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Aiming at the problem that the distribution of explosion load in the cabin and the propagation law of structural impact response was unclear, this paper established the numerical calculation model of explosion in a closed cabin by ALE (Arbitrary Lagrangian Eulerian) method. There was an apparent convergence of shock waves at the cabin's corners, and the pressure relief hole's area and its position significantly affected the peak of quasi-static pressure. The peak acceleration of the deck structure decreased exponentially as the distance from the location of charge increased. Peak acceleration decreased by approximately 50% for each bulkhead crossing. There was a "paper window effect" during the cabin interior explosion on the whole ship. It meant there was a limit to the value for the energy generated by the explosion to be transmitted along the frame structure. When the charge was 150 kg, it reached the limit of the energy transferred by the structure in this paper. The response of the distant structure did not change significantly with the increase in the charge quality. The research revealed the impact response propagation mechanism in the structure and provided a reference for designing protective structures. • The shock wave shows noticeable convergence in the cabin corner, where the area and position of the pressure relief hole significantly affect the peak quasi-static pressure. • The existence of a bulkhead greatly affects the maximum acceleration, each additional bulkhead results in approximately a 50% reduction. • The investigation reveals a remarkable "paper window effect" during the localized explosion of the entire vessel. [ABSTRACT FROM AUTHOR]

Autonomous ships are vulnerable to a spectrum of potential faults, including propeller damage, shaft-line failures, and electrical supply disruptions. Swift fault detection is critical to minimize the potentially catastrophic consequences of these issues. In this paper, we introduce an innovative digital twin-based method for diagnosing faults in autonomous ships. Our digital twin system collects data from the ship's sensor array, conducts comprehensive analysis, computes fault parameters, and provides real-time visualizations of the findings. To achieve this, we utilize the ship's dynamical model and employ a novel adaptive extended Kalman filter (AEKF) algorithm to estimate the severity of these faults. We evaluate the effectiveness of this approach through numerical simulations and practical implementation in an autonomous surface vehicle called the Otter, developed by Maritime Robotics. The experimental results, which consider both normal and faulty ship propulsion systems, underscore the significant potential of this novel approach to improve ship condition monitoring during operational activities. • This paper presents digital twin-based fault diagnosis architecture. • The fault diagnosis algorithm is based on a novel AEKF method. • The approach is demonstrated in a real-world scenario using a small autonomous vessel. [ABSTRACT FROM AUTHOR]

This paper aims at the identification and assessment of High-Impact Research Papers (HIRPs) on the Berth Allocation Problem (BAP) research at marine terminals. The BAP objective is to optimally assign and schedule ships at berthing positions along a quay, as well as to determine the berthing times and positions of ships at a port. The purpose of this study is to facilitate the work of the relevant research community and ultimately promote the research quality in this area. In meeting this objective, the paper utilizes a systematic and fair method to determine HIRPs of the BAP, which is based on the h -index and the g -index. An in-depth bibliometric analysis of the identified studies reveals their key features and characteristics. The analysis was conducted using the VOSviewer and bibliometrix R-package software programs. The main findings provide many useful insights on the BAP research development. The adopted approach and associated analysis results present an up-to-date detailed picture of the BAP research and constitute a valuable tool for its applications into other relevant research areas. The common trends in the reviewed HIRPs and important future research needs are discussed in a comprehensive manner. This survey study can be viewed as the first attempt for a comprehensive bibliometric survey of the high-impact BAP literature, which will be of a great value to researchers and industry practitioners. Furthermore, the proposed methodology for the identification of HIRPs can be used not only for the BAP research but for the literature surveys in other domains as well. [Display omitted] • A comprehensive analysis is conducted for the Berth Allocation Problem (BAP) research. • High Impact Research Papers (HIRPs) in the BAP research are identified and analyzed. • The co-authorship relations among countries, institutes, and authors are investigated. • Trending models of HIRPs and their solution techniques are discussed. • The statistical techniques for mapping and network analysis of HIRPs are presented. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) offer a significant opportunity for harnessing wind energy and achieving clean energy goals. This paper investigates the effects of mooring line failure in semisubmersible FOWTs under normal and extreme environmental conditions. The OC4 DeepCwind type semisubmersible with an NREL 5 MW wind turbine is considered for investigating the behavior of FOWT under intact and failed mooring lines. This study covers a wide range of environmental conditions, operational conditions of wind turbines, and mooring line failure scenarios. This paper investigates the mooring line failure effects on platform responses, mooring line fairlead tensions, and tower responses. The results show that the platform surge, heave, pitch responses, tower fore-aft displacement, base shear force in X -direction, and base moment in Y -direction are increased for upwind side mooring line failure during the operational condition of FOWT. Subsequently, the platform sway, roll, yaw responses, tower side-to-side displacement, base shear force in Y -direction, and base moment in X -direction are more during downwind side mooring line failure in the same environment. On the other hand, the impact of upwind side mooring line failure affects all 6 Degrees of Freedom (DOF) platform responses significantly during the parked state of FOWT. The maximum fairlead tensions observed in the remaining mooring lines remain below the mooring line breaking strength even after a mooring line failure during both operational and parked states of FOWT. It is also observed that the platform responses (excluding heave), tower responses, and fairlead tensions exhibit greater values when an extreme turbulence wind model is employed. The platform surge, heave, pitch responses, maximum fairlead tension, tower fore-aft displacement, and tower base moment in Y -direction show higher values under severe sea state condition. • Effects of mooring line failure under normal and extreme environmental conditions • Simulation of intact and mooring line failure scenarios using coupled analysis • Covering wide range of environmental conditions and mooring line failure scenarios • Effects of failure on platform responses, fairlead tensions, and tower responses [ABSTRACT FROM AUTHOR]

Icebreaker assistance is a common yet intricate operation in ice-covered waters, frequently leading to collisions between ships and icebreakers. This underscores the need for advanced kinematic models to improve safety and coordination in convoy operations. Consequently, this paper introduces a kinematic model for guiding intelligent ships under icebreaker assistance. The model, grounded in the Traffic Factor State Network (TFSN), evaluates the safety state of a fleet in various ice conditions, using data from actual convoy operations. An enhanced Proportional Integral Derivative (PID) algorithm is integrated to formulate a multi-ship following model, which accounts for the kinematic characteristics of ships in ice. The model also incorporates the transmission process of ship maneuvering commands. Its validity is confirmed through application to two ships under icebreaker assistance. The findings show that the model effectively simulates safe speeds and maintains proper inter-ship distances over time, and it generates safe kinematic instructions for the fleet. This model may contribute to navigational safety in ice-covered waters and demonstrates the potential for inclusion in ice navigation support systems. • The paper introduces a kinematic model for the collaborative operation of multiple ships. • This method is grounded in the evaluation of kinematic features of ships in various ice conditions. • The effectiveness is illustrated through actual convoy operations in the Baltic Sea. • The proposed approach has the potential to support intelligent decision-making systems. [ABSTRACT FROM AUTHOR]

This paper presents a study in which both the control and the shape of a Wave Energy Converter (WEC) are optimized simultaneously. A heaving point absorber WEC is assumed. To optimize the shape of the WEC's buoy, nonlinear hydrodynamics need to be evaluated. One main contribution of this paper is the integration of nonlinear hydrodynamics and nonlinear control during the optimization of the WEC's buoy shape. This approach is referred to as Control Co-Design (CCD). In this work, we present a control co-designed nonlinear heaving point absorber WEC that leverages the nonlinear dynamic, static Froude–Krylov (FK) forces to maximize power extraction. The nonlinear FK forces are approximated using a variation of the algebraic solution; the hydrodynamic forces of the body are computed using an analytic formulation leveraging the methods of eigenfunction expansion and separation of variables. The nonlinear geometry of the buoy is modeled as a series of inclined panels; the inclination angles are optimized to arrive at the optimal shape. The performance of the optimized shape is compared to that of a nonlinear spherical WEC. It is found that an average of 20% improvement is achieved by the optimized geometry over the spherical device. • The highlight of the research is that, generally, the dynamic equation of WECs are used to formulate innovative control methods to ensure the efficient operation of the devices. • The design of optimal control often comes at the last stage of the design process, after the mechanical, electrical, and other subsystems are completely defined. • During the earlier stages, simplified controls are employed for designing the subsystems, which may not match the final system's control requirements. • This study introduces an approach to the WEC device design process that integrates the ultimate control method and all other pertinent engineering considerations from the outset. [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicle (AUV) is currently the mainstream equipment for ocean exploration due to its long endurance and large operating range. However, the torpedo profile of traditional AUVs limits their maneuverability and hovering capabilities. This hinders the application and popularity of AUVs in near-seabed operations and accurate detection in small areas. This paper presents a novel disc-shaped micro AUV characterized by using a multi-core heterogeneous architecture to integrate control and positioning systems to obtain a lightweight design with complete functionality. Through the special structure and adaptive sliding mode controller, it can achieve high maneuvering navigation and stable hovering under different working conditions. A passive inverted ultra-short baseline (piUSBL) underwater positioning system is developed to provide accurate and instantaneous underwater position at low cost and power consumption. Field experiments, including special circular cruising and acoustic docking, were conducted in an open-water environment. The experimental results show that this vehicle has a depth control accuracy of 5 cm and a heading control accuracy of 3°, which well proves that this prototype can carry out accurate detection in a small range. In addition, this vehicle has a diameter of only 42 cm, a height of 23 cm, and a weight of 14 kg, making it easy to deploy and recover. To the best of our knowledge, this is the first AUV to be successfully tested in the field using a multi-core heterogeneous architecture with such small size and light weight. • This paper presents a novel disc-shaped micro AUV characterized by using a multi-core heterogeneous architecture to integrate control and positioning systems to obtain a lightweight design with complete functionality. • A passive inverted ultra-short baseline (piUSBL) underwater positioning system is developed to provide accurate and instantaneous underwater position at low cost and power consumption. • Field experiments, including special circular cruising and acoustic docking, were conducted in an open-water environment. The experimental results show that this vehicle has a depth control accuracy of 5 cm and a heading control accuracy of 3°, which well proves that this prototype can carry out accurate detection in a small range. • This vehicle has a diameter of only 42 cm, a height of 23 cm, and a weight of 14 kg, making it easy to deploy and recover. To the best of our knowledge, this is the first AUV to be successfully tested in the field using a multi-core heterogeneous architecture with such small size and light weight. [ABSTRACT FROM AUTHOR]

