a numerical dp module for design and ... - dynamic...

1 1PRINCIPIA © 2005 DP Conference 2005 -Numerical DP module

A numerical DP moduleFor design and operations

A. Ledoux, B Lecuyer, C. Le CunffPrincipia R.D.


Summary

Numerical Tool: DiodoreModeling of floating structureModeling of environmentShip simulator

DP moduleDP control systemAllocation/compensationType of analyses

Application: offloading


DIODORE Applications

Stability

DP module

Strength, loads & FEM coupling

Sea-keeping

Mooring & UFL design

Marine operations


Software Architecture

PREHydrostatics & mass breakdown

HYDROHydrodynamics loads & pressures

MECAFrequency/Time domain motion simulation

POSTPost-processing, animations, statistics,plots


Hydrodynamics

Diffraction-RadiationSource modelInfinite or finite depthWithout or with forward speed Drift forces Control point in the fluid (pressure &

velocities)Moonpool & side by side methodologies


Hydrodynamic model

Hydrodynamic loads based on diffraction-radiation

sink source method


Sea keeping

Motions, accelerations at any pointsSplash zone, green water, slamming occurrenceDamping formulationsMulti-structuresLong crested & short crested sea statesAdvanced features:

Sloshing/sea-keeping couplingStabilization devices (anti-roll tanks, foils…)Multi-peaks multi-directional sea statesAutomatic pilots


Mooring design

Mooring design (extreme & fatigue)

Static, quasi-static simulations

Squall windsAPI 2SK rules

applicationsCompliant to BV rule


Ship motion

6-dof response assessed from the efforts on the ship, including :

environmental loads

mooring

control units

maneuverability

(Speed not at scale)


The DP Module

DP CONTROL SYSTEM

PID

FDP DP Ship External loads

Freg

+

−

x,y,ψ +Set point

Computed position (LF)

Feedbackloop

FwindWind FFWD

+

Ideal wind feed forwardPID correctorAnti-reset windup to prevent saturation


PID regulator

DP PILOT : PID REGULATOR

Proportional = Stiffness

Integral = Mean offset correction

Derivative = Damping

PPIPIDShip response

time


The DP ModuleTHRUSTER ALLOCATION

dynamicFDP = Freg static FDP = −Fext

DP Pilot

FDP

ALLOCATION


Linking Thrusters

Should be of the same typeWill be commanded the same thrust and azimuth


Linking Thrusters

ALLOCATION

Will be commanded the same thrust and azimuthAllocated as single equivalent thrusters


The DP ModuleFIRST STEP : LINEAR ALLOCATION

Corrective effort Thruster

commands

F = BB ×× U

BB : Allocation matrix based on DP system geometry

Solved with energy cost-function optimization :

U = BB† F with BB† = BBT.(BB.BBT) −1


The DP ModuleTHRUSTER ALLOCATION


The DP ModuleSECOND STEP : COMPENSATION

Azimuth compensation

Device fixed to maximum azimuth

Re-allocation


The DP ModuleSECOND STEP : COMPENSATION

Thrust compensation

Device fixed to maximum thrust

Re-allocation


The DP ModuleSTATION KEEPING CAPABILITY ANALYSIS

Mechanical processor in frequency domain

Define thrusters + DP system (only static parameters)

Define environment (API)

Draw capability plots

TIME SIMULATION

Mechanical processor in time domain

Define thrusters + DP system & pilot

Run LF simulation together with any other mechanical model (mooring, etc)


The DP ModuleCONTROL UNITS

Tunnel thruster

Directional thruster (reversible or not)

Screw propeller & rudder

Azimuth thruster


The DP ModuleCAPABILITY PLOT : IMCA-STANDARD

Overall DP system performance :

Maximum wind speed before system saturation

vs

Incidence of mean environmental forces

Same direction for wind, wave and current

Wave and current related to wind speed

Max wind speed(knots)

0

30

60

90

120

150

180

210

240

270

300

330


The DP ModuleCAPABILITY PLOT : API-STANDARD

DP system solicitation in given environment :

Thruster solicitation

vs

Ship heading

Optimize ship availability for operations

Thrust (kN)

015

30

45

60

75

90

105

120

135

150165

180195

210

225

240

255

270

285

300

315

330345

Bow truster Stbd AzimuthalPort Azimuthal Aft Azimuthal


The DP ModuleTIME DOMAIN SIMULATIONS

Simulate ship response to environment including special events (scenario) or environmental changes (squall winds)


The DP ModuleTIME DOMAIN SIMULATIONS

DP pilot parameters :

- Gains, thrust saturation, azimuth saturation

- Set point, actualization time lap


ApplicationsTANDEM OFF-LOADING

110 000 DWT DP-tanker

L320m x B55m x T8.2m

2 x 75kN tunnel thrusters + 2 x 100kN azimuth thrusters

OCIMF coefficients for wind & current polars

Environment :

wind : 9.6knots from 75°N

wave : Hs=2.3m, Tp=12s from 300°N

current : 0.65m/s to 330°.


ApplicationsTANDEM OFF-LOADING

Capability analysis : normal / failure mode

0

20

40

60

80

100

Thrust Allocation (kN)

0

30

60

90

120

150

180

210

240

270

300

330

Bow tunnelStern tunnelPort azimuthingStbd azimuthing

0

20

40

60

80


0

30

60

90

120

150

180

210

240

270

300

330


Normal Bow thruster failureFull Safe operating range

DP unable to maintain ship position

Reduced Safeoperating range


ApplicationsTANKER RESPONSE TO SQUALL WIND

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

0 1000 2000 3000 4000 5000 6000

Win

d sp

eed

(m/s

)

0

45

90

135

180

225

270

315

360

Win

d di

rect

ion

(CW

N)Wind speed

Wind direction

Surge and Sway motions (m)

-60

-40

-20

0

20

0 2000 4000 6000 8000 10000 12000 14000

SurgeSway

Tanker Trajectory

-10

-8

-6

-4

-2

0

2

-6 -4 -2 0 2 4 6

0

20

40

60

80

100


0

30

60

90

120

150

180

210

240

270

300

330



Concluding remarks

DP Module Validation : Field Development Ship (SAIBOS)

Development : frequency domain

a numerical dp module for design and ... - dynamic...

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