Dynamic Positioning Mode Research Articles

Vessel Dynamic Positioning System Mathematical Model

This study aims to examine two potential approaches for addressing the challenge of synthesizing control laws in the Dynamic Positioning (DP) system. Both approaches pertain to the same ship model but are rooted in distinct ideologies concerning how to account for the influence of external disturbances on a closed system. The findings of this investigation could offer valuable insights for enhancing DP systems and formulating more efficient management strategies in maritime conditions. The research delves into the structure and principles of the DP system as a sophisticated control complex, identifying associated challenges in its application. Despite numerous implemented projects and considerable developer efforts, sustaining a ship in a specified position during rough seas remains a formidable task, partly due to the ship’s lack of energy armament. Exploration in the realm of regulatory system development has yet to yield the anticipated results. The present study constructs a mathematical model depicting the dynamics of a ship during positioning, considering two versions of automatic control laws aimed at stabilizing the ship’s position. The second model demonstrates superior efficiency in the control system, surpassing the first by at least 14%. A comparative analysis of two control system options with filtering properties in dynamic positioning mode for the vessel was conducted. For better results, it is recommended to implement filtering on the relevant data source before this procedure on a specific data consumer. This preliminary testing helps to remove duplicate and inaccurate data, reducing the load on the data link. Final filtering should be performed on high-performance systems. In summary, the originality and novelty of this article stem from its comparative analysis of control laws, exploration of DP system dynamics, acknowledgment of existing challenges, and practical recommendations for data filtering in dynamic positioning. The study brings a tangible contribution to the field, paving the way for advancements in the development of DP systems management and control methods.

Algorithms for controlling a quadcopter movement in dynamic positioning mode

Algorithms for controlling a quadcopter movement in dynamic positioning mode

Constrained control allocation for dynamic ship positioning using deep neural network

Dynamic positioning (DP) is one of the key technologies towards ship autonomy. Ships in DP mode use thruster devices to maintain position and perform low-speed maneuvering. The motion controller issues force requests according to the measured ship state and motion objectives. These requests must be translated into individual thruster commands. Due to constraints in the thrusters, such as inertia and limited angles of operation, state-of-the-art control allocation methods apply constrained optimization techniques. Although such methods readily capture the handling of constraints, they may require significant computational resources in searching for optimized commands in real time. Here we show that a neural network may be applied to offer an effective evaluation of the mapping between motion controller requests and executable thruster commands. An Autoencoder-like neural network is trained with data generated using knowledge about the configuration of the thrusters. Custom loss functions shape the weights of the network, such that the overall motion objectives and thruster constraints are met. Then, the network is applied to perform low-speed maneuvering and stationkeeping in a simulator. Comparison relative to a state-of-the-art variable angle, constrained control allocator indicate similar dynamic performance with reduced peak power consumption.

Characteristic of hydrodynamic derivatives for a multi-hull navigation vessel in dynamic positioning mode

The Quadmaran vessel is a maritime multi-hull vessel developed for water quality observation in aquaculture farms. The vessel’s dynamic positioning (DP) performance is essential for the accuracy of the collected data. The maneuvering characteristics in DP mode have been investigated in our previous research using a quasi-static motion prediction model based on static planar motion mechanism (PMM) tests. However, since the Quadmaran vessel has a unique hull arrangement, the motion characteristics need to be determined with greater accuracy. Therefore, in this study, the maneuvering equations are newly established with higher accuracy hydrodynamic derivatives determined through dynamic PMM tests. The higher order hydrodynamic derivatives are obtained from pure sway, pure yaw and pure yaw with a constant angle tests. Model scale experiments are conducted to establish an advanced mathematical model and compared with the quasi-static assumption results. The result shows significant improvements in the motion prediction under DP mode, and a more accurate motion prediction model is successfully established. This study is a new attempt to utilize the dynamic PMM tests method on a vessel with unique shape and motion characteristics. The advanced mathematical model deepens our understanding of the maneuverability of a multi-hull vessel in DP mode.

