Acoustic multipath structure in direct zone of deep water and bearing estimation of tow ship noise of towed line array

In the towed line array sonar system,the tow ship noise is the main factor that affects the sonar performance.Conventional noise cancelling methods assume that the noise is towards the endfire direction of the array.An acoustic experiment employing a towed line array is conducted in the western Pacific Ocean,and a strange bearing-splitting phenomenon of the tow ship noise is observed in the array.The tow ship noise is split into multiple noise signals whose bearings are distributed between 10°and 90°deviating from the endfire direction.The multiple interferences increase the difficulty in recognizing the target for the sonar operator and noise cancellation.Therefore,making the mechanism clear and putting forward the tow ship noise splitting bearing estimation method are imperative.In this paper,the acoustic multi-path structure of the tow ship in deep water is analyzed.Then it is pointed out that the bearing-splitting phenomenon is caused by the main lobe of direct rays and bottom-reflected rays,as well as several side lobes of direct rays.Meanwhile,the indistinguishability between the elevation angle and the bearing angle due to the axial symmetry of a strict horizontal line array causes the bearing to deviate from the endfire direction.Based on the theory above,a method of estimating bearing of the tow ship noise in deep water is proposed.The theoretical analysis results accord with the experimental results,which helps to identify the target and provide correct initial bearing guidance for noise cancelation methods.

Robust Position Observer for Sensorless Direct Voltage Control of Stand-Alone Ship Shaft Brushless Doubly-Fed Induction Generators

The aim of this paper is to investigate an adaptive sensorless direct voltage control(DVC)strategy for the stand-alone ship shaft brushless doubly-fed induction generators(BDFIGs).The proposed new rotor position observer using the space vector flux relations of BDFIG may achieve the desired voltage control of the power winding(PW)in terms of magnitude and frequency,without any speed/position sensors.The proposed algorithm does not require any additional observers for obtaining the generator speed.The proposed technique can directly achieve the desired DVC based on the estimated rotor position,which may reduce the overall system cost.The stability analysis of the proposed observer is investigated and confirmed with the concept of quadratic Lyapunov function and using the multi-model representation.In addition,the sensitivity analysis of the presented method is confirmed under different issues of parameter uncertainties.Comprehensive results from both simulation and experiments are realized with a prototype wound-rotor BDFIG,which demonstrate the capability and efficacy of the proposed sensorless DVC strategy with good transient behavior under different operating conditions.Furthermore,the analysis confirms the robustness of the proposed observer via the machine parameter changes.

Reliability Analysis Based on a Direct Ship Hull Strength Assessment

A method of reliability analysis based on a direct strength calculation employing the von Mises stress failure criterion is presented here. The short term strain distributions of ship hull structural components are identified through the statistical analysis of the wave-induced strain history and the long term distributions by the weighted summation of the short term strain distributions. The wave-induced long term strain distribution is combined with the still water strain. The extreme strain distribution of the response strain is obtained by statistical analysis of the combined strains. The limit state function of the reliability analysis is based on the von Mises stress failure criterion, including the related uncertainties due to the quality of the material and model uncertainty. The reliability index is calculated using FORM and sensitivity analysis of each variable that has effects on the reliability is also discussed.

A Direct Compensative Robust Optimal Control (DCROC) Law for Ship Straight-line Track-keeping

A linear quadratic optimal direct track-keeping control law was proposed based on first-order Nomoto nominal model. Furthermore, based on Lyapunov stabilized theory, considering parametric uncertainty from variations of ship speed and disturbances uncertain from wind, wave and sea current, a direct compensative robust optimal control (DCROC) law was developed. It can guarantee closed-loop system globally and uniformly converge to a remained set. High accuracy and robustness were achieved. By introducing some nonlinear blocks, closed-loop system achieves global and uniform asymptotical stableness. Numerical simulations on a Mariner Class ship are presented to validate the control law.

Model of Shipping Noise in the Deep Water: Directional Density and Spatial Coherence Functions

The shipping noise properties in the deep ocean are studied. Shipping noise exhibits the strong dual-horned directionality features in the flat-seabed ocean, and its directional density can be modeled by a Von Mises distribution. With the explicit expression for the directional density function, the spatial coherence functions of shipping noise are also derived, and the relative features are studied. The research result shows that the properties of shipping noise are different from the ambient noise of other sources, and it can be used for the sonar array design. The model is well matched with the experimental result, and it can be extended to the situations when the ambient noise exhibits the dual-horned structure.

