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This study investigates the problem of tracking the trajectory of a dynamic positioning (DP) ship under sudden surges of elevated sea states. First, the tracking problem is reformulated as an error calibration problem through the introduction of fully actuated system (FAS) approaches, thereby simplifying controller design. Second, a predefined-time control term is designed to maintain the convergence time of the trajectory tracking error within a specified range; however, the upper bound of the perturbation must be estimated in advance. The high sea state during operation can result in an abrupt change in the upper bound of disturbance, thereby affecting the control accuracy and stability of the system. Therefore, a linear control matrix is developed to eliminate the system’s dependence on the estimation of the upper bound of disturbance following smooth switching, thereby achieving control decoupling and providing a conservative switching time. Additionally, a nonlinear reduced-order expansion observer (RESO) is constructed for feedforward compensation. The stability of the system is demonstrated using the Lyapunov function, indicating that the selection of appropriate poles can theoretically enhance the system’s convergence with greater control accuracy and robustness after switching. Finally, the effectiveness of the proposed method is validated through simulations and comparative experiments.

This work studies the dynamic positioning (DP) control issue of unmanned surface vessels subjected to thruster saturation, error constraints, and lumped disturbances composed of time-varying marine environmental disturbances and model parameter uncertainties. Combining the disturbance-accurate estimation technique and the prescribed performance control strategy, a novel prescribed-time DP control scheme is established to address this challenging problem. In particular, the prescribed-time lumped disturbance observer is designed to accurately estimate external marine disturbances, which guarantees that the estimation error converges to zero within a prescribed time. Subsequently, a prescribed performance control strategy is proposed to guarantee that the positioning errors of DP surface vessels with thruster saturation constraints meet the error constraints requirements within a prescribed time. Furthermore, an anti-windup compensator is presented to mitigate the thruster saturation and improve the robustness of the DP control system. The stability analysis demonstrates that all positioning errors of the closed-loop system can converge to predefined performance constraints within a prescribed time. Finally, the numerical simulation confirms the efficacy and superiority of the proposed PTDP scheme.

The goal of this paper is to establish a motion control system for unmanned surface vehicles (USVs) that enables point-to-point tracking and dynamic positioning. This includes the heading control and path following control of USVs. A hardware and software platform for USVs using microcontrollers is designed. This paper presents the construction of a kinematics and dynamics model for an unmanned catamaran. The motion process is divided into two segments. In the target point tracking segment, the heading coordinate system and the ship coordinate system are established. Based on these, a control method using differential steering to track the desired yaw angle is designed to improve the tracking efficiency. And the accuracy of heading keeping and path following is improved by combining the cascade PID controller. In the dynamic positioning segment, a self-adjusting mechanism is designed, thereby enhancing the flexibility of thrust distribution and improving the accuracy of the USV’s positioning retention in wind and wave environments. Finally, experimental validation is carried out to verify the effectiveness of the design proposed in this paper by issuing control commands and saving the return data through the upper computer, and then analyzing the return data with MATLAB (R2022b, MathWorks, Natick, MA, USA).

Increased application of technical cybernetics- and control engineering have been considerable since the late 1960s. The driving forces have been many, such as improvements/pioneering in defense and space technology, maritime- and oil production technology, robotics and industrial control, enabled by a huge increase in available computing power. I have been involved in this development for the last 50 years. This paper sums up my work within areas such as mathematical modelling for control and estimation, Kalman filtering, and the development of software, simulators and applications for such purposes. During these years I worked, as examples, within the fields of ocean modelling for real-time estimation, oil production, dynamic positioning and industrial control in the fields of fertilizers, and aluminum production. The stories of starting up the company Prediktor and the following development of Manufacturing Execution Systems (MES systems) and my engagement in the use of optical NIR based technology for industrial control in various industries are told. My hope is that the story might be of interest to younger engineers today to understand the development in this engineering cybernetics field for 50 years as exemplified by my career.

The article presents an efficient method of optimal thrust allocation over the actuators in a dynamically positioned ship, according to the DNV-ST-0111 standard, Level 1. The optimisation task is approximated to a convex problem with linear constraints and mathematically formulated as quadratic programming. The case study is being used to illustrate the use of the proposed approach in assessing the DP capability of a rescue ship. The quadratic programming-based approach applied for dynamic positioning capability assessment allows for fast calculations to qualitatively compare different ship designs. In comparison with the DNV tool, it gives 100% successful validation for a ship with azimuth thrusters and a pessimistic solution for a ship equipped with propellers with rudders. Therefore, it can be safely applied at an early design stage.

Ship retrofitting is one alternative solution to extend a ship’s life. Several component replacements were performed in the retrofitting process, remodelings to the ship’s main dimension, and state-of-the-art equipment and technology were added. As one of the ships that require regular renewal, especially in research equipment, retrofit processes are often carried out on research vessels. The current problem in the retrofit process for research vessels, especially in Indonesia, is that retrofits are not carried out with established methodology and planning. Thus, some retrofit projects are limited to major repairs and do not extend the ship’s life or performance. To solve that problem, a developed methodology for ship retrofitting was proposed, which consists of selecting the ship and the type of retrofit and its components, determining retrofit requirements, and designing the ship based on the retrofit project. In the design process, a modified spiral design is explicitly used for the retrofit process with some alterations compared with the conventional one, which is focused on analyzing the suitability and availability of space, consumable and tank requirements, analysis of power requirements, risk analysis, and project execution plan. A case study of this developed methodology has been undertaken in the concept design phase of RV Baruna Jaya 1’s retrofit, and the results show that the methodology is considered helpful as an approach for ship retrofitting. Moreover, several considerations were also obtained from the concept design stage and had to be analyzed at the following design stage to meet the retrofit design requirements.

