PHINS for DP presentation from the iXBlue spring seminars 2013

1. PHINS for DP Applications
Jim Titcomb
North Sea Spring Seminars 2013

2. 2
PHINS & ROVINS – Inertial Products
 What is an Inertial Navigation System (INS)?
An instrument (electronic + sensors) which is using its initial state (position)
and internal motion sensors (gyroscopes + accelerometers) to measure and
calculate its subsequent positions in space with high accuracy, stability and
update rate

3. 3
INS Introduction
 What makes an INS good.. or not?
 Internal sensors (gyroscopes & accelerometers) are never perfect, bias and
scale factors accumulate over time
 Navigation is mostly about Gyroscopes
 Gross figures:
 Accelerometers errors are not heavily involved in the position drift – 4m –
Schuller period
 Gyroscope are heavily involved in the drift – 400 m
 Conclusions
 A good INS requires good gyro’s
 IXBLUE manufactures FOG (Fiber Optic Gyroscope) and controls the whole
process
 A range of FOG’s (FOG90, FOG120, FOG180…) for a range of INS

4. 4
What's in an INS?
 3 “FOG” gyrometers
monitor rotation and speed in X, Y & Z axis
 3 accelerometers
measure acceleration (>> speed >> motion) in 3 axis
 Powerful electronic / firmware package
PHINS “knows” in real time its motion in space .
Firmware (Kalman filter) calculates its position in real
time + heading, pitch, roll, heave, etc…
All integrated
small, lean, powerful!
(PHINS 6000 example)

5. 5
The problem with INS
 The best sensors are still not perfect, accumulating small errors vs. time
makes the system drift on the long term
 External sensors (aiding) are required to bound drift within acceptable limits.
PHINS & ROVINS includes interfaces for most common external sensors
 GPS
 DVL (Doppler Velocity Log)
 Pressure sensor
 Acoustic positioning references (USBL, LBL)
 …and all IXBLUE products!
 IXBLUE INS are fully integrated Inertial Positioning solutions designed for
ease of installation & operation, flexible enough to fit most requirements, with
no specialist engineer to install / operate.

6. 6
iXBlue underwater positioning solutions
the benefits of data fusion
 Data Fusion
 Use various and different technologies to measure the same parameter
 Blend (fuse all this data (Kalman filter) in order to correlate it and obtain a better
result
 A simple example GPS + INS (PHINS, GAPS)
0
0,5
1
1,5
2
2,5
3
0 20 40 60 80 100
time t (s)
positionaccuracy(m)
PHINS pure inertial drift (0.0002 x t^2
m)
Averaging of DGPS data (3 / sqrt(t)
m)
PHINS+DGPS

7. 7PHINS & ROVINS: Inertial Navigation System
Robust to Acoustic navigation solution
 Acoustic positioning can be poor, low update rate, or out of range.
INS + USBL combination / data fusion provides continued high quality
positioning:
Actual USBL data (Hipap) @ 2400 meters water depth
0
0,5
1
1,5
2
2,5
3
3,5
4

8. 8PHINS & ROVINS: Inertial Navigation System
Robust to Acoustic navigation solution
Acoustic positioning can be poor, low update rate, or out of range.
PHINS + USBL combination / data fusion provides continued high
quality positioning:
Using PHINS + USBL in extreme shallow water. RESON / ADUS 2007
Données de positionnement PHINS et GAPS
0
5
10
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5 10 15 20 25 30 35
X (m)
Y(m)
Phins
Gaps
Données de positionnement PHINS et GAPS
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0 5 10 15 20 25 30
X (m)
Y(m)
Phins
Gaps
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5 10 15 20 25
X (m)
Y(m)
Données de positionnement PHINS et GAPS
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5 10 15 20 25 30 35
X (m)
Y(m) Phins
Gaps
Données de positionnement PHINS et GAPS
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X (m)
Y(m) Phins
Gaps
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5 10 15 20 25
X (m)
Y(m)

9. 9

10. 10

11. 11
DP-PHINS What is it?
Time Signals
Time and Position
For Initialisation Only
Time stamped beacon
positions and heading
Processed
Positions
Enhanced Position
Acoustic
Positions

12. 12
DP- PHINS, Features
 Relative to Global co-ordinate transforms.
 Unlimited number of beacons
 Flexible
 Expandable
 Future Sensors
 Taught Wire
 Fan Beam
 Radascan
 Etc. Etc.

