GPS Receiver Performance Using Inertial-Aided Carrier Tracking Loop
10 Years of Experience From Acoustic Aided Inertial · • Hydroacoustic Aided Inertial Navigation...
Transcript of 10 Years of Experience From Acoustic Aided Inertial · • Hydroacoustic Aided Inertial Navigation...
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DYNAMIC POSITIONING CONFERENCEOctober 15-16 2013October 15-16, 2013
SENSORS SESSION II
Ten Years of Experience from Acoustic Aided Inertial
Are B. Willumsen
Kongsberg
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10 Years of Experience from Acoustic Aided Inertial Are B. Willumsen, Product Manager HAIN, Kongsberg Maritime
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Inertial Navigation System (INS) • Inertial measurements
• +Accelerations – accelerometers • +Angular rates – gyroscopes • = Inertial Measurement Unit (IMU)
• Integration – Orientation – Velocity – Position (integrate twice)
• Independent – Of external systems – Of vehicle dynamics
• Integration without correction inherently instable
2009-06/15_00:30 :32 :34 :36 :38
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HPR400 SSBLHAIN
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• Hydroacoustic Aided Inertial Navigation – HAIN Subsea – HAIN Reference
• HUGIN Navigation System • 2003
– First HAIN Reference trial on Seaway Osprey – First commercial use of HAIN Subsea
• 2013 – 50+ HAIN Reference sold
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(Pictures in courtesy of respective owners)
System integrity • INS never independent of aid.
– Never use both as references simultaneously.
• Unaided increasingly inaccurate. – Safety measure: exclude inertial
position if unaided 3-5 mins. • DP receive acoustics if INS fails. • INS must be GNSS independent.
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HAIN APOS/ HiPAP
Transceiver
DP Inertial position
Acoustic position
Inertial position
Acoustic position
Acoustic principles
17-Oct-13 WORLD CLASS – through people, technology and dedication / 5 /
Acoustic principals and inertial • SSBL
– High standard deviation – Almost never drift – Rapidly varying errors
• LBL – Often slow rate – Low standard deviation – Occasional drift/ – Slowly varying errors
• AINS – w/ SSBL or LBL – Less drift – Increased accuracy – Added integrity – Slowly varying errors
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2009-09/27_01:30 _02:00 :30 _03:00 :30 _04:00-10
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DP weighting
• DP weighting is a quadratic function of standard deviation. – 2 meters standard deviation gives only 1/4 weight.
• DP weighting is a linear function of update rate. – 2 seconds update period gives only 1/2 weight.
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2008-05/02_22:20:00 :30 :21:00 :30 :22:00 :30 :23:00
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Inertial Measurement Unit (IMU)
• Accelerometers are fairly cheap • Gyroscopes are more costly
• FOG – Fiber Optic Gyro
– Solid state may yield lower MTBF – OK Performance
• MEMS – Microelectromechanical systems – Cannot gyrocompass – yet – Cheaper
• RLG – Ring Laser Gyro – Hearable noise – Best performance
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(Pictures in courtesy of respective owners)
Installation
• Anywhere on vessel – RLG noise annoying – Stable temperature and humidity is good – Cannot factory align
• Mounting – Coarsely aligned with Vehicle axes – UPS – Connection to ships acoustics
• Lever arm accuracy of 0.2 meters sufficient – 150+ m – OK
• 2-4 hours IMU alignment • FMEA and performance testing
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Problems • IMUs are export restricted • INS errors
– Carries high DP weight – Drifts off and stays off
• HAIN Reference – Few problems and service – Little crew attention
• IMU – To spec or broken down
• Acoustics – Outliers and noise – Non-white errors
• Problems leads to improvement in both acoustics and INS
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2D trajectory in meters, pMBM
HPR400OutliersHAIN
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Conclusions
• Acoustic aided INS is well proven as DP Reference – 7+ years of HAIN – 50+ HAIN units
• INS will work on – any acoustics – any vessel (without tuning)
• INS is easy to use • Technical problems are few • It improves
– update rate – precision (accuracy) – integrity
• Increased DP weighting
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