Thrust allocation (TA) plays a critical role in the dynamic positioning system (DPS). The task of TA is to allocate the rotational speed and angle of each thruster to generate the generalized control forces. Most studies take TA as a single-objective optimization problem; however, TA is a multi-objective optimization problem (MOP), which needs to satisfy multiple conflicting allocation objectives simultaneously. This study proposes an improved multi-objective particle swarm optimization (IMOPSO) method to deal with the non-convex MOP of TA. The objective functions of reducing the allocation error, and minimizing the power consumption and the tear-and-wear of thrusters under physical constraints, are established and solved via MOPSO. To enhance the global seeking ability, the improved mutation strategy combined with the roulette wheel mechanism is adopted. It is shown through test data that IMOPSO converges better than multi-objective algorithms such as MOPSO and nondominated sorting genetic algorithm II (NSGA-II). Simulations are conducted for a DP ship with two propeller–rudder combinations. The simulation results with the single-objective PSO algorithm show that the proposed IMOPSO algorithm reduces thrust allocation errors in the three directions of surge, sway, and yaw by 48.48%, 39.64%, and 15.02%, respectively, and reduces power consumption by 44.53%, which demonstrates the feasibility and effectiveness of the proposed method.

As a substitute for human arms, underwater vehicle dual-manipulator systems (UVDMSs) have attracted the interest of global researchers. Visual servoing is an important tool for the positioning and tracking control of UVDMSs. In this paper, a reinforcement-learning-based adaptive control strategy for the UVDMS visual servo, considering the model uncertainties, is proposed. Initially, the kinematic control is designed by developing a hybrid visual servo approach using the information from multi-cameras. The command velocity of the whole system is produced through a task priority method. Then, the reinforcement-learning-based velocity tracking control is developed with a dynamic inversion approach. The hybrid visual servoing uses sensors equipped with UVDMSs while requiring fewer image features. Model uncertainties of the coupled nonlinear system are compensated by the actor–critic neural network for better control performances. Moreover, the stability analysis using the Lyapunov theory proves that the system error is ultimately uniformly bounded (UUB). At last, the simulation shows that the proposed control strategy performs well in the task of dynamical positioning.

Dynamic positioning systems ensure additional position accuracy in different operations in the maritime industry, such as shuttling, drilling, diving, pipe laying, and others. Although they are known to be robust systems, they are not exempt from failures leading to incidents, among which we can find human-related incidents. This research analyzes 62 human-related dynamic-positioning incidents and aims to determine which segment in the dynamic positioning system influences these occurrences by applying binary logistic regression modeling techniques in the test sample and validating the results using a control sample. The results indicate that thrusters have the most significant influence on human-related incidents; however, not all DP operations are affected in the same measure. By stratifying the database and considering the different operations in progress, it is noted that human-related incidents while drilling operations are in progress are effectively influenced using a higher percentage of thrusters online.

Real-time acquisition of location information for agricultural robotic systems is a prerequisite for achieving high-precision intelligent navigation. This paper proposes a data filtering and combined positioning method, and establishes an active screening model. The dynamic and static positioning drift points of the carrier are eliminated or replaced, reducing the complexity of the original Global Navigation Satellite System (GNSS) output data in the positioning system. Compared with the traditional Kalman filter combined positioning method, the proposed active filtering–Kalman filter algorithm can reduce the maximum distance deviation of the carrier along a straight line from 0.145 m to 0.055 m and along a curve from 0.184 m to 0.0640 m. This study focuses on agricultural robot positioning technology, which has an important influence on the development of smart agriculture.

The development of dynamic positioning (DP) algorithms for an unmanned surface vehicle (USV) is attracting great interest, especially in support of complex missions such as sea rescue. In order to improve the simplicity of the algorithm, a DP algorithm based on its own path following control ability is proposed. The algorithm divides the DP problem into two parts: path generation and path following. The key contribution is that the DP ability can be realized only by designing the path generation method, rather than a whole complex independent DP controller. This saves the computing power of the USV onboard computer and can effectively reduce the complexity of the algorithm. In addition, the fixed-time LOS guidance law is designed to improve the convergence rate of the system state in path-following control. The reasonable selection of speed and a heading controller ensures that the number of design parameters to be determined is at a low level. The above algorithms have been thoroughly evaluated and validated through extensive computer simulations, demonstrating their effectiveness in simulated and real marine environments. The simulation results verify the ability of the proposed algorithm to realize the dynamic positioning of USVs, and provide a practical scheme for the design of the dynamic positioning controller of USVs.

How does a vessel keep its position at sea without mooring? The answer is through dynamic positioning, or DP. Advanced technology, combining position reference sensors, computers, propellers and thrusters, is used to counteract environmental forces such as wind, currents and waves to dynamically position the vessel without using anchors or mooring lines. Today, DP systems are found in every ocean region in the world. The Kongsberg DP adventure began in 1975 when Kongsberg Våpenfabrikk signed its first contract. Eighteen months later, an Albatross DP system was installed on board a Norwegian diving vessel in the North Sea. Today, dynamic positioning equipment from the inland town of Kongsberg is found onboard a myriad of ship types including supply vessels, drilling rigs, pipe and cable layers, stone-dumping and bulk vessels, shuttle tankers, crane and lifting vessels, mine hunting vessels, cruise ships, floating hotels and yachts. Dynamic positioning is not limited to keeping a vessel on a fixed location but also to controlling the motions of vessels along predetermined tracks. After over 40 years in business, Kongsberg Maritime still maintains a world-leading position within dynamic positioning. This paper is based on the book “The Jewel in the Crown: Kongsberg Dynamic Positioning Systems 1975 – 2015”, (Kvaal and Østby, 2015).