To ensure that underwater remotely operated vehicles have the ability to complete trajectory tracking in the presence of external disturbances and model parameter uncertainties, this paper proposes a double-closed-loop integrative sliding mode ROV tracking control based on the nonlinear expansion state observer. Firstly, to address the issue of oscillatory vibrations in the stable state of the dual closed-loop sliding mode structure, the inner loop control adopts a combinatorial reaching rate that leverages both exponential and variable convergence rates. Secondly, addressing the impact of external disturbances and model parameter uncertainties on the ROV, this paper proposes a novel nonlinear disturbance observer inspired by active disturbance rejection control principles. The stability of the complete closed-loop cascaded system is substantiated. Simulation outcomes demonstrate that the presented scheme significantly enhances the control system's transient response, disturbance rejection capacity, and ability to suppress jitter vibrations within sliding mode control, thereby proving the robustness, viability, and effectiveness of the control strategy outlined herein. • Proposed a dual loop sliding mode control strategy based on a nonlinear extended state observer. • Designed a nonlinear extended state observer based on the ROV model to handle external disturbances. • Application of a composite convergence rate to solve the problem of inner-loop jitter in a double-loop control structure. [ABSTRACT FROM AUTHOR]

In response to the intricate marine environment and the need for diverse, intelligent, and large-scale operations, clustered Autonomous Underwater Vehicles (AUVs) have emerged as a pivotal trend in AUV oceanic applications. This paper delves into three key aspects of clustered AUV control: optimal formation assembly, dynamic cooperative control, and autonomous obstacle avoidance. The formation assembly is approached as a target point allocation problem, employing an F-Norm and Dubins Path (FNDP) based method for efficient path planning and optimal allocation. A novel hybrid control strategy, LFVS, combines leader–follower (LF) and virtual structure (VS) approaches, facilitating cohesive formation maintenance with minimal communication. Additionally, the paper introduces an intelligent adaptive artificial potential field (IA2PF) method. This technique, enhancing energy efficiency and obstacle avoidance, dynamically adjusts to current conditions, thereby overcoming limitations of traditional APF methods like unreachable targets , oscillation, and dead zones. The efficacy and applicability of these methods are corroborated through extensive simulations and practical experiments using three 260 AUVs, and compared with formation control based on the LF strategy, proving their utility and stability in real-world formation assembly and maintenance tasks. • This study developed LFVS-IA2PF, a new multi-AUV formation control strategy. • FNDP is introduced for effective target point allocation in AUV operations. • This paper proposed an adaptive algorithm for AUV formation and obstacle avoidance. • The proposed algorithms are validated with both simulations and actual experiments. [ABSTRACT FROM AUTHOR]

In this paper, oblique water wave interaction with a surface piercing box-type porous structure placed in front of a vertical rigid wall is investigated in the presence of current, which flows parallel to vertical wall. The current speed is considered distinct in different subdomains. However, in a particular subdomain current speed is uniform throughout the water depth. In this analysis, Sollitt and Cross model is used for the study of wave motion inside the porous structure. Employing small amplitude linear water wave theory, the present model of our interest is developed into a boundary value problem and solved analytically using the eigenfunction expansion method. Using the developed solution, the reflection coefficient and hydrodynamic wave forces on porous structure are computed for different values of parameters: the dimension of porous structure, the friction coefficient of porous structure, the current speed of following current and opposing current. This research paper suggests that suitable arrangement of rigid walls and surface-piercing partially extended porous structures can be an effective and economical approach for guiding ocean currents and protecting marine facilities against wave attacks. • Oblique wave trapping in the presence of current and porous structure is discussed. • Boundary value problem solved analytically using the eigenfunction expansion method. • Wave forces are higher for following current speed than the opposing current speed. • Node of standing waves are formed on the rear face of the porous breakwater. [ABSTRACT FROM AUTHOR]

Array shape calibration is commonly categorized into active calibration and self-calibration, yet both methods have their drawbacks and are generally considered less optimal. This paper proposes a novel approach based on the coherence of noise radiated from non-cooperative ships. Firstly, the time-varying law of the frequency domain coherence of ocean ambient noise received by a titled hydrophone pair when a ship passes by is investigated, which reveals the relative location of the hydrophones and passing ship. The array shape can be calibrated by analyzing the ambient noise coherence and horizontal acoustic path difference between passing ships and different hydrophones. The calibration results are consistent which are obtained from the three sections of data collected near the shipping lanes in the Qingdao offshore. One of the calibrated result is employed to simulate the coherogram of ambient noise when the ship passes by. It is shown that the simulation is in good agreement with the measured results. The main error sources are also analyzed and simulated in this paper, and the results show that the method is basically feasible and reliable. • Noise coherence coefficient model in water near shipping lanes. • Array shape calibration based on coherence coefficients of ship-radiated noise. • Simulation of noise coherogram during ships passage. [ABSTRACT FROM AUTHOR]

The current paper investigates the path following control problem for marine vehicles with multiple disturbances and input saturation. First, considering that marine vehicles exposed to the marine environment always contain stochastic components, which were ignored in most of the previous studies, the multiple disturbances in this paper are decomposed into complex nonlinear terms, slow-varying disturbances, and stochastic disturbances. Accordingly, an appropriate stochastic differential model is constructed. Second, a new stochastic path following control strategy based on the fuzzy logic system, the stochastic disturbance observer, and the auxiliary dynamic compensators is established. The fuzzy logic system is adopted for approximating the complex nonlinear terms, the stochastic disturbance observer is constructed to estimate the slow-varying disturbances in stochastic situation, and the auxiliary dynamic compensators are designed to tackle input saturation. In the end, the stability of the entire system is proven through linear matrix inequalities and Lyapunov functions. The simulation results demonstrate the proposed controller's effectiveness and robustness. • The multiple disturbances are divided into three categories, and astochastic differential model is proposed. • The fuzzy logic system is adopted for approximating the marine vehicle model's complex nonlinear terms. • The stochastic disturbance observer is constructed to estimate the slow-varying disturbances in stochastic situation. • The auxiliary dynamic compensators are adopted to overcome the input saturation. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of automatic berthing of unmanned surface vehicles (USVs) in complex scenarios and proposes a multitask optimal control berthing method (MT-OCBM). The berthing process is divided into stages, each with distinct goal constraints and path restrictions. Through a combination of topology and computational geometry, a sparse Delaunay triangulation map segmentation (SDTMS) is introduced. SDTMS reduces map complexity while preserving accuracy by extracting map feature points and dividing the map into multiple triangular regions. The application of the traditional hp-Radau pseudospectral method (hp-RPM) to solve optimal control problems (OCPs) in complex marine environments is restricted by problems such as slow convergence and susceptibility that arise because of greatly different magnitudes of path constraints. To overcome these problems, we propose the hp-normalized Radau pseudospectral method (hp-NRPM). Normalizing the path constraints equalizes the magnitudes of path constraints, thereby significantly reducing the computational complexity of solving the OCPs. In contrast to traditional approaches that separate control from path planning, the optimal control algorithm employed in this paper integrates the control variables of unmanned vessels into the planning process of berthing paths. This integration allows the planned berthing paths to reflect the motion characteristics and constraints experienced by the unmanned vessel. It uses the KCS ship model to construct the Maneuvering Modeling Group ship motion model, and using the power spectrum given in the NORSOK standard, it establishes a slow, time-varying wind field model. The hp-NRPM algorithm is used to adjust the control inputs within the constraint region, thereby deriving a berthing route that optimizes the performance function. For validating the method, Qingdao Port was used as a simulation environment, and multiple sets of experiments were performed. The experimental results confirmed that MT-OCBM is robust and effective against disturbances and various obstacles encountered during berthing. • Pseudospectral method can effectively solve the optimal control berthing problem. • Using Delaunay triangulation for map segmentation can mitigate problem complexity. • Multitasking method allows algorithm focusing on different goals at various stages. • Normalizing path constraints can expedite the convergence speed of berthing problem. [ABSTRACT FROM AUTHOR]

In almost every practical scenario, the shape of towed linear array (TLA) is always affected by current, tug vehicle speed, and other factors, resulting in the deviation of sensor positions. Furthermore, maneuvers bring significant changes to array shape, i.e., array mismatch, which will greatly degrade the performance of array processing system. To deal with this problem, this paper first establishes a hydrodynamic model to fit the law of motion of turning cables. Then, a time difference of arrival (TDOA) method is utilized to estimate the real-time array shape, which exploits the near-field tug vehicle noise. Finally, the array shape is estimated by combining the hydrodynamic model and the TDOA method. The simulation results exhibit that the proposed array shape estimation method can resolve the array mismatch problem when turnings happen. Compared with the state-of art array shape estimation methods, this paper provides similar estimation accuracy without extra gyros or auxiliary sources. The lake trial results validate its feasibility and stability for estimating far-field target bearings in practical applications. • Different motion states of towed linear array during turning is derivated and classified. • Tug vehicle noise is utilized to estimate array shape other than gyros or auxiliary sources. • Time difference of arrival method (TDOA) combining hydrodynamic model. • Lake trial data support with practical significance. [ABSTRACT FROM AUTHOR]

