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eBird – control of marine seismic streamersITK/NTNU 60 år - Kybernetisk fagdag 7.november 2014

Dr.ing. Ola Erik Fjellstad

Ola Erik Fjellstad, PhD

IPR Manager

Kongsberg Seatex AS

• PhD Engineering cybernetics, NTH 1994

– 6 DOF control of autonomus underwater vehicles

– Professor dr.ing. Thor Inge Fossen supervisor

– Professor dr.h.c. Jens Glad Balchen advisor

• Principal Engineer R&D, Kongsberg Seatex 1994 - 2013

– Seapath - Integrated GNSS/IMU navigation system for pos/vel estimation

– MRU - Inertial sensor system for motion measurement and RPH estimation

– eBird – Steering device system for positioning of towed streamer spread

• IPR Manager, Kongsberg Seatex 2014 – today

– Coordination of and participation in all IPR activities18.11.2014Page 2 WORLD CLASS - through people, technology and dedication.

Marine seismic survey

18.11.2014 WORLD CLASS - through people, technology and dedication Page 3

Streamers need steering

Conventional operation

è/ 4 /è18-Nov-14

Worlds biggest controlled structure

18.11.2014 WORLD CLASS - through people, technology and dedication Page 5

eBird - Streamer steering device

• Mounted inline, low vibration noise

• Typically 300m separation

• Power and communication through streamer

• Wing profile optimized for maximum lift and minimum acoustic noise

• Batteries in wings autonomous operation for several days

• 3 wings independently rotatable

• Decoupled roll, depth and lateral control

• Provides ~400 N at 4.5 kt through water

• 3 degrees feather angle

è/ 6 /è18-Nov-14

eBird body

• Length 370 mm Ø 74 mm titanium tube

• Inline mounting – stored on reel

• Sensors for roll angle and depth estimation

• CPU running bird local motion control loops

• Calculated wing deflection transferred to wings

• Wireless connections to wings

• 3 wing docking slots

è/ 7 /è18-Nov-14

eBird wing

• Attached/detached at deployment/retrieval

• Contains CPU, motor/gear and batteries

• Shaft coupling for motor/gear protection

• Wireless power/comms

• Batteries charged in sea in normal operation

• Provides power to body when loss of streamer power

• Stored in charging station onboard vessel

è/ 8 /è18-Nov-14

Wireless connection body-wing

• Wireless connection between body and wing

• No electrical parts exposed to water

• Easy snap on/off mechanism

• Identical iron cores surrounded by coils in body and wing

• Inductive energy transfer utilizing electro-magnetic resonance

• Radio communication: connector = antennae

• Two-way power and communication

•Back-deck operations: body and wing operated using hand-held radio-unit

è/ 9 /è18-Nov-14

Challenges

• Robust control - sea current, waves, objects in sea

• Low acoustic noise – wing profile

• Power distribution over 10 km – voltage drop

• Noise free power – constant load

• Noise free communication – modem

• Loss of power/comms – autonomous operation

• Multicomponent interactions

è10è11/18/2014

Hydrophone RMS noise

èConventional bird

èeBird

èNo bird

è/ 11 /è18-Nov-14

How many eBirds in one flock?

è/ 12 /è18-Nov-14

There have been issues..

è13è11/18/2014

Lift envelope

è11/18/2014 èContract MAR-2008-0080 è14

Clever choice of roll angle reference will enhance stability capacity

Control system

è/ 15 /è18-Nov-14

Robust control

è/ 16 /è18-Nov-14

Rapid depth change

0 20 40 60 80 100 120 140 160 180 2004

6

8

10

Depth [m] and lateral force [%] step response at 4.5 kt

Depth

[m

]

0 20 40 60 80 100 120 140 160 180 200

0

20

40

60

80

100

Forc

e [

%]

Time [sec]

è/ 17 /è18-Nov-14

Lateral control

è/ 18 /è18-Nov-14

Feather angle capability: >3º

0 minutes

40 minutes

100% lateral force portside300 m inline separation

è/ 19 /è18-Nov-14

eBird – The movie

è20è11/18/2014

AcuWing

• Acoustics integrated in eBird wing = AcuWing

• Bi-directional acoustic transducers in wing tip

• Acoustic source attached to stabilized platform

• Cross-line and in-line range measurements

è/ 21 /è18-Nov-14

Magnetic compass

• Heading estimation from 3-axis magnetometer

• Located in wing tip - redundancy

• Magnetic field compensation:

– wing angle

– wing slot position

– roll and pitch

• Calibration in 3-axis Helmholz coil

• Algorithms for bird magnetic signature estimation

/ 22 /18-Nov-14

PosWing

• GNSS receiver and antenna in wing

• GNSS-wing pointing up in surface

mode

• Ephemerides and clock aiding for fast

aquisition (5-10 seconds)

• In combination with– AcuWing sound speed calibration

– Compass streamer shape

– Inertial sensors integrated filter

– Radio aiding data or differential corrections

• No need for tail buoy, fully submerged

streamer spread

• Easy to find from work-boat

/ 23 /18-Nov-14

è/ 24 /è18-Nov-14

Thank you for your attention!