ollt of BOIl lvisla Newfoundland

on June 17th 2009 where the left is subset of t he data ;howillg the depthballast pump power and measured ballfL


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CHAPTER VEIlICLE Mom:LLING

9O .. r . .

6

8

7o

o

oo

o o

oo

3

o1 ~ L O - - 4 - - 0 - - ~ 6 0 - - ~ B L O L O - - , L 2 0 - - - - 4 0 - - ~ 6 - 0 - - BLO 2

epth m]Figure 2 : : [lIstantanOOttS bal last pump power at given kptli z Th e outliers ar c du e to th e

motor startup currt nt.


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C I I P T ~ R 2 VBIIICLI MODBLLING

X 1O >2 . 5 ; r = ~ ~ _ _ _ _ r ~ ~ ~

17

0 5

20 40 60 80 100Depth [m] 120 140 160

Figure 2 : l3allast pump olumetric rate for a given depth computed from the l30navista2 9 mission while at depth where the volullie is in Teasing


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CHAPTER VEHICLE M O I ~ L L I N 18

where Q is t he volumetric ra te when the vohnne is increasing determined using aleast. S


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C I I M T E I t 2. Vlmlc J vIODI::LLING

0.5iII :g 1

1.5

-;;;


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CIIAPTEIl V I ~ I I l L MODELLING 20

given by convert.ing t.he inst.ant.aneous power t.o energy consumed per u p a nd downprofile pe with o ne use of t.he buoyancy pump at the surface and one at d ep th , an ddividin g by t he t ot al profile t im e l p as in

_ E. . -lOp

213)

2.14)Here the shallow inAection depth is assumed to always be at the surface z = 0 and

t he t im e used to compute the ballast pump elect rical energy is found by dividingt he t ot al volume c ha ng e V by the volumetric rate Q where \/n = 4.5OE-4 m 3 . TheOtH ime for the b.: lllast pump was computed using the vohlluC tric rate to remove thealiasing errors due to the slow sampling rate of he glider. The total cycle time l pcall be measured from the mission data, how V r, C xtended periods at. the surfaceand the bottom for m any of t he profiles made it difficult to accurately estimate thisvaluC . Therefore, the steady state depth r at e was uS< d to stilllatc the glide 1ime as< function of depth for half a profile as in

2.15where tlte steady state depth rate z was calculated frotH the lllel1,Surf d vailles shownitl Fig. 2.6.

Prolll Fig. 2.6 it is evident that there is a signifkall1 lllis. Hrim in the vehicledue to he difference between the descending alld ,lS C lIdillg st< ady state depth ratesof z = 0.1187 m/s an d i = 0.2657 m/s. To calculate lhe depth ra te t he averagebetween the descending and ascending steady state d ep th rate S of z = 0.11 7 m/san d z= 0.2657 Ill/s was taken to give z= 0.1922 m/s. Prom a plot of the steady state


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CIIAPTIm V ~ H I L ~ ~ I O E L L I N G 2

0 . 3 r ~ ~ ~ ~ ~ ~25

0.2 20

1510

: 0.1 51

15

2

25160420_ 0 . 4 L _ ~ ~ ~ ~ ~ _ . Jo 20 40 60 80 100 epthm

F igurc 2.6: D cpth ratc for a givcll dcpth with thc p it ch showll a s thc markcr


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CHAPTER 2. VEIIlCLE MODELLING 22

o . 1 5 r _ _ r _ _ . ~ _ _ r _ _ . r _ . _ _ _ _ r r _ .

0.1

0.05

L005i 0 1o

0.15

0.2

0.25

- O J : . 5 - - - . . : 2 - - - - . L . 5 : - - - 1 ~ - - 0 . . : . c : - 5 ~ 0 - : - 0 . L 5 - ~ 1 - - , . L . 5 : - ~ ~ - - - : 2 . 5Volume of Ballast Pumped Im1 x 1 4

Figure 2,7: Line conllccLing the ascelldillg am i dt,* C nding stt ady stllte d ep th r at e as fUll ;-tion of t h e b a ll as t pUlllped showillg tlit, ballast IIdjll stlllcn t l C


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CIIAPTEIt VEHICLE MOm:LLINC

2 . 5 r r ~ ~ _ _ _ _ . . . . _ _ _ _ _ _ _ _

i kii i

5

6 8 100 120 epth [m 14 16 18 2

Figurc 2 8: Tilll< averaged electrical input powef to the lmlla:;t plllllp fOf a given depth ofprofile


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CIIAPTER 2 V I ~ I I I C L E MODELLING

2.3 lider fficiency Modelling24

The transport efFicicncy is an effective way of comparing the overall effectiveness ofthe buoyancy and the propcller based propulsivc methods. Ib estimate the efficicncyof the glider wc can lise the geometric relationship defined in Fig. 2.1 between theglide path angle and the vertical velocity of the glider z to determine thc advancevelocity as

2.16)and the horizontal velocity 1: as

= ~L a n ~ 2.17)The hydrodynamic power may then be calculated u ~ n 2.3), 2.5) and 2.16) as

ill

2.18)A ltleaSlll ( of thc hydrodynamic efficiency of the buoyancy drivell glider tl 1/11 lIlay

b estimated llsing 2.14) and 2.18) as in

2.19)Additionally, the IlW :hallical efficiency of the ballm;I PUlllP bpm lIlay be calculated

lIsing (2.1 1) And 2.8) a s in

2.20)The cfficiency and time avcraged power r Sults arc plotted in Fig. 2.9 with an

assumed angle of attack Ct = 2.g.: [3J.


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CIl WTEB 2. VEIIICLE r .l0DELLING 25

2 . 5 r - - ~ - ~ - ~ - ~ - - - - ~ - - - - - - - ; : = = =I= f~ : ~ - - - - - . - - - - - - ~ - ~ - ~ _ _ 1

Q 0 5 - - - - - - - - - - - - - - - - - ~80 100 120 140 160 180 20000o L - - ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -20

j ~0 40 60 80 100 120 140 160 180 200 epthm]Figure 2 9: Ballast pump Xlwer an d efficiency for Craver s Slocum glider hydrodynamic

model ]


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C I- IA P TE R 2 . V E ~ I I L E MODELLING 26

Table 2.5: Hydrodynamic drag coefficients for the model taken from Williams et al. [21

An additional hydrodynamic model presented by Williams el . al [21 pres( nts th edrag coefficient from field data that is different from (2.5) i . ;

221)

where the coefficients for (2.21) are defined as in Tab. 2.5Th e C4 coefficient in this model is significantly less than C2 in (2.5) due to th e

author assuming a larger angle of attack than in Graver s model [lJ. T he efficiencyan d time averaged power results for th e Williams model are ploUed in Fig. 2 1 withan assumed angle of attack = 6.53 [21.