In this paper, a new adaptive maximum correntropy unscented Kalman filter (AMCUKF) Time-Difference-of-Arrival (TDOA) tracking algorithm is proposed for autonomous underwater vehicles (AUVs) in the complex and variable marine environment. Firstly, the measurement model of the acoustic tracking system is established based on the multi-layer isogradient sound speed profile (SSP) model to correct tracking errors caused by the bending of sound transmission trajectory. To resist the impact of measurement gross errors caused by instrument measurement anomalies or accidental environmental interference, the maximum correntropy unscented Kalman filter (MCUKF) TDOA tracking algorithm is constructed by introducing the maximum correntropy criterion into the UKF. Then, this paper introduces the innovation-based covariance-matching method and moving window method to improve the algorithm's adaptability, which can reduce the influence of covariance variable measurement noise caused by marine environmental changes. Finally, we compare the effectiveness of the proposed AMCUKF algorithm with the UKF algorithm, adaptive unscented Kalman filter (AUKF) algorithm, and MCUKF algorithm, which indicates the AMCUKF algorithm has better tracking performance in the marine environment with covariance variable measurement noise, measurement gross errors, and Gaussian mixture noise. [ABSTRACT FROM AUTHOR]

Submarine pipelines are crucial to the safe and efficient transportation of offshore oil and gas, and conducting risk assessments is pivotal to mitigating the potential hazards associated with submarine pipelines and ensuring their safety. This paper proposes a comprehensive risk assessment model based on the expanded Failure Mode and Effect Analysis (FMEA) framework by incorporating the gray relational projection method and the compromise ranking method (GRP-VIKOR). The proposed GRP-VIKOR model combines the compromise rationality of VIKOR with the comprehensive indicator relationship evaluation of the gray relational projection method to effectively enhance the reliability and precision of the risk assessments. Initially, the risk structure of submarine pipelines is outlined, and an elaborate one and two-level evaluation index system for submarine pipeline failure risk assessment is established using the expanded FMEA, which ensures the precision and rigor of the risk assessment framework. In the data processing segment of GRP-VIKOR, interval type-2 fuzzy sets (IT2FSs) are employed to represent expert judgment language, thus augmenting the capability of the model to describe uncertainty. The introduction of the gray relational projection method combines gray correlation numbers with positive and negative ideal solutions, thus addressing deviations in the VIKOR method related to the judgment of alternative solutions with similar degrees of proximity to positive and negative ideal solutions. In the weight assignment segment of GRP-VIKOR, cooperative game theory is utilized, integrating three weight assignment methods to enhance the accuracy of indicator weights, effectively resolving issues associated with the dominance of a single method in the multi-attribute evaluation weight assignment. Finally, the risk priority of failure factors is determined through the analysis of actual submarine pipeline data and comparative analyses of different model results and parameter sensitivities. The experimental results demonstrate that the model accurately analyzes risk priorities, offering effective theoretical support for the field of submarine pipeline safety assessment. Submarine pipelines are crucial to the safe and efficient transportation of offshore oil and gas, and conducting risk assessments is pivotal to mitigating the potential hazards associated with submarine pipelines and ensuring their safety. This paper proposes a comprehensive risk assessment model based on the expanded Failure Mode and Effect Analysis (FMEA) framework by incorporating the gray relational projection method and the compromise ranking method (GRP-VIKOR). The proposed GRP-VIKOR model combines the compromise rationality of VIKOR with the comprehensive indicator relationship evaluation of the gray relational projection method to effectively enhance the reliability and precision of the risk assessments. Initially, the risk structure of submarine pipelines is outlined, and an elaborate one and two-level evaluation index system for submarine pipeline failure risk assessment is established using the expanded FMEA, which ensures the precision and rigor of the risk assessment framework. In the data processing segment of GRP-VIKOR, interval type-2 fuzzy sets are employed to represent expert judgment language, thus augmenting the capability of the model to describe uncertainty. The introduction of the gray relational projection method combines gray correlation numbers with positive and negative ideal solutions, thus addressing deviations in the VIKOR method related to the judgment of alternative solutions with similar degrees of proximity to positive and negative ideal solutions. In the weight assignment segment of GRP-VIKOR, cooperative game theory is utilized, integrating three weight assignment methods to enhance the accuracy of indicator weights, effectively resolving issues associated with the dominance of a single method in the multi-attribute evaluation weight assignment. Finally, the risk priority of failure factors is determined through the analysis of actual submarine pipeline data, and comparative analyses of different model results and parameter sensitivities. The experimental results demonstrate that the model accurately analyzes risk priorities, offering effective theoretical support for the field of submarine pipeline safety assessment. [Display omitted] • An extended FMEA structure is used to construct a risk assessment indicator system. • This paper proposes a risk assessment model based on the combination of the gray relational projection method and VIKOR. • The proposed GRP-VIKOR model is applied to submarine pipeline risk assessment problems. [ABSTRACT FROM AUTHOR]

The safety of pier foundations is an important issue in bridge construction, where local bridge scour is a major cause of bridge damage worldwide, exacerbated by ice sheets. This paper offers a live bed scour experimental investigation that assesses the impacts of the new anti-scour device guide pillar of different sizes on geometric properties of scour, downflow velocity distribution, and turbulence intensity around the pier under different flow velocities and roughnesses, and to select the optimum installation position and size of the guide pillar. The results demonstrate that the guide pillar has a considerable effect on the scour hole and downflow around the pier, and the maximum reduction rate of scour depth is 59.3% in the optimal installation position (2 d). By arranging distributed thin-film pressure sensors on the pier and measuring the pressure distribution on the facing water surface of the pier and the position of the center of gravity, this paper analyzes the distribution characteristics of the water flow force on the pier and the impact resistance of the guide pillar to the pier scour. The study found that the guide pillar reduces the water flow force by 61.3% without considering the effect of hydrostatic pressure. • Designed an anti-scouring device with a good anti-punching effect and high stability - guide pillar. • The first attempt to apply thin-film pressure sensors to bridge piers to monitor water flow force. • Thin film pressure sensor has good applicability, and it can be tried to continue to be applied in this field. • The effect of anti-scouring devices on local bridge scour at different flow velocities and different roughness rates was investigated. • The guide pillar has a strong anti-impact ability, and the water flow force can be reduced by 61.3%. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative switching control method to stabilize the posture of an underwater robot. The method leverages the passivity property of the robot's open-loop dynamics and factors in inertial effects that could impact its motion. Its primary goal is to guide the robot's position to a user-defined small level set using a potential function, achieved through consecutive switching. Additionally, the method ensures the convergence of the robot's orientation angle to a desired value. By employing a passivity-based switching control approach, the robot alternates between two submanifolds while reducing the potential function during each switch, ultimately leading the robot's position to the potential function's minimum. Through exploiting the passivity property of the robot's dynamics, the method designs a controller to stabilize the robot's posture using a switching strategy guided by the potential function. Results indicate that this method effectively stabilizes the posture of the underwater robot, surpassing conventional control methods in terms of stability and convergence rate. • The main contributions and achievements of this paper are as follows: • Proposing a new passivity-based control algorithm for the stabilization of an underwater robot. • Analyzing the stability of the closed loop system using the passivity property. • Investigating switching logic and obtaining necessary conditions for the designed algorithm. • Presenting case-studies in order to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

An automatic mooring system is not only safer and more economical than a traditional mooring system with ropes but also significantly reduces the mooring time. In this paper, we propose an automatic mooring system designed to securely berth vessels entering a port, along with an efficient control method aimed at constraining vessel movement within a specific range. To assess the operational range and control performance of the proposed system in a marine environment, a dynamic analysis program was employed to create a simulator. The simulator incorporated a parallel structured Stewart platform to replicate the 6-DOF motion of a marine vessel. The proposed automatic mooring system controller regulates the position using a time-delay controller (TDC). TDC has proven to be excellent for effectively predicting system uncertainty and handling changes in system dynamics. However, given the unpredictable nature of extreme disturbances in marine environments, it is essential to adaptively modify the control parameters to ensure optimal performance. The method presented in this paper employs a fuzzy logic controller (FLC) to dynamically adjust the control parameters of the TDC, enabling effective adaptation to rapidly changing marine conditions, including waves and wind. • A novel design is proposed for an automated mooring system. • A Cartesian robot is used to ensure the stable mooring of a vessel at a pier. • PPP-type serial manipulator moves x, y, z axes in space. • Fuzzy logic and time delay controllers for automatic mooring device control. • Dynamic analysis program validates the proposed control method in marine environment. [ABSTRACT FROM AUTHOR]

In a complex and changeable ocean environment, the initial alignment of the ship will be challenging due to the sway induced by the wind and waves, and large initial attitude misalignments cannot satisfy the linear model. Hence, this paper proposes a strapdown inertial navigation system (SINS) transfer alignment method under large misalignment, introduces the Lie group theory, and simultaneously incorporates the attitude and velocity state variables into the special euclidean group (SE (3)), redefining the nonlinear state error to improve the problem of state space inconsistency. The error equation obtained through logarithmic mapping also need satisfies the affine condition. In contrast to the group state model employed in the widely utilisedinertial frame, the local-level frame takes the earth's rotation and Coriolis effect, strong coupling making it challenging to fulfil the group affine property. Therefore, based on the local-level frame, this paper re-derives the error state space model by improving the dynamic equation, thereby realizing the state independence of the group affine model and constructing a new model of transfer alignment under large misalignment. Simulation and experimental test results further verify the effectiveness and superiority of the proposed alignment method under large initial misalignment angles. • This paper proposes a strapdown inertial navigation system (SINS) transfer alignment method under large misalignment, introduces the Lie group theory, and simultaneously incorporates the inertial navigation attitude and velocity state variables into the Special Euclidean group (SE (3)), redefining the nonlinear state error to improve the problem of state space inconsistency. • Based on the local-level frame, this paper re-derives the error state space model by introducing auxiliary velocity through the dynamic equation, thereby realizing the state independence of the group affine model and constructing a new model of transfer alignment under the condition of large misalignment. To the best knowledge of the authors, this is the first time in open literatures of transfer alignment. • Simulation and turntable test experimental results prove that the improved error state model can achieve better transfer alignment under the condition of large initial misalignment, which is significantly better than the traditional method, thus proving the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

