Search Results (1,162)

Due to the complexity of shipyards’ operating scenes and the inconsistency of ship parts’ type and size, current sorting operations for ship parts mainly rely on laborers, resulting in weak control over the production process and key nodes. With the gradual advancement of intelligent manufacturing technology in the shipbuilding process, the trend of machines replacing humans is obvious. In order to promote the automation of the sorting process, intelligent scene recognition and route planning algorithms are needed. In this work, we introduce a localization method based on a laser line profile sensor and ship parts layout analysis algorithm, aiming at obtaining the information needed for sorting route planning. In addition, a heuristic-based route planning algorithm is proposed to solve the built mathematical model of the ship part sorting process. The proposed method can optimize the sorting order of parts, realize stable stacking, shorten sorting distance (taking about 490 m for 43 parts), and thereby improve operation efficiency. These results show that the proposed approach can make intelligent and comprehensible sorting route planning for the ship parts layout. Full article

This study examines the efficiency trade-offs of Controllable Pitch Propeller (CPP) systems by comparing Combination and Fixed operation modes using real ship operational data. The analysis focuses on mechanical efficiency (η_mech), propulsive efficiency expressed through the normalized Relative Propulsive Efficiency Index (RPEI_norm), and fuel consumption. Combination mode consistently maintained higher η_mech across all load conditions, with pronounced advantages at low load and low speed (<50% load, <12 knots), where both propulsive efficiency and fuel economy improved. In contrast, Fixed mode outperformed Combination mode at high load and high speed, exceeding approximately 50% load and 12 knots, as propeller performance approached its optimal operating point despite some sacrifice in engine efficiency. To integrate these effects, a proxy overall efficiency index (η_{overall,proxy} = η_mech × RPEI_norm) was introduced, revealing a crossover point at 0.525 load where the efficiency dominance shifted between modes. These findings demonstrate that neither mode is universally superior, but rather their advantages depend on operating conditions. The results provide practical insights for adaptive operational strategies, enabling real-time switching between modes to optimize fuel consumption and overall propulsion performance while supporting compliance with environmental regulations. Full article

Xiamen, a rapidly developing coastal metropolis and tourist hub in southeastern China, faces air quality challenges due to its dense population and tourism reliance. This study investigates PM_2.5 sources and temporal variations during autumn 2013–2017 via chemical characterization, mass reconstruction, and receptor modeling. The Positive Matrix Factorization (PMF) model identified five sources: secondary sulfate (31%), coal/vehicle emissions (28%), industrial emissions with secondary organic aerosols (SOA, 20%), ship emissions (14%), and fugitive dust (7%). Interannual variations in source contributions highlighted impacts of anthropogenic activities, meteorology, power plant upgrades, and stricter vehicle standards. PM_2.5 declined 19% (2013–2017), driven by emission controls, while SOA surged 42% (2015–2017) due to VOC oxidation and lower temperatures. Backward trajectory and Potential Source Contribution Function (PSCF) analyses revealed significant regional transport from northern industrial zones (32% contribution) and maritime activities. Ship emissions, which have remained relatively stable over the years, underscore the need for stricter marine regulations. Fugitive dust peaked in 2015 (25.8% of PM_2.5), linked to urban construction. The findings emphasize the interplay of local emissions and regional transport in shaping PM_2.5 pollution, providing a scientific basis for targeted control strategies in coastal cities with similar socioeconomic and geographic contexts. Full article

Accurate identification of mechanical excitation forces is of great significance for the control of ship radiated noise and structural design. Currently, the identification of excitation forces mostly relies on indirect calculations, which suffer from ill-conditioned problems. Regularization correction is one of the main means to solve this problem. Although regularization methods have been widely developed, their application in the field of ships is relatively rare. Currently, the commonly used methods are truncation singular values and Givonov regularization methods. This paper starts from the practical application of ships and addresses the problem of poor correction effect of traditional regularization methods. Two optimized regularization methods, quasi-optimal discriminant criterion and B-spline interpolation function method, are proposed. These methods are verified through simulations and experiments. The results of the scaled model experiments show that compared with using the L-curve alone, the Q-O method reduces the regularization error by 29%, while the BL curve improves the robustness by 38% under a 15 dB noise condition. Full article