Th e ] Jph is less in William s model than in Craver s model. This difference isattributed to th e difference in th e glide path angle ; due to the differetlt Il..


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CIIAPTER VEIlICLE MODELLINC 27

i ~40 60 80 100 120 140 160 180 200 ~::: 4 0 ------ ,., .. . , . , . : .0 30 it 2 - bph .

1020 40 6 8

i 100 120 140 160 180 200Depth [m]

Figlll c 2.10: Bullast pump power and efficiency for the William s Sloculll glider hydrody-llHillic model [2


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CHAPTER 2 VEl lIeu; MODELLING

hydrodynamic efficiencies h difference s mainly due th assumptions surroundingth glider s angle of attack y measuring Q directly a more accurate hydrodynamicmodel may be created


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hapter 3Propulsion Module esignA design for an auxiliary propulsion module for an underwater glider is presented. Thepropulsion module is designed u sing a n integrated approach where hydrodynamic,llll:,dlanical and eJet rical performances are considered as }\ whole to ma.ximise thepropulsive effi ien y of the vehi le

3.1 esign onstraintsTo lIlillilllisc the i mp ac t of the propulsioll unit Oil the pCl fOnnnllcc oft.he glider, certainconstrailJt,s were placed on the design. The module shollld be able t.o be t.urned onand of \ allow the glider to retain it.s normal buoyancy-driven method of operation.In light of this, during regular operations, the influcl\ :c of t.he propulsion unit on thehydrodynamic performance of the glider should be minimised. The impacl, of thepropulsion module on the glider s endurance and range when propdlcd for horizontalflight at typical glide spccd.s should be such that the propulsor should consume equalor I


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CII PTl R 3. PROPULSION ~ I O U L ~ I ~ S I G N 30speed for short. durations. These constraints provide a unique challenge in developinga high efficiency, low power propulsion module.

3 2 DesignTo design a prototype device withill these constraints an overall concept was chosenut.ilising an electric motor, magnetic coupling and folding propeller. These compo-nents require careful design mat ching to ens ur e that the peak operational regionsoverl ap onc another . To t hi s end, e1cctric mot ors provide t he nccC S:Xu y energy den-sity for a small low powef devke and provide good efficiency matching potential topeak propeller efficiencies. A magnetic coupling was selected to millimisc frictionallosses due to shaft seals.

Figure J : Ellcrgy flow diagram showil lg thc inputs n outputs for f'1 eh stageof cllcrgyl. OIIVCl'siOli

Initial malching of the motor, gearbox and propeller was done using the simplifieddrag force model from section 2 and nominal glider operational paranwle rs as arderence fOf drsign. The energy flow for the system is shown in Fig. ;.U, where theproduct of the inlIts over the product of the outputs is C


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CHAPTER PROPULSION MODULE I ~ S [ N 31

31where 1} , is the motor efficiency, 11gb is t.he gear box cfficiellcy, /me is the magneticcoupling efficiency and 1 p is t.he propeller efficiency. The efficiency of t,he motorcontrol ler may be includ .>d ill I as well However, for t.his design a high qualitybrtlshed motor with precious metal brushes was chosen with the final design to bedriven directly from the rail voltages of 14.4 V and 3.3 V to give a high and low speedoperation point. The motor controller efficiency was t.herefore left out. of t.he systemefficiency definition. Also left on t of the syst.em efficiency definit.ioll is the butteryperformance which is a product of envirotlmental conditions and the electrical loadrequirements. The efrects of the environmental conditions are left. out because theyapply t.o buoyancy driven vehicles and propeller driven vehicles. The elect.rical loadfor the auxiliary propulsion module is a continuous load and intermittent. for t.hebuoyancy engine. This difference can impact the battery performance differently dueto 2 losses. The instantaneous i losses for I,he auxiliary propulsion module are011 the order of 0.001 Wand for t.he buoyancy engine they are on the order of 0.01 W,where R, in this ca. e, is the internal resistnnce of the batteries equal to 0.150 [70].However, since the buoyancy engine use is int.ermittent, the /2R losses arc reduced toa negligible level. Both /2 loss cases arc therefore considered to be irrelevant whencompared to the time a.veraged power consumption.

In general the motor efficiency may be given as [

3.2where the motor torque T and the motor speed arc given by

33)


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constant and to is the motor no-load current.

\Va < l,hercfore removed from the parameter space for the purposes of propeller, illataI

32

34

35)

3.6)

3.7)

kl i - io [uk - k3k l i - i o)12JrTIm = tu 6

Substituting 3.3) and 3.5) into 3.2) gives

CI IAPTER 3. PROPULSION MODULi: : DBSICN

with 3.3)

clIrrent i where is the torque constant k is the speed constant k3 is the motor

MATLAB scripting [72 The gearbox was assigned a fixed efficiency dill to mcchan-icallosscs as given by the data sheet from the manufacturer. The rnagnetic coupling

A propeller was modelled as a small blade area ra,lio propellpr using the OpenPVL

showing that the resulting motor efficiency depends on only the illpUl, voltage t and

and gearbox matching. The propeller torque constant f{r [73J limy b e w rittp n as

efficiency was assumed to be constant irrespective of motor or propeller :;clection and

r TIl = p ~ 2 e l ~

which may be re-wri\.t.en to give the propeller torquc Tp

3.8)wherc Tp is the propeller torque, ll is the propeller diameter and r is the propellertorque constallt.. The propeller torque constant r shaft speed arc outputs fromthe OpenPVL MATLAB scripting.


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CI IAPTER 3 PROPULSION MODULE DESIGN 33The peak efficiencies for electric mot.ors generally occur for RPMs that arc higher

than the peak efficiency for propellers. Gearboxes are therefore used to match t.heRPM of a given motor to th e peak operational region of the propeller. the gearboxratio is too small the motor efficiency will be small due to t.he propeller speed requirements being well below the motor s peak opemt.ional region. However, for each stageof gear reduction additional mechanical losses arc accrued by the gearbox thus reducing its emciency. These parameters compet.e against one another and by iteratingth e gearbox and motor parameters a motor and gearbox combination showing peakperformance for the theoretical small blade-area-ratio propeller and nominal glideroperational conditions may be chosen.

Th e propeller efficiency generat{, l by th e OpenPVL MATLAB script was plot.tedagainst the output of the motor model for different motor and gearbox l:Ombinationsto match the peak efficiencies for a given shaft speed p and propeller torque T

as

in Fig. 3.2 - 3.5. Th e script for these figures is included in Appendix A. The voltageinput to the motors was limited to the vehicle ba.ttery voltage of 15V to maint.nin theopcmtional region of the motors. The propeller design shaft speed Wa. ; 100 RPrv foran advance velocity of 0.35 m/s and 0.4 N of thrust resull,ing in a / T 0.0051.

The motor s considered in Fig. 3.2 - 3.5 have motor coefficients as defined in Tab.3.1 with gearbox s having coefficients as defiu{, { ill Tab. 3.2. This data is suppliedfrom manufacturers data sheets [71].

From Tab. 3.1 and 3.2 the 1 Inotor and gbl gearbox were selected. The predictedmotor performance for this motor and gearbox combination is shown ill Fig. 0.2. [nthis figure it is shown that th e m5 motor results in a high motor efficiency for thedesign propeller speed of 100 RP1\1. However, this m otor when combined with thegb1 gearbox wa :> too long to fit inside or the mot.or hOllsing and th e m1 motor wasselected instead.


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CIIAPTEB; PROPULSION t\IODULE ~ S I G N 34

45000500000 250Q[RPM]

l lgbl l lm2 l lgbl

~ ~ ~ _ : l lm3 Ilgbl l lm I lgb l IlmS gbl Ilm611gbl m? 1gM lmellg l

I l prop150

::-

100

.1 . :-;: :::

50

90

80

7

6i 50J 4

30

20

00

Figure 3 2: t\lotor and propellcr cflkicncies plot showillg motors 8 combincd with gearbox


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C I I A P T ~ R 3 PnOPULS N I \ l o o u l ~ D I ~ s [ G N 35

~ ~ ~ ~ lm Tlgblm Tlgblm3 Tlgblm4 Tlgblms lgbIlm6 lgbm7 lgbm8 lgb

TJprop

1

9

8

7

~ 650

~w 43

1

I;I

5 1 15 2 25Q[RPM] 3 35 4 45

Figurc l\lotor and propellcr cfficicllcies plot showing motors 8 combincd wit h gcarix>x


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II PTEIl PnoPuLsJON l\IODULE DESIGN 36

1

9

8

7

6i 5 m gbm2 gb~ 4 l lm3 gb

l lm4 gb3 llmS gb2 llm6 gb

llm7 gllmS g1prop

15 15 2 25 3 35 4 45Q[RPM]Figurc x


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CIIAI:>TEH PHOPUI SION ~ I O U L DI::SIGN

9

80

7

~ 60 5w 4

30

2

10

00

50 150 200 250Q[RPMJ 300 350

lm lgb4 lm2 lgb4 l lg >4 lm4 lg >4 lm5 gb4 lm6 gM m7 lg >4 mB lgb4 lprop

400 450

Figure 3.5: l\ otor lind propeller efficiencies plot showing motors 1 8 combillcd with gearbox4


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CHAPTER 3 PROPULSION rVIO ULE E SIGN 38

kl Units [NmjA] [RPMjV [NmjRPM [A]

Illl 9.92 E 3 9.62 E2 8.04 E5 7 35 3m 1 39 B 2 6 85 E2 1 64 E6 4 27 B 3m3 3 33 B 3 2 9 E3 1 11 E6 2 34 B 1m4 1 63 B 2 5 84 82 8 25 85 6 45 B 3mS 1 9 B 2 5 2 E 4 04 E5 4 63 E 3m6 9 17 B 3 1 04 E3 2 60 E6 9 54 B 3m7 1 07 B 2 8 93 E2 2 6 E6 9 69 E 3 8 8 23 E 3 1 16 E3 2 32 E6 4 88 B 2

Table : : Motor coefficients for motors considered during selection The selected motor isshown in bold

l gb gb gb4atio 9 4 84 5 4

g 8 73 9Table 3 : Gearbox coefficients for gearboxes considered during ~ k i o n The selected

gearbox is shown in bold


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CIIA :>Tlm 3 PROPUI SIO l\IODULI ; OI:::SICN 39

Since the level of input energy is very low on the order of lW all stages ofenergy conversion were considered and all losses were minimised. Shaft seal frictionallosses, which in a more powerful system account for only a fraction of the totalpower, dominal,e in low power systems. To t.his end, a tllagnetic cOllpling was usedalld designed such that the pull-oul. torque was just beyond what the theoreticalrequirements were for the propeller to move the glider at a sprint speed of 0.75 m/slagnctic couplings often require additional bearings and the lubrication and sealson bearings consume a large portion of a single Watt system s power. Therefore,

u t r ~ o w friction, dry-lubricated, ceramic bearings were used to reduce these losses.The losses from the magnetic coupling and bearings were quantified through onalysisof t.he motor input. current before and aft.er assembly. For the IlltLxilll111ll voltagecondition, this difference equates to a change in current of 3 lilA resulting il l less than0.001 Nm frictional torque in the magnetic coupling assembly, which is 10 of theno-load torque and I of the full load torque. These losses are a result of frictionallosses in the bearings as well as eddy current losses due to the rotal ing magneticfields.To summarise lhe motor selection process has been detailed showing the matching

of motor and gearbox to l simulat.ed propeller perfOnnlltIC( . A brief disCllS. ;ioll of theSOIlJ S of llH,:chanicallosses highlights the importance of careful compollelll selectionand tolerances.