With the development and deepening of ocean research, the cooperative technology of multi-UUVs draws more attention. However, the optimization for underwater cooperative detection of heterogeneous swarms is still relatively less explored. The cooperative detection configuration significantly impacts the accuracy of the cooperative detection system. Considering the characteristics of heterogeneous swarms, this paper proposes a new three-dimensional (3-D) optimal configuration design method for target detection in heterogeneous cooperative unmanned swarms based on dilution of precision (DOP) analysis. Firstly, the minimum DOP acquisition conditions on nested cone configuration were derived on the basis of Time of Arrival (TOA)-based cooperative detection. Secondly, we set a certain swarm consisting of unmanned surface and underwater vehicles to carry out Monte Carlo experiments with the consideration of the positioning errors brought by priori information to analyze the robustness of the designed configuration. Then, we analyze the impact of positioning errors of detection nodes on detection accuracy to research the configuration's stability, which would be further enhanced by designing the anchor group. Finally, various simulation examples verify the effectiveness of the optimal detection configuration designed for accuracy in this paper. A comparison of the proposed method with the traditional algorithms proves that the detection accuracy and system stability or robustness are effectively improved. • The problem of optimizing the design of the topology of a multi-objective UUV 3D cooperative positioning configuration based on TOA measurements is investigated. • The evaluation function of single-target-point DOP based on TOA measurements with a priori area-weighted average DOP in an underwater 3D environment is given. • The robustness of different optimal localization configurations to the detection node'slocalization error is analyzed and evaluated. • A cooperative detection method for heterogeneous swarms has been established, which utilizes cooperative localization to improve the localization accuracy of the detected UUVs. [ABSTRACT FROM AUTHOR]

Ice-class propellers are prone to generating severe cavitation in ice blockage environments, deteriorating hydrodynamic performance. In this paper, the IDDES method based on hybrid RANS/LES is first applied to research the hydrodynamics, excitation forces, and cavitation of an ice-class propeller in ice blockage and cavitation flow. And the internal influence mechanisms of ice-propeller distance and advance coefficient on the hydrodynamics, excitation forces, and cavitation are analyzed though high-fidelity flow field. The results indicate that the IDDES method performs well, the numerical and experimental errors are less than 3.0%, and the details of induced vortex cavitation are presented. An increase in the advance coefficient leads to a decrease in the mean thrust and torque, which is due to a reduction in the angle of attack. The ice blockage increases the excitation force of the blade behind the ice owing to an increase in pressure on the pressure surface. Meanwhile, ice blockage enhances flow separation, forming a large number of separation vortexes, which become conjoined vortexes under the influence of the propeller. The conjoined vortexes are sucked towards the propeller, forming induced vortex cavitation on the suction surface, and the pressure surface occurs pressure fluctuation. It is also found that the decrease in ice-propeller distance causes a delay in the excitation force. This paper provides a theoretical basis for the hydrodynamic and structural design of ice-class propellers, and offers a reference for the evolution of the flow fields. • The IDDES method is applied to research on an ice-class propeller. • The ice blockage increases excitation force, and enhances flow separation. • The separation vortexes are induced into conjoined vortexes by the propeller. • The decrease in ice-propeller distance causes a delay in the excitation force. [ABSTRACT FROM AUTHOR]

With the development of digital technology, the maritime industry is under continuous digital transformation. For example, from manned engine room to control room and even to remotely controlled or autonomous ships. Maintenance has also changed from being a reactive or scheduled procedure to a predictive and proactive activity. Proactive maintenance relies on the condition monitoring (CM) of equipment. Condition Based Maintenance (CBM), Reliability Centered Maintenance (RCM) and Prognostics and Health Management (PHM) primarily focusing on three technical processes, namely condition monitoring, fault diagnosis and prognosis, and maintenance decision-making. Over the recent years, research has been on these topics through two main approaches: data-driven approaches and model-based approaches. Especially data-driven approaches with Deep Learning (DL) techniques have become a popular direction with successful implementation in different domains. Classification Societies are also developing new standards and methods with the industry to provide assurance of these emerging services. This paper presents a comprehensive review of state-to-art methods for PHM techniques for the past few years (2017–2023). First, a general introduction to different approaches with a focus on data-driven methods is presented. Subsequently, a detailed review of techniques applied to PHM is provided, where unique contributions, advantages, limitations and challenges are discussed. This is followed by a chapter that discusses the technical rules and standards from classification societies (DNV and ABS). The paper then explores the benefits, challenges, existing problems, and recommendations for PHM from the perspective of classification societies. Maritime stakeholders may find this article to be a valuable guide or reference for the development of such services. • A comprehensive review of PHM in the maritime industry is implemented. • Evaluation of diverse PHM methodologies like physics-based, and data-driven methods. • Introduced a new categorization and data flow analysis for the reviewed PHM papers. • Reviewed DNV and ABS rules on PHM, summarizing classification societies' insights. • Presented challenges and future opportunities for PHM in maritime from DNV's view. [ABSTRACT FROM AUTHOR]

In order to improve the autonomous navigation capability of autonomous underwater vehicles (AUV), this paper applies Deep Reinforcement Learning (DRL) to realize autonomous path planning. In response to the limited detection range and difficult tracking DRL policy in three-dimensional unknown environments, this paper proposes an improved deep reinforcement learning method. Firstly, performing AUV modeling and processing obstacle detection information. Second, under a framework of reinforcement learning with the control system, an improved environmental interaction method was designed by analyzing the motion characteristics and controller performance of the AUV. Finally, based on this method, a policy network that can generate paths that satisfy obstacle avoidance and navigation is trained in combination with a twin delayed deterministic policy gradient (TD3). The simulation results show that the proposed method can achieve AUV path planning in a three-dimensional unknown environment. The proposed framework can ensure that the planned path meets the dynamics constraints and is trackable. The improved algorithm can enhance the convergence of training and the attitude stability of AUV. • This article applies forward-looking sonar to achieve three-dimensional path planning in unknown environments based on deep reinforcement learning, relying on the limited obstacle detection range of AUV itself. • The proposed path planning algorithm considers the characteristics of the model and controller in the process of deep reinforcement learning. • In other algorithm details, the reciprocal obstacle distance, and dense reward function are designed. These methods can significantly improve the efficiency of training. [ABSTRACT FROM AUTHOR]

This paper aims to study the higher-harmonics wave-induced surge force on the CENTEC-TLP platform in regular head waves with non-breaking assumptions, using a CFD-based numerical wave tank model, which is a useful tool for the analysis of the nonlinear interaction of waves and structures. Moreover, the influence of change in the wave diffraction and the incident wave angle on the surge force subject to operational and extreme wave conditions is investigated. The numerical analysis is conducted using the CFD toolbox OpenFOAM. The link between Secondary Load Cycle and the wave scattering Type2 is apparent and it is concluded that they are all inertia-driven and that 2nd harmonics play an important role. • This paper studies the higher-harmonics wave-induced surge force on the CENTEC-TLP platform. • The influence of change in the wave diffraction and the incident wave angle on the surge force is investigated. • The numerical analysis is conducted using the CFD toolbox OpenFOAM. • The link between Secondary Load Cycle and the wave scattering Type2 is apparent. • They are all inertia-driven and that 2nd harmonics play an important role. [ABSTRACT FROM AUTHOR]

The study of fluid–structure interactions in elastic structures is highly important in hydraulic structural engineering. This paper adopts the smooth particle hydrodynamics (SPH) coupling method to simulate dam failure water impact elastic plate flow and solid coupling problems. In addition, a numerical simulation is performed on the study of the free surface flow impact of the elastic plate structure on the main dynamic characteristics, including the impact force distribution and the change process. Additionally, the elastic structure of the vibration amplitude and frequency change rule, as well as the drastic changes in free surface flow, are also carried out. In this paper, the synchronous finite element algorithm is used to analyze the problem to obtain FEM results Additionally, two-dimensional benchmark physical tests are designed for dam-break water flow impacting an elastic plate are conducted, focusing on a comparative analysis of the numerical results of the SPH method with the results of physical tests and verifying the validity, accuracy, and superiority of the SPH coupling method for solving the problem of fluid‒solid coupling in elastic structures. On this basis, to explore the relevant physical quantities that cannot be measured or described during the test process, the flow–solid coupling characteristics of the elastic plate impacted by water flow are further understood by analyzing the nature of the flow field, the change in the flow–solid force of the elastic plate and the change rule of the frequency spectrum. The results show the following: (i) The jumps in velocity between the streams and the strong curvature of the free liquid surface lead to the creation of vortices at the cavities. (ii) The flow solid force under the impact of water flow increases and then decreases, and the smaller the deformation of the elastic structure is, the greater the force is. (iii) The vibration frequency of the fixed end of the elastic structure gradually decreases along the free end frequency, and the larger the deformation of the free end of the elastic plate is, the weaker its vibration response is. In addition, the natural frequency of the elastic plate under water flow impact is slightly lower than that under free vibration of the elastic plate. The related research results provide reference and guidance for the fluid–structure interaction problem. • Physical tests of elastic plates impacted by dam break water flow are studied. • Dynamic characteristics of elastic structures based on the SPH solver are analyzed. • The generation of vorticity, fluid-solid forces, and spectral changes are analyzed. • The water flow impacting the elastic plate based on SPH and FEM solver is studied. [ABSTRACT FROM AUTHOR]

