Marine Control Systems - Asgeir J. Sørensen [2013, PDF]

Contents

Contents
Preface i
Acknowledgements ii
1 Introduction 1
1.1 Marine Cybernetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Main Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 MarineControlSystems 5
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 SystemOverview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Power System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Propulsion System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Marine Automation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5.2 Data Network and Process Stations . . . . . . . . . . . . . . . . . . . . . 12
2.5.3 Operator Stations and HMI . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.5.4 Integration Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.6 Dynamic Positioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.6.1 Position Reference Systems and Sensors . . . . . . . . . . . . . . . . . . . 14
2.6.2 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.6.3 Functionality andModules . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.6.4 Advisory and Surveillance Systems . . . . . . . . . . . . . . . . . . . . . . 20
2.6.5 DP Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.7 Power and EnergyManagement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.7.1 Blackout Restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.7.2 Load Reduction and Blackout Prevention . . . . . . . . . . . . . . . . . . 23
2.7.3 Diesel Engine Governor and AVR Fault Tolerance . . . . . . . . . . . . . 25
2.8 Maritime Industrial IT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.9 Rules and Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.9.1 Class Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.9.2 Reliability and Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.9.3 Failure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.10 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.10.1 Simulator Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.10.2 Module Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
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2.10.3 Hardware and Software Platform . . . . . . . . . . . . . . . . . . . . . . . 38
2.10.4 Hardware-In-the-Loop Testing . . . . . . . . . . . . . . . . . . . . . . . . 38
3 Maritime Electrical Installations and Diesel Electric Propulsion 41
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1.1 Scope and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1.2 Motivations for Electric Propulsion . . . . . . . . . . . . . . . . . . . . . . 42
3.1.3 Power Flow and Power Efficiency . . . . . . . . . . . . . . . . . . . . . . . 43
3.1.4 Historical Overview of Electric Propulsion . . . . . . . . . . . . . . . . . . 45
3.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.2.1 Passenger Vessels — Cruise Ships and Ferries . . . . . . . . . . . . . . . . . 49
3.2.2 Oil and Gas Exploitation and Exploration: Drilling Units, Production
Vessels and Tankers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.2.3 Field Support Vessels and Construction Vessels . . . . . . . . . . . . . . . 50
3.2.4 Icebreakers and Ice Going Vessels . . . . . . . . . . . . . . . . . . . . . . . 52
3.2.5 War Ships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2.6 Research Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.2.7 Trends and New Applications . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3 Overview of Electric Power System . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3.2 Electric Power Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.3.3 Electric Power Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.3.4 Motor Drives for Propulsion and Thrusters . . . . . . . . . . . . . . . . . 62
3.3.5 Propulsion Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.3.6 Trends and New Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.4 Power and Propulsion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.4.1 Introduction - Control Hierarchy . . . . . . . . . . . . . . . . . . . . . . . 73
3.4.2 User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.4.3 High Level Control Functionality . . . . . . . . . . . . . . . . . . . . . . . 75
3.4.4 Low Level Control Functionality . . . . . . . . . . . . . . . . . . . . . . . 78
3.5 Electric Propulsion Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.5.2 Variable SpeedMotor Drives . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.6 SystemDesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.6.2 Life Cycle Cost Assessment of Conceptual Design . . . . . . . . . . . . . . 98
3.6.3 Standard Network Analysis and Electrical Power System Studies . . . . . 98
3.6.4 Extended Analysis and Studies . . . . . . . . . . . . . . . . . . . . . . . . 103
3.7 Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
3.7.1 Harmonics of VSI Converters . . . . . . . . . . . . . . . . . . . . . . . . . 105
3.7.2 Harmonics of CSI Converters . . . . . . . . . . . . . . . . . . . . . . . . . 107
3.7.3 Harmonics of Cycloconverters . . . . . . . . . . . . . . . . . . . . . . . . . 107
3.7.4 Limitations by Classification Societies . . . . . . . . . . . . . . . . . . . . 108
3.7.5 Harmonics of Ideal 6- and 12-pulse Current Waveforms . . . . . . . . . . 108
3.7.6 Calculating Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . 110
3.7.7 Managing Harmonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
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3.8 Example Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
4 Computer-Controlled Systems 122
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.2 Basics in Linear SystemTheory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.2.1 Causality and State Definition . . . . . . . . . . . . . . . . . . . . . . . . 124
4.2.2 Continuous-time State SpaceModel . . . . . . . . . . . . . . . . . . . . . 125
4.2.3 Basic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