Режим слежения за целью на современных судах, оснащенных системой динамического позиционирования (DP)

The article highlights the results of studying the follow target mode on board the ships equipped with dynamic positioning (DP) systems. There is analyzed the position of a ship in a follow target mode when the DP mode is on, as well as the ability of a ship following a target to hold the position and course under given environmental conditions. Ships equipped with the DP system have strict requirements regarding the parameters of the follow target mode. There are listed the advantages for specific operations: technical servicing the oil and gas fields, examining the pipelines, hydrographic surveys, etc. Functionality of the hydroacoustic reference system, which is the main component of the ship follow target system, is studied. It has been stated that the follow target mode allows the ship to follow the target automatically. In most cases, the target is an unmanned remotely operated vehicle (ROV). ROV is a robot performing specific tasks under water controlled from the ship. ROV support vessels specialize on such operations. The ROV equipment and capabilities depend on the complexity of the task. The simplest tasks are inspection of the pipeline, platform supports, watching divers, visual inspection of an object lowered to the bottom, etc., when ROV is equipped with cameras, searchlights and, occasionally, sonars. To carry out the construction work or maintain the underwater facilities there are needed the servicing ROVs equipped with tools for specific purposes. There has been illustrated a model chart of the ship motion and dislocation of the ROV working area. Connection between ROV and the ship by means of a fiber optic cable is considered in detail, the advantages and disadvantages of this connection are listed. Conclusions are drawn about the widespread use of DP systems on modern ships, in particular those operating in the oil and gas industry, as well as in other areas of marine operations.

A Quasi-Static Motion Prediction Model of a Multi-Hull Navigation Vessel in Dynamic Positioning Mode

A Quadmaran vessel is a maritime navigation vessel with four hulls, and is expected to be utilized for high-density water quality observation in aquaculture farms. The performance of the vessel during dynamic positioning (DP) is integral to the accuracy of collected data. However, there are no models available to understand the motion characteristics of the multi-hull vessels in DP mode. Therefore, a computational model was developed to predict the DP motion of the Quadmaran vessel based on quasi-static assumptions. The fluid forces on the hulls, the thrust force of the propellers, and the external wind forces are modelled systematically, assuming the average speed while in DP does not exceed 0.25 m/s. A series of oblique towing tests and static turning tests were conducted on a 1/3 scale model to determine the hydrodynamic coefficients, while the Propeller Open Test was conducted to survey the propeller performance. The wind load was also incorporated into the computational model. Experimental validation tests were conducted in calm water and actual sea areas, and the correlation between experiment and simulation results was good. We concluded that the computational model can predict the DP motion of the Quadmaran vessel with an accuracy of roughly 2 m.

Automated maneuvering using model-based control as key to autonomous shipping

Abstract The paper discusses methods to increase the level of automation in ship handling towards autonomous operations with a focus on conventional vessels in maneuvering situations. In this context, a model-based approach for control system design of maneuvering vessels is introduced. The resulting model is applied to a multivariable control system including allocation, feedforward, and feedback modules. The established hybrid control system distinguishes between a transit mode with control in two degrees of freedom in compliance with the prevailing traffic regulations and a dynamic positioning mode in three degrees of freedom for the final stages of a berthing maneuver. The supervisor switches automatically between these two modes. The methods are validated on board the German research vessel DENEB in the port of Rostock.