3 3 Propeller Selection and TestingIn this section the propeller design process for the propulsion module is pr( scllted.This process t.akes the thrust requirelllents and advallce velocity frotll the y r o y ~Halllie model. As all initial estimat.e Ihe ideal actuator disk efflciellcy lllay be


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C I l I T l m PROPULSION MODULi:: DESIGN

computcd as in [740

2~ ~ ~I J ~ 1 vwher(' Fr is th e thrust This equatioll may be r('-wriUell to show th e relationshipbetw('('n th e hull diameter and propeller diameter at steady state and le\'el Right byslIb:;tilliting {2.3} for Fr as in

~ 2 (3.10)1+ r ff+ Iwhere dv is the vehicle diameter an d t is the propeller diameter; for th e Slocum 200m

glidC r dv = 0.21 m Th e ideal efficiency for a gin n propeller diameter is plotted inFig. 3.6

Th e idC al efficiency shows that for larger diameter propellC'rs the I>ropeller effi-ciC llcy increases. Additionally, it gives the upper bOllnd for expected efllciency forI he propeller that is selected. In order to the drag froUl I,he propeller whilet be propulsion module is not in usc foldillg propellers w('re sclC< led for usc. However,no sllit.ablC folding propellers wcre foulld with publishC'd torque and thrust data forlow advfltl('e vclocit ies and low levels of thrnst Therefore', Il propeller was designedusing t.he Open Prop tvlATLAB code wit.h a cord lenglh to diameter ratio as shownill Fig. 3.7

Additiollal inputs include an advance velocilY of V 0.; 5111.S, thrust of FT D N Hud n lOOHPM for a two blade


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II PTEll 3 PROPULSION MODULE O ~ S N 4

9

9

85 8

75

7

6

6

55

5 1 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3Propeller Diameter dp m

Figure : 6: Ideal propeller cfliciency for different pro X lll r diallwtNS with a propeller 10cl\te


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CH PTER 3 PROPULSION MODULE DESIGN 42

0 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~0.090.08

E0.07o: 0.06

0.050 0 40

0.03II

0.02 1

1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Ratio of Radial Location Blade Radius

0 9

Figurc :t7: Input ratio of cord length to diamcter for the prope lkr dt l;iglwd lIsing th cOpellProp r..IATLAB code


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CHAPTER PROPULSION M O U ~ DESIGN

0 . 2 7 5 ~ r ~ ~ ~ ~ ~

0.225 0.25 0.275Propeller iameter [m}

0.250.225

I 0.2j j 0.175 X

eX. 0.15

0.125 X0.1 X

0.075 0.2.175

X X X

x

0.3 0.325

Figure :l.8: Sel ,tion of propellers tested in the fo,lcmorial Ullivcr:;;i1.y of Newfoundland numetank

of this work a series of R folding model airplane propC llers were selected to betested experimentally to determine their operatillg parameters. These propellers usea graphite reillforced plastic which provides II good dcgrC


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CHAPTER PROPULSION M O I U L ~ O ~ S I G N

r 7 iF

ADV

...........Sample Volume

44

Figure 3.9: ~ I e m o r i a l University of I ewfoundland flume t ank tes t schematic for propulsionsystem characterisation.

voltage divider. he thrust was measured lIsing lever to amplify the force and anO me ga LCA8 -6 kg load cell w it h a D at af or th DSCA38-05 signal con ditioner. helever arm for thrust measurement r was calibrated \Ising knowll masses attachedt.hrough pulleys to t he cent.erline of t be propulsion 1I10dule as shown il l Fig. J.IO heresult aliI conversion formula. is given by

r 1.8715 1 - I ;, 3.11)

where 1.8715 is the lever ratio, o is the drag force on the lllCl\sur IIl lIt appl\rat.usand M is t he measured force. These values were rcad illiO .\IATLAB for furtherprocessing using the Data Acquisition Toolbox and a National InstrumCl\lS USB-6211data aC


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CI IAPTER 3 PROPULSION MODULE D8SlGN

1 2 r - - - - - - - - - - - . - - ~ - - _ _ _ - - _ _ _ _ ; _ _ - - _ - -

1

2 3 4 5Load Cell Force Measurement ]

Figmc 3 1 : alibrationof the load cell in thc r kmorial University of NcwfOllndland f umtallk expcriment


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CHAPTER; . PHOPULSION MODULE DE::SICN 46

for flow speeds of 0.3, 0.4 and 0.5 m/s where the input current to the motor wascontrolled from 0 A to the pull out torque at 0.3 A. The measured system efficiency1/S S is calculated as in

312

Using the illataI model presented in (3.6), the propeller efficiency may be deducedfrom the system efficiency as in

(3.13)whcre T is (3.3) and ft is (3.4). The 1Il010r efficiency is also computed accordingto (3.6). It should be noted that the mechanicallOSS< S in the magnetic coupling andbearings are lumped in with the propeller efficiC llcy. ThC remits from these testsshowing the system efficiency 1 s/ls the thrust r and the vC hidC drag force at = 0.3, 0.4 and 0.5 mls are shown in Fig s. 3.11 3.1 J.

A nOlIfolding 0.2 m diameter propeller with 1\ pitch of 0.15 II I was also selectedfor test illg to compare lhe performance of folding f\nd fixed btadC d propellers. Thefixed propeller results arc showll with the folding propellel results in Fig. 3.14. Theseresul ts arc shown only for advance velocities of 0.3 and 0.5 mls as there was a loosecOlluC et ion on t hf electrical current sensing dcviC c for thC with an advancevelocity of 0.4 m/s and the data was ullusable.

The fixed propeller effidcndes are higher than the efJidcllC iC s for the sl\Iue size offolding propeller. This difference is attributed to the size of thC hub for the foldingpropellN as well a the differences in the blade area. ratio. The folding propeller has alarger hub size relative to the fixed proj>eller to accommodate the folding mechanism.The fixed propeller also has a larger blade area ratio when compared with the folding


68/152


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CIlAPTIm PIlOPULSION vloDULE DESIGN 48

5 0 ~ _ _ . _ . r ~ . _ _ _ _ r _ _ r

4540

10 0

FD 0 4 mls)o 0.3xO.25o 0.275xO.175o 0.25xO.175o O.225xO.1750.2xO.1750.2xO.15

0.2xO.1250 2xO 1o o - - o : - . : : - 2 - - - - : o C - . 4 , - - - - - - - : - o ~ . 6 - - 0 : . 8 : : - - . L , - - - - : 1 . : - 2 - - , , . . . 4 : - ~ 1 ~ . 6 ~ ~ , . : : = 8 = = J

Thrust FTIN]

