A MOOS-based AUV forMagnetic Signature Assessment

Presented by Dave Billin

University of Idaho, Moscow IdahoAt MOOS-DAWG July 21, 2011

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Team Members

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Motivation

Influence mines and torpedoes can be triggered by a ship's magnetic field.Vessel's magnetic field may be canceled or reduced using • Deperming (degaussing)• Active cancellation

Pictured:USS RAMAGE (DDG-61) at Lambert's Point deperming facility near Norfolk, VA(Robert J. Sitar 10-23-1995)

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Motivation

Challenges:Optimal field cancellation requires precise measurement.Vessel's magnetic “signature” is unique.Magnetic signature changes during travel.

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Motivation

Objective:A forward-deployable system for magnetic signature assessment

Scalable to vessel sizeMeasurement precision of 100 nTMeasurement range of 100,000 nT

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Strategy

Magnetic signature measurement using multiple AUV's

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U of I AUV

Portable, deployableSmall magnetic footprintLow Cost (approx. $19k USD)Collaborative autonomy

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AUV Instrumentation

Billingsly Aerospace triaxial fluxgate magnetometer6-channel, 200 kHz data acquisition systemGarmin GPS-18xRevolution digital compassArchangel IMU3900 MHz radio modemWHOI Acoustic Micro-modem

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AUV Measurement Pattern

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Measurement Results

-10 -5 0 5 10-20

-15

-10

-5

0

5

10

Right [m]

For

war

d [m

]

Deviation from mean of 53540 [nT]Calibrated PPEkf

-350

-300

-250

-200

-150

-100

-50

0

50

Multi-AUV measurementof 448 Am2 source anchored at fixed position

Single-AUV measurementof 135 Am2 source attached to bow of a moving ship

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MOOS-based AUV Design

Legacy U of I AUVGeneration 1 MOOS AUVCurrent work (Generation 2)

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Gen.1 MOOS-based AUV

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Gen.2 Design Objectives

Reduce power consumptionEliminate redundancies and bottlenecksHardware extensibilityStreamlined integration

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Gen.2 MOOS AUV Design

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Gumstix Integration

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MOOS Software

MOOS InstrumentsFSD MOOS interfaceNavigation, support applicationsIvP Behaviors

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MOOS Instruments

iArchangelIMUiWhoiMicroModemiRevolutionCompassiYellowSubDAQiRadioModem

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Front-side controller

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libYellowSubNav

U of I AUV core navigation libraryEKF Base class and derived classes• VehicleEKF, SyncVehicleEKF • ShipEKF

Acoustic Navigation classes• LBLPositionEstimator, LBLBeacon

Unit tests for module verification

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pVehicleEKF

Estimates current AUV position Combines:

GPS, compass, acoustic navigation, IMU, pressure sensor, prop RPM

Publishes:Local Grid (East, North) locationSpeedBias-compensated yaw

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pAcousticCommsAgent

Implements acoustic TDMA controlUtilizes GPS time synchronization of AUV'sText file based configuration of time slotsActive time slot may conditionally publish to one (or more) MOOSDB variablesRuntime re-configurable

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pMissionMonitor

Monitors vehicle safety conditionsMonitor target objects “enforce” logical conditions imposed on MOOSDB variables.If monitor conditions evaluate “FALSE”, one or more variables are published to the MOOSDB.Operational even when pHelmIvP is suspendedConfiguration via text file using Behavior-like syntaxRuntime re-configurable

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IvP Behaviors

BHV_ReverseDiveImplements 3-stage sequence enabling the positively-buoyant U of I AUV to dive aft-first.

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IvP Behaviors

BHV_YellowSubReBalanceProduces objective function in speed, pitch domainsUsed when U of I AUV travels at water surface.

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Acknowledgements

Office of Naval Research

Magnetic Signature Assessment System using Autonomous Underwater Vehicles (AUVs)Phase 1 (N00014-08-1-0779)Phase 2 (N00014-09-1-0711)Phase 3 (N00014-10-1-0883)

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Acknowledgements

“Autonomous Underwater Vehicle Navigation using Moving Baseline on a Target Ship”Amanda Folk, Benjamin Armstrong, Eric Wolbrecht, Håvard Fjær Grip, Michael Anderson, and Dean Edwards

Proceedings, IEEE OCEANS 2010 Seattle, WA

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University of Idaho

TitleTeam MembersMotivation - Sea mines, torpedoesMotivation - ChallengesMotivation - ObjectiveStrategyU of I AUVAUV InstrumentationAUV Measurement PatternMeasurement ResultsMOOS-based AUV DesignGeneration 1 MOOS-based AUVGeneration 2 Design ObjectivesGeneration 2 MOOS AUV DesignGumstix Peripheral IntegrationMOOS SoftwareMOOS InstrumentsFront-side controllerAUV Navigation LibrarypVehicleEKFpAcousticCommsAgentpMissionMonitorIvP Behaviors - Reverse DiveIvP Behaviors - Re-balanceAcknowledgementsNavigation AcknowledgementsEnd Titles