In free-running ship simulations, PID control gains for rudder and propeller revolution are often selected based on empirical experience without a standardized procedure, leading to inconsistent results under varying operational conditions. This study examined PID control gains by implementing a simulation framework using STAR-CCM+. The Ziegler–Nichols tuning method was applied to derive control gains, and their behavior was analyzed across different wave conditions (calm, short, medium, and long waves), PID period condition, ship speeds (low and design speeds), and scale ratios. The simulations showed that the PID gains derived under moderate wave conditions provided stable and reliable control performance across various sea states. Furthermore, the influence of scale ratio changes on the control performance was evaluated, and a non-dimensional scaling formula for PID coefficients was proposed to enhance applicability across different model sizes. Validation against experimental data confirmed the reliability of the simulation setup. These findings offer a systematic guideline for selecting the PID control gains for free-running simulations, promoting improved accuracy and stability under diverse environmental and operational conditions. This research contributes to developing standardized practices for maneuvering performance evaluations in realistic maritime environments. Full article

For the motion control of ships in confined and curved waterways, from broad coastal channels to narrow river bends, conventional methods often struggle to ensure both tracking accuracy and navigational safety. A key deficiency is the inability of standard algorithms to incorporate the nuanced principles of good seamanship. To address this, a novel, hierarchical adaptive control framework is proposed. The core novelty of this framework lies in its versatile and adaptive guidance rules, which embed maritime practice into the control loop for different navigating scenarios. In general maritime channels with wind and current, these rules function to ensure robust, high-fidelity route tracking. For the most challenging inland river curved channels, it is further enhanced to generate a strategic, non-centerline trajectory that replicates the crucial inland navigational practice of “holding high and taking low”. This is complemented by a reinforcement learning-based strategy at the control layer, which performs real-time tuning of PID gains to adapt to the vessel’s dynamics. The framework’s dual capabilities were systematically validated. The core adaptive algorithms proved effective for robust control in curved channels under wind and current disturbances. Furthermore, the full framework, including the seamanship-informed strategy, demonstrated superior performance in the most complex inland river scenarios. Compared to a conventional controller, the proposed method reduced the peak cross-track error by over 40% and increased the minimum safety margin from the bank by more than 49% under a strong 3 m/s cross-current. An effective solution for motion control is thus provided, bridging the gap between modern control theory and the context-dependent expertise of practical pilotage. Full article

We propose a control method that integrates adaptive fuzzy sliding-mode control (AF-SMC) with a fixed-time disturbance observer (FTDO) to address modeling errors, external disturbances, and input saturation in ship path tracking. The designed adaptive fuzzy system dynamically adjusts the SMC gain to enhance adaptability to parameter variations and modeling errors. Furthermore, the proposed method enables rapid estimation of the total uncertainty term by incorporating an FTDO, ensuring fixed-time estimation and feedforward compensation of the total matched uncertainty without requiring prior knowledge of the disturbance bound. Lyapunov stability analysis was employed to verify the bounded stability of the closed-loop system. Simulation results indicate that the proposed method provides high control accuracy and robustness. Full article

Controlling air pollution from sea-going vessels is crucial to the sustainable development of maritime transportation. However, emissions of intermediate volatility organic compounds (IVOCs), an emerging aerosol precursor, remain poorly understood. This study developed a ship-type-, fuel-, and operating-mode-specific IVOC emission factor dataset based on existing real-world vessel measurements, and a ship-call-based IVOC inventory methodology tailored for regulatory applications. We quantified IVOC emissions from sea-going ships (excluding fishing and military vessels) entering or departing from the ports in the Economic Zone on the West Coast of the Taiwan Straits in 2014. The total IVOC emissions were 481.4 ± 220.0 t, with Xiamen Port contributing the highest share. Cargo and passenger ships accounted for 65% and 21% of emissions, respectively. While switching to low-sulfur and ultra-low-sulfur fuels increased IVOC emissions by 87% and 49% compared to high-sulfur fuels, the greater reductions in particulate matter and SO₂ emissions still yielded net environmental benefits. The ship IVOC emissions might have become more important in recent years due to enhanced port activity and fuel switching. Uncertainty analysis emphasizes the urgent need for IVOC emission testing on more vessel types. By providing a high-resolution profile of IVOC emissions from selected ports, this study underscores the urgency of adopting shore power and zero-emission vessels to mitigate organic aerosol pollution and offers a foundation for refining environmental impact assessments and efficient emission control policies to achieve sustainability in maritime transportation. Full article