In this paper, various modern model based optimal control methods (as well as one model-free or data-driven) are applied to the dynamical positioning problem of vessels, i.e. we seek to control the surge, sway and yaw motion, using the thrusters and propellers, subject to environmental disturbances, i.e. wind and current. The low-frequency part of Balchen's nonlinear vessel model is selected for these tests.

In this paper, we present a novel nonlinear model predictive control (NMPC) algorithm based on the Laguerre function for dynamic positioning ships to solve the problems of input saturation, unknown time-varying disturbances, and heavy computation. The nonlinear model of a dynamic positioning ship is presented as a linear model, transformed from a standard affine nonlinear state-space model by precise feedback linearization. The environmental disturbance is overcome using an integrator. The time cost of the proposed nonlinear control algorithm is decreased by inducing the Laguerre function to describe the feedback-linearization system input increments. The Laguerre function reduces the matrix dimensions of the nonlinear optimization problem. The simulation results for a DP supply vessel showed that the novel algorithm maintained the effective control performance of the original nonlinear model predictive control algorithm and had a reduced computation load to satisfy the requirements of real-time operation.

This paper surveys the recent advances in dynamic positioning (DP) control for marine crafts. DP of marine crafts means that a craft can maintain a fixed position and heading, or move along a predetermined trajectory slowly without the anchoring system, using only its own thruster system to counteract ocean disturbances. The survey is by no means exhaustive but provides a survey of some of the major technological advancements in DP controller design over the years of research and development. Firstly, the model of marine crafts and some difficult problems in DP control are introduced including the impact of multiple source disturbance, unavailable velocity measurement information, resource conservation and performance optimization, destabilizing impact of faults and network security and compound multi-constraint restrictions. Then, the DP control schemes in recent years are summarized and classified in detail. Finally, some theoretical and technical problems are proposed, including online data-driven model-free control, man–machine combination intelligent control and composite hierarchical anti-disturbance control to guide future investigations.

This work addresses the motion control problem for a 4-degree-of-freedom unmanned underwater vehicle (UUV) in the presence of nonlinear dynamics, parametric uncertainties, system constraints, and time-varying external disturbances. A disturbance observer-based control scheme is proposed, which is structured around the model predictive control (MPC) method integrated with an extended active observer (EAOB). Compared to the conventional disturbance observer, the developed EAOB has the ability to handle both external disturbances and system/measurement noises simultaneously. The EAOB leverages a combination of sensor measurements and a system dynamic model to estimate disturbances in real-time, which allows continuous estimation and compensation of time-varying disturbances back to the controller. The proposed disturbance observer-based MPC is implemented by feeding the estimated disturbances back into the MPC’s prediction model, which forms an effective adaptive controller with a parameter-varying model. The proposed control strategy is validated through simulations in a Gazebo and robot operating system environment. The results show that the proposed method can effectively reject unpredictable disturbances and improve the UUV’s control performance.

Cargo transfer vessels (CTVs) are designed to transfer cargo from a floating production storage and offloading (FPSO) unit into conventional tankers. The dynamic positioning system allows the CTV to maintain a safe position relative to the FPSO unit using a flexible cargo transmission pipe, and the CTV tows the tanker during operating conditions. The operation mode can be considered a synchronization tracking control problem. In this paper, a synchronization control strategy is presented based on the virtual leader–follower configuration and an adaptive backstepping control method. The position and heading of the following vessel are proven to be able to globally exponentially converge to the virtual ship by the contraction theorem. Then, the optimization problem of the desired thrust command from the controller is solved through an improved firefly algorithm, which fully considers the physical characteristics of the azimuth thruster and the thrust forbidden zone caused by hydrodynamic interference. To validate the effectiveness of the presented synchronous following strategy and thrust allocation algorithm, a scale model experiment is carried out under a sea state of 4 in a seakeeping basin. The experimental results show that the CTV can effectively maintain a safe distance of 100 m with a maximum deviation of 3.78 m and an average deviation of only 0.99 m in the wave heading 180°, which effectively verifies that the control strategy proposed in this paper can achieve safe and cooperative operation between the CTV and the FPSO unit. To verify the advantages of the SAF algorithm in the thrust allocation, the SQP algorithm and PSO algorithm are used to compare the experimental results. The SAF algorithm outperforms the SQP and PSO algorithms in longitudinal and lateral forces, with the R-squared (R2) values of 0.9996 (yaw moment), 0.9878 (sway force), and 0.9596 (surge force) for the actual thrusts and control commands in the wave heading 180°. The experimental results can provide technical support to improve the safe operation of CTVs.

THE PURPOSE. Consider the use of special purpose vessels with a dynamic positioning system. To conduct observations and research of the operation of electrical power systems of such vessels for the existence of problems in them that affect the performance of technological operations. To propose methods and means aimed at eliminating situations and processes that adversely affect the operation of shipboard electrical power systems when laying pipelines.METHODS. For observation and research, the unified electrical power systems with electric rudder propellers and a system for laying an underwater pipeline of the "Seven Vega" cable layer was considered. Collected information on all the main electrical systems of the vessel "Seven Vega". Experimental studies were carried out aimed at studying the operating modes of the electrical power system during the laying of pipelines.RESULTS. Experimental oscillograms of currents of parallel operating diesel-generator sets in different modes have been obtained. The existence of power exchange oscillations during the operation of the unified electric power system of the cable-laying ship “Seven Vega” is noted. The data on the negative influence of power oscillations on the operation of tensioners during the laying of underwater pipelines were obtained.CONCLUSION. The use of sea-going vessels with dynamic positioning for laying pipelines and performing oil and gas production operations requires ensuring the operation of their electrical power systems. To ensure the high-quality operation of tensioners in pipeline laying systems, it is necessary to ensure the adjustment of their regulators and to exclude the occurrence of power exchange oscillations during parallel operation of generator sets.

