Albac Glider

8/2/2019 Albac Glider

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Distinctive featuresof the vehicle are summarizeds fol-lows: 1) The ALBAC does not have a propeller thrusterbut moves aside by gliding[']. Thus, the vehicle carriesonly a small battery of00W. To get large lift force a pairof wings is fitted t the middleof the body as illustrated inFig. 1. 2) The ALBAC controls its trajectory changingpitch angle and roll angley displacing the center of grav-ity. Two actuators in a hull move a weight longitudinallyand laterally. Thus the major mechanism for control is notfitted outside the hull and the actuator system is not ex-pose to the sea water. The total hardware system, there-fore, becomes highly reliable. 3) Diving depth is limitedto 300 meters so that the mass is only 45 kg. 4) The ve-hicle does not have a communication link to the operator,so that the ALBAC can be called a fully stand alone ve-hicler21. 5) It is easy to design a vehicle which can divedeeper according to the same concept.

2401'800 - L 3 6 0

Fig. 1 Dimensions of the ALBACMission ScenariQ

Deployment of the ALBAC consistsof three stagesas illustrated in Fig. .1) Decent stage The ALBAC descends to the destination depth and measures scientific dataf water column along a

gliding trajectory.2) Drop of a weight When the vehicle comes to the destination depth,t drops a decent weight and becomes positivebuoyant for ascent. In caseof emergency, for instance the vehicle dives over the design depth of 00 meters or theranging sensor finds n obstacle, the vehicle lso drops a weight.3) Ascent stage:The ALBAC glides upwardn the same manner s the decent stage and the oceanographic measure-ment can be continuously carried out through this stage.

At present theALBAC is able to carry out

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Estimation of Glidine PerformanceThelidingerformance ofhe ALBAC wassti- L

mated and evaluated in the first design stage, because itcompletelyependsnhehape of hull. Supposehathe Body Center Linecenter of gravity of the vehicle 0 is gliding at speed V. ---Configurationof the vehicle is ill"strated in Fig. Horizontallanethe gliding angle and the anglef attack are denoted byeanda, espectively. The proportional gliding anglee andstatictability ofheystemreiveny 8 :Center of Gravity

tan ye =CD/Q,d c m l d a < 0. (2) Fig. 3 AUV in Gliding

Here, : ift coefficient, C, : drag coefficient, Cm moment coefficient, a ngle of attack. These Coefficients arefunctions of the shape and the angle of attack, and cane calculated on the basis of USAF DATCOM31compiled forestimation of the stability and for improvement ofEquilibrium equations of forces and moment which determine, e and V are givenby

Here, B: buoyancy, G dryweight,L, wing lift,D, :wingdrag,4 : ail lift, D, : tail drag, L, :body lift, D, :bodydrag, 1 : ocation of center of gravity from body apex,Y: ocation of center of buoyancy from body p e x , L,: ero-dynamic center location of wing from body apex,: ero-dynamic center locationof tail from body apex, andbody :aerodynamic center location of body from body apex.

At the first stage of development, a 30 cm lengthmodel was made and tested to evaluate gliding perfor-mance. Results of the test show good agreement with theestimated valuesas n Fig. 4.

Construction of the ALBACShape of The ALBAC The body of the ALBAC con-sists of a1/2 ellipse shape front cap, a cylindrical pressurehull, a corn shape tail cap with a vertical stabilizing fin, apair of wings andailwings, which re made of RF' exceptthe pressure hull,

The dimensions of the vehicle basically depend onthat of the cylindrical part of the body which should pro-vide enough space for electricnd electronic devices,.e., a

" L

Distance (m)0.5 I

Calculationp 0.1

0 5 10 15 20Time (sec)

20 Calculation

0 Time(=)105 20Fig. 4 Resultsof Gliding Experiment with a SmallModel

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Fig. 5 General Arrangem ent of the ALBAC

Table1 nstruments of the ALBACa) CPU

INTEL 8087) Math ProcessorNEC V50 2

Table1 nstruments of the ALBACa) CPU

128 Kbyte 2) Memory CapacityINTEL 8087) Math ProcessorNEC V50 2

a) Interfacebl Power SUDD~V 13.6v, 7Ah (Ni-Zn Battery)

RS-232C, PIO, Counter,Pulse Generator, AD ConverterIa) Memory Capacity I128 Kbyte 21 . - . - ,a) Interface RS-232C, PIO, Counter,Pulse Generator, AD Converter

lbl Power SUDD ~V I1 3 . 6 ~ Ah (Ni-Zn Battery)I c l Actuators 11 set Id) Gravity Sensor

