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THSiS INS

A review of the application of INS within Fugro

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THSiS INS

Outline

History – quick review of INS

Fugro Uses – Where and how we use INS

Fugro Developments – Off the shelf v In house developments

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History

INS has been around for a while….

Western Geophysical W-INS, late 1970’s (We invariably needed SHORAN)Shelltech/Itech land seismic use of INS for control (helicopter based Zupt’s) Mid/late 1970’sExxon/Honeywell’s DP reference systems – Riser and INS –1979British Oceanics/Intersub INS for manned submersible construction positioning (“used in place of unreliable acoustic systems”) – early 1980’s

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What is it

IMU block diagram

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What is it

Inertial Measurement Unit (IMU)What is it ?3 sensors measuring rotation around X, Y & Z axis3 accelerometers measuring acceleration along the X, Y and Z axisTime

Software takes raw rate and raw acceleration into a moreuseful product.AHRS Attitude Heading Reference SystemINS Inertial Navigation System

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What is it

Conceptually an INS uses dead reckoning navigation

It adds results from current epoch to the sum of the previous

With no aiding there will be a growth in error

10 minutes 15 minutes

5 metres

20 metres

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What is it

Many Aiding Observations can be usedDGPSDoppler Velocity (Acoustic and Radar)AltimetersDepth sensorsRange/Range

But why use a positioning system to aid ?

If I know where I am why do I need to be told ?

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What is it

Conventional Positioning Sensors are characterised by Short Term NoiseLong Term StabilityLoss of AvailabilityE.g. USBL

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What is it

Integrate INS with aiding or positioning system to –

Remove Short Term NoisePreserve Long Term StabilityImprove Availability

ScenariosDeep water untethered and or unmanned vehiclesAirborneReduced availability of positioning –

Environmental Effects

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Fugro Uses

AUV and UUV positioning

HP DGPS /HiPAPLinkQuest Acoustic ModemIXSEA IMU 90RDI DVLDigiquartz DepthTritech Altimeter

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Hugin AUV Main Components

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Recent AUV Positioning Verification

• Water Depth 1300m• Box in around as-supplied wellhead

position • 4 Lines – 4 Picks - mid swathe of

EM2000

Multibeam Survey

Easting Northing

M1_01 (090°) 619641.5 9376430.8

M1_04 (180°) 619639.1 9376431.0

M1_02 (270°) 619640.0 9376432.4

M1_03 (000°) 619641.8 9376432.0

Average 619640.6 9376431.6

Median 619640.8 9376431.5

ΔE/ΔN from as-supplied 0.1 -0.2

Absolute separation 0.2

SD 1.3 0.8

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Fugro Uses

Deep Water ROV Positioning

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Fugro Uses

• Sensors– Motion sensor, DVL– Position aiding: HP GPS HiPAP USBL– Finetrack L200 Post Processed

Pipe in trench

6m x 3m Matt

Pipeline Support

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Fugro Uses

Surface Navigation Under Cover

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Fugro Uses

• Sensors– Motion sensor, DVL– Position aiding: RTK

GPS (dual system)• Environment

– Signal masking, outliers in GPS positions

– GPS MOVIE

– INS MOVIE

Bad GPS position

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Fugro Uses

Airborne Surveys

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Fugro Uses

Reduced Navigation

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To Develop ?

Various INS/IMU units on the market

Numerous aiding positioning systems

Some integrated systems available but manufacturer specific

HAIN good example

Fugro along with other contractors use this in Hugin 3000 AUV

Mother ship must have HiPAP

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Finetrack

• Fugro developed family of filters for different hardware combinations

• Hardware Independent• Developed in house and in conjunction with other partners• FINETRACK

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Finetrack

L series Loosely CoupledAid System Position/VelocityINS Position/Velocity Enter into Kalman

T series Tightly CoupledAid System raw observationsINS rate & accelerationsEnter into Kalman

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Finetrack

T100 integrates Honeywell IMU, Sonardyne LBL and DopplerL100 primarily Doppler aided USBL or LBL with IMU as high precision MRUL300/400 Take manufacturers integrated IMU/Doppler solution and bring in to global co-ordinates by integrating LBL, USBL, Depth and or DGPS ( L300 Kearfott T16/ RDI DVL)

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Where Next ?

MEMS (micro-electro-mechanical systems )

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Summary

INS after a long gestation is here to stay

Can be used in numerous applications

Off the Shelf availability, if tie to one manufacturer is OK

INS in Action