13. 13
DP-PHINS, Why?
 INS improves USBL
 USBL improve INS
 We still have a single point of failure
 INS will drift quickly if the acoustics fail.
 3m in 2 min,
 20m in 5 min.
 0.6Nmi in an hour.
 INS can make USBL almost as good as GPS (depending on depth).
 Adding INS with USBL alone does not increase redundancy.
 What else is available?

14. 14
What about LBL?
 At Least three ranges are
required for LBL positioning.

15. 15
Pure LBL
 With only two ranges
positioning is not possible
 There are two possible
locations which match the
received ranges.

16. 16
INS aided by LBL
 Station keeping with only
two ranges is possible with
INS and LBL combined.
 The system must be
initialised to the correct
position first.
 The two ranges will
constrain the INS drift.
 Positioning accuracy is
directly related to the range
measurement accuracy.

17. 17
INS LBL Accuracy and Geometry
 Accuracy of results is
dependant on a
combination of geometry
and range measurement
accuracy
 If the beacons are “in
line” with the vessel
results will be poor.
 But accuracy will be
good if there is a high
“Angle of cut”

18. 18
INS Velocity Aiding
 INS measures rotation rate and acceleration.
 First integration produces heading and velocity
 Second integration produces position
 USBL aids INS at the second integration level
 DVL aids INS at the First integration level.
 INS aiding data is used to estimate errors. The errors are fed back in to the
calculation in order to correct at a low level.
 Aiding at the first integration level has more effect than aiding at the second
integration level.

19. 19
Effect of Velocity Aiding
 INS free inertial specification is based on time. The more time, the greater
the drift.
 DVL aided INS specification is based on distance travelled. If you don’t move
the error can’t grow (as much).

20. 20
The problem with DVL
 Deep water.
 DVL is only available in water depths up to around 1,000m.
 In deeper water DVL update rate will be slow.
 Remember DVL aids INS at a more fundamental level than other sensors.
 The INS only needs a velocity aiding input infrequently in order to correctly estimate
the error on the sensors.
DVL Update
Rate
Error,
% distance
travelled.
Drift speed
m/h
1S 0.03% 0.18
2S 0.13% 0.82
3S 0.26% 1.67
4S 0.27% 1.77
6S 0.32% 2.08
8s 0.30% 1.98

21. 21
Acoustic Aiding Examples - Recap
 ROV on Seabed.
 850m water depth
 Well calibrated USBL
 About as good as it gets with
USBL
Standard
Deviation
X Y Position
USBL 1.03 0.86 1.34

22. 22
INS Aided with USBL - Recap
 Spikes in USBL rejected
Automatically.
 Much higher update rate.
 Smoother positioning.
 Reduced spread of positions.
 5 X improvement with INS
Standard
Deviation
X Y
USBL 1.03 0.86 1.34
INS 0.16 0.2 0.26

23. 23
INS Aided with USBL & DVL
 DVL update only every 3
seconds
 Positioning now better than
high accuracy GPS even in
850m
 17 x Better than raw
acoustics.
Standard
Deviation
X Y
USBL 1.03 0.86 1.34
INS 0.16 0.2 0.26
With DVL 0.05 0.06 0.07

24. 24
What if we lose acoustics?
 DVL update only every 3
seconds
 Positioning now better than
high accuracy GPS even in
850m
Standard
Deviation
X Y
USBL 1.03 0.86 1.34
INS 0.16 0.2 0.26
With DVL 0.05 0.06 0.07
INS DVL 0.04 0.02 0.05

25. 25
Conclusions
 INS is a proven technology on Land, Under water, in Space, why not in DP?
 INS has a long track record, Modern FOG based systems bring extreme
robustness and reliability.
 INS can produce heading and attitude data as well as positioning.
 INS Should not be aided just by GPS for DP applications.
 INS can make your acoustics as good as high accuracy GPS.
 The biggest benefits can be obtained by combining aiding sensors.
 With the addition of DVL, INS can now be considered a stand alone PME for
a significant period of time.