This work is devoted to the formation of dynamic positioning system for autonomous underwater vehicle with multipurpose structure. Such vehicles are applied to oceanographic research and bottom exploration. To dock with an underwater station or obtain more accurate information about the bottom, it is necessary to stabilize the vehicle at a given point in space, in other words, position the device. The problem of dynamic positioning is one of the primary control problems of marine objects. Numerous solutions to this issue have been presented for vessels. Fewer results were obtained for underwater vehicles due to a rather complex mathematical model. However, simplifications of the dynamic equation are possible in the case of positioning in shallow water, which make it possible to apply existing approaches to vessel control for underwater vehicles. The purpose of this work is to enhance the control system with multipurpose structure obtained on the basis of the separation principle by introducing into the control law an additional term. The resulting system consists of the observer, which restores the speed components of the vehicle’s movement and clears measurements of noise, and the controller, which positions the vehicle in a given position, provides the integral action of the closed-loop system and the economical mode of operation of the actuators. The integral action allows us to eliminate the deviation of the vehicle from the desired position when exposed to a constant disturbance (underwater and wind currents). Economical mode of control components makes it possible to lower their wear and reduce overall fuel consumption. A simulation is run in Simulink to illustrate the effectiveness of the obtained system.

In this paper, different power balance control methods for hybrid marine vessels are analyzed. First, the power grid of a marine vessel is modeled using MATLAB and Simulink. Simulations are then performed using real power plant load data captured from an actual vessel. Isochronous control is used to control the power of the diesel gensets, and different control methods, such as isochronous control and average load power estimation, are used for the battery energy storage system. The system is simulated with different control parameters, and the effects of parameter changes are presented. It is shown that these presented control schemes can be adapted to manage the energy balance in a hybrid vessel, thereby enabling efficient use of the battery energy storage system. A diesel genset and battery energy storage system failure during a dynamic positioning operation is also simulated, and the effect of the failure on the frequency of the power grid of the vessel is presented.

Solving time-varying linear equation and inequality (TVLEI) problem has attracted extensive attention in numerous scientific and engineered fields. In this article, it is basically considered that the commonly used dynamics neural network in the virtual environment is inevitably interfered with by the variable measurement noises while dealing with the TVLEI problem. An adaptive enhanced and noise-suppressing zeroing neural network (AENSZNN) model is proposed as an improved algorithm for solving the TVLEI problem. An adaptive scale factor based on the residual error norm is designed to make the proposed AENSZNN model converge to the theoretical solution faster. Furthermore, the momentum enhancement terms added to the model enables the AENSZNN model to effectively solve the TVLEI problem in real-time under the obstruction of different measurement noises. Besides, theoretical results and numerical experiments indicate that the AENSZNN model has advantages in convergence accuracy and robustness to noises compared with the existing algorithms. Note that, the proposed AENSZNN model is successfully exploited for the estimation of mobile object localization.

Many offshore projects, such as offshore oil and gas exploration and offshore wind farm development, have required controlling the position of elevating the hull in a stable and balanced manner in recent years. The Jack-up Rig (JuR) jacking control systems are a revolutionary innovation that is already being employed in offshore drilling and other maritime structures. The system is utilized automatically to control and stabilize the position of the JuR during sea state disturbances to keep platforms from being displaced. As a result, developing an improved control theory for the Jacking system (JS) of a JuR is very important. In this paper, first, we investigate how to adapt to the effects of external forces and hydrodynamic amplification using a particle swarm optimization strategy based on a fuzzy controller. Then, using the fuzzy controller as the foundation, we proposed the PSO - Self Adaptive Fuzzy Controller (PSO-SAFC) guaranteed by Lyapunov criteria and compares it with other fuzzy-based algorithms to show the benefit of adaptively and stability of the system. To verify the proposed algorithm, embedded STM32F746VG central processor used to build the algorithm and run Simulink models on Matlab, the collected data on the positions of the legs and the tilt compared it to the setting command values to move the Rig body and provided control signals to the Drive system. Eventually, the advantages of the proposed approach are demonstrated by the simulation and experiment outcomes.

Installation of jacket platforms requires simultaneous and combined operations of multiple assets. Once the whole process has to be planned, it is necessary to predict in a fast and reliable way the possible weather limitations that may occur during the operations. The paper will present the major challenges of this unusual and innovative Dynamic Positioning analysis which has been carried out for Ana Jacket installation. The obtained results show that the Dynamic Positioning system of the core vessel in intact configuration is capable to hold the position for the investigated vessels' arrangements and design operative weather conditions. Lifting, upending and installation of Ana Jacket were carried out successfully in 2021.