4.2.4 Laplace Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
4.2.5 Fourier Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
4.3 Sampler and Zero-Order Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
4.4 Discrete-time State Space Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
4.4.1 ZOH Equivalent of Continuous-time State Space Model . . . . . . . . . . 130
4.4.2 Discrete-time Approximation . . . . . . . . . . . . . . . . . . . . . . . . . 132
4.4.3 Solution of Discrete-time SystemEquation . . . . . . . . . . . . . . . . . 133
4.4.4 Controllability and Observability of Discrete-time Systems . . . . . . . . . 134
4.5 Discrete-time Approximation Methods . . . . . . . . . . . . . . . . . . . . . . . . 135
4.5.1 Euler’sMethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
4.5.2 Backward Euler’sMethod . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
4.5.3 Combined Backward and Forward Euler’s Method . . . . . . . . . . . . . 136
4.5.4 Trapezoidal (Tustin’s)Method . . . . . . . . . . . . . . . . . . . . . . . . 137
4.5.5 Second Order System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
4.6 Nyquist Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
4.7 The -Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.7.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.7.2 Stability Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.8 The Pulse-Transfer Function and the Pulse Response . . . . . . . . . . . . . . . . 142
4.8.1 Pulse-transfer Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.8.2 Pulse Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
4.9 Shift-operator Calculus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4.9.1 Shift Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4.9.2 Pulse-transfer Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
4.10 Stability Regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
4.11 Order of the System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.12 Relation Between Shift-Operator Calculus and -Transform . . . . . . . . . . . . 150
5 Signal Quality Checking and Fault Detection 151
5.1 Testing of Individual Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
5.1.1 Windowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
5.1.2 Signal Range Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
5.1.3 Variance Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
5.1.4 Wild Point Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
5.2 Handling of Redundant Measurements . . . . . . . . . . . . . . . . . . . . . . . . 154
5.2.1 Voting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
5.2.2 Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
5.2.3 Enabling and Disabling of Sensors . . . . . . . . . . . . . . . . . . . . . . 156
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6 Filtering and State Estimation 158
6.1 Analog and Digital Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
6.1.1 Nonideal Lowpass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
6.1.2 Nonideal Highpass Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.1.3 Notch Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.1.4 Digital Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
6.2 State Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.2.1 Deterministic Estimators . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
6.2.2 Least Squares Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
6.2.3 Discrete Kalman Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
6.2.4 Extended Kalman Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7 Mathematical Modeling of Dynamically Positioned Marine Vessels 175
7.1 EnvironmentalModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
7.1.1 Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
7.1.2 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
7.1.3 Water CurrentModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
7.2 Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
7.2.1 Reference Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
7.2.2 The Euler Angle Transformation . . . . . . . . . . . . . . . . . . . . . . . 195
7.3 Vessel Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
7.3.1 Nonlinear Low-Frequency VesselModel . . . . . . . . . . . . . . . . . . . 201
7.3.2 Environmental Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
7.3.3 LinearWave-FrequencyModel . . . . . . . . . . . . . . . . . . . . . . . . 209
7.3.4 Thrust ServoModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
7.4 Static Analysis of Cable Segments . . . . . . . . . . . . . . . . . . . . . . . . . . 211
7.4.1 Basic Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
7.4.2 Catenary Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
7.4.3 Catenaries as Boundary Value Problems (BVP) . . . . . . . . . . . . . . . 222
7.4.4 Hydrodynamic Drag Loads . . . . . . . . . . . . . . . . . . . . . . . . . . 224
7.5 Mooring Systemfor FPSOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
8 Dynamic Positioning Control System 228
8.1 Survey of Scientific Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
8.2 Observer Design for Dynamic Positioning . . . . . . . . . . . . . . . . . . . . . . 231
8.2.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
8.2.2 Control PlantModel: VesselModel . . . . . . . . . . . . . . . . . . . . . . 233
8.2.3 Extended Kalman Filter Design . . . . . . . . . . . . . . . . . . . . . . . . 235
8.2.4 Nonlinear Observer Design . . . . . . . . . . . . . . . . . . . . . . . . . . 236
8.2.5 Adaptive Observer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
8.2.6 Nonlinear Observer Design for Extreme Seas . . . . . . . . . . . . . . . . 244
8.2.7 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
8.3 Controller Design for Dynamic Positioning . . . . . . . . . . . . . . . . . . . . . . 252
8.3.1 Control PlantModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
8.3.2 Horizontal-plane Controller . . . . . . . . . . . . . . . . . . . . . . . . . . 254