26. 26
Nautronix Cooperation
NASDrill RS925 SBL / LBL Overview
 Premier DP acoustic positioning reference for
deepwater operations
 Uses Nautronix ADS2 signalling for robust and
reliable operation in extreme acoustic noise
 High level of system redundancy (hardware and
acoustics)
 Independent SBL only, LBL only or combined
SBL/LBL operation
 Compatible with all major DP systems
 Now with PHINS Inertial Navigation

27. 27
Nautronix Cooperation
NASDrill RS925 SBL / LBL Overview
 Proven performance since 1998 with operation in
water depths down to 5,830m.
 Fast position update (SBL <2 seconds)
 High Accuracy:-
 SBL only = 0.15% slant range
 LBL only = 1m irrespective of water depth
 SBL/LBL combined = 2.5m @ 3,500msw
 Allows for integration with:
 NASNet® DPR
 NASeBOP

28. 28
Nautronix Cooperation
NASDrill RS925 – Stability
• Standard deviation on the
calibration was 1.7m RMS
• Spread of position data very small,
approx 5m
• Highlights suitability of RS925 as
reliable position reference input for
DP systems which demand
regular, stable & accurate position
data.
• Meets Rig Positioning
requirements in deep water on
acoustics alone
The following results were taken during calibration of the NASDrill RS925
system on board the Deepwater Discovery in 2,870m water.
5m radius

29. 29
Nautronix Cooperation
NASDrill RS925 Position Accuracy - INS
 Interface between NASDrill RS925 and PHINS created
 Single PHINS (no redundancy):
Non-redundant
RS925/PHINS
configuration.
Provided in addition
to standard RS925
output(s) to DP

30. 30
Nautronix Cooperation
NASDrill RS925 Position Accuracy - INS
 Interface between NASDrill RS925 and PHINS created
 Dual PHINS (full redundancy):
Dual redundant
RS925/PHINS
configuration.
Provided in addition to
standard RS925
output(s) to DP

31. 31
Nautronix Cooperation
NASDrill RS925 PHINS Testing
 Initial integration tests completed
 RS925 SBL simulated data fed into PHINS
 Simulated SBL data configured to have a noise level of 4.5 m RMS.
Equivalent to a SBL system operating in 3000m depth of water, with a noise
level of 0.15% slant range
 SBL position output compared to SBL aided PHINS output...

32. 32
Nautronix Cooperation
NASDrill RS925 SBL 3000m Easting (m)
547044
547046
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385
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457
469
481
493
Easting(m)
Time
RS925 SBL
Phins Output

33. 33
Nautronix Cooperation
NASDrill RS925 SBL 3000m Northing (m)
6341538
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1
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397
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457
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481
493
Northing(m)
Time
RS925 SBL
Phins Output

34. 34
Nautronix Cooperation
NASDrill RS925/PHINS Test Results
 SBL raw position data with a noise level of 4.5m RMS (3000m depth
equivalent)
 PHINS output data with a noise level of 1.6m RMS
 Approximately three fold increase in precision (as is typical of various
acoustically aided INS systems)
 Above are static tests with simulated data. Dynamic results are expected to
be very similar, with a slight increase in accuracy expected

35. 35
Nautronix Cooperation
Summary
 NASNet ® DPR & PHINS:
PHINS used to enable sparse array positioning capability from a standard
NASNet ® deployed field
Increase in accuracy of less importance, due to existing capability of
NASNet ® BLBL
• NASDrill RS925 & PHINS:
PHINS used to significantly increase the precision of SBL. Providing a
higher accuracy, higher update rate, input to DP
Sparse array capability of less importance, due to the deployment of
beacons dedicated for the drill rig/vessel – risk of no acoustic return
extremely low