Visual-based positioning technology plays a pivotal role in spatial artificial intelligence, facilitating precise perception and comprehension of the physical world for robotic platforms and augmented reality devices. In this study, we propose a binocular camera-based method for spatial localization of targets using CNN for instance segmentation while simultaneously providing target location information. The method encompasses image acquisition and correction, target recognition and segmentation, and stereo matching, among other components. Building upon this foundation, we introduce a pedestrian recognition segmentation network model with an attention mechanism. To accurately locate the target, we employ a multi-feature fusion feature point extraction and matching algorithm that combines edge information with semantic information. Finally, our proposed method is evaluated for dynamic pedestrian targets in indoor environments, achieving a horizontal positioning error of less than 0.25 m.

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel’s dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

Planar type docking enables a convenient underwater energy supply for irregularly shaped autonomous underwater vehicles (AUVs), but the corresponding control method is still challenging. Conventional control methods for torpedo-shaped AUVs are not suitable for planar type docking due to the significant differences in system structures and motion characteristics. This paper proposes a two-step adaptive control method to solve the planar type docking problem. The method makes a seamless combination of horizontal dynamic positioning and visual servo docking considering ocean current disturbance. The current disturbance is estimated and canceled in the pre-docking step using a current observer, and the positioning error is further compensated for by the vertical visual servo technique in the docking step. Reduced order dynamic models are distinctively established for different docking steps according to the motion characteristics, based on which the dynamic controllers are designed considering the model parameter uncertainties. Simulation is conducted with an initial distance of 10 m in the horizontal direction and 3 m in depth. Stable and accurate dynamic positioning under up to 0.4 m/s of current disturbances with different directions is validated. A 0.5 m lateral positioning error is successfully compensated for by the visual servo docking step. The proposed control method provides a valuable reference for similar types of docking application.

Nowadays, many maritime structures require precise dynamic positioning (DP) of the constructive elements that compose them. In addition, the use of preconstructed elements that are later moved to the final location has become widespread. These operations have not been automated with the risks involved in carrying out the complex operations required. To minimize these operational risks and to perform a correct DP of floating structures, a new approach based on the L1 adaptive control technique is proposed. As an example of application, a proposed L1 adaptive controller was implemented in the dynamic positioning of a floating caisson. Several simulations of the system with wave disturbances were carried out, and the results were compared with those obtained by applying other classical and advanced control techniques, such as linear quadratic Gaussian control (LQG) and model predictive control (MPC). It was concluded that the proposed L1 adaptive controller performs correct dynamic positioning and reduces the tension generated on the lines concerning the other advanced control techniques with which it was compared. This reduction in line tension leads to an important improvement due to the possibility of reducing the size of the actuators or reducing their number, with the important economic and safety repercussions that these actions entail.

In recent years, for many offshore projects, including offshore oil and gas exploration and offshore wind farm construction, it is necessary to control the position of elevating of Jack-up Rig (JuR) in stable and balanced control. Designing the elevating control systems of JuR is an upcoming technology, which is extensively used in offshore drilling and other marine structures. To maintain the position of platforms from displacement, the jacking system is used automatically to control and stabilize the position of the JuR in sea state disturbances. In recent years, the theory of modern control has been studied and developed in terms of robustness and stability to achieve greater accuracy and reduce the movement of the platform caused by environmental disturbance and other affecting factors. This paper presents a state-of-the-art review of approaches for JuR control strategies and architectures. In addition, it recommends possible control principles and makes a matching between the advantages and disadvantages of existing literature. Some details for future research on control challenges are discussed in this paper.

[Objectives] To solve the issue of thrust loss caused by the interaction between the ship thrusters and the excessive power fluctuation in the power system, an improved A success-history adaptive differential evolution(SHADE)algorithm is proposed.[Methods] A multivariable optimization problem is established,which takes the power consumption of the propulsion system as the objective function,the thrust and the directional angle of the thruster as the control variables,and the change rate of the thrust and the directional angle of the thruster as the constraint conditions. For the traditional SHADE algorithm, an improved SHADE algorithm based on the degree of iteration is proposed to solve the thrust distribution optimization issue. The simulation results of the traditional SHADE algorithm and the improved SHADE algorithm are compared.[Results] The simulation results show that under the same simulation environment,the error between the actual thrust torque instruction obtained by the traditional SHADE algorithm and the desired thrust torque instruction generated by the dynamic positioning controller is large,and the power of the thruster fluctuates greatly;while the improved SHADE algorithm can control the torque command error of the expected thrust and the actual thrust within a small range,in which the surge and the sway error is within ±5×10-5 kN,and the yaw error is within ±3×10-5 kN·m.[Conclusions] The improved SHADE algorithm can transfer the dynamic positioning command controller more accurately under the action of environmental disturbance, to solve the problem of ship power system thrust distribution,and lay the foundation for how to use the thrust distribution to maintain the stability of the ship's power system.

[Objectives] In order to improve the positioning ability of the semi-submersible platforms under different sea conditions,three optimal thrust allocation modes based on genetic algorithm were proposed for their dynamic positioning system.[Methods] By analyzing the influence of different items in the objective function on system power,propeller wear and thrust error,the weight coefficients of the thrust angle and relaxation matrix were determined. Then a limited selection method was proposed to reduce the thrust loss,and the hydrodynamic interference between the propellers was avoided by the method of setting the upstream propellers to be prohibited from entering the thrust forbidden zone. Finally, the three proposed strategies were used for the simulation under complex and variable sea conditions.[Results] The results show that the limited selection method can effectively reduce the energy consumption,propeller wear and thrust error;the proposed thrust allocation strategy is effective under complex sea conditions.[Conclusions] The proposed method and strategies can provide ideas and references for the design of dynamic positioning system to a certain extent.