Hydrodynamic Forces of DP Jack-Up Leg when Operating in Vicinity of Seabed

_ Leg placement and removal are the two most critical operational modes for dynamically positioned jack-ups when working close to an offshore asset. Any positional deviation may lead to collision and damage to the asset. The industry operates with a weak link between the dynamic positioning (DP) system and the jacking system. Current DP systems operate without any sensors identifying the hydrodynamic force variations on the legs and spudcans, which vary between different leg and spudcan designs. When the spudcan is near to the sea bottom, the hydrodynamic force must be reported to avoid large positional deviations driven by the DP system. This article promotes a mechanism to measure these forces using Computational Fluid Dynamics (CFD) analysis to analyze the jack-up behavior, when the spudcan assembly is operating close to the sea bottom. Introduction A jack-up’s dynamic positioning (DP) control system requires minimum 23–30 minutes for the mathematical model to learn the vessel’s hydrodynamic behavior and response to the environment. Although when moving between locations, DP jack-up vessels provide time for the DP model to learn the hydrodynamic behavior, the spudcan that holds the vessel position and headings does not allow the mathematical model to learn. The residual current remains constant until the spudcan is in the seabed. As a result, the DP mathematical model-building process does not help the DP system to estimate the additional forces in the form of residual current. Soon after the spudcan detaches from the seabed, the vessel drift occurs because the vessel thrusters’ response need a rapid response of thrust and azimuth (directions). The DP system manufacturers currently use a sensorless approach to account for the hydrodynamic forces on the legs and spudcans to build a factor into the mathematical model. The jack-up DP system addresses two simultaneous forces on the legs. The leg element in the air is subject to aerodynamic effects and the leg and spudcan elements in the water are subject to hydrodynamic effects. DP systems currently use drag coefficients (Cd) to compute drag forces, however the hydrodynamic force variations during the complete lowering and raising processes are never completely considered. This weak link in the overall operation leads to positional error and is generally unrecognized by the vessel operators. The risk falls to DP officer and the jacking master to handle. The DP and jacking simultaneous operations mode (SIMOPS) may easily last between 15 and 90 minutes, depending on jacking speed, operational water depth, and field procedures, on approach to the asset. The area of operation is close to the asset, which increases the risk of collision with the asset. Most of the studies on jack-up vessels focus on impact force acting on the leg during touchdown or penetrations, such as Elkadi et al. (2014) and Kreuzer et al. (2014).

Invasive Sun Coral Species Challenges Decommissioning of Structures Offshore Brazil

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30656, “Decommissioning of Subsea Structures in Brazil: Effect of Invasive Species and Genome Sequence of the Azooxanthellate Coral Tubastraea sp.,” by João Humberto Guandalini Batista, SPE, Repsol; Mauro Rebelo, Universidade Federal do Rio de Janeiro; and Giordano Soares-Souza, SENAI CETIQT, prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4–7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. Decommissioning of offshore assets in Brazil is subject to high levels of uncertainty because of Tubastraea, an invasive species of sun coral. This species has a high capacity for dispersion and recruitment and has been associated with the replacement of native species in rocky shores, exerting a serious effect on native biodiversity. The complete paper explores the biology of the invasive species, aiming to identify methods to eliminate or diminish its spread. The authors write that data generated in this study will foster the development of effective technologies in coral-species management, whether species are invasive or threatened. Introduction Originally from the Coral Triangle in the Pacific Ocean—a highly diverse region with hundreds of coral species—Tubastraea was first observed in the Campos Basin in the 1980s. Tubastraea sp. have high fecundity and growth rates with the ability to reproduce asexually, establishing very dense populations. This fast reproduction allows larvae to outcompete native species in both natural and artificial substrates in the sea. Sun coral is extremely resistant to environmental change. It has been found in shallow waters, sometimes exposed to air, showing tolerance even to short periods of desiccation. Recently, new species have been identified in Brazilian waters, heightening concern over the proliferation of sun coral. In the past, the common understanding was that subspecies coccinea and tagusensis were those found in Brazilian waters. However, recent studies dedicated to the research of the Tubastraea genus raised suspicion of the presence of diaphana and aurea, with the possible occurrence of hybrids as well. The preference of Tubastraea is to live in structures that are static or mostly motionless, such as production platforms, subsea structures, and drilling rigs. This trait has made sun coral a major challenge for the local oil and gas industry. While in the Campos Basin, the main objective is to decrease dispersion of already bioencrusted production units and subsea structures, in the Santos Basin, the goal is to avoid colonization in structures in operation or those scheduled to be installed soon. To further complicate matters, drilling and intervention vessels and rigs are contracted to service both basins. They work in dynamic-positioning mode, stationary around the production units and subsea structures for lengths of time that exceed the reproduction cycle time of the sun coral, allowing larval dispersion.