8.3.3 Horizontal-plane Controller with Roll-Pitch Damping . . . . . . . . . . . 257
8.3.4 Controller Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
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8.3.5 Thrust Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
8.3.6 Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
8.4 Hybrid Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
8.4.1 Control PlantModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
8.4.2 Observer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
8.4.3 Vessel Operational Condition . . . . . . . . . . . . . . . . . . . . . . . . . 270
8.4.4 Concept of Hybrid Control . . . . . . . . . . . . . . . . . . . . . . . . . . 271
8.4.5 Example: Switching fromDP to PM . . . . . . . . . . . . . . . . . . . . . 273
8.5 Weather Optimal Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
8.5.1 MathematicalModeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
8.5.2 Weather Optimal Control Objectives . . . . . . . . . . . . . . . . . . . . . 283
8.5.3 Nonlinear and Adaptive Control Design . . . . . . . . . . . . . . . . . . . 284
8.5.4 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
9 Propulsion Control 297
9.1 Propellers and Thrusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
9.1.1 Shaft Propulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
9.1.2 Thrusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
9.1.3 Podded Propulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
9.1.4 Mechanical Pod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
9.1.5 Water Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
9.2 Control ProblemFormulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
9.3 Propeller Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
9.3.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
9.4 Propulsion Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
9.5 Propeller and Thruster Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
9.5.1 In-line Velocity Fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . 309
9.5.2 Transverse Velocity Fluctuations . . . . . . . . . . . . . . . . . . . . . . . 309
9.5.3 Ventilation and In-and-out-of Water Effects . . . . . . . . . . . . . . . . . 311
9.6 Propeller ShaftModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
9.6.1 Torque Loop in an ElectricalMotor Drive . . . . . . . . . . . . . . . . . . 317
9.6.2 Resulting Thruster Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . 317
9.6.3 Thrust, Torque, Power, and Shaft Speed Relations . . . . . . . . . . . . . 319
9.7 Low-Level Thruster Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
9.7.1 Control Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
9.8 Thruster Control in Normal Conditions . . . . . . . . . . . . . . . . . . . . . . . 320
9.8.1 Controller Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
9.8.2 Control PlantModel Parameters . . . . . . . . . . . . . . . . . . . . . . . 321
9.8.3 Reference Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
9.8.4 Inertia Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
9.8.5 Friction Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
9.8.6 Torque and Power Limiting . . . . . . . . . . . . . . . . . . . . . . . . . . 323
9.8.7 Shaft Speed Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . 324
9.8.8 Torque Feedforward Control . . . . . . . . . . . . . . . . . . . . . . . . . . 324
9.8.9 Power Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
9.8.10 Combined Torque and Power Control . . . . . . . . . . . . . . . . . . . . 325
vii
9.9 Thruster Control in Extreme Conditions . . . . . . . . . . . . . . . . . . . . . . . 326
9.9.1 Loss Estimation and Ventilation Detection . . . . . . . . . . . . . . . . . . 326
9.9.2 Anti-spin Thruster Control . . . . . . . . . . . . . . . . . . . . . . . . . . 328
9.9.3 Implementation aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
9.10 Sensitivity to Thrust Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
9.10.1 Shaft Speed Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . 332
9.10.2 Torque Feedforward Control . . . . . . . . . . . . . . . . . . . . . . . . . . 332
9.10.3 Power Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
9.10.4 Combined Power and Torque Control . . . . . . . . . . . . . . . . . . . . 333
9.10.5 Positioning Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
9.10.6 Sensitivity Functions Summary . . . . . . . . . . . . . . . . . . . . . . . . 333
9.11 Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
9.11.1 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
9.11.2 Nominal Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
9.11.3 Sensitivity Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
9.11.4 Dynamic Tests inWaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
9.11.5 Anti-spin Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
9.11.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
10 Modeling and Control of Ocean Structures 350
10.1 Mathematical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
10.1.1 Ordinary Differential Equations (ODE) . . . . . . . . . . . . . . . . . . . 351
10.1.2 Partial Differential Equations (PDE) . . . . . . . . . . . . . . . . . . . . . 357
10.1.3 Methods for Numerical Solution of the Relevant Systems . . . . . . . . . 358
10.2 Modelling and Control Top Tensioned Risers . . . . . . . . . . . . . . . . . . . . 371
10.2.1 Motivation and ProblemDescription . . . . . . . . . . . . . . . . . . . . . 371
10.2.2 Tension Leg Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
10.2.3 MathematicalModelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
10.2.4 Model Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
10.2.5 Control plantmodel analysis . . . . . . . . . . . . . . . . . . . . . . . . . 397
10.2.6 Controller SystemDesign . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
10.2.7 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
10.2.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
10.3 Control of Drilling Riser Angles by Dynamic Positioning of Surface Vessels . . . 422
10.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
10.3.2 MathematicalModelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
10.3.3 High Level Positioning and Riser Angle Controller . . . . . . . . . . . . . 432
10.3.4 Local Optimization: Optimal Setpoint Chasing . . . . . . . . . . . . . . . 433
10.3.5 Numerical Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
11 Modelling and Control of High Speed Craft 443
11.1 Ride Control of Surface Effect Ships . . . . . . . . . . . . . . . . . . . . . . . . . 444
11.1.1 MathematicalModelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
11.1.2 Robust Dissipative Controller Design . . . . . . . . . . . . . . . . . . . . . 456
11.1.3 Simulation and Full Scale Results . . . . . . . . . . . . . . . . . . . . . . . 466
A Linear Algebra 496
viii
B Digital PID-Controllers 499
B.1 Continuous-Time PID-Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . 499
B.2 Discrete-Time PID-Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500
C Definition of Electro-technical Terms 502
C.1 DC — Direct Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502
C.2 AC — Alternating Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
C.2.1 One phase AC sources and resistive loads . . . . . . . . . . . . . . . . . . 504
C.2.2 Three phase AC sources and resistive loads . . . . . . . . . . . . . . . . . 506
C.2.3 Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509
C.3 Modelling of Components in Electric Power Generation and Distribution . . . . . 513
C.3.1 Generatormodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513
C.3.2 Distribution switchboards . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
C.3.3 Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
C.3.4 Synchronous motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
C.3.5 Asynchronous motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
D Standards, rules, and regulations on electric propulsion 518
D.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518
D.2 International regulations, applicable standards or code of practice . . . . . . . . . 519
D.3 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521

Introduction

Introduction
Marine control systems or Marine cybernetics is defined to be the science about techniques and
methods for analysis, monitoring and control of marine systems.
The main application fields for marine control systems are the three big marine industries:
Sea transportation (shipping), offshore oil and gas exploration and exploitation and fisheries and
aquaculture. So far most of the examples are collected from the mature industries like shipping
and offshore oil and gas exploration and exploitation. It is believed that these industries will
be even more technology demanding with focus on safe and cost effective solutions in the years
to come. More of the offshore activities is assumed to take place in deeper water based on
floating solutions in combination with subsea installations. The need for conducting all-year
marine operations in the ocean space with varying complexity will increase and motivate to the
development of underwater robotics with increased autonomity. Due to increased industrialization
within the fisheries and aquaculture, the industrial content and thereby the introduction of
advanced technology are expected to increase. It is foreseen that there is a huge potential for
technology transfer among all the marine industries.
Concerning marine control systems it is suggested to divide the control structure into two
main areas: real-time control and monitoring and operational and business enterprise management,
see Figure 1.1. We will here in particular focus on the various aspects related to the design
of real-time control and systems. The integration of real-time systems with operational management
and business transactional systems is by the automation industry denoted as Industrial IT.
The real-time control structure is as shown in Figure 1.1 divided into low-level actuator
control, high-level plant control and local optimization. We will in the text use demonstrating
examples from the offshore oil and gas industry. In particular, examples with dynamically
positioned (DP) offshore vessels will be used. A DP vessel maintains its position (fixed location
or pre-determined track) exclusively by means of active thrusters. Position keeping means
maintaining a desired position in the horizontal-plane within the normal excursions from the
desired position and heading. The real-time control structure for a DP system may then consist
of (Sørensen [299] and [300]):
• Actuator control : The actuators for DP systems are normally thrusters, propellers, and
rudders. Local control of propellers and thrusters may be done by controlling e.g. the speed
• Plant control : In station keeping operations the DP system is supposed to counteract the
disturbances like wave (mean and slowly varying), wind and currents loads acting on the
vessel. The plant controller calculates the commanded surge and sway forces and yaw
moment needed to compensate the disturbances. A multivariable output controller often
of PID type using linear observers e.g. Kalman filter or nonlinear passive observers may
be used. Setpoints to the thrusters are provided by the thruster allocation scheme.
• Local optimization: Depending of the actual marine operation the DP vessel is involved in
optimization of desired setpoint in conjunction with appropriate reference models for e.g.
drilling operations, weather vaning, pipe laying, tracking operations, etc. are used. Notice
that in the guidance, navigation and control literature local optimization corresponds to
the guidance block.
As the controllers rely on proper measurements to work on, signal processing is of vital
importance for the stability and robustness of the control system. This will be the first topic of
the text.

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