This paper introduces an algorithmic method for the design and resistance prediction of hydrofoil vessels for fast ferry applications, using only design speed and mass as input parameters. A database of resistance estimates has been created and shared online. Furthermore, a simple model is introduced for the extension of the results to off-design speeds. The efficacy of the models is demonstrated through three case studies. Firstly, the importance of accounting for the power requirement during take-off is investigated, concluding that a simple assumption of constant speed yields accurate energy estimates for routes exceeding approximately six nautical miles. Case study number two entails a comparative analysis of hydrofoil vessel resistance to that of slender catamarans across a wide range of vessel sizes and speeds. The results reveal a potential for reducing the energy requirement of passenger fast ferries by 30% to 50% through the use of hydrofoils. The paper concludes with an investigation into the influence of surface roughness on hydrofoil resistance, indicating significant deteriorating effects even at moderate roughness levels. • An algorithmic hydrofoil design method. • A database of hydrofoil resistance estimates. • A comparison of the resistance of hydrofoils and slender catamarans. • A study of the importance of take-off energy. • An investigation into the importance of roughness. [ABSTRACT FROM AUTHOR]

Accurate prediction of ice resistance plays an important role in ensuring the safety of ship navigation when sailing in ice regions. This paper focuses on the design of a data generation deep learning model and an interpretable ice resistance prediction deep learning model. By selecting the appropriate ship, ice parameters and model experimental data to build the dataset, the influence of different data preprocessing methods on the model results are discussed. The processed data is expanded by Deep Convolutional Generative Adversarial Network (DCGAN). On this basis, a Graph Neural Network (GNN) is built to explain the distribution of network weights and the generalization effect of the model. The established model (GNN-DCGAN) and several ice resistance prediction methods are compared and analyzed. In addition, the design of polar ships needs to comprehensively consider the dynamic changes of ship design parameters and the mechanical properties of ice. In this paper, taking MT UIKKU as an example, the parameter sensitivity analysis is carried out to study the scope of application of the model and the contribution of different parameters. The results show that the DCGAN method can improve the prediction accuracy and application scope of GNN model. The predictions exhibit a high level of agreement with the experimental data, which can provide valuable references for the design of ship in ice regions. • We built a deep learning model of data generation to expand the ice resistance dataset. • The influence of different data preprocessing methods on model training is discussed. • An interpretable deep learning model is built to explain the weight and generalization effect of the network. • The ice resistance prediction model is compared with empirical formula methods, model tests and full-scale tests etc. • The MT UIKKU is selected for parameter sensitivity analysis and the parameters are analyzed dimensionless. [ABSTRACT FROM AUTHOR]

Maritime Traffic Situation (MTS) is crucial for enhancing the efficiency and safety of maritime navigation, with the complexity of ship traffic serving as a key aspect of identifying and managing maritime risks. This paper proposes a ship traffic complexity measurement model for MTS. The proposed model quantifies the complexity between ships by evaluating factors such as density, proximity factor, and mitigation index, and then integrates these evaluations into multiple ships interaction scenarios to enable a comprehensive assessment of ship traffic complexity. The results of case study have fully demonstrated the model's capability in identifying potential collision risks during the interaction processes of multiple ships situation within a navigational sea. Research on the ship traffic complexity measurement model can provide strong theoretical and practical support for maritime traffic management and navigational safety. • Building on an in-depth exploration of the intrinsic attributes of ships, this paper introduces ship domain (SD) into the calculation of proximity factor within the ship traffic complexity measurement model. By constructing different SDs for different ships, the model can more accurately assess collision risks. • Incorporating the mitigation index, based on ships' speed and course parameters, into the ship traffic complexity measurement model enables the quantification of ships' movement trends within specified temporal and spatial domains. This integration allows the model to accurately assess the mitigation complexity of ships in various MTS, taking into account their dynamics. • Expanding the ship traffic complexity measurement model from focusing on pairs of ships to encompassing the quantification of traffic complexity in multi-ship interactive scenarios has significantly enhanced the model's practical application value. [ABSTRACT FROM AUTHOR]

Monopiles are important structures in offshore wind engineering, primarily serving as foundations for wind turbines. When installed on a sandy seabed, local scour around monopiles can reduce their capacity, and is a significant hazard to be addressed in the design process. This paper provides a review of research related to local scour around monopiles, focusing on the following aspects: (1) identifying flow structures related to local scour, (2) synthesizing existing data on equilibrium scour depth and scour time-scale, (3) summarizing technology for observing local scour through laboratory experiments, numerical simulations and field observations, and (4) outlining the existing challenges and research opportunities. • This work reviews local scour around monopiles, covering flow processes, engineering assessment and scour observations. • The equilibrium scour depth and time scale around monopiles under various flow conditions has been summarized. • A discussion about filed observation of monopile scour is presented. • Knowledge gaps and research opportunities have been identified and listed in this paper. [ABSTRACT FROM AUTHOR]

This study aims to investigate the problem of event-driven distributed formation control for marine surface vehicles (MSVs) system, including prescribed performance constraint and actuator input saturation. By constructing a novel prescribed performance function based on second-order step response, the intuitive physical significance is realized, and the performance specifications imposed on the output tracking errors are achieved. Subsequently, a double-layer adaptive sliding-mode disturbance observer (ASMDO) is presented to compensate for lumped uncertain terms. Within the controller design stage, an auxiliary dynamic system is built to introduce the auxiliary intermediate control law, thus avoiding the need to directly design anti-saturation generalized control input for the MSVs system. Then, by incorporating external dynamic variable, a dynamic event-triggered mechanism (DETM) is proposed to regulate the transmission between the controller and actuators. Under the DETM, the designed controller only transmits the control force and torque into actuators at the specified triggering moment, and the trigger moment is independent of the internal state of the system. After that, the minimum inter-event time (MIET) of the proposed DETM is proved to be strictly positive, which ensures Zeno-free behavior. Lastly, the efficiency and advantages of the proposed event-driven distributed formation controller are verified through numerical simulations. • 1)In contrast to the existing performance function in (Lai et al., 2023 ; Wang et al., 2021c), the performance function proposed in this paper can ensure that the system response has a minimal system overshoot, which reduces unnecessary actuator actions. Furthermore, unlike the error transformation function in (Lai et al., 2023), the error transformation function in this paper can guarantee the control input amplitude is reduced in the initial stage. • 2)Different from the existing nonlinear disturbance observer (Dai et al., 2022), the ASMDO has the finite-time convergence property due to the application of fractional power. Subsequently, the lumped uncertainties are accurately estimated with minimal oscillation during sliding motion. In addition, the auxiliary intermediate control law is designed by introducing the auxiliary dynamic system, thus avoiding the need to directly design an anti-saturation generalized force for the MSVs system. • 3)In accordance with (Zhou et al., 2022), we present the DETM framework, which is designed to be independent of measurement errors that are related to control input. In other words, the triggering moment and inter-event time for the MSVs system are only associated with the evolution of the external dynamic variables. Combined with DETM, the proposed control scheme enables the controller to discretely transmit the control force and torque into actuators. Therefore, this allows for more efficient signal transmission management and reduces unnecessary actuator action. [ABSTRACT FROM AUTHOR]

Using robots to detect Marine structures is very important for maintaining the safety of Marine structures. This paper presents an underwater inspection robot specifically engineered for the assessment of underwater structures. The integration of reliable adhesion technology is identified as a critical factor in the development of such robots. The vortex suction cup, employed by the robot as its primary adhesion mechanism, outperforms traditional adhesion methods by enabling non-contact attachment while consuming less power. As the vortex suction cup is the core component of the underwater inspection robot , this study comprehensively investigates how variations in the vortex suction cup's structural and operational parameters influence its adhesion performance, measured from an energy efficiency ratio perspective. Initially, we delineate the vortex suction cup's design and succinctly explicate the mechanism underpinning the generation of negative pressure. Subsequently, we establish an evaluative parameter, the energy efficiency ratio (η = F / P), that is, the adsorption force obtained per watt of power consumption of the suction cup, serving as a metric for the adhesion performance. By simulating the structural and operational parameters of the suction cup, we extract the corresponding adhesion force, torque, and energy efficiency ratio. Lastly, we construct an experimental apparatus to measure the suction cup's adhesion force and output torque, validating the veracity of the simulated outcomes. Our simulation and experimental findings indicate that increasing the height of the suction cup housing enhances the adsorption force, however, this simultaneously diminishes its energy efficiency ratio performance. Likewise, an increase in the chamber inner radius amplifies the adhesion force, and the energy efficiency ratio commensurately increases. Augmenting the radius of the negative pressure effect board improves the adhesion force, decreases the required torque, and consequently amplifies the energy efficiency ratio. The suction cup's adhesion force and required torque display a direct relationship with its speed, but the energy efficiency ratio is minimally affected by speed. When the distance is close (h ¡ 4 mm), changes in the adhesion gap profoundly impact the suction cup's torque and energy efficiency ratio. However, when the adhesion gap ranges between 5–15 mm, the energy efficiency ratio exhibits a gradual decline. • This paper presents an underwater inspection robot with two vortex suction cup to adsorb on the surface of the underwater structure. • The effects of the structure and operating parameters of the vortex suction cup on their adsorption performance are explored. • A CFD method and a test platform are proposed to verify the adsorption performance of the vortex suction cup. [ABSTRACT FROM AUTHOR]