Development, software implementation, and research of multilink manipulator control system for UUV in dynamic positioning mode above underwater objects

Development, software implementation, and research of multilink manipulator control system for UUV in dynamic positioning mode above underwater objects

Thrusters Physical Model Formalization With Regard to Situational and Identification Factors of Motion Modes

Within the framework of the research of diagnos-tics and prediction of technical state of ship power plants (SPP) of combined propulsion complexes (CPC) depend-ences of correcting factors influencing components of thrusts and moments, proportional dimensions of model and real thrusts (THRs), tied to the original geometry were obtained. This was done by formalizing the physical model of the azimuth thruster with the means of identifying the degradation effects on the flow lines of the propellers by methods of computational hydrodynamics. The technique of improving the structure of the mathematical models of the SPP CPC according to experimental studies by measur-ing the input and output parametric coordinates of the THRs CPC of a vessel operating in the dynamic positioning mode is announced.

Voltage Drop Investigation on Electrical Distribution Systems of AHTS Vessel in Dynamic Positioning Mode

Voltage Drop Investigation on Electrical Distribution Systems of AHTS Vessel in Dynamic Positioning Mode

Data-Driven Methodology for the Analysis of Operational Profile and the Quantification of Electrical Power Variability on Marine Vessels

Measurements from the on-board systems of marine vessels are increasingly available for data analysis and are growing in importance as the ship industry enters a phase of digitalization. The purposes of the data analysis from vessels in operation include the verification of the power system design in general and improvement of the electrical power load analysis in particular. In this paper, we show how to extract valuable information from the data-driven operational profile analysis, which reveals the real power demand, and how the vessel was operated. Using the real power range analysis, we emphasize the significance of rarely occurring high power demands, which are critical for power system design and optimization. We propose a methodology for the quantification of variability in the generated power, which explains the tails of probability distributions of a power signal based on signal decomposition. The proposed methodology makes use of the data and it can facilitate the selection of the optimal size, number, and configuration of generators or batteries when designing new power systems. Measurements from a data collection system are used to demonstrate the methodology for dynamic positioning mode of the operation of a platform supply vessel.

Theoretical-applied aspects of the composition of regression models for combined propulsion complexes based on data of experimental research

Based on the study into internal properties of components of the ship power plants (SPP) in the combined propulsion complexes (CPC) and considering special features in the construction of equations that characterize energy processes in the specific SPP of the particular CPC, we developed the principles of constructing their regression models according to data from experimental research. The function is defined that connects input variables and the output variable based on data of the experiment with the certain number of common observations of the input and output parameters. The check for adequacy of the obtained model was performed according to the experimental data. Such studies are necessary in order to develop specialized software modeling tools that are used when designing CPC SPP whose structure may vary in certain specified operational limits and situational factors. Similar empirical models also make it possible to improve simulation modeling algorithms involving the use of statistical tests and construction of CPC SPP models based on experimental data. As the result of present research, according to data obtained in the course of experiment, which contained 14 joint observations of the input and output parametric coordinates of the thruster drives (TDs) of CPC of the ship that operates under dynamic positioning mode, we estimated variation in the coefficients of regression equation and determined coefficients b 0 =0.4527; b 1 =–0.1126; b 2 =0.0848; b 3 =–0.0277; b 4 =0.0856, which refine the structure of regression model of SPP of CPC. For different levels of significance and degrees of freedom, the Student's t-criterion was computed for significance level α=0.06 and for the number of degrees of freedom 30 f y =30t(0.06; 30)=t(0.06; 2)=4.823, as well as the Fisher’s F-criterion F e (0.06; 12; 2)=5.43, on the basis of which the conclusion was made that confirms adequacy of the obtained model according to the experimental tests. Based on the constructed regression model, it is possible to adjust the position of CPC TD relative to each other and to the diametrical plane of the ship, as well as directions of TD rotation in the process of optimization of parameters of physical models of control systems of TD electric engines.