500 kHz\ Ranaina SensorX, V, Z Axis Output) Magnetic Sensor X, V, Z Axis Output

Ih\ Deothensor lo to 30 atm. I7jDeballastork) Thermistor

23 kHz) TransponderOil-Immersed Solenoid

Oil-Immersed Solenoid)Tail Angle Trigger-5 o30 C (kOV Output )

depth sensor, a gravity sensor, a magnetic sensor,two CPUs, interface boards and two actuators to and roll. A ranging sensor, a velocity sensor, adeballastor, a ail angle trigger and a transponder arefitted in the front and the tail caps (cf. Table 1 andFig. 5) . Consequently, a prototype vehiclef 140cmin length,120cm in span and approximately5kg inmass was designed and constructed as shown inPhoto 1,Figs. 1,5and Tables1,2.

Table 2 Specifications of the ALBACIDiameterof Bodv0.236 meter IVolume Overall 155 litersMass 145 kgPay Load Space litersGliding S peed

20 degreesaximum Gliding Angle1-2 knots

~~ ~

Enduran t Time of Gliding300 meter Maximum O60 minutes Endurantim e of CP U30 minutes

Pressure Hull Thepressurehullmade of alu-minum alloy is designed for diving to 300 meterdepth with2.0 safety factor, and provides a space foinstruments listed in Table 1 including a 3-liter drypay load space of 1-atmospheric pressure for scien-tific measurement devices.

Wings Wings and horizontal ail wings have a NACA 0009 symmetrical foil section considering both upwardand downward gliding. The vertical stabilizing fin which prevents side slip has a NACA 0018 foilBattery Since the instruments consume 44 watt electric power and time for one mission is estimated about 30minutes, a nickel-zinc battery cellof.100 watt hour is selected and fitted on the fore bulkhead of the pressure hull.Ultra Sonic ADuaratuses A forward ranging sensor of 500kHz with 4 degrees in beam width to detect obstacles,and a transponder with which relative position from the mother shipan be detected using aSBL system, are fitted inthe front cap and the tail cap. The transponder is self-contained andas not a link to the CPUf the vehicle.Attitude Angle Sensing: System A compact inertial navigation system which consistsf a three-axis gravity sensorand a lux gate magnetic sensor is installed to measure the attitudef the vehicle. From the roll, pitch and yaw anglestheir angular velocities are calculated at every.1 second.Sensors A propellerypeelocitymeterithlectric Pressurehambermagnetic encoder to measure the forward velocity and atemperature compensated pressure transducer for the depthare fitted at the top f the front cap and the fore bulkhead,respectively.Actuators o Dimlace theCenter ofGravity To con-trol the location f the center of gravity, two DC servo mo-tors are driven with PWM by a computer system as illus-

RollMo r Line

Pitch Motion ControlFig.6Mechanism of Actuators

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trated in Fig. 6 .Capacity of motors are enough to movethe weight even if the pitching angles 90 degrees.ComDuter Svstem Desim The computer system con-sists of two NEC V50 CPUs, i.e., one for control ofattitude of the vehicle and the other for data logging.The structure f computer system is schematically illus-trated in Fig. .Data Transmission Data transmission to load a pro-gram and to acquire measured data is utilized RS-232cserial interface between the computer systemf the AL-BAC and a host computer on deck.

Omration SeauenceA program for one mission is loaded from a host

computer to the CPUsf the ALBAC ondeck, then the

.....................+( Pulse Generator>-

I W I

tData Acquisition IFig. 7 Schematic Diagram of Computer System

umbilical is disconnected and the vehicle is hung from the deck and released to the sea. When the outputf pressuretransducer is over a specified level for example.6 meters, the control andata acquisition sequence is started. Asnthe same way of starting, the control anddata acquisition sequence s ended when the vehicle ascends to the specificshallow depth. The vehicle on deck is connected to the umbilical and the measurement data are saved. A chargedbattery is exchanged for the next operation.

Sea TrialsGliding Performance of the ALBAC To investigate the relation between the location of the center of gravity andthe proportional gliding angle, sea trials were conductedt the Ashinoko Lake and the Suruga Bay. The gliding angleof the vehicle s calculated by the next equation basedn the forward velocity and the ratef pressure,

ye = sin-*(Dk), (6 )Fig. 8 shows examples of time histories ofdata of one test. The proportional gliding angle is measured 18.7 degreeswhich shows good agreement to the estimated value 20 degrees. Fig. 9 shows the correlation between the longitudiallocation of the centerof gravity and the proportional gliding angle in both the descent and ascent stages, where rein the next empirical formulas (in deg).