Multi-static InISAR imaging for ships under sparse aperture

This paper concentrates on super-resolution imaging of the ship target under the sparse aperture situation.Firstly,a multi-static configuration is utilized to solve the coherent processing interval(CPI)problem caused by the slow-speed motion of ship targets.Then,we realize signal restoration and image reconstruction with the alternating direction method of multipliers(ADMM).Furthermore,we adopt the interferometric technique to produce the three-dimensional(3D)images of ship targets,namely interferometric inverse synthetic aperture radar(InISAR)imaging.Experiments based on the simulated data are utilized to verify the validity of the proposed method.

Practical Solutions for Reducing Container Ships' Waiting Times at Ports Using Simulation Model

The main challenge for container ports is the planning required for berthing container ships while docked in port.Growth of containerization is creating problems for ports and container terminals as they reach their capacity limits of various resources which increasingly leads to traffic and port congestion.Good planning and management of container terminal operations reduces waiting time for liner ships.Reducing the waiting time improves the terminal’s productivity and decreases the port difficulties.Two important keys to reducing waiting time with berth allocation are determining suitable access channel depths and increasing the number of berths which in this paper are studied and analyzed as practical solutions.Simulation based analysis is the only way to understand how various resources interact with each other and how they are affected in the berthing time of ships.We used the Enterprise Dynamics software to produce simulation models due to the complexity and nature of the problems.We further present case study for berth allocation simulation of the biggest container terminal in Iran and the optimum access channel depth and the number of berths are obtained from simulation results.The results show a significant reduction in the waiting time for container ships and can be useful for major functions in operations and development of container ship terminals.

扩展P-ROQR环流抑制策略在船舶MMC-MVDC电力系统中的应用

为了解决船舶中压直流(MVDC)电力系统中应用的模块化多电平变换器(MMC)存在的环流问题,分析自阻型MMC的拓扑结构及环流产生机理,采用基于2阶广义积分器(SOGI)的滤波器过滤环流中的直流分量。对于环流中的交流分量,提出一种基于比例降阶准比例谐振控制器的新型环流抑制器对其进行抑制。在MATLAB/Simulink软件中搭建船舶自阻型MMC-MVDC电力系统模型。仿真结果表明:所提策略能有效抑制环流中的交流分量;自阻型MMC应用于逆变侧时具有直流故障闭锁能力。所提策略应用于船舶MMC-MVDC电力系统的环流抑制效果优异,同时具有减少桥臂电流畸变,稳定子模块电容电压的作用。

基于先导发展模型的船舶直击雷防护分析方法

大型船舶平台搭载的精密仪器和探测装置相对其他设备高度较高,有尖端突起且抗干扰性较差,是海面上明显的突出物,雷电防护成为现代船舶重要的研究内容。本文提出一种基于海洋复杂环境改进Wiesmann-Zeller(WZ)模型概率发展函数的船舶雷电防护分析方法,建立了海面雷电先导发展模型,以大型远洋调查船为对象,研究其雷击点的概率分布,并结合船舶特点进行了多避雷针的分析计算。基于本文提出的模型,通过Matlab软件模拟雷击船舶过程,揭示了防护范围、效果与避雷针位置、数量高度之间的关系,对比分析了不同避雷针数量和避雷针高度下的雷击概率和防护效果,验证了三针不等高为最优方案,能够指导和完善实际工程实践,保证船舶雷电防护效果的充分发挥。

