A numerical DP module For design and operations A. Ledoux, B Lecuyer, C. Le Cunff Principia R.D. PRINCIPIA 1 2005 1
Summary Numerical Tool: Diodore Modeling of floating structure Modeling of environment Ship simulator DP module DP control system Allocation/compensation Type of analyses Application: offloading PRINCIPIA 2 2005 2
DIODORE Applications Strength, loads & FEM coupling Sea-keeping Stability DP module Mooring & UFL design Marine operations PRINCIPIA 3 2005 3
Software Architecture PRE Hydrostatics & mass breakdown HYDRO Hydrodynamics loads & pressures MECA Frequency/Time domain motion simulation POST Post-processing, animations, statistics,plots PRINCIPIA 4 2005 4
Hydrodynamics Diffraction-Radiation Source model Infinite or finite depth Without or with forward speed Drift forces Control point in the fluid (pressure & velocities) Moonpool & side by side methodologies PRINCIPIA 5 2005 5
Hydrodynamic model Hydrodynamic loads based on diffraction-radiation sink source method PRINCIPIA 6 2005 6
Sea keeping Motions, accelerations at any points Splash zone, green water, slamming occurrence Damping formulations Multi-structures Long crested & short crested sea states Advanced features: Sloshing/sea-keeping coupling Stabilization devices (anti-roll tanks, foils ) Multi-peaks multi-directional sea states Automatic pilots PRINCIPIA 7 2005 7
Mooring design Mooring design (extreme & fatigue) Static, quasi-static simulations Squall winds API 2SK rules applications Compliant to BV rule PRINCIPIA 8 2005 8
Ship motion 6-dof response assessed from the efforts on the ship, including : environmental loads mooring control units maneuverability (Speed not at scale) PRINCIPIA 9 2005 9
The DP Module DP CONTROL SYSTEM Wind FFWD F wind + + F DP DP Ship External loads F reg PID Feedback loop x,y,ψ Computed position (LF) + Set point Ideal wind feed forward PID corrector Anti-reset windup to prevent saturation PRINCIPIA 10 2005 10
PID regulator DP PILOT : PID REGULATOR Proportional = Stiffness Integral = Mean offset correction Derivative = Damping Ship response PID time PRINCIPIA 11 2005 11
The DP Module THRUSTER ALLOCATION DP Pilot ALLOCATION F DP = Freg dynamic F DP static F DP = Fext PRINCIPIA 12 2005 12
Linking Thrusters Should be of the same type Will be commanded the same thrust and azimuth PRINCIPIA 13 2005 13
Linking Thrusters ALLOCATION Will be commanded the same thrust and azimuth Allocated as single equivalent thrusters PRINCIPIA 14 2005 14
The DP Module FIRST STEP : LINEAR ALLOCATION B : Allocation matrix based on DP system geometry Corrective effort Thruster commands F = B U Solved with energy cost-function optimization : U = B F with B = B T.(B.B T ) 1 PRINCIPIA 15 2005 15
The DP Module THRUSTER ALLOCATION PRINCIPIA 16 2005 16
The DP Module SECOND STEP : COMPENSATION Azimuth compensation Device fixed to maximum azimuth Re-allocation PRINCIPIA 17 2005 17
The DP Module SECOND STEP : COMPENSATION Thrust compensation Device fixed to maximum thrust Re-allocation PRINCIPIA 18 2005 18
The DP Module STATION 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) PRINCIPIA 19 2005 19
The DP Module CONTROL UNITS Tunnel thruster Directional thruster (reversible or not) Screw propeller & rudder Azimuth thruster PRINCIPIA 20 2005 20
The DP Module CAPABILITY PLOT : IMCA-STANDARD Overall DP system performance : Maximum wind speed before system saturation 330 Max wind speed (knots) 0 30 vs Incidence of mean environmental forces 270 300 60 90 Same direction for wind, wave and current 240 210 150 120 Wave and current related to wind speed 180 PRINCIPIA 21 2005 21
The DP Module CAPABILITY PLOT : API-STANDARD DP system solicitation in given environment : Thruster solicitation vs Ship heading 300 315 330 345 Thrust (kn) 0 15 30 45 60 285 75 Optimize ship availability for operations 270 255 240 120 90 105 225 210 195 Bow truster Port Azimuthal 180 135 150 165 Stbd Azimuthal Aft Azimuthal PRINCIPIA 22 2005 22
The DP Module TIME DOMAIN SIMULATIONS Simulate ship response to environment including special events (scenario) or environmental changes (squall winds) PRINCIPIA 23 2005 23
The DP Module TIME DOMAIN SIMULATIONS DP pilot parameters : - Gains, thrust saturation, azimuth saturation - Set point, actualization time lap PRINCIPIA 24 2005 24
Applications TANDEM 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. PRINCIPIA 25 2005 25
Applications TANDEM OFF-LOADING Capability analysis : normal / failure mode Full Safe operating range 300 Normal 0 100 330 30 80 60 40 20 Thrust Allocation (kn) 60 Bow tunnel Stern tunnel Port azimuthing Stbd azimuthing Reduced Safe operating range 300 330 Bow thruster failure 0 80 60 40 20 30 Thrust Allocation (kn) 60 Bow tunnel Stern tunnel Port azimuthing Stbd azimuthing 270 0 90 270 0 90 240 120 240 120 210 180 150 DP unable to maintain ship position 210 180 150 PRINCIPIA 26 2005 26
Applications TANKER RESPONSE TO SQUALL WIND 8.0 360 Surge and Sw ay motions (m) Wind speed (m/s) 7.5 Wind speed 315 7.0 Wind direction 270 6.5 225 6.0 180 5.5 135 5.0 90 4.5 45 4.0 0 0 1000 2000 3000 4000 5000 6000 Wind direction (CWN) 20 0 0 2000 4000 6000 8000 10000 12000 14000-20 -40 Surge Sway -60 Thrust Allocation (kn) Tanker Trajectory 300 330 0 100 80 60 40 20 30 60 Bow tunnel Stern tunnel Port azimuthing Stbd azimuthing 2 0-6 -4-2 0 2 4 6-2 270 0 90-4 240 120-6 210 150-8 180-10 PRINCIPIA 27 2005 27
Concluding remarks DP Module Validation : Field Development Ship (SAIBOS) Development : frequency domain PRINCIPIA 28 2005 28