Ship Engineering

Formation Navigation Control Method Under Icebreaker Pilotage Conditions

[Purpose] A formation navigation control method is proposed to effectively mitigate disturbances from complex time-varying environments on formation control accuracy and configuration maintenance during icebreaker-assisted navigation, while balancing formation efficiency and safety. [Method] In the aspect of path planning, a non-uniform Theta algorithm was developed to optimize the global path considering the navigation cost and risk factors. In the aspect of piloting icebreaker control, improved adaptive line of sight(IALOS) algorithm is proposed to compensate the rapid change of sideshow angle caused by time-varying environment interference, and course controller is designed to improve the path following accuracy of piloting icebreaker. In the aspect of following ship control, a trajectory tracking controller based on nonlinear model predictive control(MPC) is designed to adjust ship spacing and speed adaptively to improve the efficiency and safety of formation navigation. [Result] The position deviation of formation sailing can be controlled within 0.25 m, and the spacing of formation can be adjusted according to the ice condition. Under the interference of random wind speed and random wind direction, the position deviation of the formation sailing is not more than 0.6m, and the course Angle of each ship is stable, which ensures the control accuracy and safety of the formation. [Conclusion] The proposed formation navigation control method can provide an efficient and robust solution for formation navigation under the pilotage conditions of icebreakers, effectively deal with complex time-varying environmental interference, and provide technical support for shipping in the Arctic and other polar regions.

Marine Scientific Research Equipment

Review and Outlook on Pipeline Systems for Ships Navigating in Ice-Covered Areas

[Purpose] In order to solve the problems of inaccurate prediction of fluid-structure interaction responses under complex environmental loads, insufficient systematic analysis under extreme conditions, high practical application costs and low reliability of active control technologies for the piping systems of ice-going vessels in polar regions with extremely low temperatures, ice-breaking impacts and strict noise restrictions, [Method] a systematic review is conducted from the aspects of vibration, vibration reduction and noise reduction, and safety assessment, and the key technical challenges under complex working conditions are deeply analyzed. [Result] Ice-zone vessel piping system technology is evolving from traditional static analysis toward fluid-structure interaction dynamic forecasting, full-lifecycle safety assessment, and intelligent sensing with adaptive control. [Conclusion] The research results point out the future development direction of the piping systems of ice-going vessels and can provide support for the research and development of China's polar vessels.

Real-Time Lightweight Underwater Target Detection Based on Starnet and Transformer

[Purpose] Underwater marine organism detection is crucial in marine science and ecology. [Method] Leveraging deep learning-based object detection techniques facilitates the accurate identification and counting of underwater marine life, which is essential for understanding the structure and function of marine ecosystems. However, challenges such as light attenuation, image blurriness, and multi-scale variations complicate the detection process in underwater environments. A novel marine object detection method based on real-time detection transformer(RT-DETR) is proposed, termed RTL-StarDETR. By utilizing the high-dimensional feature expression capabilities of star operations, we construct an improved backbone network using the modified StarNet module, ensuring effective extraction of target features while significantly reducing model parameters and computational complexity. Furthermore, the designed dynamic grouped convolution and shuffle mechanism module(DGCSMM) module demonstrates enhanced feature fusion capabilities and a reduced parameter count compared to the Repblock module. [Result] Extensive experiments conducted on the URPC2021 and ROUD datasets reveal that the proposed method achieves a 1.3% increase in m_AP0.5 and m_AP0.5-0.95 compared to the original RT-DETR-r18 model, while simultaneously decreasing the number of parameters and computational cost by 33.7% and 37.2%, respectively. [Conclusion] These results suggest that RTL-StarDETR effectively addresses the challenges of underwater object detection.

Ship Extrication Path Planning and Control Method Under Severe Ice Conditions

[Purpose] With the increasing demand for Arctic shipping channels, the safety and extrication capabilities of ships in severe ice conditions have become significant challenges. To address this issue, [Method] a risk and angle constraints-based Theta*(RAC-Theta*) algorithm combined with a nonlinear model predictive control(MPC) method has been proposed for the extrication strategy. The RAC-Theta* algorithm can dynamically adjust the route to select the optimal steering time and escape route, considering both the ship's navigational risk and the extrication cost. The nonlinear MPC effectively follows the extrication path, enhancing the ship's extrication control in complex ice conditions. [Result] Simulation results demonstrate that the control system can maintain navigational stability in dense ice areas, particularly when the ship encounters large ice floes, allowing for rapid extrication through path planning and secondary planning. The nonlinear MPC controller exhibits strong robustness in controlling surge and sway speeds, which improves the ship's navigation safety and maneuverability. [Conclusion] In conclusion, the proposed extrication strategy optimizes the timing and path of extrication, providing crucial technical support for the safe navigation of ships in ice-covered areas.