An improved evaluation method based on AHP-EWM-TOPSIS method is proposed to mitigate the subjectivity inherent in the expert evaluation method. Due to lack of practical vessel data for autonomous navigation equipment, the improved expert evaluation method is used to evaluate failure modes of autonomous navigation equipment. In this study, four experts participate in assessing 85 distinct equipment failure modes in autonomous navigation vessels, and the AHP method is used to objectively calculate these experts' weights. The evaluation data are standardized using the refined Entropy Weight Method (EWM) by Max-Min method, and the weights of evaluation criteria Severity, Occurrence and Detection are established. The TOPSIS method is utilized to rank the failure modes in autonomous navigation equipment, ultimately pinpointing the Emergency fire pump and drive equipment (equipment risk is Vessel main engine failure) as the most critical failure mode. Different expert weights are used to compare the ranking results of failure modes of autonomous navigation equipment, which confirms the reasonableness and effectiveness of the improved expert evaluation method in this paper. • An improved expert evaluation methodology based on AHP is proposed and used for risk evaluation of autonomous navigational equipment in order to reduce the subjectivity of the experts. • The maximum-minimum method is used to preprocess the assessment results, and the risk prioritization of autonomous navigation equipment is calculated by the AHP-EWM-TOPSIS method. • Based on the results of Spearman's Footrule method, the accuracy and validity of this paper's method is demonstrated by comparing the risk prioritization of autonomous navigation equipment under different expert weights. [ABSTRACT FROM AUTHOR]

The study of multiphase flow characteristics of hydrate slurry was crucial for controlling the risks associated with hydrate slurry transport in deep-water oil and gas operations. Currently, multiphase flow research on the hydrate slurry flow system focuses on two-phase (solid-liquid) flow studies in single short straight pipes or elbows. This paper established a geometric model based on an experimental loop of high-pressure natural gas hydrate slurry. The Euler model contained n momentum equations and continuity equations for each term, and the Euler model can couple the pressure term with the surface exchange coefficients. Therefore, Euler model was suitable to deal with complex fluid motion problems. Such as bubble flow problem, floating problem, particle suspension problem and fluidized bed problem. In this paper, the hydrate particles in the grout were set as regular round spheres and do not decompose, so the Euler model was suitable for the simulation of the gas-liquid-solid three-phase flow of hydrate grout in the loop. The Euler model was used to simulate the three-phase (gas-liquid-solid) expansion in the loop, focusing on the influence of hydrate slurry inlet flow rate, inlet hydrate volume fraction, liquid phase viscosity and pipe diameter on slurry flow characteristics. The results are as follows:1) Based on orthogonal experiments, pipe diameter has the most significant impact on the pressure drop of the entire pipe section, while liquid phase viscosity has the greatest impact on the average aggregation particle diameter of hydrate on the cross section.2) The distribution of hydrate phase is related to the direction of the loop. Under the influence of gravity, hydrates are primarily dispersed in the liquid phase, with a high concentration in the solid-liquid mixing zone, tend towards the gas phase zone. Hydrate particles are symmetrically distributed in the vertical cross-section, with smaller particle diameters in the solid-liquid mixing zone compared to the gas phase and liquid phase zone 3). In the elbow section, centrifugal force and density difference cause hydrate particles to aggregate towards the lower pipe wall on the outside of the elbow. This results in the disappearance of the liquid phase zone, higher hydrate concentration on the outside of the elbow, and smaller hydrate particle diameter in the solid-liquid mixing zone compared to the gas phase zone.4). Throughout entire loop, the viscosity of the slurry in the solid-liquid mixing zone was the highest, and the volume fraction of hydrate particles was symmetrical both vertically and horizontally. To validate the simulation results, high-pressure multiphase flow hydrate generation experiments were conducted in a 6 MPa hydrate slurry experimental loop. The stable flow pressure drop value of the slurry was compared to the simulation results. The relative error between the simulated and experimental pressure drops is less than 15%, falling within an acceptable range and matching the experimental results. This proved that the multiphase simulation technique of hydrate slurry gas-liquid-solid in the loop can effectively guide the safe transportation of hydrate slurry under actual working conditions. • Establishing a geometric model based on an experimental loop of high-pressure natural gas hydrate slurry. • The Euler model effectively simulate multiphase flow both before hydrate formation and during hydrate flow. • The distribution of hydrate phase in multiphase flow simulation is closely related to the pipeline profile. • To enhance transmission efficiency, the flow rate can be appropriately increased to avoid dynamic loss and the transmission pipe diameter can be enlarged. • Flow velocity and pipe diameter exhibit similar degrees of influence, indicating that the average aggregate particle size on the cross-section can be effectively regulated by adjusting the liquid phase viscosity to improve the flow ability of hydrate slurry. [ABSTRACT FROM AUTHOR]

The maritime transportation system heavily depends on sea lanes of communication. Unfortunately, the surge in shipping activities has also resulted in an increase in maritime incidents, encompassing both conventional accidents and piracy-related events. This paper presents a novel object-oriented Bayesian network framework for assessing the risk of traditional maritime accidents and piracy-related incidents. Furthermore, an enhanced machine-learning-based Tree augmented naïve learning approach is proposed to address the correlation relationships among the influential factors and the distinctions between mathematical and practical meanings. The paper also introduces mutual information theory and an improved scenario construction approach to identify the key influential factors on maritime risks and unveil the non-linear relationships among them. The findings indicate that both the degraded natural environment and social environment contribute to the risk levels of maritime accidents. Furthermore, the type of ship is recognized as the most significant factor contributing to unsafe conditions. The research results will offer valuable insights to the maritime industry, specifically aiding ship owners, ship crew, and shipping companies in understanding the key influential factors in multiple types of maritime accidents and assessing potential risks. • A novel Object – oriented Bayesian network is developed to assess the accidents along the sea lanes of communication. • The key influential factors on both maritime accidents and piracy accidents are identified. • Both the traditional maritime accidents and non-traditional piracy accidents are considered. • An improved Tree augmented naïve learning structure learning approach is proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of the pulse width and amplitude on the scouring of sand beds by vertical submerged pulsed jets using a combination of experimental and numerical calculations. The reliability of the numerical calculations is verified through a comparison between the numerical simulations with the sedimentation scour model and the experimental data at a low pulse width T 2 of 0, with the result that the various errors are within 5%. The results show that the scour hole depth | h min | grows with the relative low pulse width T 3 throughout three intervals: a slowly increasing zone I, a rapidly increasing zone II, and a decreasing zone III, producing a unique extreme value of | h min |. The optimal scouring effect equation was obtained by analytically fitting the relationship curve between the pulse amplitude V and the relatively low pulse width T 3. Including the optimal T 3 and optimal duty cycle ƞ. The difference in the scour hole depth | h min | under different pulse amplitudes is reflected in the initial period F of the jet. With an increasing pulse amplitude, | h min | goes through three intervals: an increasing zone M, decreasing zone N, and rebound zone R. It is found that the scouring effect in the pulse jet is not necessarily always stronger with a larger amplitude. The results of the research in this paper can provide guidance for optimizing low-frequency pulsed jets for related engineering practices, such as dredging and rock-breaking projects. • Numerical simulations and experiments were combined to investigate pulsed jet scour. • The effect mechanism of pulse amplitude on the variation of scour hole depth was analyzed. • Models for the prediction of relative low pulse width with the inlet pulse amplitude have been developed. [ABSTRACT FROM AUTHOR]

In this paper, non-fragile control associated with exponential stability for unmanned surface vessels(USVs) with the rudder failure and dynamic event-trigger is presented. To begin with, the event trigger and switch system are introduced, taking into account the distribution characteristics of faults and resource efficiency, and a class of independence-distributed random failure models are built. Furthermore, acknowledging the practical challenges associated with parameter uncertainties, USVs are used as uncertain Nomoto model(NM) and the rudder system is described with uncertain second-order underdamped system(UDS). Then, in the presence of dynamic disturbances, an appropriate non-fragile controller is proposed to demonstrate that the closed-loop system states can be exponentially stabilized through the application of the Lyapunov–Krasovskii functions(LKF) and Linear Matrix Inequalities (LMIs). Lastly, the simulation results confirmed that control design methods proposed are effective. • Considering dynamic event trigger and switch system. • An uncertain Nomoto model and second-order under damped systems are presented. • A stochastic failure model with distribution dependence is constructed. • This paper covers non-fragile controller. • Exponential stability is given to prove the system stability. • Lyapunov-Krasovskii function method and linear matrix inequalities (LMIs) are used. [ABSTRACT FROM AUTHOR]

This paper focuses on the adaptive output-feedback event-triggered control strategy for the formation tracking and obstacle avoidance activity of unmanned surface vessels (USVs) with unmeasurable velocity, constrained communication and actuator fault. By using the neural networks and minimal learning parameter, a novel output-feedback event-triggered controller is deigned, effectively alleviates constraints related to continuous feedback signal acquisition in dynamic systems. Subsequently, by incorporating an adjustable threshold, the event-triggered condition is established, thus facilitating updates to the state and adaptive law solely within the discrete-time domain. Then, only two aperiodic adaptive laws are derived to mitigate actuator faults and system uncertainties. As for the path planning, benefiting from the artificial potential field method, a novel obstacle avoidance mechanism is developed for obstacle avoidance and waypoint-based path navigation. Considerable effort has been made to guarantee the semi-globally uniformly ultimately bounded stability. Finally, two numerical simulations are illustrated to demonstrate the remarkable performance of the proposed control strategy. • This paper proposes an output-feedback based event-triggered control strategy. • An event-triggered observer is designed to achieve the discrete sampling observation. • Only two adaptive parameters are designed for updating in the discrete-time domain. • The proposed algorithm can effectively implement the reasonable obstacle avoidance. [ABSTRACT FROM AUTHOR]