35g30w 25

u 20gJ 15

Figure 3 12: Efficiencies of propellers for gh en thrust for a flume tank water velocity of0 4 m s the drag force for a glider with an advance velocity of 0 4 lll/s isshown a a venieal line


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CIIAPTEn 3 PnOPULSION t-.IODULE DESIGN 49

1 8.646 0 8 1 1 2Thrust FT [Nj0 4.2

50

OJO m s ~ o 0 0 0 0 0 0 i, 00 0~ \ l q o i\ ,0Q 0, , n .i

o C D ~ b o; 0 0 , p l lo 5 00 c Jeoe O oooQ 0 8 3o/ i: 0 000 ~ 1 > 05 00 0 00 F0 0.5 mls)0

0 0 0 0.3xO.255 0 0 0.275xO.1750 0.25xO.1750 b 0 0.225xO.1750 O 2xO 1755 0 0 O 2xO 150 0.2xO.125

0 O 2xO 10

Figure :U;I: Eftlciencics of propellers for 11 gi\ cn thrust for a f1lll11e lallk water velocity of0 5 m/s. the drag forcc for a glider with lU I ad\ ancc velocity of 0 5 s isshown as a vertical linc


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CIIAPTEH 3 . PIIOPULSION ~ I O I U L DESIGN 50

9 O r - - - . - - - - - r - - - - - - - ~ - - _ _ - - -

70

60

30

c c 8 o ~ [ C b D [ D [ [ 0 [ .o 0 Q [ 0 [b . ; ; , 0 o c l b 8 g c ~ ~ t 0 b Be 00 000~ o 0 (folding 3Ocmls)LYe propOW 0 0 0 0 0 11prop fixed 3Ocm/s

20 O ~ 0 0 lprop(folding 4Ocm/s0 lprop(fixed 4OCm/s

10 0 0 11prop fOlding OCmlso lprop(fixed SOem/s

~g40

0.5 1.5Thrust FT N] 2.5

figure 3.14: Fixed propeller and folding proJX lIer compnrison for H propeller with 8 di81n-etel of 0.2 III and a pitch of 0.15 III at flow speeds of 0.3 Ill S and 0.5 m/s.


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C IlAPTEH PROPULSION ~ I O D U L I ~ DESIGN 5\

Figure 3.15: Image showing the differell :e; between lhe fixed Ilnd folding propellers with I ldiameter of 0.2 II I and \ pitch of 0.15 I l l

propeller. he difference between the fixed nd folding propellers is shown in Fig.3.15

l3y analysing the peak efficiencies from the d t in Fig. :J.lt - 3.13 an optimumpropeller of 0.225 In diameter and 0.175 11\ pitch may be selected for usc on thehybrid glider. However, the selection above docs 1I t take into aCCOllnt the interactionbetween the propeller and the hull of the glider. he wake fnlC lion and thrustdeduction t factors affect the performance of the propeller through the hull efficiency h to give the total propulsive efficiency } [74 as shown by

\ 1 1 d = l s l l s h = I I I . f ~ 3.14


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C I I M T ~ B : 3 . P OPULSION r\ IODUt O I ~ S I G N 5

5OOt8SaUlll 1aua l 0_10040 11891

O l ~ UalliS8 5 lnUU 5 8 N 10_12915011llOll2-Figure 3.16: Velocity contours for a Slocum glider CF D model shown llt the location o f t he

propeller with a 0.2 II I an d 0.225 m circle overlaid to show the propeller diskarea where th e advance \docity is 0.5 m/s.

Estimates of the wake fraction from a computational fluid dynamic CrO) modelshoWIl in Fig. 3.16 give values of w=O 4 and w=0 296 for 0.2 and 0.225 m diameterpropellers for VA = 0.5 m s These values combined wit h an assumed thrust deduct-iollfaelor of = 0.2 from [74J, results ill Ill = 1.212 for the sillaller propeller and Iii = 1.13Gfor the larger propeller as shown in Fig. 3.17; however, the relative diffcrcllee in theopel water system efficiency from the ~ U flume tank tests for these two propellersis only 2 . Additionally. th e torque requirclIlellts of the 0.175 pitch propeller weresuch that th e magnetic coupling stalled at full power. For these reasons. a propellerwith 0.2 II I diameter and 0.15 II I pitch was selected for the propulsiolllllodule. Th emotor and propeller efficiency for this propeller may be extracted from the datapre;cnted earlier using 3.13) and 3.6).

In Fig. 3.18 the molOr. propeller and system efficiencies for th e propulsion module


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C I l M T E R 3. PROPULSION M O D U L I ~ I ~ S I N 53

1 2 S I - ~ - - ~ - ~ - - ~ - - - - ~ r _ ~ = _ C o = . 2 = m = = j l e 0.225 m 0 _120 ~ -

g ~ __ -_o

f~

5

O L . 3 - - - - , O ~ . 3 : c S - - O - . 4 - - - , O - : . 4 c : - S - - - - O L . 5 - - 0 - . 5 - 5 - - ~ O . c : - 6 O : . 6 S . JO.7Advance Velocity V [m s]

Figure 3.17: Ilull efficiency from a computatiollal fluid dynamic lllodel r 0.2 III find 0.225II I diameter propellers.


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CIIAPTIm 3 PIlOPULSION t \ I O D U L l ~ ~ S I G N

80

70 00 o 0 0c 000 0060 q l l ~

10 00 ~

eOlPi ~ l o _ o O ~ , o F0 0.3 mls)50 DC C C C C C 0 0 llsys 0.3 m1S

~ a C 0 0 , 0.3 mls)0 0 llm O,3 rnIs)40 oOS 00 0000 < 9 ~ o 0 0 0 0 F0 0.4 m1s0 0 llsys 0.4 m1s30 0 0 o 0 cecco 000 0 llprop 0.4 rnIs) 0 llm 0.4 m1s20 00 F0 0.5 m1s0 0

0 , ,0 llsys O,5 rnIs)0 llprop 0.5 m1s0 llm O,5 m1s

5

0.5 1.5Thrust FTIN] 2.5

Figure :.1.18: Propulsion module cfficicllcies for a pro X'llcr witll 0.2 dialllctcr iUld 0.15 pitch at adw\Ilcc \'clocities of 0.:3. 0.4 and 0.5 Ill/S. Thc \'chicle drag forceis o\'crlaid as \ 'crtical lines increasing frOIll left to right for n gi\ cll a d \ ~ U I C evelocity.


