1. TMR4225 Marine Operations, 2009.01.27 Lecture content:
Linear submarine/AUV motion equations
Dynamic stability (stick-fixed stability)
Neutral point
Critical point
AUV hydrodynamics
Hugin operational experience

2. Linear motion equations
Linear equations can only be used when
The vehicle is dynamically stable for motions in horisontal and vertical planes
The motion is described as small perturbations around a stable motion, either horisontally or vertically
Small deflections of control planes (rudders)
For axi-symmetric bodies the 6DOF equations can be split in two sets of equations
2 DOF for coupled heave and pitch
3 DOF for sway, yaw and roll

3. Dynamic stability
Characteristic equation for linear coupled heave - pitch motion:
( A*D**3 + B*D**2 + C*D + E) θ = 0
Dynamic stability criteria is:
A > 0, B > 0 , BC – AE > 0 and E>0
Found by using Routh’s method

4. Roots of stability for a submarine

5. Speed variation of damping ratio for a submarine

6. Transient response for vertical motion – variation of the damping ratio

7. Neutral point position (from Hoerner ”Fluid Dynamic Lift”)

8. Critical point – variation with forward speed

9. Dynamic stability (cont)
For horizontal motion the equation (2.15) can be used if roll motion is neglected
The result is a set of two linear differential equations with constant coefficients
Transform these equations to a second order equation for yaw speed
Check if the roots of the characteristic equation have negative real parts
If so, the vehicle is dynamically stable for horizontal motion

10. Traditional approach Manoeuvring problem Seakeeping problem Calm water
Large vessel motions in the horizontal plane only
Problem formulated in a body-fixed coordinate system
Seakeeping problem
Incident waves
Focus on vertical motions (heave and pitch)
Body motions assumed small about mean position of vessel
Problem formulated in a coordinate system fixed with respect to the mean position of vessel

11. New formulation including manoeuvring in waves
Inconsistent behaviour if hydrodynamic model is based on traditional approach
The asymptotic solution of the sea keeping formulation when ω -> 0 will NOT give the traditional manoeuvring equations
Seakeeping model will also give time-independent forces
Use of rudder and propulsive forces will introduce dynamic forces in the sea keeping model
New formulation including manoeuvring in waves
The traditional maneuvering equations must be obtained by setting the frequency to zero

12. The different reference frames
The north-east-down reference frame (NED frame)
Main coordinate system of ship simulator
Wave/wind/current environment
The hydrodynamic reference frame (HYDRO frame)
Fixed with respect to mean position of ship
Seakeeping formulation
The body-fixed reference frame (BODY frame)
Manoeuvring formulation

13. Unified formulation – Development steps
Establish transformations between the BODY and NED frames
Establish transformations between the BODY and HYDRO frames
Formulate unified formulation in the BODY frame in the frequency-domain (ie transform the sea keeping formulation from the HYDRO frame to the BODY frame).
Formulate the unified formulation in the time-domain
Calculate 2D hydrodynamic coefficients and exciting forces
Calculate frequency dependent added mass and damping coefficients in unified formulation
Calculate retardation functions

16. AUV overview AUV definition: UUV definition:
A total autonomous vehicle which carries its own power and does not receive control signals from an operator during a mission
UUV definition:
A untethered power autonomous underwater vehicle which receives control signals from an operator
HUGIN is an example of an UUV with an hydroacoustic link

17. AUV/UUV operational goals
Military missions
Reconnaissance
Mine hunting
Mine destruction
Offshore oil and gas related missions
Sea bed inspection
Pipe line inspection
Sea space and sea bed exploration and mapping
Mineral deposits on sea floor
Observation and sampling

18. Generic axis system for AUV

19. Vector definitions

20. 6 DOF matrix equation for AUV motion

21. Mass matrix

22. HUGIN history AUV demo (1992-3) HUGIN I & II (1995-6)
Diameter: m Length: 3.62/4.29 m
Displacement: m**3
HUGIN I & II (1995-6)
Diameter: m Length: 4.8 m
Displacement: m**3
HUGIN 3000C&C and 3000CG ( )
Diameter: m Length: 5.3 m
Displacement: m**3

24. HUGIN family

27. Initial HUGIN design

29. Hugin UUV

30. Forebody pressure drag (Hoerner)

31. Resistance coefficient – aft body

32. Drag coeffient variation with slenderness ratio

33. Radius effect on drag for 2D bodies (Hoerner)

34. Drag measurement – Hugin prototype

35. Panels for added mass calculation

36. Added mass matrix for HUGIN prototype

37. Stinger for AUV testing in cavitation tunnel

38. Heave force variation with pitch angle

39. Offshore oil and gas UUV scenario
Ormen Lange sea bed mapping for best pipeline track
Norsk Hydro selected to use the Hugin vehicle
Hugin is a Norwegian designed and manufactured vehicle
Waterdepth up to 800 meters
Rough sea floor, peaks are 30 – 40 meter high
Height control system developed for Hugin to ensure quality of acoustic data

40. Phases of an AUV/UUV mission
Pre launch
Launching
Penetration of wave surface (splash zone)
Transit to work space
Entering work space, homing in on work task
Completing work task
Leaving work space
Transit to surface/Moving to next work space
Penetration of surface
Hook-up, lifting, securing on deck

41. AUV – Theoretical models
Potential theory
Deeply submerged, strip theory
VERES can be used to calculate
Heave and sway added mass
Pitch and yaw added moment of inertia
VERES can not be used to calculate
Surge added mass
Roll added moment of inertia

42. AUV- Theoretical models
Viscous models
Solving the Navier Stokes equations
Small Reynolds numbers (< 1000) : DNS
Medium Reynolds numbers (< 10**5) : LES – Large Eddy Simulation
High Reynolds numbers (> 10**5) : RANS – Reynolds Average
Navier Stokes

43. AUV – Theoretical models
3D potential theory for zero speed - WAMIT
All added mass coefficients
All added moment of inertia coefficients
Linear damping coefficient due to wave generation
Important for motion close to the free surface
More WAMIT information

44. NTNU/Marine Technology available tools:
2 commercial codes
Fluent
CFX
In-house research tools of LES and RANS type
More info: Contact Prof. Bjørnar Pettersen

45. AUV – Experimental techniques
Submerged resistance and propulsion tests
Towing tank
Cavitations tunnel
Submerged Planar Motion Mechanism tests
Oblique towing test
Lift and drag test, body and control planes

46. AUV – Experimental techniques
Free sailing tests
Towing tank
Ocean basin
Lakes
Coastal waters
Free oscillation tests/ascending test
Water pool/ Diver training pool

47. NTNU/MARINTEK HUGIN involvement
AUV demo (1992-3)
Model test in cavitation tunnel, open and closed model, 2 tail sections (w/wo control planes)
Resistance, U = {3,10} m/s
Linear damping coefficients for sway, yaw, heave and pitch, yaw/trim angles {-10, 10} degrees
3D potential flow calculation
Added mass added moment of intertia
Changes in damping and control forces due to modification of rudders
Student project thesis

48. NTNU/MARINTEK HUGIN involvement
Resistance tests, w/wo sensors
Model scale 1:4
Max model speed 11.5 m/s
Equivalent full scale speed?
Findings
Smooth model had a slightly reduced drag coefficient for increasing Reynolds number
Model with sensors had a slightly increased drag coefficient for increasing Reynolds numbers
Sensor model had some 30% increased resistance

50. HUGIN 1000 layout

51. Hugin navigation system

52. HUGIN navigation system - items

53. HUGIN communication system

54. HUGIN sub system overview

55. HUGIN information New vessels have been ordered late 2004 and 2005
One delivery will be qualified for working to 4500 m waterdepth
New instrumentation is being developed for use as a tool for measuring biomass in the water column
Minecounter version HUGIN 1000 has been tested by Royal Norwegian Navy
More Hugin information: see Kongsberg homepage for link

56. HUGIN field experience
Offshore qualification sea trials (1997)
Åsgard Gas Transport Pipeline route survey (1997)
Pipeline pre-engineering survey (subsea condensate pipeline between shore based process plants at Sture and Mongstad) (1998)
Environmental monitoring – coral reef survey (1998)
Fishery research – reducing noise level from survey tools (1999)

57. HUGIN field experience
Mine countermeasures research (1998-9)
Ormen Lange pipeline route survey (2000)
Gulf of Mexico, deepwater pipeline route survey (2001 ->)
Raven, West Nile Delta, Egypt, area of 1000 km**2 was surveyed late 2005 by Fugro Survey
Sites for subsea facilities
Route selection for flowlines, pipelines & umbilicals
Detect and delineate all geo-hazards that may have an impact on facilities installation or well drilling
Survey area water depth: 16 – 1089 m (AUV used for H > 75 m)
Line spacing of 150 m and orthogonal tie-lines at 1000 m intervals
Line kilometers surveyed by AUV: 6750 km
Distance to seabed (Flying height): m
Operational speed: 3.6 knots

61. Fugro survey pictures

67. Actual HUGIN problems Inspection and intervention tasks
Adding thrusters to increase low speed manoeuvrability for sinspection and intervention tasks
Types, positions, control algorithms
Stabilizing the vehicle orientation by use of spinning wheels (gyros)
Reduce the need for thrusters and power consumption for these types of tasks
Docking on a subsea installation
Guideposts
Active docking devices on subsea structure (robotic arm as on space shuttle for capture of satelittes)

68. Actual HUGIN problems Roll stabilization of HUGIN 1000
Low metacentric height
4 independent rudders
PI type regulator with low gain, decoupled from other regulators (heave – pitch – depth, sway – yaw, surge)
Task: Keep roll angle small ( -> 0) by active control of the four independent rudders
Reduce the need for thrusters and power consumption for these types of tasks
Docking on a subsea installation
Guideposts
Active docking devices on subsea structure (robotic arm as on space shuttle for capture of satelittes)

69. Future system design requirements
Launching/ pick-up operations up to Hs = 5 m when ship is advancing at 3-4 knots in head seas
Increasing water depth capability
Increased power capability
Operational speed knots
Mission length 3- 4 days

70. Hugin deployment video
Video can be downloaded from Kongsberg homepage