Crude oil cargo discharging operations can be performed by cargo oil pumps in tanker ships. Considering the harmful effects of crude oil, any failure during the cargo oil pump operation may pose acute hazards such as temperature and pressure increase in pipelines, leakage, fire, and following undesired events that lead to marine environmental pollution and toxic effects to humans. The process is managed by the ship's crew, and it requires following the operational steps in order. This paper aims at performing a detailed human reliability analysis (HRA) for the operational process of cargo oil pumps on a tanker ship. In the paper, the Cognitive Reliability and Error Analysis Method (CREAM) is used to calculate human error probability under a fuzzy set which deals with the uncertainty and ambiguity of the CPC (Common Performance Condition). The Bayesian Network (BN) approach is adopted to determine the probability distribution of the control modes in reliability assessment. In view of the findings, the human reliability for the entire process of cargo oil pump operation on tanker ship is found 8.82E-01. The outcomes of the paper provide valuable insight into the improvement of tanker safety in shipboard operation and performance reliability assessment. • Quantitative human reliability analysis is performed under fuzzy and Bayesian Network CREAM (Cognitive Reliability and Error Analysis Method) modelling. • Human reliability is predicted for the cargo oil pump operation process on tanker ships. • Insight can be provided to maritime stakeholders to improve process safety on tanker ships. [ABSTRACT FROM AUTHOR]

For the design of sailing vessels, the use of Dynamic Velocity Prediction Programs is expanding, as naval architects start to consider the effects of waves and varying wind conditions in order to design faster, safer and more efficient vessels. Many models that predict the unsteady hydrodynamic response are available, but for sail aerodynamics, few models have been presented, and the quasi-steady assumption is instead commonly used. The aim of this paper is to develop a time-domain model for unsteady sail aerodynamics that can handle arbitrary motions and requires only limited input. The proposed model is based on the Indicial Response Method, with specific adaptations to handle the additional complexity of sail aerodynamics. The model's predictive performance is evaluated against URANS CFD results for several cases of increasing complexity. This includes a 3D upwind sail plan subjected to pitching motion, where comparisons are also made with the common quasi-steady (Q-S) assumption. Compared to this, the proposed model delivers significantly better predictions for the amplitude of lift, thrust and sideforce. However, the drag amplitude is over-predicted by the model, and as a result, there is a significant misprediction of thrust phase. While there is a need to improve the prediction of unsteady drag, this paper shows that the model represents a significant improvement over the Q-S assumption, for unsteady performance prediction on timescales shorter than the wave period. • A time-domain model for unsteady upwind sail aerodynamics using the Indicial Response Method. • Specific considerations for sail aerodynamics are presented, along with related adaptations of the method/model. • Model performance is compared against URANS CFD results for several cases of varying complexity. • Limitations of the model applicability are qualitatively indicated. • The model is shown to be a considerable improvement over the quasi-steady approximation. [ABSTRACT FROM AUTHOR]

This paper conducts a comparative study into the hydrodynamic loads and bearing reaction forces between T-deck and box-deck bridges under freak waves. Initially, a high-fidelity numerical flume is established and validated to accurately simulate the freak wave-bridge interaction. Subsequently, a comprehensive analysis distinguishes the hydrodynamic characteristics associated with equivalent-sized freak waves, Stokes fifth-order waves, and solitary waves. Utilizing the developed numerical flume, the detailed comparisons of hydrodynamic loads on T-deck and box-deck bridges under freak waves are conducted, considering various focus locations, wave height to significant wave height ratios (α 2), and wave crest to wave height ratios (α 3). The study then delves into the seaward and landward bearing reactions for both bridge types. Additionally, the ultimate resistance envelope for a tension-compression bearing is explored through a finite element model, and the safety evaluation of the bearings under freak waves is carried out. Key findings reveal that (a) freak waves pose a more significant threat to structures than the other two wave types; (b) strengthening the seaward bearing for the box-deck and the landward bearing for the T-deck is recommended in the bridge design under the impact of freak waves; and (c) the ultimate resistance capacity envelope efficiently evaluates the bearing capacity when encountering freak waves with the working conditions used in this paper. • The force induced by freak wave, Stokes-5th order wave, and solitary wave is compared. • Hydrodynamic distinctions between T-deck and box-deck under freak waves is examined. • The bearing reaction force under varying parameters of freak waves is analyzed. • An ultimate resistance envelope is obtained for a tension-compression bearing. [ABSTRACT FROM AUTHOR]

The use of autonomous vehicles for marine and submarine work has risen considerably in the last decade. Developing new monitoring systems, navigation and communications technologies allows a wide range of operational possibilities. Autonomous Underwater Vehicles (AUVs) are being used in offshore missions and applications with some innovative purposes by using sustainable and green energy sources. This paper considers an AUV that uses a hydrogen fuel cell, achieving zero emissions. This paper analyses the life cycle cost of the UAV and compares it with a UAV powered by conventional energy. The EN 60300-3-3 guidelines have been employed to develop the cost models. The output results show estimations for the net present value under different scenarios and financial strategies. The study has been completed with the discount rate sensibility analysis in terms of financial viability. • This paper considers an AUV that uses a hydrogen fuel cell, achieving zero emissions. • This paper analyses the life cycle cost of the UAV and it is compared with a UAV powered by conventional energy. • The EN 60300-3-3 guidelines have been employed to develop the cost models. • The output results show estimations for the net present value under different scenarios and financial strategies. • The study has been completed with the discount rate sensibility analysis in terms of financial viability. [ABSTRACT FROM AUTHOR]

As mankind continues to exploit marine resources, there is a growing need to use unmanned surface vessel (USV) platforms for maritime security and surveillance of the operational environment at sea. Satellite remote sensing imagery is now the most common means used for maritime surface security surveillance. Satellite images are susceptible to cloud cover, while camera-equipped USVs can prevent the effects caused by cloud cover. However, there are virtually no vision-based target tracking solutions for the USV perspective. This paper proposes a tracking solution for multiple target tracking at sea named Sea-IouTracker. It can address the potential problems when the USVs are at sea, such as the target loss, anchor frame drift and even serious Re-ID phenomena due to wind and waves and other environmental effects. We chose Sort as the basic tracking framework and we picked Buffered-IoUs based on two different buffer scales instead of traditional IoUs for matching targets in neighbouring frames. And the innovation of the neighbouring frame matching mechanism lies on that the position of the Buffered-IoU is predicted using a motion prediction model and matched with the next detection frame because both matches are unsuccessful. This method increases the stability of the tracking model and reduces the phenomenon of re-ID. We have also developed a detector that adaptively fuses image features for the tracking scheme. The detector proposed is based on the ASFF (Adaptively Spatial Feature Fusion) detector head, CBAM (Convolutional Block Attention Module) and Yolov7 baseline for maritime target detection. This paper verifies that the Sea-IoUTracker can achieve MOTA = 77.5, ID SW = 1.5% when tracking multiple targets on the MOT17 dataset. We have also proved our detector proposed is superior to other SOTA detectors in accuracy when detecting sea surface targets in the Singapore Maritime Dataset (SMD). We have also verified that the target tracking scheme proposed in this paper outperforms to the current state-of-the-art(SOTA) tracker C-BIoU (Yang et al., 2022) Tracker and ByteTrack based on four tracking video sequences in SMD. In this case, the accuracy is improved by about 2% with respect to the latter, while the ID SW phenomenon is reduced by about 20%. • The target tracking scheme proposed in this paper is a maritime target tracking scheme for maritime security requirements. • After two failed B-IoU based matches, we add a re-matching mechanism between the predicted target anchor and the target detection frame based on the buffered area to increase the probability of re-matching the lost target and thus improve the tracking effect. • We propose a detector which outperforms than other SOTA detectors when detecting targets with multi-scale features at sea. [ABSTRACT FROM AUTHOR]

A joint control scheme based on linear active disturbance rejection control (LADRC) and incorporating finite time control (FTC) and adaptive control (APC) is proposed to address the difficulty of controlling uncertain surface vessels (USV) under enhanced sea conditions. This joint controller combines the advantages of three control algorithms. Firstly, a new finite time linear extended state observer (FT-LESO) is studied, which not only has all the functions of traditional LESO, that is, real-time estimation of all uncertainties and internal and external disturbances of the system, then giving the feedback of its estimates to the PD controller for compensation, but also considers the finite time convergence of the estimation errors. Finite time convergence is guaranteed. Then, finite time control is introduced into the PD controller and combined with a finite time observer to form a control system with finite time convergence characteristics. In addition, to address the difficulty of parameter tuning in PD controllers in LADRC, adaptive control is introduced into the designed FT-LADRC to adjust controller parameters in real time, effectively solving this problem.Finally, the tracking and control problem of surface vessels is verified, and the simulation results show the effectiveness of this scheme. • A tracking control scheme for uncertain surface vessels based on linear active disturbance rejection control and finite time convergence characteristics is proposed, and adaptive control is introduced, which does not rely on specific mathematical models and has strong anti-interference ability and good tracking accuracy. The two displacement channels and yaw attitude angle of the surface ship are controlled by LADRC, with LESO estimating the total interference of the system in real-time and PD controller compensating. • Compared to the linear extended state observer (LESO) of references (Huang et al., 2018 ; Zhang et al., 2021), the finite time linear extended state observer (FT-LESO) proposed in this paper has finite time convergence characteristics and can achieve semi global finite time convergence. • Compared with references (Cao et al., 2020 ; Yang et al., 2022), this paper combines finite time control with PD controller in LADRC to ensure the finite time convergence characteristics of tracking error. The combination of the two methods takes into account the finite time convergence of both interference error and tracking error, and has a finite time convergence that is close to global convergence. • By incorporating adaptive control as an optimization mechanism into the control scheme, the direction of optimization is to design a new adaptive law based on the PD controller, while ensuring finite time convergence. This enables the new controller AP-FT-LADRC to adjust the parameters of the PD controller in real time based on tracking errors, further enhancing the robustness and response speed of LADRC, And it provides a new method for proving the stability of the system. [ABSTRACT FROM AUTHOR]

