New functionality and improved performance of an integrated INS/DGNSS sensor

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By Product Manager Finn Otto Sanne, Kongsberg Seatex AS

Oceanology International 2012 – London, March 13th

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CONTENT

• Seabed mapping requirements

• INS/DGNSS integration

• MEMS based gyro development

• Conclusion

Seatex MRU – In the Forefront of Technology

• Accurate roll compensation of the vessel motion is required to get minimum depth errors on the outer beams

• Accurate synchronization of the echosounder signal and the motion sensor data is crucial to minimize the depth error due to difference in timing

• Surveys in areas with high buildings and on rivers passing bridges are challenging when it comes to obtain stable GNSS data

Typical Seabed Mapping Requirements

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INS/DGNSS Sensor Scheme

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Total satellites in constellation 31 SC

Operational 24 SC

In commissioning phase 1 SC

In maintenance 2 SC Spares 3 SC In flight tests phase 1 SC

GLONASS – Satellite Status

26 24

21

20 18 18

14 12

11 10 8

7

11 12 13

16

22

24

16

12 12 12 14

12 10

9

0

3

6

9

12

15

18

21

24

27

30

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

GLONASS-M Flight Test (7 years life-time)

GLONASS-K Flight Test (10 years life-time)

GLONASS Initial Operation Capability

(12 NSV , 3 year life-time )

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Satellite geometry (EPE) – GPS+GLONASS

GPS

GPS

GPS +

GLONASS

GPS +

GLONASS

• Principle: Foucault’s pendulum

• Year: 1851

• Length: 67 m

• Mass: 28 kg

• Alternative implementation: a small, vibrating structure

• The pendulum is fixed relative to the resonator

• Rotation causes transfer of energy to the pick-off axis, 45º relative to the pendulum axis

• Pick-off amplitude is proportional to the rotation rate

• Typical MEMS implementations

• Resonator area: 5 – 50 mm2

• Excitations: < 5 µm

• Frequencies: 4 – 20 kHz (typical)

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(*) MEMS – Microelectromechanical System

MEMS Based Gyro Implementation

Eight transducers,

can apply or

measure force

F1

F2

ωr

Vibration

pattern Node

Top view

• Continuous development in performance improves price/performance

• Lifetime (MTBF> 120 000 hours)

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Pe

rfo

rman

ce

Time 30 mm

MEMS Gyro Advantages

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Desired: Low Position Drift

-Driven by Attitude Errors (βerr)

-Equivalent to Roll/Pitch Angle Noise

-Caused by Gyro Noise

βerr

g

aerr (equivalent

acceleration)

IMU Requirements for Low Position Drift

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-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

0 0.25 0.5 0.75 1 1.25 1.5 1.75An

gle

[d

eg]

Time [hrs]

Roll: 0.0015°RMS

Pitch: 0.0012°RMS

Typically: 0.001-0.002°RMS

Peak-to-peak: <0.006°

New IMU (MRU 5+) Angular Noise Achievements

Typical Gyro Performance Achievements

Typical Gyro Performance Achievements

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1

10

100

1000

10000

0.001 0.01 0.1 1 10 100 1000 10000

Sca

le F

acto

r E

rro

r [p

pm

]

Gyro Bias [deg/hr]

GYRO PERFORMANCE

The Gyro World Development

EM2040 data with Seapath 330+ in Japan Kaiyo Maru

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Pier support 2*2 m

• For hydrographic survey where the IMU is turned on 24 hours a day, every day, the use micromachined vibratory gyros has an advantage due to long lifetime

• The MRG MEMS gyro performance surpasses FOGs on many parameters and especially on noise

• 0.01º roll/pitch accuracy capabilities is achieved by combining the low noise MRG gyro with high performance accelerometers in new IMU

• The combined GPS/GLONASS solution added with the new IMU increases the position availability passing bridges and close to high buildings

• The MRG gyro integrated with GPS/GLONASS has demonstrated excellent results in seabed mapping surveys with high resolution multibeam echosounders

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Summary

WORLD CLASS – through people, technology and dedication www.kongsberg.com

Thank you for the attention!