-1.443x103x+7.02x102 (Downward)-1.O2x1O3x+4.91x1O2 WPWW

Here, x s the ratioof body length and the longitudinal location of the center of gravity measured from the body apeIt is shown n Fig. 9 that the gliding angle in a descent stage cane changed from15to 30 degrees.Turning Performance of the ALBAC When the location of the center of gravity is shifted laterally, the ALBACrolls and starts to turn in a constant yaw rate as shown in Fig. 10. Becausef small misalignmentof the tail wings, thevehicle rolls a ittle even if the weight has not been moved. The relations between the lateral locationf the centerofgravity and steady state yaw rate are determined as shown in Fig.1both in the descent and ascent stages. From theseresults, the following empirical formulasf yaw rate (indedsec) are obtainas,

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p 30s 0Distance (m)

A

2 0 1I LI, I6-10E -20.z -300 100 30 40 50 60 70- 16:0.9F 0.8g 0.5g0.72 0 . 63 0.4' .33i-me405 -2 0$49 60

Q 2;

B " oO 10 ' 20 30 40 50 60 70Distance (m)Fig. 8 Resuits of Gliding Experiment of 0.47881.

Longitudinal C.G. Locationc 1 , I

jj O F I0 10 20 30 40 50 80Distanca (m)-10

0- 020

$3040

50-50 -40 -30 -2 0 -10 0 IOXdistance (m)Fig. 10 Results of Step Responce Experiment n

Lateral Motion

308 25;0.- 10- 15g 5

00.47.475 0.40 0.485.49Center of Gravity Location(Oody Lengthfrom Nose)

Descent08 -5;;; 10

F 15F 203-m

-25-30

0.49.495 0.5 0.505.51Centerof Gravity Location %Body Lengthfrom Nose)

AscentFig. 9 CorrelationbetweenLongitudinalCenter of

Gravity Location and Gliding Angle12

h108$18z 6

LongitudinalC.G. Location

a 46* 200 0.2 0.4 0.6 0.8 1 1.2 1.4

LattralC.G.LocatonShift(mm)Decent

Longitudinal C.G. ocation

0 0.2 0.4 0.6.8 I 1.2 1.4LateralC.G.Location Shift (mm)Ascent

Fig. 11 CorrelationbetweenLateralCenter of GravityLocation and Yaw Rate

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3.26y-2.64~10-' (Downward)5.275y+2.45x101 W P W W (8)

Here, y denotes lateral shiftf the location of the Center ofgravityfrom the body center line. Exactly speaking, the proportionalgliding anglemay increase when the vehicle rolls because of de-crease of vertical component of lift force. From the results ofri-als, however, it is concluded that this effects negligible.OceanotzraDhicmeasurementof the ALBAC Fig. 12 showsan example of the distribution of temperature in a shallow waterat the Suruga Bay measured by the ALBAC. Resolution and re-sponse of the thermistor are 1/100 degreend 1 sec, respectively.From these curvesofdata, it s expected that shuttletypeAUVscanbe competitive to the expandable bathythermograph (XBT).

14 14.5 15 15.5 16 16.5TemperaturePC)

Fig. 12 Distribution of Temperature in ShallowWater, Mito-Hama, Numazu, Shizuoka on

January 20th, 1993Conclusion

The ALBAC was constructed as a practical AUV for oceanographic measurement.This paper introduced theprocess of design and details of the ALBAC.t is concluded that shuttle type AUVs are practical for oceanographicmeasurement of water column. The ALBACs the first vehicle and can be modified for deeper dives by slight change.

AcknowledmnentThe authors wish to thank Kobe Steel, LTD., OKISEATEC CO. LTD., Ashinoko Fishery Association and

Central Workshop of Institute of Industrial Science of University of Tokyo for supporting the construction andseaaids of the ALBAC.

References[l]T. Ura, "Free Swimming Vehicle "FTEROA" for Deep Sea Survey",roc.of Remotely Operated Vehicle Confer-

ence& Exposition '89,San Diego (1989), pp.263-268123K.Kawaguchi, T. Ura, Y. Tomoda andH. Kobayashi, "Developmentof a ShuttleAUV for Oceanographic Mea-surement", Proc. of Pacific Ocean Remote Sensing Conference, Okinawa (1992), pp.876-880[3] D. E. Hoak, "United States Air Forces Stability and Control Data Compendium", McDonnell Douglas Corp.

Douglas Aircraft Division, (1960)[4] H. Maeda and S. Tatsuta, "Prediction Method of Hydrodynamic Stability Derivatives of an Autonomous Non-Tethered Submerged Vehicle", Proc. of Conference on Offshore Mechanics and Arctic Engineering, Netherlands

(1989), pp.105-114[5 ]IRAH. Abbott, "Theory of Wing Sections", Dover Publications NC., ew York, (1959)

Albac Glider

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