Royal Thai Navy. Phillip Wilson(13-03-55)/rtn1.pdf · 1 Models of marine structures are complex. 2 Control engineers often base their models on models used by naval architects, which

Guest Talk

University of Southampton

Royal Thai Navy

Professor P A Wilson

University of Southampton

March 11, 2012

Professor P A Wilson Royal Thai Navy

Guest Talk

Modelling and Simulation of Marine Surface Vessel

DynamicsFirst Presentation


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Lecture Goals

1 Model vessels and environmental loads in 6 DOF.


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Lecture Goals



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2 Use state-of-the-art hydrodynamic codes to compute modelparameters: added mass, potential damping, 1st and2nd-order wave loads.


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3 Derive control plant models by postprocessing data fromhydrodynamic codes (Matlab GNC toolbox).


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4 Use system identification to fit hydrodynamic data tostate-space models.


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5 Add viscous effects/manoeuvring terms.


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6 Time-domain simulation in Matlab Simulink


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Applications

Applications


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Modelling and Control

1 System designers make decisions to satisfy conflictingrequirements based on some knowledge of the system theyintend to design: this knowledge is represented inmathematical model


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2 Modelling is an essential part of control design and preliminarytesting, which can consume up to 60% of effort in these tasks.


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Modelling of Marine Structures

1 Models of marine structures are complex.


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2 Control engineers often base their models on models used bynaval architects, which sometimes are not control-designoriented.


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3 In this tutorial, we will look at the models commonly used innaval architecture and ship theory from the control systemsperspective.


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Obtaining Models

Obtaining Models

Mathematical

Models(Simulation,GNC-design

HIL-testing, Diagnosis)

System

Identification

Data-base Model testing

Full-scale

Experiments

Numerical

Hydrodynamics

ScalingSystem

Identification

System

Identification

Main focus of

this tutorial


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Manoeuvring and Seakeeping

Ship theory has traditionally been separated into two main areas.

Manoeuvring

The aim is to study steeringcharacteristics of vessels withforward speed and the responseto the command of propulsionsystems and control surfaces.This is done in calm water.


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Manoeuvring


Seakeeping

The aim is to study thebehaviour of the vessel in waves

while keeping a constant speed

and course


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Manoeuvring


Seakeeping

The aim is to study thebehaviour of the vessel in waves

while keeping a constant speed

and course

Although both areas are concerned with the study of motion,

stability and control, this separation allows one to makeassumptions that simplify the study in each case.


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Manoeuvring Models

1 Nonlinear parametric models(classical and Lagrangian):

x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ

2 Obtained by fitting data fromscaled model experiments


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ


3 Calm water models.


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ


3 Calm water models.4 Horizontal motion models

(surge-sway-yaw).


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ



(surge-sway-yaw).5 Restricted to a few

speeds/loading conditions of theexperiment.


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ





6 Not commonly available.


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Manoeuvring Models


x = f(x, u)

Mν + C(ν)ν +D(ν)ν + g(η) = τ





6 Not commonly available.


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Seakeeping Models

Linear non-parametric models

H(jω)

Obtained from hydrodynamic calculations based on simplifyingassumptions:Constant course and speed Linear wave loads.


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Seakeeping Models


H(jω)

Obtained from hydrodynamic calculations based on simplifyingassumptions:Constant course and speed Linear wave loads.Potential theory.


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Seakeeping Models


H(jω)

Obtained from hydrodynamic calculations based on simplifyingassumptions:Constant course and speed Linear wave loads.Potential theory.Viscous effects can be added


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Seakeeping Models


H(jω)

Obtained from hydrodynamic calculations based on simplifyingassumptions:Constant course and speed Linear wave loads.Potential theory.Viscous effects can be addedFor the design of control systems, seakeeping models are very useful.


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Seakeeping Models


H(jω)

Obtained from hydrodynamic calculations based on simplifyingassumptions:Constant course and speed Linear wave loads.Potential theory.Viscous effects can be addedFor the design of control systems, seakeeping models are very useful.

They provide preliminary models based on little data of the ship.


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Recent Results on a Unified Manoeuvring and Seakeeping

Models

Fossen, T. I. and . N. Smogeli. Nonlinear Time-Domain Strip TheoryFormulation for Low-Speed Manoeuvring and Station-Keeping,Modelling, Identification and Control, MIC-25(4):201:221, 2004.Fossen, T. I. A Nonlinear Unified State-Space Model for ShipManoeuvring and Control in a Seaway, Journal of Bifurcation and Chaos,September 2005. (Plenary Talk ENOC’05, Eindhoven, The Netherlands).Perez, T. and T. I. Fossen. Kinematic Models for Sea-keeping andManoeuvring of Marine Vessels. Modelling, Identification and Control,MIC-28(1):1-12, 2007.Perez, T. and T. I. Fossen. Time-Domain Models of Marine SurfaceVessels for Simulation and Control Design Based on Sea-keepingComputations (Plenary Talk). Proc. of the IFAC MCMC’06, Lisbon,Portugal, September 20-22, 2006.