The paper is devoted to the problem of multi-purpose control law synthesis for marine vessels, which are controlled by a dynamic positioning system under sea wave disturbance. The proposed approach is based on a special control law structure constructed using nonlinear asymptotic observers, that allows decoupling of synthesis into simpler particular optimisation problems. The designed dynamic of a closed-loop system provides an economical mode of vessel motion by reducing general fuel consumption and preventing the wearing down of actuators. The actual value of the external disturbance main frequency is estimated online and used for dynamical corrector tuning. Applicability and efficacy of this approach are illustrated by the practical example of DP system synthesis.

Objectives In order to make the dynamic positioning of azimuth thrusters respond to external environmental forces in time, avoid the large-scale rotation of the thrusters and achieve high precision dynamic fixed-point positioning control, research on the optimal workspace of azimuth thrusters is carried out. Methods Taking the dynamic positioning self-driven model with two azimuth thrusters and a lateral thruster as the research object, the problem of the current thrust allocation singularity optimization index is analyzed, and the thrust limits of the thrusters are further considered. The method of traversing the thrust and azimuth of the thruster to establish the axial maximum capability matrix is applied. According to the external environmental force mean and variance, the minimum axial capability requirements are calculated, the optimal workspaces of the thrusters in different external environments are determined by combining the prohibition angle, and a new thrust allocation logic framework is proposed. The fixed-point positioning experiment of a dynamic positioning ship model based on the traditional singularity index and optimal workspace is carried out. Results The experimental results show that the proposed method can overcome the shortcomings of the previous singularity index and achieve control accuracy of 0.1 m radius position and 0.5 degree direction control accuracy under the propeller azimuth within the range of fifty degrees.Conclusions This method can replace the singularity index; it also satisfies the requirements of the ship model dynamic positioning experiment and has certain practical engineering value.

This paper investigates a fault-tolerant control problem for the dynamic positioning of unmanned marine vehicles based on a Takagi–Sugeno (T-S) fuzzy model using an integral sliding mode scheme. First, the T-S fuzzy model of an unmanned marine vehicle is established by taking the yaw angle variable range into account. An integral sliding mode control scheme combined with the H∞ performance index is then developed to attenuate the initial influence of thruster faults and ocean disturbances. The unknown nonlinear function is approximated using a fuzzy logic system based on a representation of marine data, which provides a good tradeoff between resolution of the unknown nonlinear term approximation and computational complexity for marine engineering by adjusting the number of fuzzy logic system rules. In addition, the fault estimation information is utilized to design the sliding mode surface on the basis of an adaptive mechanism and a matrix full rank decomposition technique, which reduces conservatism. The validity of the proposed approach is finally demonstrated by an analysis of simulation results using a typical floating production vessel model.

Trajectory tracking is a fundamental task of the dynamic positioning (DP) system. This paper studies the problem of trajectory tracking of DP ships constrained by control inputs under environmental disturbances. To solve this problem, we develop a novel anti-disturbance Lyapunov-based model predictive control (ADLMPC) scheme. Firstly, an extended state observer (ESO) is designed to estimate environmental disturbances. By combining the ESO with Lyapunov-based model predictive control, the ADLMPC scheme is devised. Secondly, a virtual controller which satisfies input constraints is developed by backstepping and the auxiliary dynamic system, and it is integrated into the Lyapunov contraction constraint in ADLMPC. We show that if the parameters for the virtual controller are appropriately determined, the recursive feasibility of ADLMPC is theoretically guaranteed, and the uniform ultimate boundedness of all signals in the trajectory tracking control system is achieved. Finally, the simulation results display the efficacy and superiorities of the ADLMPC scheme.

The pseudo-inverse method cannot optimize the angle and needs to give the azimuth angle artificially, therefore, when the dynamic positioning system has variable vector propellers and rudders, the pseudo-inverse method cannot be applied to the full automatic control and cannot realize the optimal exactly. In this paper, in view of the above problems, considering the propeller and the environment load conditions, a thrust allocation scheme based on the pseudo inverse algorithm with weight is proposed for minimizing the energy consumption. The thrust allocation scheme distributes the thrust after optimizing the angle. It combines the full-revolving propulsion angle optimization with the thrust optimization to realize the ship thrust allocation reasonably and efficiently and achieves the minimum energy consumption and wear. Finally, the experimental results verify the effectiveness of the proposed method.

In this article, combinations of linear and nonlinear feedback terms are investigated for 3 degrees-of-freedom pose and velocity control of ships. Nonlinear control algorithms that are found in the literature often have linear feedback terms, which result in nice globally exponential stability properties when assuming no actuator constraints. However, considering that all actuators have saturation constraints, such stability properties are not feasible in practice. Applying nonlinear feedback terms can be a step to handle such constraints. As a result, this article explores nonlinear feedback terms for both the kinematic and kinetic control loops. Specifically, three controllers based on a cascaded backstepping control design are implemented and compared through simulations and model-scale experiments in an ocean basin. Stability properties and tuning rules for all the controllers are also provided. Interestingly, the use of nonlinear feedback terms gives the ability to constrain the feedback control inputs globally while simultaneously being able to change the convergence rates locally. The price to be paid is the introduction of additional tuning parameters. The three controller types are compared using performance metrics which consider both control accuracy and energy use.

Offshore operations have been moving towards ultra-deep waters where rich resources are detected and mined in a challenging environment. Dynamic Positioning (DP) control remains a challenge due to time delay in the input control and unknown wave or wind disturbance. In this paper, robust control is proposed for the DP of an accommodation vessel in the presence of the input time delay. In order to overcome the unknown dynamics and external disturbances, a robust controller with predefined tracking constraints is developed to guarantee a safe operation. Time delay caused by the control input is also considered on the predictor-based method. The boundedness of all closed-loop signals is demonstrated via rigorous Lyapunov analysis. Simulation studies help demonstrate outstanding performance and feasibility of the proposed control structure.

