1. TMR4225 Marine Operations, 2004.02.21 UUV/AUV definitions
Critical design parameters for a seabed mapping system
Critical parameters for vehicles used for intervention tasks on subsea structures
Linear motion equations

2. 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

3. AUV/UUV operational goals
Military missions
Reconnecaince
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

4. Offshore oil and gas UUV scenario
Ormen Lange sea bed mapping for best piperoute trace
Norsk Hydro selected to use the Hugin vehicle
Waterdepth up to 800 meters
Rough sea floor, peaks are 30 – 40 meter high
Height control of Hugin to ensure quality of acoustic data

5. C & C Technologies – Track record
Operational areas
Gulf of Mexico
West coast Africa
Brazil
Mediterranean
More than survey line kilometers
Waterdepths down to 2850 m
Cost 33-50% of traditional deep-tow system

6. 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

7. Group work no. 1
Describe physical factors to be considered when analysing different phases of an AUV/UUV mission
Select on of the following missions:
Mapping seabed for selection of optimal pipeline track
Inspection of a subsea gas export pipe
Seabed mapping for deep sea mining
Select the three phases you rank as most critical for a successful mission

8. Group work no. 1 – Student feedback (2004)
Launching
Launching arrangement; A-Frame, crane etc
Readiness for operation, eg. various equipment on board
All openings on the hull surface must be closed (watertightness)

9. Group work no. 1 – Student feedback (2004)
Penetration of splash zone
Impact loads
Hydro-elasticity
Relative motion; phase, amplitude, frequency
Change of parametres from air to water (buoyancy, eigenfrequency, etc.)
Wire tensions

10. Group work no. 1 – Student feedback (2004)
Transit to work space
Navigation/control system (current/flow/(diving)), DP
Buoyancy during transit ( different layers of salinity in the sea)
Resistance/propulsion/endurance/power supply
Material/hullform ( the vehicle has to withstand high external pressure)

11. Group work no. 1 – Student feedback (2004)
Completing work task
Battery capacity
Check if mission is completed
Check the current conditions
Safe manoeuvring to avoid collisions, damage of propellers
Interaction between thrusters

12. Group work no. 1 – Student feedback (2004)
Transit to surface/Moving to next work place
Changing buoyancy (pressure/gravity)
Resistance forces (transit between workfields)
Current forces
Wave influence near surface

13. Group work no. 1 – Student feedback (2004)
Penetration of surface
Movements induced by:
Waves
Current (viscous forces)
Buoyancy/gravity
Reaching the surface -> change of:
Wetted surface (viscous)
Buoyancy (volume)
According to the sea state, we can have very unstable system

14. Group work no. 1 – Student feedback (2004)
Hook-up, lifting, securing on deck
Sea state; ship motion, AUV motion
Effect of wind in the crane
Centre of gravity of AUV
Lifting
Splash zone, wind, safety distance
Securing on deck
Safe bed, fastening devices, operation in heavy seas

15. Motion equation for AUV
Read Chapter 2 in project work of Jon E. Refnes
For small perturbation of a constant speed motion, motions can be described by two sets of linear equations
Heave and pitch
Sway, roll and yaw
Studying streamlined AUVs the horisontal plane motion can be reduced to coupled sway and yaw
See equations
Horisontal motion
3.3 – Vertical motion

16. Dynamic stability
For horisontal plane motion, see section 2.4 in course note
Final criteria is G1 > 0 (or C >0 in blackboard notes)
No speed dependence on stability criteria
Vertical motion, see section in course note
Note that the characteristic equation is of third order
More complex stability criteria
Stability criteria is speed dependent
Characteristic equation has to be solved for all possible operational speeds of the vehicle

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