Prediction of Ship Motion Based on Collaborative Model

[Purpose] To address the limitations in applicability and accuracy of single-mode ship motion state prediction methods using physical models or neural network models， [Method] the combination of physical model and long short-term memory network is used to predict and analyze the ship motion state， and the characteristics of different types of ships are obtained by changing the physical parameters， and the stability and feasibility of the method are verified by Transformer. [Result] The results show that compared with the single-mode model， the collaborative model has obvious advantages in prediction accuracy and effect， in which the error percentage is within 5%， and the coefficient of determination is stable above 0.85， [Conclusion] The research results can provide some references for predicting the motion state of ships.

Experimental on the Mechanical Behavior of Multiplanar Thin-Walled Circular Steel Tubular KK Joints with Concrete Filled in the Joint Area

[Purpose] To investigate the effect of concrete filling in the joint area on the mechanical performance of multiplanar thin-walled circular steel tubular KK joints， [Method] two specimens are designed: one filled with concrete in the joint area， and the other left empty. By hinge-connecting the ends of the four braces of the specimens and applying axial tensile force at the end of the chord， the failure modes， ultimate capacity， and load-displacement curves of the two specimens are obtained. By hinge-connecting the ends of the four braces of the specimens and applying axial tensile force at the end of the chord， the failure modes， ultimate capacity， and load-displacement curves of the two specimens are obtained. [Results] The test results indicated that circular steel tubular KK joints are more susceptible to plastic failure in the chord near the compressed brace. After filling with concrete， the failure mode shifted to punching shear failure in the chord near the tensile brace， demonstrating that the infilled concrete significantly improves the joint's mechanical performance. The test results are compared with the specification's punching shear bearing capacity formulas for circular steel tubular KK joints and existing multiplanar thin-walled circular concrete-filled steel tubular KK joints， revealing that these formulas are found to be relatively conservative. [Conclusion] The research results can provide some references for the design of KK joints.

Marine Vessel Speed Optimization Method Based on an Improved NSGA-Ⅲ Algorithm

[Purpose] In order to reduce energy consumption and carbon emissions during marine vessel operations and improve voyage efficiency， this study develops a multi-objective speed optimization model targeting the energy efficiency operational indicator (EEOI)， fuel consumption， and voyage time. [Method] This study proposes an improved non-dominated sorting genetic algorithm Ⅲ (NSGA-Ⅲ) that integrates a cosine-decreasing strategy and Gaussian mutation to balance global and local search while enhancing population diversity， thereby improving solution convergence and distribution uniformity. The proposed method is validated using real operational data from the Danish vessel M/S Smyril. [Result] The results show that， while maintaining a comparable voyage time， the optimized strategy reduces fuel consumption by 2.32%. The obtained solution set also demonstrates better performance in terms of Pareto front distribution and diversity of objective values. [Conclusion] The research findings can serve as a reference for intelligent speed decision-making in marine vessels and demonstrate strong engineering applicability and potential for broader implementation.

Research on Vibration Response and Vibration Reduction of Jacket Offshore Wind Turbines

[Purpose] This study investigates the impact of blade pitch faults on the dynamic response of offshore wind turbine structures with concrete-filled steel tubular jackets and evaluates the vibration control performance of a tuned mass damper (TMD) under different operational conditions. [Methods] An integrated coupled numerical model under combined wind and wave actions was established to analyze the dynamic response of the jacket-supported wind turbine structure. The vibration reduction performance of the TMD was systematically assessed during normal operation， shutdown， and fault conditions. [Results] The results indicate that blade pitch faults lead to a sudden increase in hub thrust and a rise in rotor speed， resulting in significant growth in tower top displacement， nacelle acceleration， as well as shear forces and bending moments at the tower base and mudline. While the TMD demonstrates effective vibration suppression under normal operation and shutdown conditions， its control performance is limited during fault conditions due to energy concentration in the 1P frequency range. [Conclusion] This research clarifies the significant influence of pitch faults on the dynamic response of jacket-supported offshore wind turbines and defines the applicability and limitations of TMD under various operational scenarios， providing valuable references for vibration control and safety design of offshore wind structures.

Research on Wave Generation in Small Experimental Water Pools

[Purpose] To establish a test model pool with cross-water domain characteristics by constructing a water level fluctuation and solitary wave generation device based on the dam-break water level difference model. [Method] By controlling the initial water level storage in the upstream of the dam-break device， the variation trends and rules of water level fluctuations and solitary wave heights at designated cross-water domain positions were studied. The RANS method was used to construct a digital pool to calculate and verify the extreme test conditions with strong nonlinearity， and the feasibility and accuracy of the test method were verified through bidirectional convergence. [Result] The test results show that the method of generating water level fluctuations and solitary waves through the dam-break model is effective. [Conclusion] Isolated waves with controllable amplitudes ranging from 2 mm to 39 mm were generated at fixed positions in the test pool， and the wave generation rules and motion characteristics under this method were analyzed and summarized.