双桨双舵内倾船型的横甩失稳运动预报研究

目前国际海事组织(IMO)已经发布了第二代完整稳性衡准骑浪/横甩直接稳性评估方法的最终指南,如何准确高效地数值预报骑浪/横甩运动是目前骑浪/横甩直接稳性评估方法中亟待解决的关键问题。本文构建一个纵荡-横荡-垂荡-横摇-纵摇-首摇六自由度运动耦合的数学模型,该数学模型首先在纵荡-横荡-横摇-首摇四自由度操纵性数学模型基础上考虑垂荡和纵摇运动的影响,采用基于加强积分的切片法求解垂荡和纵摇运动的幅值和相位,可以有效解决尾浪中高航速船舶直接耐波性时域计算容易发散的问题;其次,船舶在波浪中的Froude-Krylov力和绕射力是通过对船体平均湿表面进行压力积分获得的。同时,在数学模型中还考虑非线性水动力导数、静水横倾产生的水动力和非线性横摇阻尼等因素。在螺旋桨推力和舵力模型中考虑由于波浪粒子速度和船舶速度共存产生的水动升力的影响,舵力模型中还加入了垂荡、纵摇运动对波浪中双舵实时出入水导致的舵力动态变化。最后,以双桨双舵的ONR内倾船型为研究对象,开展尾斜浪中骑浪/横甩数值预报,分析船-波的初始相对位置对船舶骑浪/横甩运动的影响。计算结果表明,文中建立的六自由度骑浪/横甩数学模型具有足够的计算精度,可以用于骑浪/横甩的直接稳性评估。

基于车船直取模式的集装箱海铁联运衔接优化

为解决车船直取模式下集装箱海铁联运衔接优化问题,基于固定的船期,本文考虑火车班列和集装箱船在时间和运量两个维度上的衔接,以衔接班列数量最大化、衔接船舶数量和时刻表调整最小化为目标,构建海铁联运班列时刻表优化的混合整数非线性规划模型,并基于分层优化方法进行求解。以深圳盐田港为例,对模型进行分析验证。结果表明:考虑时间和运量衔接的班列时刻表优化,可以带来衔接的班列数量增加6个,车船直取集装箱总量增加466 TEU,提高了75%;衔接的船舶数量增加了1个,3艘船装载的车船直取箱量分别提高了2.6%、4.2%和2.5%;集装箱在港口总停留时间缩短了26%。研究表明,该模型可为改善港口车船直取模式下海铁联运衔接水平提供有益参考。

基于EXCEL的ACCESS起重船数据库的实现

针对船型资料繁杂众多,录入麻烦的问题,提出有针对性地建立ACCESS数据库,并且通过VBA使用ADO获取数据库中的资料,实现与EXCEL的无缝连接,达到船舶型值表输入与输出完全自动化的目的,不仅可保证数据的准确性,而且可为船舶的性能计算以及连接其他软件做必要的准备。

船舶发电机定子绕组匝间短路故障预警

为保障船舶的安全航行,需要对船舶发电机定子绕组早期匝间短路故障进行预警。首先,通过同步发电机的数学模型对正常运行和不同程度的匝间短路故障进行仿真,选取负序电流分量和电磁转矩作为故障特征量并进行信息融合;然后,使用CNN-BiLSTM网络对特征量进行回归预测得到网络预测的残差;最后,根据残差的变化趋势和设定的阈值来判断故障的发展情况。结果表明,建立的模型可以实现定子绕组匝间短路故障的预警,并且基于自适应原理设置的动态阈值会比固定阈值提前确认故障。

基于改进YOLOv5的船舶多尺度SAR图像检测算法

针对复杂场景下合成孔径雷达(Synthetic aperture radar, SAR)图像船舶目标像素尺度差异大和船舶密集排列造成目标漏检的问题,提出一种基于改进YOLOv5的船舶多尺度SAR图像检测算法。对于YOLOv5的颈部网络,采用双向特征金字塔结构(Bi-directional feature pyramid network, BiFPN)提升网络多尺度特征融合能力,并在其自下而上的特征融合支路中,基于深度可分离卷积(Depthwise separable convolution, DSC)和通道MLP构建EC-MLP(Enhanced channel-MLP)模块,从而丰富语义信息,提供更充分的船舶目标上下文特征;引入全局注意力机制(Global attention mechanism, GAM),使网络对输入特征进行针对性提取并运算,减少网络的信息丢失;此外,使用SIoU损失函数进一步提高网络的训练收敛速度和检测精度。在SSDD和HRSID数据集上与其他8种方法(Faster R-CNN、Libra R-CNN、FCOS、YOLOv5s、PP-YOLOv2、YOLOX-s、PP-YOLOE-s和YOLOv7-tiny)进行对比实验。实验结果表明:改进后算法在SSDD数据集上的AP50达到了96.7%,在HRSID数据集上AP50达到了95.6%,优于对比方法。