In this paper, a control system is designed for dynamic positioning of an ROV with unknown dynamics, subject to external disturbances using passive arm measurements. To estimate uncertain dynamics and external disturbances, a new method based on time delay estimation (TDE) is proposed. The proposed TDE, not only maintains the advantages of conventional TDE, but also eliminates its sensitivity to sensor noise and fast-varying external disturbances which in turn, results in smooth control signal. The proposed control system is considered as a nonlinear PD-type controller together with feedforward of estimated dynamics and disturbances. This structure presents good performance against uncertainties and external disturbances which is guaranteed via stability analysis presented. To evaluate the performance of proposed TDE, simulations are conducted and comparison are made with conventional TDE. Besides, the performance of the proposed control system is compared with conventional time delay controller (TDC) and PID controller to verify its performance. Simulations show high accuracy and superior performance of the proposed control system.

The coupling effect between the offshore platform and the riser in the offshore platform-riser multi-body system might be greatly increased under heavy external maritime stresses. The system will become significantly more nonlinear. The partial secondary development of OrcaFlex is carried out considering the strong non-linearity of the dynamic positioning (DP) offshore platform-riser multi-body system, combined with the actual offshore construction engineering background and the lumped mass method, based on Python-language embedded programming with the basis of the operation principle of the application program interface (API) and the composition of its modules. To regulate the dynamic positioning of the offshore platform-riser multi-body coupling system, a UKF-PID control approach based on an unscented Kalman filter is presented. Based on the procedures described above, a classical calculation model is created, and the model’s calculation results are compared to those of relevant references, confirming the method’s validity and viability. Finally, the model of the PID-controlled dynamic positioning offshore platform-riser rigid–flexible multi-body system is developed, and a dynamic simulation is performed under specified sea conditions. The findings have implications for engineering practice.

Focusing on dynamic positioning (DP) systems for ships, which are subject to environmental disturbances and actuator constraints, this paper presents a finite-time controller that uses a disturbance observer with the aid of a backstepping technique. First, to estimate the time-varying and unknown environmental disturbances in finite time, two sliding-mode disturbance observers are constructed. Specifically, an adaptive disturbance observer (ADO) effectively decreases undesired chattering without the need for prior information on environmental disturbances. Then, to handle the actuator constraints, the designed control forces are distributed into multiple actuators using a control allocation algorithm to obtain the actual forces. Next, an auxiliary dynamic system is built to compensate for velocity tracking errors induced by the mismatch of the DP control law and thruster forces. Then, with the designed ADO and the auxiliary dynamic system, a finite-time controller with a fast exponential-reaching law is designed; this ensures that the positioning errors and the sliding surface converge to zero at a fast convergence rate. Finally, numerical simulations are presented: these present a cable-laying ship experiencing wind, currents, and waves in different sea states. The results show the effectiveness of the presented control scheme.

In this study, the robust fuzzy observer-based control scheme for the dynamic positioning of marine vessels is presented. The proposed controller assumes that the environmental disturbances are unknown but bounded with known upper limit. First, the authors apply the Takagi–Sugeno fuzzy model to approximate the ship model. Using formulated fuzzy model, the robust fuzzy observer is developed to approximate the unknown states. Then, by employing optimal [inline-formula] disturbance attenuation technique, the effects of the environmental disturbances can be attenuated to least value. Finally, the linear matrix inequality technique is hired for solving the optimal robust problem. Model ship is used for simulation, and results are given to prove the validity of the presented controller.

The IEC 62065 is the standard with operational requirements, methods of testing and the required test data for tracking systems and the systems of automatic control used in sea navigation. Mathematical modeling in these systems is used to create control algorithms with a proactive effect on the monitored values such as heading of ship and coordination of her location. These algorithms instantly compensate influence of the external environment, unlike systems with management algorithm based on PID-regulation. This way of mathematical modeling in IEC62065 is true only for vessels with standard propulsion and steering complex, i. e. a complex with a single-shaft screw vessel with a rudder located along a screw axis. The way of transforming the mathematical model of the moving ship according to IEC 62065 standard for vessels with a nonstandard propulsion and steering complex has been considered. As an example for transformation the vessel with two azimuthal thrusters and the nasal bow-thruster has been used. Such complete set is characteristic of supply vessels, tows and various vessels using the dynamic positioning. Using the principle offered in the paper it is possible to transform the model for the vessel with any propulsion and steering complex type. The important feature of the model is the absence of the need for hydrodynamic calculations in favor of the values received during trial runs and the analysis of maneuver "circulation". The flowchart of the initial and final models has been given explaining the differences and necessary transformations, as well as the diagram of the maneuver "circulation" and speed schedules for MIBSV "Vitus Bering" from SCF co. Ltd. with the analysis of the received error.

Due to the ship dynamic positioning control system is a complex nonlinear system, the conventional PID parameters are difficult to achieve the desired control effect, and the immune electromagnetism-like mechanism(IEM) algorithm is proposed for PID controller parameter self-tuning. In view of the weakness that the electromagnetism-like mechanism(EM) algorithm is easy to fall into the local optimum, the immune information processing mechanism is introduced, and the unique concentration selection mechanism is used to preserve the fine and the particles are close to the optimal position by the immune operator. The performance analysis shows that the IEM algorithm has better stability and better convergence in the self-tuning of PID parameters compared to EM and PSO algorithm. Finally, the position and bow of DP four stage sea condition model are simulated. The simulation results show that compared with the conventional PID controller, the PID controller solved by IEM method has faster response, better stability and smaller steady-state error.

A stable adaptive control scheme for multi-point mooring system (MPMS) with uncertain dynamics is proposed in this paper. The control scheme is designed by a hybrid controller based on RBF (Radial Basis Function) NN (Neural Network) and SMC (Sliding Mode Control), which learns the MPMS dynamic changes, and the compensation of external disturbances is realized through adaptive RBFNN control. Meanwhile the RBF-SMC control parameters are adapted by the Lyapunov method to minimize squares dynamic positioning (DP) error. The convergence of the hybrid controller is proved theoretically, and the proposed mooring control scheme is applied to the “Kantan3” mooring simulation system. Finally, the simulation results are compared with the traditional PID controller and standard RBF controller to demonstrate the effective mooring positioning performance of the control scheme for the MPMS.

In this paper, an output feedback fault-tolerant control (FTC) scheme is presented for the dynamic positioning of vessels subjected to external disturbances, dynamic uncertainties, and thruster saturation constraints under thruster faults. A high-gain observer is constructed to acquire the estimates of vessel velocities. An auxiliary dynamic system is introduced to compensate the effect of the thruster faults and saturation constrains. Neural network with iterative updating laws is employed to approximate the lumped uncertainties caused by unknown environmental disturbances and dynamic uncertainties of vessels. Furthermore, the control allocation is accomplished to distribute the FTC forces and moment among individual thrusters. It is theoretically proved that the derived FTC scheme has the capability to maintain the vessel position at the desired values and guarantees that all signals in the closed-loop control system are uniformly ultimately bounded. Finally, the simulation results demonstrate the effectiveness of the proposed control scheme.

The working face footage acquired by traditional artificial static measurement technology has non-continuous and poor time-effectiveness, and ca't satisfy requirement of on-line real-time warning. For the above problem, an on-line monitoring system of working face footage based on radar ranging was designed. The system uses combination arrangement process of response radar ranging sensor and reflection radar ranging sensor to overcome shortcomings of short measuring range of the reflection radar and solve problem of difficult installatipn and maintainance of the response radar. Principle of the radar ranging was analyzed, and mine-used intrinsically safe radar ranging sensor composed of the reflection radar ranging sensor and response radar ranging sensor was developed. The test result shows that the system can stably and reliably realize on-line monitoring, real-time collection and analysis of working face footage. When measuring distance is less than 200 m, the maximum absolute error is 0.24 m, and the measuring distance and accuracy can meet the needs of gas disaster early warning.

The main goal of the research is to design an efficient controller for a dynamic positioning system for autonomous surface ships using the backstepping technique for the case of full-state feedback in the presence of unknown external disturbances. The obtained control commands are distributed to each actuator of the overactuated vessel via unconstrained control allocation. The numerical hydrodynamic model of CyberShip I and the model of environmental disturbances are applied to simulate the operation of the ship control system using the time domain analysis. Simulation studies are presented to illustrate the effectiveness of the proposed controller and its robustness to external disturbances.

This paper presents the application of an linear quadratic gaussian (LQG) control strategy for concrete caisson deployment for marine structures. Currently these maneuvers are carried out manually with the risk that this entails. Control systems for these operations with classical regulators have begun to be implemented. They try to reduce risks, but they still need to be optimized due to the complexity of the dynamics involved during the sinking process and the contact with the sea bed. A linear approximation of the dynamic model of the caisson is obtained and an LQG control strategy is implemented based on the Kalman filter (KF). The results of the proposed LQG control strategy are compared to the ones given by a classic controller. It is noted that the proposed system is positioned with greater precision and accuracy, as shown in the different simulations and in the Monte Carlo study. Furthermore, the control efforts are less than with classical regulators. For all the reasons cited above, it is concluded that there is a clear improvement in performance with the control system proposed.

Offshore vessels (OVs) often require precise station-keeping and some vessels, for example, vessels involved in geotechnical drilling, generally use Spread Mooring (SM) or Dynamic Positioning (DP) systems. Most of these vessels are equipped with both systems to cover all ranges of water depths. However, determining which system to use for a particular operational scenario depends on many factors and requires significant balancing in terms of cost-benefit. Therefore, this research aims to develop a platform that will determine the cost factors for both the SM and DP station-keeping systems. Operational information and cost data are collected for several field operations, and Artificial Neural Networks (ANN) are trained using those data samples. After that, the trained ANN is used to predict the components of cost for any given environmental situation, fieldwork duration and water depth. Later, the total cost is investigated against water depth for both DP and SM systems to determine the most cost-effective option. The results are validated using two operational scenarios for a specific geotechnical vessel. This decision-making algorithm can be further developed by adding up more operational data for various vessels and can be applied in the development of sustainable decision-making business models for OVs operators.

This paper deals with the problem of transient events in model-based observers for dynamic positioning of marine surface vessels. Traditionally, model-based observers experience a deterioration of performance during transients, and there is a give or take relationship between transient and steady state performance. To remedy this problem, we propose to use time-varying gains for a model-based observer. The gains are aggressive during transients to improve transient performance, and relaxed in steady state to lower the oscillations of the estimates. The proposed observer is analyzed with regard to stability. Its performance is verified in both a high-fidelity simulation model, and on experimental data with the research vessel (R/V) Gunnerus. In addition, a partial closed-loop validation with R/V Gunnerus has been performed.