With the rapid expansion of offshore wind farms (OWFs), ensuring maritime safety in adjacent waters has become an increasingly critical challenge. This study proposes an innovative dynamic risk assessment method that integrates a fusion gravity model into a complex network framework to comprehensively evaluate ship importance in OWF areas. By treating ships and wind farms as network nodes and modeling their interactions using AIS data, the method effectively captures spatiotemporal traffic dynamics and precisely quantifies ship importance. Multiple network indicators, including centrality, clustering coefficient, and vertex strength, are fused to comprehensively assess node criticality. A case study in the Yangtze River Estuary empirically demonstrates that ship importance is not static but dynamically and significantly changes with trajectories, interactions with other vessels, and proximity to OWFs, successfully identifying high-risk ships and sensitive OWF areas. The contribution of this research lies in providing a data-driven, quantifiable, novel framework capable of real-time identification of potential threats in maritime traffic. This approach offers direct and practical insights for traffic control, early warning system development, and optimizing maritime traffic management policies, facilitating a shift from reactive response to proactive prevention. Ultimately, it enhances safety supervision efficiency and decision-making support in complex maritime environments, safeguarding the sustainable development of the offshore wind industry. Full article

Ship waterway tunnels are a new and special type of navigation facility that has emerged in the construction of complex hubs in high mountain valleys and rivers, and they have demonstrated broad applications worldwide. Due to their characteristics of long length, a dim visual background, and enclosed space, waterway tunnels are prone to causing tension and cognitive fatigue in ship officers on watch, affecting their decision-making and control abilities. This study constructs the visual navigation environment of a typical waterway tunnel in China using a ship maneuvering simulator. By monitoring the physiological data of ship officers, such as through electroencephalograms (EEGs) and electrocardiograms (ECGs), the temporal and spatial patterns of their physiological and psychological characteristics are analyzed systematically. Based on this, a quantitative model of the cognitive load of a ship officer working in a waterway tunnel is constructed. At the same time, the navigation risk of waterway tunnels of different lengths is quantized based on the entropy weight TOPSIS method, and finally, high-risk sections in waterway tunnels are identified and visualized, providing theoretical support for the management of safety in waterway tunnels. Full article

The advent of remote control and autonomous technologies is fundamentally transforming ship manning models, necessitating adaptations in seafarer standards for L2-class autonomous vessels. To address these challenges, the International Maritime Organization’s (IMO) Maritime Safety Committee (MSC) is developing a non-mandatory Code for Maritime Autonomous Surface Ships (MASS). This paper first conducts an in-depth analysis of the immutable legal obligations and variable technical standards governing seafarer manning for L2 autonomous ships, drawing on the China Classification Society’s (CCS) Rules for Intelligent Ships. It then scrutinizes the international legal barriers confronting CCS manning requirements, particularly concerning remote operator qualifications. The study focuses on aligning China’s regulatory framework with emerging IMO standards and proposes four targeted reforms to facilitate this alignment for L2 vessels: broadening the “seafarer” definition, updating minimum manning principles and procedures, modernizing competency standards, and establishing inclusive operational testing systems. Full article