基于Modelica的船舶直流区域配电系统建模与仿真

直流区域配电网具有结构简单、可靠性高和线路损耗较小等优点,但其复杂的拓扑结构、多变的运行工况和结构的高度电力电子化等特点给其稳定运行带来了挑战。本文以船舶直流区域配电系统为研究对象,采用模块化建模方法,对船舶直流区域配电系统进行合理划分,基于多领域统一建模Modelica分区域建立了配电模型自下而上建立了直流变换电源模型、单相逆变电源模型、三相逆变电源模型等电力变换模型,构建了基于Modelica的某船舶直流区域配电系统模型。

船舶滚装通道设备的结构设计衡准研究

船舶滚装通道结构分析问题较为复杂,中国船级社《钢质海船入级规范》在车辆甲板尺寸要求等方面目前仍有适用性问题,因此有必要进一步研究。该文以船舶滚装通道的板、梁结构和主要构件为研究对象,采用理论公式推导和数值拟合方法,建立了车辆甲板板厚、骨材构件尺寸描述性要求,同时形成了符合国际船级社协会统一要求、涵盖各类载荷的通道主要支撑构件直接计算要求,并进行实例计算验证。结果表明:优化后的描述性要求和直接计算要求具有良好的适用性,对于提高滚装通道结构设计的安全性与轻量化水平具有重要意义。

混合动力船舶双向充电装置高性能控制策略

充电装置作为混合动力船舶最重要的组成之一,保证了系统主交流电网与主电池之间的能量转换。因此,研究其控制策略以及充电效率等问题对今后混合动力船舶的发展具有重要的指导意义。基于此,本文首先针对混合动力船舶充电装置的电路拓扑进行了分析。其次,重点对系统中不同工作模式的控制策略进行了研究,在充电和馈网模式下,提出了一种基于三相PWM整流器的预测直接功率控制的新型整体控制策略,对传统的控制策略进行了改进,简化充电/馈网模式的控制策略并提高了充放电效率和集成度。最后通过Simulink软件的仿真平台以及样机实验平台,仿真和实验分析验证了所提出控制策略的有效性和准确性。

基于业务特性和负载均衡的HWNs接入选择算法

针对传统的网络接入选择算法没有考虑不同用户的业务偏好和网络负载均衡性的问题,论文提出了一种基于业务特性和负载均衡的异构无线网络接入选择算法。算法综合考虑业务特性、用户偏好和网络属性,计算网络属性的主客观权重和用户偏好权重,根据效用值对候选网络进行排序,并引入网络负载控制机制为业务匹配网络。经仿真验证,该算法能够为业务精准匹配网络,相比于同类算法,在业务满意率性能方面提升了6.9%,且网络负载空闲度方差仅为同类较好算法的47.1%,网络整体负载均衡性能得到提升。该算法应用于海上船舶编队异构无线网络场景可有效提升船舶通信保障性能。

基于Access数据库船舶设备智能诊断系统

船舶的轮机管理人员通常仅能解决一些普通的维修问题,大多数疑难、综合故障仍得靠船舶维修专家来处理。特别是现代化的船舶,机舱设备种类众多,结构复杂,自动化程度高,对轮机人员的专业水平要求更高,一旦出现故障,部分轮机人员往往束手无策,这将会影响航行安全和航期,船舶公司每年要为此花费大量的成本。因此开发智能诊断系统并装船使用就显得非常必要。

进出口大宗货物“船边直提”“抵港直装”监管机制与风险防控

为深入落实党中央、国务院优化口岸营商环境坚持稳中求进工作总基调的决策部署,张家港海关基于风险控制理念优化进出口货物“船边直提”“抵港直装”监管模式,积极探索开展扩大进出口货物“船边直提”“抵港直装”试点工作,更好服务市场主体,筑牢国门安全防线。研究表明建立“船边直提”“抵港直装”风险控制体系不仅能够提高进出口货物通关效率,同时能够防范化解重大风险。该研究为符合条件的港口推行“船边直提”“抵港直装”监管模式风险防控提供了参考。