On Manoeuvrability Prediction for Multipurpose Cargo Ship

In this paper,taking an 27000 DWT multipurpose cargo ship as an example, the calculation has been carried out both for the model and actual ship.Moreover, the comparison between theoretical and experimental results has also been made in the paper.

Present Situation of Welding Production and Development Trend of Welding Technology in China

In this paper, it is verified that the consumption of steel for welded structures in China in 2004 has exceeded 100 million tons, which makes China the world number one welding manufacture country. Since the beginning of the reforming and opening policy in China, many important and large welded structures have been made and welding has played an indispensable role in the development of national economy. The production and application of welding consumables, the distribution of welding robots, the education and training of welding professional are analyzed. Although the yield of welding consumables and welding wires have been expanded rapidly and China has become the largest welding consumables production and consumption country, the rate of manual welding electrodes is still beyond 75%, the welding mechanization and automation rate is around 35% and the ratio between the annual yield of welding consumables and steel is up to 0.77%. These problems should be solved in a shorter time. According to the development trend of welding technology, the applications of welding robot system, fully digital welding power sources, laser and laser hybrid welding, friction stir welding as well as high efficient welding processes should be emphasized in China’s shipbuilding industry. Our international competition strength should be improved by attracting excellent welding professional to the production front and improving the cooperation between governments, enterprises, universities and research institutes as well as with our predominance of high quality, high efficiency and low production costs.

A Review of Approaches to Mechanism of Ship-bridge Collision And Its Nonlinear FEM Simulation

An overview on the mechanism of the ship bridge collision is given in this paper. Employing MSC/DYTRAN program, a normal collision between ship and bridge is simulated. The history of ship bridge collision force, the exchange of energy, the displacements and the stress distribution of the ship bow and various parts of the bridge are presented. Some mechanical rules and characters during the simulated collision are given which are of great value for bridge design, maintenance and damage estimation.

A Mathematical Model for Motion Control and Simulation of Underwater Vehicle

The six degrees of freedom manoeuvrability equations of the underwater vehicle are given first,these differential equations are transformed to matrix equations with matlab tools which is better applid in motion control and simulation.Then environment simulation,thruster simulation and rudder simulation are discussed.Some trials are carried out with this simulation system,and the results shown relative good comparability between the model and the real vehicle.This simulation system is a normal,generalized and practical model which takes into account all nonlinear hydrodynamic,has better accuracy,and can be applied to all UV which are very useful for the research of maneuverability and adaptive control of underwater vehicles.

A Summary of Statistical Energy Analysis Method and Its Loss Factor's Determination

Statistical Energy Analysis(SEA)has been widely applied to predict vibration and noise transmission through complex structures at medium and high frequency bands.In this paper,SEA's advantages and shortages are analyzed,especially when it is applied to a ship.In SEA,a structure is divided into a number of subsystems which are characterized by quantities of stored vibration energy and the mode numbers within a narrow band.The coupling and energy losses between the subsystems are described by coupling loss and loss factors,which are the important parameters in application of SEA.Methods for determining loss factors in SEA for the recent 40 years at home and abroad are reviewed.

Present Situation of Welding Production and Development Trend of Welding Technology in China

In this paper, it is verified that the consumption of steel for welded structures in China in 2004 has exceeded 100 million tons, which makes China the world number one welding manufacture country. Since the beginning of the reforming and opening policy in China, many important and large welded structures have been made and welding has played an indispensable role in the development of national economy. The production and application of welding consumables, the distribution of welding robots, the education and training of welding professional are analyzed. Although the yield of welding consumables and welding wires have been expanded rapidly and China has become the largest welding consumables production and consumption country, the rate of manual welding electrodes is still beyond 75%, the welding mechanization and automation rate is around 35% and the ratio between the annual yield of welding consumables and steel is up to 0.77%. These problems should be solved in a shorter time. According to the development trend of welding technology, the applications of welding robot system, fully digital welding power sources, laser and laser hybrid welding, friction stir welding as well as high efficient welding processes should be emphasized in China’s shipbuilding industry. Our international competition strength should be improved by attracting excellent welding professional to the production front and improving the cooperation between governments, enterprises, universities and research institutes as well as with our predominance of high quality, high efficiency and low production costs.

Design Study of a Single Point Mooring System in Ultra Shallow Water

On the study of the main form,the type characteristics and the application scope of single point mooring(SPM) system,soft yoke single point mooring system is chosen for the new SPM of "HaiYangShiYou 113" FPSO.The difficulties in the design is studied and the key factors for the design of a SPM in ultra shallow water should be paid more attention,which are design basis,low frequency wave force,bottom striking and green water.The experience is significant for other SPM design in ultra shallow water.