Amid growing global concerns over environmental sustainability, the shipping industry is under increasing pressure to implement innovative power systems that minimize ecological impact. A promising approach is the marine gas–electric hybrid system, which combines conventional marine propulsion with electric power to offer a cleaner energy solution. Characterized by the integration of continuous and discrete variables, these systems reflect the hybrid nature of gas–electric propulsion. Despite their potential, research on marine hybridization remains limited. To address this gap, a hybrid system model has been developed to optimize energy allocation while accurately capturing the hybrid characteristics of gas–electric systems in ships. Additionally, an energy distribution strategy based on predictive control has been proposed to validate the model’s practical applicability. A weighted evaluation method was employed on a marine gas–electric hybrid test platform to verify the performance of both the model and the control strategy. Results show that different weighting configurations lead to varying torque distribution patterns, confirming the effectiveness of the hybrid system model. Moreover, tuning the weighting parameters within the energy allocation strategy yields diverse control behaviors, further demonstrating the system’s viability for marine applications. Full article

Lead–acid batteries are widely used in modern battery-powered ships. During the charging process of lead–acid batteries, hydrogen gas is released, which poses a potential hazard to ship safety. To address this, this paper first establishes a turbulent flow model for hydrogen deflagration. Then, using FDS6.7.9 software, simulations of hydrogen deflagration are conducted, and a simulation model of the ship’s cabin is constructed. The changes in temperature and pressure during the hydrogen deflagration process in the ship’s cabin are analyzed, and the evolution process of hydrogen deflagration in the ship’s cabin is derived. Hydrogen deflagration poses a significant threat to the fire safety of battery-powered ships. Additionally, a comparative analysis of hydrogen deflagration under different hydrogen concentrations is performed. It is concluded that battery-powered ships using lead–acid batteries should pay attention to controlling the hydrogen concentration below 4%. Full article

Ship emissions represent a significant challenge to environmental sustainability and public health. The widely implemented Emission Control Area (ECA) policy aims to mitigate these emissions; however, existing research often overlooks inland and underdeveloped coastal regions. This study evaluates the impact of China’s Domestic Emissions Control Area (DECA) policy on SO₂ and PM_2.5 air concentrations in three inland cities along the Yangtze River and three underdeveloped coastal cities since its inception in 2018. Employing regression discontinuity (RD) and difference-in-differences (DID) methodologies, this analysis seeks to provide a comprehensive understanding of the DECA’s effects on air quality and its implications for sustainability in these areas. This study revealed that DECA policies resulted in significant improvements in both SO₂ and PM_2.5 concentrations, contributing directly to environmental sustainability and potential public health co-benefits in inland urban areas as well as underdeveloped coastal cities. In the case of inland cities, the daily average concentrations of SO₂ in Yichang and Taicang decreased by 5.3% and 18.9%, respectively, while the average daily concentrations of PM_2.5 saw reductions of 21.9% and 13.9%, respectively. Among the underdeveloped coastal cities, the average daily concentration of SO₂ in Haikou, Danzhou, and Sanya declined by 1.6%, 20.2%, and 21.2%, respectively; additionally, the average daily concentrations of PM_2.5 in Danzhou and Sanya decreased by 13.8% and 9.5%, respectively. The effectiveness of this policy exhibited geographical variation within inland cities and was influenced by urban development indicators in coastal areas. These findings not only underscore the success of the DECA policy in enhancing air quality but also highlight its role in advancing sustainable development goals. They provide essential evidence for formulating effective and sustainable emissions control strategies applicable to similar inland regions and underdeveloped coastal settings worldwide. Full article

When a policy trained with deep reinforcement learning (DRL) in simulation is deployed in the real world, its performance often deteriorates due to the Sim2Real gap. This study addresses this problem for Autonomous Surface Vessels (ASVs) by developing a robust collision-avoidance framework. We integrate a MATLAB-based ship dynamics model with ROS and Gazebo, and employ the Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm. To enhance robustness and generalization, we combine domain randomization and curriculum learning. As a result, the trained agent consistently achieved a high success rate of over 90% in unseen environments, significantly outperforming a baseline TD3 agent and a conventional PID controller. This demonstrates that the proposed Sim2Real methods are highly effective for creating robust control policies for ASVs. For future work, we plan to validate the learned policy through real-world experiments. Full article