Ship Dynamic Positioning Research Articles

A Simulation Platform for Dynamic Positioning Ship with Guidance, Navigation and Control Function

In order to study the whole system performance of dynamic positioning ship, a simulation platform which contains environment and ship model, as well as basic guidance, navigation and control functions is established. Besides the ordinary ship and environment modeling, a guidance method for waypoint following is designed by using path interpolation and circle of acceptance. A sensor-fusion based federated filter is proposed to deal with the problem of state estimation and wave filtering. To make the whole system becomes a closed loop feedback system, a PID method are applied to deal with the control problem. By using this simulation platform, this paper simulates and studies the basic functions of a typical dynamic positioning ship. Finally, the simulation proves the validity and excellent performance of this dynamic position ship simulation platform.

Thrust Allocation and Management for Dynamic Positioning Ship with Azimuth Thrusters

In order to solve the complex thrust allocation problems of dynamic positioning ship with azimuth thrusters, thrust allocation and management system was built. The power optimal thrust allocation was formulated as a quadratic programming problem by the linear treatments of inequality constraints and the optimal solution could be found in a finite amount of time. And some influence factors of thrust allocation were separated from algorithms and treated as a superstratum management module. Using this system, online adjustment of input constraints and singularity avoidance can be realized, and the reliability and adaptability of thrust allocation are improved consequently. Finally, the validity and excellent performance of this method is proved by the simulations.

Multiple Model Adaptive Nonlinear Observer of Dynamic Positioning Ship

Considering the filtering problem of dynamic positioning (DP) ship for the slowly varying sea state, a multiple model adaptive observer (MMAO) for dynamic positioning ship is presented. The MMAO consists of a bank of nonlinear subobserver and a dynamic weighting signal generator, in which each sub-observer is designed based on different peak frequency of wave spectrum model. To improve the performance of the observer, subobserver using the measurement of position, velocity, and acceleration is used to update the estimated velocity of ship. The observer parameters are optimized using particle swarm optimization (PSO). Finally, the method is verified effective by the computer simulation.

Sensor fusion-based dynamic positioning of ships using Extended Kalman and Particle Filtering

SUMMARYThe paper examines the problem of dynamic ship positioning with the use of Kalman Filter- and Particle Filter-based sensor fusion algorithms. The proposed approach enables to estimate accurately the ship's state vector by fusing the vessel's position and heading measurements coming from on-board sensors together with distance measurements coming from sensors located at the coast (e.g. radar). The estimated state vector is used in turn, in a control loop, to regulate the horizontal position and heading of the vessel. The performance of dynamic positioning of the ship based on Kalman and Particle Filtering is evaluated through simulation experiments.

Robust Controller for Ship Dynamic Positioning Based on H∞

This document explains how to design a robust controller for the uncertain model of the ship dynamic positioning based on mixed sensitivity, which include environmental excitations. The computer simulation shows that it validated that the robust control system has a good performance.

Passivity-based control applied to the dynamic positioning of ships

A family of passivity-based controllers for dynamic positioning of ships is presented. The authors exploit the idea of shaping the energy function of the closed-loop system to obtain different formulations of the passivity-based control law using the interconnection and damping assignment-passivity-based control (IDA-PBC) methodology. A salient feature of this study is that the proposed control laws are output feedback controllers and the relative velocity measurement is not required. First, we design and analyse two static controllers which can be seen as a non-linear version of the conventional proportional-derivative (PD) controllers. In presence of unknown disturbances, these controllers do not provide the desired regulation properties. To remove this discrepancy we propose, also in the context of the IDA-PBC technique, a dynamic extension of the system and obtain two new controllers that have the desired regulation properties. These new control laws can be seen as a non-linear version of the conventional proportional-integral-derivative (PID) controllers. Simulations are included to validate the theoretical results.