Estimates of acoustic noise generated by supply vessels working with oil-drilling platforms

The paper presents results on spatial measurements of acoustic noise generated by two types of tugs during their movement near the Molikpaq platform and in a dynamic positioning mode during operation with the PA-B platform. Based on the results of these measurements with the aid of simulation and preliminary research of the loss function conducted on acoustic profiles spanning from the platforms to the nearshore Piltun gray whale summer—fall feeding area, the spectra of equivalent point sources are constructed, which make it possible to construct the 1/3-octave spectra of anthropogenic noise at any point of the western profile and estimate the value of their level in a given frequency band with an accuracy of up to 2 dB. Field measurements have shown that in the dynamic positioning mode, the tugs generate 10 dB more noise than during movement; in fact, a diesel electric tug in both modes produced approximately 5 dB less noise than a diesel tug.

Fast Production Recovery of a Typhoon-Damaged Oil Field in the South China Sea

Summary The Huizhou oil field is located at the Pearl River mouth in the continental-shelf region of the South China Sea, with an average water depth of approximately 117 m. The oil field's main facilities include eight fixed-jacket platforms, two subsea-production wellheads (HZ32-5 and HZ26-1N), and one floating production, storage, and offloading (FPSO) vessel (Nanhai Faxian). Fig. 1 illustrates the general layout of the field. The peak daily oil production is approximately 70,000 BOPD. In September 2009, after a strong typhoon (Koppu) passed over this oil field, the FPSO vessel's permanent mooring system was seriously damaged. All production risers connected to the FPSO vessel's turret were ruptured, and production was forced to shut down. To resume production in a fast-track manner, several engineering cases were studied. Finally, the concept of using a dynamic-positioning (DP) FPSO vessel to temporarily resume production was selected. Detailed design and operability analysis was performed by the owner of the DP-FPSO vessel, and various flexible pipes and other materials were sourced quickly in local and international markets. The offshore installation took place throughout the harsh winter monsoonal season from November 2009 to February 2010. Finally, the field was brought back into production after 5.5 months of production stoppage. The DP-DPSO system operated for more than 18 months and proved safe and effective. This was world record time for an FPSO vessel operated in DP mode.

Optimization of Stabilization Processes of Marine Mobile Object in Dynamic Positioning Mode

Optimization of Stabilization Processes of Marine Mobile Object in Dynamic Positioning Mode

Modelling and Simulation of Variable Speed Thruster Drives with Full-Scale Verification

In this paper considerations about modelling and simulation of variable speed thruster drives are made with comparison to full scale measurements from Varg FPSO. For special purpose vessels with electric propulsion operating in DP (Dynamic Positioning) mode the thruster drives are essential for the vessel operation. Different model strategies of thruster drives are discussed. An advanced thruster drive model with a dynamic motor model and field vector control principle is shown. Simulations are performed with both the advanced model and a simplified model. These are compared with full-scale measurements from Varg FPSO. The simulation results correspond well with the measurements, for both the simplified model and the advanced model.

Modelling and Simulation of Variable Speed Thruster Drives with Full-Scale Verification

In this paper considerations about modelling and simulation of variable speed thruster drives is made with comparison to full scale measurements from Varg FPSO. For special purpose vessels with electric propulsion operating in DP (Dynamic Positioning) mode the thruster drives are essential for the vessel operation. Different model strategies of thruster drives are discussed. An advanced thruster drive model with a dynamic motor model and field vector control principle is shown. Simulations are performed with both the advanced model and a simplified model. These are compared with full-scale measurements from Varg FPSO. The simulation results correspond well with the measurements, for both the simplified model and the advanced model.