Ross, A., T. Perez and T. I. Fossen. A Novel Manoeuvring Model

Based on Low-Aspect Ratio Lift Theory and Lagrangian Mechanics.

Proc. of the IFAC CAMS’07, Croatia.


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The Force-Transfer-Functions are computed using

hydrodynamic SW (WAMIT, VERES or SEAWAY )

Unified Manoeuvring and SeakeepingModel for Time-Domain Simulation

! J !!"

M"# " CRB" " D""dn !, ! g!" ! #env

!" ! Ar! Br #, 0 0

Cr! ! Dr "

For 6 DOF this model will

typically be represented by

6 + 6 + 90 = 102 ODEs

which are computed using

hydrodynamic SW (WAMIT,

VERES or SEAWAY )

These terms are found using

experimental results/curve

fitting or semi-empirical

methodsProfessor P A Wilson Royal Thai Navy

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Speed–Environment Envelope

Hull supported by

mostly by hydrostatic

pressure (forces)

Aero and

hydrodynamic

forces; strong

flow separationHydrostatic and

hydrodynamic forces; LiftProfessor P A Wilson Royal Thai Navy

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The 3 Speed Regimes for ControlDynamic positioning systems

• 3D potential theory

• 2D potential theory (strip theory)

0 1.5 m/s (3 knots) …. …..Speed

Station-keeping

Low-speed

maneuvering

Manoeuvring at

moderate speed

(transit)

Manoeuvring/motion damping

• 2D potential theory (strip theory) up to

Froude numbers of 0-3-0.4

• 2.5 D potential theory for high-speed craft

LgU 3.0

Manoeuvring at

high speed

(high-speed craft)


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The 3 Speed Regimes for Control

1 Dynamic positioning systemsLow-speed manoeuvering Manoeuvring at moderate speed(transit)

1 3D potential theory


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1 3D potential theory2 2D potential theory (strip theory)


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2 Manoeuvring/motion dampingManoeuvring at high speed (high-speed craft) Station-keeping

U = 0.3√

Lg

1 2D potential theory (strip theory) up to Froude numbers of0.3− 0.4


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2 Manoeuvring/motion dampingManoeuvring at high speed (high-speed craft) Station-keeping

U = 0.3√

Lg

1 2D potential theory (strip theory) up to Froude numbers of0.3− 0.4

2 2.5 D potential theory for high-speed craft


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Motion in WavesMotions and loads of floating structures due to waves can be separated into:

1 Wave-frequency: linearly excitations and motion in the wavefrequency range. Periods in the range 5-20s


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2 Higher than wave frequency (ringing & springing): nonlineareffects, which can produce resonance in TLPs, with naturalperiods of 2-4s.


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2 Higher than wave frequency (ringing & springing): nonlineareffects, which can produce resonance in TLPs, with naturalperiods of 2-4s.

3 Slow and mean drift: nonlinear effects with mean value andsub harmonic excitation that can produce oscillations withnatural periods of 20-30s.


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Motion and Control

Then, motion control problems can have different objectives:

1 Control only the non-oscillatory motion (wave filtering needed)1 Autopilots,


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Motion and Control


1 Control only the non-oscillatory motion (wave filtering needed)1 Autopilots,2 Dynamic positioning (DP)


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Motion and Control


1 Control only the non-oscillatory motion (wave filtering needed)1 Autopilots,2 Dynamic positioning (DP)3 Thruster assisted position mooring (TAPMOOR)


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Motion and Control



2 Control only the oscillatory motion1 Ride control of high speed vessels (roll and pitch stabilisation)


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Motion and Control



2 Control only the oscillatory motion1 Ride control of high speed vessels (roll and pitch stabilisation)2 Heave compensation of offshore structures


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Motion and Control




3 Control both1 Dynamic positioning in extreme seas (DP + roll & pitch

stabilisation)


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Motion and Control





stabilisation)2 Autopilots with rudder roll stabilisation


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Motion and Control





stabilisation)2 Autopilots with rudder roll stabilisation3 Unmanned Surface Vehicles USV


Documents

Royal Thai Navy. Phillip Wilson(13-03-55)/rtn1.pdf · 1 Models of marine structures are complex. 2 Control engineers often base their models on models used by naval architects, which