Multiple Model Adaptive Dynamic Positioning

This paper describes a procedure to design multiple model adaptive controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads. To this effect, a linear design model is obtained, based on practical assumptions, describing the dynamics of the vessel. Four Linear Quadratic Gaussian (LQG) DP controllers (with the same structure) are designed, covering the different sea conditions from calm to extreme seas. Tools from multiple model adaptive control (MMAC) theory are used to exploit the information provided by the different observers (models) in order to select the appropriate controller. Numerical simulations carried out using a high fidelity nonlinear DP simulator illustrate the efficiency of the MMAC techniques proposed. To bridge the gap between theory and practice, the results of the simulations were experimentally verified by model testing with a DP operated ship, the Cybership III, under different simulated sea conditions in a towing tank equipped with a hydraulic wave maker.

Robust Dynamic Positioning of Offshore Vessels using Mixed-μ Synthesis Part I: A Control System Design Methodology

This paper describes a procedure to design robust controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads using ℋ∞ and mixed-μ techniques. To this effect, practical assumptions are exploited in order to obtain a linear design model with parametric uncertainties describing the dynamics of the vessel. Appropriate frequency weighting functions are selected to capture the required performance specifications at the controller design phase. The proposed model and weighting functions are then used to design robust controllers. The problem of wave filtering is also addressed during the process of modeling and controller design. The key contribution of the paper is twofold: i) it affords system designers a new method to efficiently obtain linearized design models that fit naturally in the framework of ℋ∞ control theory, and ii) it describes, in a systematic manner, the different steps involved in the controller design process. Part II in a companion paper contains the details of simulations and results of experimental model tests in a towing tank equipped with a hydraulic wave maker.

Global robust and adaptive output feedback dynamic positioning of surface ships

A constructive method was presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind, and ocean currents. The ship’s parameters were not required to be known. An adaptive observer was first designed to estimate the ship’s velocities and parameters. The ship position measurements were also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control was then designed based on Lyapunov’s direct method to force the ship’s position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presented a new method to design an effective control system for dynamic positioning of surface ships.

Fuzzy Controller Design Subject to Actuator Saturation for Dynamic Ship Positioning Systems with Multiplicative Noises

This paper deals with the fuzzy controller design problem for the dynamic ship positioning systems with multiplicative noises. The Takagi—Sugeno (T—S) fuzzy model is employed to represent the non-linear dynamic ship positioning systems. Subject to actuator saturation, some sufficient conditions are derived to guarantee the stability of the closed-loop systems. The stability conditions developed in this paper can be coordinated to the linear matrix inequality (LMI) constraints. By solving these LMI stability conditions, a parallel distributed compensation (PDC)-based fuzzy controller is obtained to stabilize the T—S fuzzy models with multiplicative noises. In order to illustrate the availability and practicability of proposed fuzzy controller design approach, a numerical simulation is provided to express the controlled responses of dynamic ship positioning systems with multiplicative noises.

A Multiple Model Adaptive Wave Filter for Dynamic Ship Positioning

This paper addresses a filtering problem that arises in the design of dynamic positioning systems for ships subjected to the influence of sea waves. Its key contribution is the use of a multiple model adaptive wave filter that relies on measurements of the ship's position and heading only. To this effect, a bank of Kalman filters is designed for a finite number of parameter values, each corresponding to a different peak frequency of the assumed wave spectrum model. Tools from multiple model adaptive estimation (MMAE) theory are exploited to blend the information provided by the different observers, yielding position and velocity estimates of the ship. These estimates are then be used in an appropriately designed feedback control law. Simulations illustrate the efficacy of the MMAE techniques proposed.

A Backstepping Controller for Dynamic Positioning of Ships: Numerical and Experimental Results for a Shuttle Tanker Model

Abstract Dynamic Positioning System (DPS) is a complex control system composed of several algorithms, such as controllers, filters and optimal thrust allocation. The design, analysis and performance prediction of a DPS are normally done by a combination of numerical simulations and tank tests with a reduced model. This paper presents a comparison of numerical and preliminary experimental results of a dynamic-positioned shuttle tanker model, using a backstepping controller.

Automatic weight selection for controller synthesis

This article is concerned with the development of a procedure to calculate the parameters of weighting functions used in controller designs to achieve a desired system performance. The synthesis problem is formulated as a multi-criterion optimization problem. A Genetic Algorithm is then employed to search for suitable solutions. To cope with the imprecision and vagueness that arises in the description of objective functions and constraints of the process and actuators, concepts from the fuzzy logic are incorporated into the solution. A multi-objective fuzzy optimization is stated and a fuzzy convex decision-making is established. To demonstrate the advantages of the proposed method, the tuning of SISO and MIMO controllers are investigated. The method is applied to the tuning of controllers of a ship autopilot and of a dynamic ship positioning system. Results are presented, analyzed and compared to former works.