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CIIAT Tl:: l PROPULSION IvIO ULI OI SIGN in t he MUN flume tank are shown By examining the intersections of t he d ra g forcelines wit h t he propeller data for the same velocity the predicted operat ing point isdetermined Using this procedure th e propeller dficiency is S { l l to increase with and the motor efficiency decreases with load rcsulting in a systelll efficiency whichincreasc slightly with an increase in advance velocity

The propeller selection and design is prrseuted using an integrated approach re-sulting in a system that is well matched to the glider hull form and to the propulsiverC


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Chapter 4System Integration andModificationThe integration of the propulsion module into the glider is pr( S{ lIted. From the designrcquircillcllts this inl cgrat ion was dOlle sud I that minimal Chflllg( S would be necessarybeyond what is easily accomplished by an experienced glider user.

4 MechanicalMechanically, be propulsion module was d ~ i g l l d such 1hal it replaces l,he 0.5 kgemergency drop weight at the rear of the glider. To this {,(f('ct t.he weight in waterof ti le propuls ion module is matched to th e wcighl.. in wMC' ' of the drop wC'ighl. Thislocation has the added benefit of being directly in line with til( elltre of buoyancy ofthe vchide; how(,\ er. it. currently removes the function of the Clllf rge lcy drop weight.Also, it inlC rfcrcs wilh the power plug used to turn the glider on nud off rC


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CIIAPTEn SYSTEM INTECRATION AND MODIFICATION

of the tail sect.ion requires the tail COliC to be loosely placed over the tail. Thepropulsion module is inserted into the drop weight location and the cable connected tobulkhead connector. The tail cone is then secured into location. Future versions of thepropulsion module will ease some of the installation and modification requirementsas well as either adding an additional drop weight mechanism or incorporating anejection mechanism into the propulsion module.

4 ElectricalElectrically, the glider has two Persistors; low power, single board computers.nected by a communications bus. The glider computer handles all control and lowlevel fUlltlions while the science computer is used for illte . ation of new payloads andsensors. To avoid changing the existing glider architecture the propulsion module isconnected to the power pins on tile sciellcc computer board llsed for powering payloadinstruments.

POl testing purposes, the motor of lhe propulsion module is controlled through anL 9 N molar controller with the drive voltage being snppli(, d from the science boardpayload power pins and logic level pOWN from the Persistor stack s :.tJ V snpply. Apulse width modulated P W ~ I signal is input into the motor controller 1,0 control theinput voltage to ,he mot.or and the logic inputs flrc fixed high or low to make the motorulli-directional. In future versions the Illotor will be run off the rail supply voltagesin the glider to remove the electricallosscs associated wilh the Illolor controller.

To measure power into the propulsion module POW( I monitoring board was developcd to mcasure the input current find voltage lIsing the salllc hall cf[Nt scnsor andresistive voltage divider as in Section 3.3. The schematic for this device is included inAPllCndix 3 The voltages were rcad in using the ~ I A X 127 analog to digital converter


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CIIAPTE:R 4. SYSTEM I NT E GR A TI ON A ND MODIFICATION 58ADC which is also used elscwhere in the glider allowing for easy int.egrat.ion intothe code. This chip uses the serial peripheral interface SPI) to communicate withthe science computer Persistor board and is powered from the 3.3V power bus o n thePersistor stack.

A Microstrain 3DM-GX3 inertial measurement unit It-,/IU was also integratedinto the s ys tem to measure the eulcr angles, angular rates and linear accelerationsof t.he vehicle during the unconstrained opcn water tests. This dcvice uses a RS-232bus to interface with the science computer and is powered t.hrough a step down linearvoltage rcgulator from payload power pins on the Science bomd.

4 SoftwareIn soft.ware, int.erfacing to t.he science computer rcquires the use of proglets, which usea manufacturer specified finite state machine template to control science Imyloads.The hybrid progl et takes one i nput from t.he glider comput.er, t.he commanded dutycycle for the motor cont.roller. The motor controller is powered 011 whell the proglet.is enabled from the glider computer.

The power monitoring proglet utilises the SPI interface to receive t.he voltage andcurrent data from t he ADC. This dat.a is logged on the science computer flash alongwith the glider time-stamp. By default. this data is als o Sent to the glider at a slowelrate but may be disabled. Since the power for the power monitor is supplied frolllthe Persist.or stack, the power llionitor is powered on with the science computer.

The Mi cr os tr ain lMU pr oglet uses one of t.he RS-232 lines on the s< ipJl bORrd.Commands are sent to t.he devi


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I l P T ~ R SYSTEM INTEGRATION AND MODIFICATION 59proglel is enabled y t glider computer The complcte code listing or t aboveproglel s may be obtained y contact ing the author


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C ha pt e r 5System Evaluation and TestingThe testing of th e vehicle with the propulsion module is prCS( llted. Th e evaluationof i ts performance was done incrementally using different. lest. facilities here in St..John s. Validation o f t he drag model at zero angle of attack is presented. To evaluateth e vehicle s stability th e Luning of th e depth controller is detailed as well.

5 1 Tow Tank Self Propulsion ExperimentsSC ]f propliision tests were performed ill the tow tflnk L UN to cvnlllal.c t.he glider spropulsive capabilities. The experimental sptup for these tests involved a tensionedguide wire being strung the length of th e tank I below th e waLer surface. The gliderwmj al.lac led to the guide wire sHch that was able to movc under self propulsionwhile bring conslraincd directionally. The dirccliollal constraints arc Ilcccs. .ftry du eto th e illability of t.he magnetic heading refefellce to function in th e tow lank.

For thCS tests the electrical input voltage and CUITent was measured. The adv811Cvelodly of th e glider \Va< mca


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CflAPTElt 5 S Y S T ~ EVALUATION AND TESTING 61

wire Lo minimise the friction due to the attachment. I>oints. Initial tests used tiewraps through tic-wrap mount points, however, after bringing the glider ou t of thewater and investigating the state of the tie-wraps significant wear was present. Tefloncoated wire taped to the underside of the hull WiL i also uS< < which worked well forscveral runs until the wire slipped from the tape The final setup had the tensionedguide cable passing through plastic tubing and tie-wrapped to the tie-wrap mountingI>oints.

This S< tup allows for testing of many different propulsion configurations to analysethe relative impact of a change in prol>eller or hull configuration. The standardwllfiguration for wmparison to others is the glider with wings attached the sensorhole on 1he tail-cone taped over and the power I}lug pla 1 inside the tail-cone asshown ill Fig. 5.1

In this configuration two propellers were tested, a propeller with 0.2 m diameterand 0.15 II I pitch and another propeller with 0.225 I II dianlct t r Ilnd 0.175 m pitch.The snlflller propelle-r, Le., the propeller selected during the design phase, was runat seven diffe-rent voltages and the larger propeller at, only three different voltages.Thcfie refillits are shown in Fig. 5.2 with the Illotor duty cycle- shown in Fig. 5

In Fig. 5.2 Hnd 5.3 the larger propeller was 1ll1abl 10 be- t llll at higher power levelsdue t.o torqllC limits in the magnetic coupling. From these result.s thc larger propelleris capable of higher overall speeds at higher power IcvC lfi. 1I0wC ver, to achieve higheradvalLcc vC locitiC s tile magnetic coupling requirC s ndjLlstillg 10 illCfeas( the pull-outtorque-.

The inrJuellce of sensor holes in the tail-COile, the power plug external to the tail( one and the removal of the wings were also e-x3mi l( d. Each variable was testedilldividllally, only making one change frolll the standard configuration. To test thesensor hole inAuencc the tape covering the hole was removed. For the I>ower plug test


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. ~ ~

CIIAPTEH SYST lI l EVALUATION AND T ~ S T N 62

Figure 5 1: Glider showing the st n r testing configurntioll of a t pe sensor hole npower plug inside of tail colic


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CHAPTER SYSTEM EVALUATION AND T ~ : S T J N C

3 5

~a 2

1 5

5 9 0 2 m x 15 m

OL - - , = - - - = : , = = 0 = . 2 = 2 5 = m = x = 0 . : c 7 = 5 = m ~Q2 0 3 0 4 0 5 0 6 0 7

Advance elo ity VA 1m 5

Figure 5 2: Power rt


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CIIAPTER SYSTEM EVALUATION AND TESTING 64

00

90

80

70u 60.9

50

40

300.2 0.3-- -0.2 m x 0.15 ma 0 225 m x 0.175 m

0.4 0.5 0.6 0.7Advance Velocity [m S]

Figlll e rl :I: fo lot or duty cycle at a given advllll


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CIIAI TEH 5 SYSTEr l EVALUATION AN D T ~ ~ S T N 65

th e plllg was t ake n out of t he tail-cone and placed in its housing abovc the thruster. heremoval of the wings necessitated th e re-ballasting of the glider. For this purposeweights were added to th e wing attachment rails. heresults or these tests ar e shownill Fig. 5.4.

o3.5

o1.5

7.4 0.5 0.6dvance elocity [m s30.5L- LO -- =--- -- = : : = ~ ~ ~ = = . J

0.2

Figure 5.4: Power requirements a t a gi \ c n advance \ clodty for different t xlenllli cOlllponcntconfigurations in th e ~ e l l l o r i l University of Ncwfoulldiand to\\ tank

From Fig. 5.4 th e sensor hole t(>St lilld lh e power plug te st show higher powerrequirements for the samc velocity when compared wilh th e standard configuration. hi sincrease is attributed to a decrease in propeller p rformance du e to the distur-bance of the inflow characteristics. heglider (< Sts willi no wings attached shows


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C I I A r n R 5 Y T ~ EVALUATION AND T ~ S T N

lower power requirements for the same velocit.y when compared to the standard configuration. This reduct.ion ill power is attributed to the removal of t.he wings contribution to the vehicle drag. The tow tank self propulsion tests provide a comparisonof the relative benefits of one configuration over another. The results are presentedto inform the selection of a configuration warranting further testing.

5 2 Flume Tank D rag and Propulsion TestsUsing the selected vehide configuration from the tow tank self propulsion tests, fullscale drag and propulsion tests were performed al the ~ a r i n { Institute's fhllne tankwith a test section 8 I I I .x 4 I II x 22.5 I I I and ( apable of gellerating now speeds fromo to I m s These tests \vere done to verify the glider's hydrodynamic model and toevaluate its propulsion abilities. The general experimental set up is shown in Fig. 5.5with an expanded view of the attachments to the glider in Fig. 5.6. In this setup theglider is attached to a guide wire which constrains the glider in yaw, pitch and roll.Drag lneflsurcments were t ten performed through a load ('ell allached to tbe forwardclld of the glider. Additional drag and self propulsion C'xpcrinlents wcrc performedwit h fill addit iOlJal load cell attached to the aft end of the glider and pre-tensionedwith a counterbalallce weight. The forward attachment. point was through I,he noseand the aft attflchment was through a twin-bridle barileI:'.'> attached we outboard one,lCh wing in OHler 1 provide clearance for the propeller to spin frcely.

The drag tests were performed for the glidtr at z('ro angle of aHack with wings,withollt. wings and with wings and the counterbalance weight. Self propulsion testswere performed for the glider with the counterbalance weighl by varying the voltageto the motor. These tes ts were performed for advance \'elo('ities of 0.2 to 1.0 m sin increments of 0.1 m s F'or all tests the motor voltage- C' ('( trical current


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CHAPTlm SYSTEM EVALUATION AND TESTINC 67

Figure 5.5: r- lnrine nstitute m x 8 x 22 flullle t nk experirncntfll selilp r full scaleglider hydrodynamic nd propub;ioll te:- tillg.


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CIlAPn;n SYSTEM EVALUATION AND TESTINC

\ \ Guldewlre tensionedl tlsliding rtKhmenl pointForward sliding attachment point

P; i_ Upatrumloadcell 2SH \ \- - ~ I

FigHrp 5 : EXpl\llded view of the t\larine nstitute flulIle t nk experimental setup


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II PTEl l 5 S Y S T I - ~ ~ I EVALUATION AN D T ~ S T N 69

and glider drag force were recorded. For the counterbalanced measurements, was calculated by subtracting the aft load cell readings from the forward load cel1reading to remove the effect of the prc-Io.: \ding. The ~ l a r i n e Institute s flume tankhas been previously calibrated such that the advance veiocil.y was recorded from therommanded set point and not actively measured. The effect of the harness attachedto the wings for the counterbalance was ; 0.5 N and the predicted drag forc wa.,; 0.34 a difference of nearly 50 .This difference can partially be attribul.ed to parasitic drag in th( test setup; however,the drag presented in (2.6) is based on illdirect measurements and extrapolated totile zero angle of attack condition. Therefore, til{ lllellSUrelllcllts presented here areconsidered to be more aCCllrate for this case. tor tht 110 wing tests thc harncss couldllOI. bC lIsed fl it al t3ches t.o the wiugs. TIl( lllt U:-;Ul I11ClltS for this tcst were therefore:-;ubjcct. to higher levels of noise fl the force levels were low. Therefore, alt.hough t.hetest, shows h drag to bc lower wit h t,he wings not ilttached, t w dat.a is det.erminedto be [( SS reliable.For the tcsts with the propulsion module til< for( c differellcc bclwccn the upstream

ami dowllstrcam load cell forces was measured as ill Fig. 5.8 Whcrc Ihe force crosseszero in Fig 5.8, shown by crosses. is the elcctrical pOWCI rcquired for the givcn velocityat stcady state This data as summarisro in Fig. 5.9.

The amount of electrical power required for horizontal flight lIsing the auxiliarypropulsion module is shown to be


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CIIAPTEB SYSTEM V LU TION N T ~ S T l N

4 5

3 5

2 5 9u c

e~ 80> 1 5 i 5

c

no harness test c standard test no wings test

0 5 1 2 3 5 6 7 8 9Advance Velocity vA Im/s

Figurc 5 7: Marinc Institute flume tauk glider h yllrodynHlIlic drag force lllel.l.SUl ell\cnt cali

bmtion and testing


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CIIAPTEH S Y S T ~ ~ I EVALUATION AND TESTING

4 5

3 2 5

2i

1 5

0.5

- -O,2m1s-- -0.3 mls 0 4 mls0 5 m 1 s----6- 0.6 mls----9- 0.7 mls

7

~ 3 ~ : 2 ~ 0 ~ ~ : :rag Force F [N]

Figure 5.8: Self propulsion test results showing the force difference octween the upstrealllllnd downstream l oad cell forc :> for a givell elcctrical input power. The selfpropulsion condition for each cun e is marked by un x


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CIlAI TEIl 5 SVSTEr EVALUATION AN D T ~ S T N

4.5

3.5~ 3

ll 2.5 2iii

1.5

72

0.5 flume tank

0.2 0.25 0.3 ~ 0 4 0.45 0.5 ~ 0.6 0.65Advance Velocity [m1s]

Figure 5.9: Self propulsion test rcsults showing the pow r r< C\uired for ~ v l l advancevelocity t ste y st te


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CHAPTER SYSTEM EVALUATION AND T ~ S T N 73

51)using a polynomial cubic fit to the flumc tank powcr data in Fig. 5.9. Where

the cocfficients for 5.1) are defined as in Tab. 5.1

P 1 1 kg m sP3 -1.0 kg/

13 2 kg/mTable 5.1: Coefficients for the electrical power to t he propeller

Prom 2.18) and 2.6) a cubic relationship is exp


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C ~ I A P T l : l 5 SYSTl :rvt EVALUATION AND TESTING

1009080

70 60is5 500 40 30

20100 3 2 1 0Drag Force F0 IN]

- -0.2 mig e 0 3 mig--- - 0.4 mig--- - 0.5 mig 6 0.6 mig lii1 0 7 mig

74

Figure 5 10: Self propulsion tcst rcsults showing th e force difference bctwecn tile npstreamand downstream load ccll forccs for a given motor duty cycle Th e self propul~ i o n condi tion for each curve is marked by an x .


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CIlAPTER S Y S T ~ EVALUATION AND TESTING

10090

70~

~ 60

~ 500I 4030

2010

7

o L _ ~ ~ ~ ~0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65Advance Velocity Im ]

Figure 5.11: S< if propulsion t.est results showing the motor duty cycle r{ luired for a givenadvance velocity t ste dy st te


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CIIM TEIl 5. SvSn M EV LU T ION ND TESTING 76

glider with zcro advance vclocity, th c pitch a nd d ep th controllcrs may be consideredindcpendent. This assumption does not hold for nonzero advance velocities as th epitch and depth are strongly coupled in this case. 1I00 cvcr, to tune th e controllersth e assumption is used as a starting point.

.

F igure 5.12: Depth controller structure

For testing purposes th e drift -at-depth behaviour was used as it incllldes a pitchcontroller and depth controller. A dingram of the d< pt ( o11trollcr stl llctlll { is showilin Fig. 5.12 where c depth is th e desired depth control point flud e dmdband is th edepth deadbfllld for determining th e hovering statc . Initially, th e nenl,ral ballastlookup tablc modc was used but this did not. allow for n prcdictflble stan value forX_hovCLballast th e output to the ballast :-;ystel l, as the lable is unpopulated for th efirst divc after th c glider is turned on making th e r( Spansc unpredictable. Therefore,an illitia.1 x_hoveLballast valuc \1 based on experimental tests was 1lS 1. The controller stcps x hovc ballast by th e ballast p um p d el ta valuc bpdepending on whichstate it dctermines th e glider to be in. If th( glider is outsidc of th e hovering depth


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CIIAI)Tlm 5. SYSTEM EVALUATION AND Tf.;sTINC 77

zone defined ye depth and c_deadband, the controller will decrement x..hoveLbaliastif it is above the depth zone and moving up and will increment x..hover-l,allast if it isbelow the del}th zone and moving down. If the vehicle is inside the depth zone thereare two additional states in which the controller will change x_hovcLbaliast, movingdown too quickly and moving up too quickly. The controller determines these statesby comparing the measured depth rate with the hovering depth rate Zh which iscalculated using the user oonfigurable maximum depth rate to be considered hoveringZ as in

(5.2)

when. the factory se t hovering depth rate zf 0.1425 m s by default. If the glideris moving lip and i is greater than the Zh the glider is moving up t.oo fast. andLhovcLballa.st is incremented. Similarly, if the glider is moving down a

Documents

Development of an Underwater Glidejkghr Equipped With an Auxiliary Propulsion Module