This paper proposes a saturation-tolerance control algorithm for the limited behavioral capability of actuators, particularly when facing external disturbances in the formation control of underactuated surface vehicles (USVs). An auxiliary subsystem that takes into account saturation-tolerant behavioral boundaries is included, which performs comprehensive compensatory control in the presence of input signals exceeding the real-time behavioral boundaries of the actuators' capability. For purpose of enhancing the precision of the guidance algorithm, a higher accuracy L1 virtual ship (L1-VS) guidance law is proposed for considering an effect of time on the dynamic virtual ship guidance principle. The computational dependence on time in the generation of the target path is lessened in the guidance design, thus indirectly realizing the reduction of the degree of the deviation of the execution route and the improvement of the stability of the system. Moreover, a robust neural damping technique and a dynamic surface control (DSC) approach are utilized in the control design for improving the system stability and reducing the danger of "explosion of complexity". One has done tremendous work to ensure semi-global uniform ultimate bounded (SGUUB) stability. The final three numerical examples are provided to evaluate the effectiveness of the proposed algorithm. • In this paper, a novel L1-VS guidance principle is proposed under the premise of higher guidance accuracy. • The L1-VS guidance eliminates the need for time-based computations on straight and turning paths. • A saturation compensation strategy is developed, thus mitigating the risk of faults stemming from behavioral overshoots. • By setting the saturation-tolerance behavior boundary, the effect of the auxiliary subsystem can be more clearly displayed. [ABSTRACT FROM AUTHOR]

This paper proposed an equivalent model for the hydraulic characteristics of the umbilical with hydraulic resistance, hydraulic inductance and hydraulic capacitance. Based on the model, an umbilical simulator is designed for subsea control model tests. The simulation of the pressurizing and relieving, and production master valve opening and closing are conducted through SimulationX. The simulator's performances are verified through the sea trials. In the umbilical simulator, the slender pipe, the accumulator, and the hydraulic motor and flywheel can be employed as the hydraulic resistance, hydraulic capacitance and inductance, respectively. Their sequence affects the simulator's performances and the best sequence is capacitance-inductance-resistance. The simulation results of the simulator and the umbilical are analyzed and compared. The pressurizing and relieving times of the umbilical are 529s and 192s, while that of the simulator are 572s and 165s. The opening and closing times of the umbilical are 4.4s and 8.3s, while that of the simulator are 4.8s and 8.2s. The sea trials show that the errors for the simulator of the pressurizing time, the production master valve opening and closing time are 11.12%, 11.62% and 7.89%, respectively. • This paper proposed an equivalent modelling method for the hydraulic characteristics of the umbilical with the hydraulic resistance, hydraulic inductance and hydraulic capacitance. • An umbilical simulator was designed with the equivalent hydraulic resistance, capacitance and inductance on the base of the model. • In the umbilical simulator, the slender pipe can be used as the hydraulic resistance, the accumulator can be used as the hydraulic capacitance and the hydraulic motor and flywheel can be used as the hydraulic inductance. • The sequence of the hydraulic resistance, capacitance and inductance affects the simulator's performance and the best sequence of the component arrangement is capacitance-inductance-resistance. • The simulator performance was verified with the subsea production system through the sea trials. [ABSTRACT FROM AUTHOR]

The subsea jumper, a crucial pipeline connector facilitating liquid transport between underwater structures, experiences dynamic alterations in flow direction, rate, and phase volumes owing to its distinctive design. These complex flow characteristics can trigger flow-induced vibrations, potentially causing fatigue damage to the jumper. This paper explores the multiphase flow patterns (oil, gas, and water) in a rigid M-shaped subsea jumper under varied mixing velocities (2–4 m/s) and different volume fractions of each phase (0.1–0.7). It analyzes the factors influencing structural vibration response. The findings reveal diverse flow patterns within the jumper, each exhibiting distinct characteristics based on flow parameters. Concurrently, spatiotemporal oscillations from fluid dynamics impact each bend. Pressure on jumper walls gradually diminishes with changing flow direction. Furthermore, the study performs structural modal and frequency domain analyses of pulsating pressure to evaluate potential resonance conditions. The results of this paper contribute to a deeper understanding of the multiphase flow characteristics in jumpers, offering valuable insights to enhance the reliability of underwater oil and gas production. • The three-phase flow pattern evolution of oil, gas, and water in the M-shaped jumper was studied through simulation. • The flow characteristics of slug flow induced by multiphase flow in the jumper were investigated. • Explored the pressure drop characteristics of oil, gas, and water flow in the jumper at different flow rates. • Through one-way fluid-structure interaction, the jumper's vibration under multiphase flow was obtained. [ABSTRACT FROM AUTHOR]

Very Large Floating Structure (VLFS) plays a crucial role in mitigating land resource scarcity in developed coastal areas. This paper introduces an innovative VLFS concept consisting of numerous concrete box-type floats interconnected by steel tie rods, designed for a 4000-m-long floating marine airport. Based on three-dimensional potential flow theory, two numerical models for the VLFS are established: the single-float model and the multi-float model interconnected by joints, where each float treated as rigid. The research explores the impact of wave direction, wave period, and real sea conditions on the hydrodynamic response of the VLFS. Additionally, this paper focus on the discrepancies in dynamic characteristics between single-float and muti-float, and investigate the special response principles of the muti-float model that closely resemble the actual hydrodynamic features of VLFS. The findings show that local deformation in the VLFS results in elevated wave loads on the structure, posing a significant challenge in designing the VLFS mooring system. Higher structural stiffness correlates with decreased mean and pulsation values of mooring cable tension. Incident waves at 0° induce local deformation on the wave-facing side of the VLFS; however, the deformation rapidly dissipates, exerting minimal impact on the floats supporting the airport runway—thus, creating an indirect wave-absorbing mechanism. When waves incident at 90°, the VLFS bends, adversely impacting the operations of marine airports and causing uneven stresses on the connectors, making them susceptible to fracture and damage. Hence, it is advisable to install marine airports parallel to prevailing wave directions. Furthermore, the hydroelastic behaviour of VLFS contribute to alleviating internal stresses within the structure. The focus of future research lies in balancing the impact of VLFS hydroelasticity on both system motion performance and structural internal stresses. The VLFS concept presented in this study performs effectively under various real sea conditions. The rationality and feasibility of the proposed VLFS concept are substantiated. The study lays the foundation and presents ideas for the future development of marine space. • A novel Very Large Floating Structure (VLFS) concept is presented. • A multi-float hydrodynamic coupled model of VLFS is established. • Comparing the hydrodynamic response of single-float and multi-float VLFS model under different wave conditions. • Summarizes the potential relationship between VLFS hydroelasticity and rigid body motion. [ABSTRACT FROM AUTHOR]

To generate autonomous collision avoidance encounter scenarios for inland waterway vessels, according to the characteristics of inland waterways, this paper presents a method for parametric modeling of encounter scenarios for ship avoidance testing in inland waterways, which is employed to automatically generate inland waterway ship encounter scenarios. Starting from the utilization of AIS and radar data acquisition and fusion methods, a ship navigation data acquisition and fusion system was established. Taking the waterway between Three Gorges dam and Gezhouba Dams waterway segment in China as an example, the ship navigation data was collected and analyzed to identify key factors for collision avoidance scenarios. A parameterized modeling approach for generating encounter scenarios in inland waterway ship collision avoidance testing was proposed, enabling the automated generation of collision encounter scenarios by setting relevant parameters. By testing encounter scenarios between two or more ships, a series of test scenarios were generated. The simulation demonstrated the effectiveness of this parameterized scenario generation method in supporting the testing of autonomous collision avoidance algorithms for inland ships. • This paper constructed a ship navigation data collection system based on AIS (Automatic Identification System) and maritime radar. Methods for AIS data reception and restoration, radar data processing, and fusion of AIS and radar targets is proposed. This system enables automatic data collection and fusion of ship navigation data between the Three Gorges Dam and the Gezhouba Dam in the Yangtze River. • A motion control model based on inland waterway bulk carriers is established, and a three-degree-of-freedom MMG hydrodynamic model is used to better fit the motion characteristics of inland waterway ships for the characteristics of more curves and larger drift angles. • Key elements in the autonomous collision avoidance test scenarios for inland waterways were identified. A parameterized modeling method for autonomous collision avoidance scenarios in inland waterways was proposed. Test results demonstrated that the proposed method can rapidly generate a large number of simulation collision avoidance testing scenarios that comply with actual ship traffic flow characteristics. These scenarios can be used to test the reasonableness and reliability of the decision-making algorithm for autonomous collision avoidance of ships in the future research. [ABSTRACT FROM AUTHOR]

This paper introduces a prescribed-time extended state observer (PTESO) guidance law specifically developed for the path tracking of underactuated unmanned surface vehicles (USVs) navigating under time-varying ocean current conditions. The PTESO is utilized for accurate determination of the sideslip angle of the USV, particular during maneuvering along curved trajectories or in the presence of time-varying ocean disturbances. This process guarantees a prompt and accurate calculation of the sideslip angle, thus enabling more accurate path tracking in the presence of external disturbances caused by wind, waves, and currents. The stability of the closed-loop system's input-state is established using cascade theory. Furthermore, in order to improve the accuracy of USV positioning, the paper suggests utilizing ultra-wideband (UWB) technology for USV localization. A layout scheme has been developed for the placement of UWB devices on the vessel, and an equation has been derived for calculating the heading angle. The proposed approach's effectiveness is substantiated through the validation of simulation results, while the feasibility of the method is confirmed by experimental results. • The prescribed-time extended state observer is employed for the estimation of sideslip angle. • It effectively suppresses the initial peak phenomenon of the extended state observer (ESO). • Ultra-Wideband (UWB) technology is applied to ship positioning. [ABSTRACT FROM AUTHOR]