Automatic weight selection for H ∞ controller synthesis

This article is concerned with the development of a procedure to calculate the parameters of weighting functions used in H∞ controller designs to achieve a desired system performance. The H∞ synthesis problem is formulated as a multi-criterion optimization problem. A Genetic Algorithm is then employed to search for suitable solutions. To cope with the imprecision and vagueness that arises in the description of objective functions and constraints of the process and actuators, concepts from the fuzzy logic are incorporated into the solution. A multi-objective fuzzy optimization is stated and a fuzzy convex decision-making is established. To demonstrate the advantages of the proposed method, the tuning of SISO and MIMO controllers are investigated. The method is applied to the tuning of controllers of a ship autopilot and of a dynamic ship positioning system. Results are presented, analyzed and compared to former works.

T–S fuzzy model with nonlinear consequence and PDC controller for a class of nonlinear control systems

In this paper a new Takagi–Sugeno (T–S) fuzzy model with nonlinear consequence (TSFMNC) is presented which can approximate a class of smooth nonlinear systems , nonlinear dynamical systems and nonlinear control systems . It is also proved that Takagi–Sugeno fuzzy controller with nonlinear consequence (TSFCNC) can be used to approximate a class of nonlinear state-feedback controllers using the so-called parallel distributed compensation (PDC) method. The inverted pendulum problem has been simulated with TSFCNC and compared with Takagi–Sugeno fuzzy controller with linear consequence (TSFCLC) and the results show that TSFCNC performs better than TSFCLC. A real-life example of dynamic positioning of ship is simulated and the results also show that TSFCNC performs better than TSFCLC.

Multivariable PID tuning of dynamic ship positioning control systems

This paper introduces the ship dynamic positioning (DP) control problem, details a nonlinear multivariable simulation model for a floating production, storage and offloading (FPSO) vessel and proposes a new model-free linear method for rapid tuning of the DP multivariable PID controllers. Three existing model free tuning methods are compared for their performance and stability properties and a procedure is developed for rapid tuning of DP control systems. Controller structures are discussed and the methods are applied to the simulation model at an operating point, thereby justifying the use of linear tuning techniques. It is shown that some of the methods are appropriate and that it is straightforward to produce a controller of acceptable performance within the thruster input constraints of the ship. Simulation results are presented and analysed. The propose methods are particularly useful for the cases where an adaptive DP control system is required to meet the desired performance.

Development of a robust non-linear observer for dynamic positioning of ships

A robust non-linear observer, utilizing the sliding mode concept, is developed for the dynamic positioning (DP) of ships. The main advantage of the proposed observer is its robustness. The observer is based on work by Fossen and Strand, providing estimates of linear velocities of the ship and bias from slowly varying environmental loads. It also filters out wave frequency motion to avoid wear of actuators and excessive fuel consumption. In particular, the observer structure with a saturation function makes the proposed observer robust against neglected non-linearities, disturbances and uncertainties. A non-linear output feedback controller is derived on the basis of the developed observer using the observer backstepping technique, and the global stability of the observer and control law is shown by Lyapunov stability theory. A set of simulations was carried out to investigate the performance of the proposed observer for dynamic positioning of a ship.

Development of a robust non-linear observer for dynamic positioning of ships

Development of a robust non-linear observer for dynamic positioning of ships

Optimal setpoint chasing in dynamic positioning of deep‐water drilling and intervention vessels

Conventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal-plane about desired position and heading co-ordinates defined by the operator. A three degrees-of-freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi-submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust-induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work-over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co-ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi-submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd.

Optimal setpoint chasing in dynamic positioning of deep‐water drilling and intervention vessels

AbstractConventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal‐plane about desired position and heading co‐ordinates defined by the operator. A three degrees‐of‐freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi‐submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust‐induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work‐over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co‐ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi‐submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd.