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1.
降雨条件下的导航X波段雷达海浪参数反演算法研究   总被引:1,自引:0,他引:1  
X波段的电磁波受降雨影响容易产生衰减,这导致导航X波段雷达在降雨时无法用于海浪观测。本文提出了一种新的降低降雨影响的算法来反演海浪参数。首先,对X波段雷达图像做主成分分析,获得波浪变化的主成分,利用一维傅里叶变换得到波数谱,对其滤波减小降雨对雷达图像的影响;然后,选取JONSWAP(Joint North Sea Wave Project)谱作为理论谱,建立以观测谱与理论谱的最小化差异为目标函数的模型,求解该模型估算海浪的有效波高。与浮标测量的有效波高相比,该方法反演的有效波高的均方根误差是0.23 m,证明了该方法的可行性。  相似文献   

2.
根据海浪波高序列的长期相关性和自仿射分形结构,本文提出了两种新的波高序列模式:Cauchy统计模式和分式统计模式.前者将实测的有限个波高值作为Cauchy初始条件,应用自仿射定理对波高序列今后的取值在统计意义上作出预报;后者适用于在计算机上模拟海浪波高的统计特性.应用实测资料对模式的检验结果表明,上述两种模式在预报和模拟海浪波高序列时均能达到较高的精度;它们为海洋工程设计人员提供了有力的手段.  相似文献   

3.
无论是对于各种涉海水工建筑物的设计还是对于它们的防护而言,最大波高的预测都是非常重要的工作。目前常用的海浪预报模式多以相位平均模型为主,其能直接给出的计算结果是海浪谱,因此基于海浪谱给出合理的最大波高估算具有重要的意义。前人对波陡、谱宽等参数对最大波高公式的影响都有了较为清楚的认知,然而相关研究大多围绕单峰谱开展,尚没有考虑包括双峰谱在内的海浪谱型最大波高公式的影响。本文首先探讨了海浪谱对最大波高的影响特性,进而提出了海浪谱谱型的参数化定义,最后给出了考虑谱型因子的最大波高公式。  相似文献   

4.
本文根据相干斑噪声的时间快变特征和非海浪纹理现象的时间缓变特征,基于交叉谱提出了一种对相干斑噪声和大尺度非海浪纹理的抑制的方法,进而结合SAR图像谱和海浪谱之间的准线性映射关系,基于SAR数据对海浪参数进行了反演。在反演过程中,首先仿真分析了不同海况下准线性近似法的海浪反演能力,结果表明:风浪引起的方位向截断效应会显著影响反演精度,因此该方法在低风速时的涌浪反演精度更高。通过将基于Sentinel-1卫星2020年的波模式SAR数据的反演结果与欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)提供的再分析数据进行对比,发现高海况海浪有效波高反演结果明显偏低,而且该反演误差与风速、方位向截断波长之间存在显著相关性。为了提高有效波高的反演精度,本文进一步给出了海浪有效波高反演误差与风速、方位向截断波长之间的经验校正函数模型,结果显示,通过该模型修正后的海浪有效波高反演结果与ECMWF数据和浮标测量数据具有良好一致性。  相似文献   

5.
最大波高作为表征海浪强度和危险程度的重要指标,既是设计波浪推算的依据,同时又对海洋预报有重要的作用。基于瑞利分布得到的最大波高公式,不能体现波陡和谱宽度等非线性因素的影响,由该公式得出的理论最大波高与实际观测值有偏差。采用相位平均方法的海浪数值模型分析,可以根据海浪谱计算得到有效波高,却无法给出最大波高。本文通过分析挪威北海定点十年的船测波面资料,得出波浪谱,进一步推算出波陡和谱宽度对最大波高的影响。首先提出一种实测波数的替代方式,然后分别研究波陡和谱宽度对最大波高的影响。研究发现随着波陡和谱宽度的增加,Hmax/Hs逐渐减小,并拟合出最大波高与Cartwright谱宽度参数的公式,得到较好的拟合效果。  相似文献   

6.
X-波段雷达近海海浪频谱反演的神经网络模型   总被引:2,自引:1,他引:1       下载免费PDF全文
X-波段雷达作为国内海浪观测的一种新工具,在海浪频谱获取和有效波高反演方面仍存在较多问题.本文利用非线性回归方法,将现场实测浮标数据频谱和雷达一维图像谱分别与标准频谱模型进行拟合,发现浮标频谱和一维图像谱具有标准频谱的特征,能够较准确地获取相应的谱参数.提出了建立由雷达一维图像谱参数反演海浪频谱参数的神经网络模型,同时在模型中加入影像序列信噪比,进而反演有效波高,并将反演结果与现场实测数据和传统算法(建立影像序列信噪比与有效波高之间的线性回归方程)进行了对比,结果表明,获取谱参数的误差和反演有效波高的平均误差在20%以内,而传统算法计算有效波高平均误差在20%以上.  相似文献   

7.
海浪波高测量是海洋勘探的主要内容之一.结合Ku波段多普勒相栓雷达,运用虚拟仪器根据海浪回波的多普勒频率来判断海浪变化,测出海浪波高存储数据.系统硬件部分采用了NJ(National Instruments 美国国家仪器)公司的高性能数据采集卡USB-6251.替代传统的DSP处理芯片.软件方面采用了Labview7.1图形化编程实现,具有很好的直观性和形象性.初步实现了潮位测量的基本功能.  相似文献   

8.
最大熵原理与海浪波高的统计分布   总被引:12,自引:2,他引:10  
吴克俭  孙孚 《海洋学报》1996,18(3):21-26
将自然界中普遍存在的物理规律──最大熵原理应用于海浪波高的统计分布研究,在两个外部约束条件下,导出了海浪波高服从Weibull分布。借此说明,Rayleigh分布用以描述实际海浪的波高有其物理上的必然偏差,作为一种经验分布经常使用的Weibull分布有着深刻的物理根源。并对依赖于水深的经验波高分布进行了可能的物理解释。  相似文献   

9.
波浪观测是海洋观测的主要内容之一,对海浪的现场观测和深入研究对准确预报海浪具有十分重要的意义。本文设计了一种新型漂流式波浪浮标,采用高精度惯性导航模块作为测量元件,同时高频获取三轴加速度、角加速度、欧拉角、地磁数据,通过内置ARM处理器对测量数据进行波浪参数的采集和解算。浮标具有整体体积小、成本低的特点,既可以漂流观测,也可以定点锚系观测,能够实现对海浪的长期、大范围、高精度观测应用。本文通过该漂流式波浪浮标在2019年西北太平洋航次的观测应用,对西北太平洋黑潮延伸体海区和日本海区域海浪的有效波高、周期等波浪要素的时空变化特征进行了详细分析,取得了良好的测量结果。  相似文献   

10.
海浪传真图包括海浪实况分析和海浪预报两部分,是为船舶安全航行、海上安全作业、海上最佳航线选择以及防止海难事故等目的而制作的。 海浪是一种久被习知而又十分复杂的现象。在久远的年代,人们在生产斗争中早已熟悉,它之所以受到注意,是由于它影响着海上活动的诸方面。这首先表现在波浪对船舶的影响,由于波浪的颠簸,船体各部结构会受到各种变形应力的作用,有些在第二次世界大战期间建造的船舶,因对海浪情况估计不足而遭到很大的损坏;颠簸对乘客的舒适和货物的储放是不利的;颠簸可引起船舶的共振;海浪还影响船舶航行的方向和速度,自五十年代起开展的最佳航线服务,就是利用海浪等水文气象预报选择最佳航线,已收到显著的效果,在最佳航线上航行的船舶,除能减少海损以外,还大大地缩短航时,如使用航线预报的船舶与自我航行的船舶相比,横渡太平洋平均缩短19小时的航海时间,横渡大西洋平均缩短9~15小时的航海时间。 海浪与海港的设计和建筑有着密切的关系。这不仅是因为海浪能推动数千吨重的石块和激起数十米高的水柱,而且还可以引起港内破坏性的付振动,这种振动可使停泊的船只遭到损坏。  相似文献   

11.
A wave-height meter using a simple microwave Doppler radar,simeq10mW in power and 10.525 GHz in frequency, is proposed so that we can measure oceanic waves effectively while the ship is steaming. It was first applied to the measurement of the variation of water level generated in a wave tank, which suggested that it is adequately applicable to the measurement of oceanic waves. A field test was carried out off the cape of Nojimazaki by installing the Doppler radar 5 m above the sea level at the bow of the ship. The result agreed reasonably well with that measured simultaneously by the ultrasonic wave-height meter installed at the same position. Another test is running successfully on a larger ship with the wave-height meter installed at 9 m above the sea level. The significant wave height measured by the present meter is being compared with that observed visually by the navigation officers.  相似文献   

12.
主动声呐系统中,平台运动会导致目标回波信号存在多普勒频偏,目标的径向速度会估计错误.文中推导了本舰运动产生多普勒频偏的原因和两者之间的关系,并结合主动声呐的工作特点,提出在接收机和发射机同时进行舰速补偿的方案,可以实时响应舰船运动状态变化,准确补偿本舰运动引起的多普勒频偏.提出在发射机信号源中采用插值法,通过改变发射信...  相似文献   

13.
人工神经网络在潮位探测系统中的应用研究   总被引:1,自引:0,他引:1       下载免费PDF全文
叙述了人工神经网络算法在“Ku波段微波海洋波高/潮位探测系统”中的应用研究成果,介绍了检测微波回波信号中的中频信号和9/256点插值神经网络的设计方法及训练模型,并把这两个网络应用于探测系统,使系统波高/潮位的探测精度提高了1个数量级,还保证了监测的实时性,提出了某些减少训练时间的方法。  相似文献   

14.
在SAR与AIS联合探测探测舰船目标实验中,通过对2010-11-05T06:51渤海海峡Radarsat-2影像的和与之时空匹配的AIS数据比较,发现2种手段探测到的静止的舰船目标能够精确的匹配,但是运动的舰船目标存在一定的偏差.分析了偏差产生的原因,其中距离向偏差是由时间误差引起的;方位向偏差主要是由多普勒频移造成的;这与运动舰船目标的航速、航向及SAR与AIS的探测时间误差有关.在此基础上建立了数学模型,分析上述参数对偏差的影响,并对偏差加以修正,从而实现了SAR与AIS探测结果的匹配.  相似文献   

15.
This paper describes how simplified auxiliary models—metamodels—can be used to create benchmarks for validating ship manoeuvring simulation models. A metamodel represents ship performance for a limited range of parameters, such as rudder angles and surge velocity. In contrast to traditional system identification methods, metamodels are identified from multiple trial recordings, each containing data on the ship’s inherent dynamics (similar for all trials) and random disturbances such as environmental effects and slightly different loading conditions. Thus, metamodels can be used to obtain these essential data, where simple averaging is not possible. In addition, metamodels are used to represent a ship’s behaviour and not to obtain physical insights into ship dynamics. The experimental trials used for the identification of metamodels can be found in in-service recorded data. After the metamodel is identified, it is used to simulate trials without substantial deviations from the ship state parameters used for the identification. Subsequently, the predictions of the metamodels are compared with the predictions of a tested manoeuvring simulation model. We present two case studies to demonstrate the application of metamodels for moderate turning motions of two ships.  相似文献   

16.
A moving particle image velocimetry (PIV) system was successfully developed and used in a large towing tank for ship model tests to observe velocity fields near ship models. The experimental method involved adjustable optical devices for various test conditions and a special particle-seeding device. The streamwise and cross-streamwise flow fields of a yacht model and a tanker model were measured. Ship type, bottom shape, and towing speed were found to be the causes of problems affecting optical access and image quality. Possible solutions, deeper optical ducts, dark painting color, and pre-processed analysis method, were proposed and discussed.  相似文献   

17.
通过引入合理的撞击模型,建立了水面运动船只低速撞击埋置框架结构的传递矩阵-节点耦合矩阵动力分析模型。该模型可模拟船只与结构在撞击过程中的短暂脱离,并分析撞击力时程曲线和整个撞击系统的动力响应。与有限元方法的比较验证了结构传递矩阵-节点耦合矩阵动力分析方法的有效性。不同于规范计算方法,分析发现撞击过程中的最大撞击力不仅与船只的初始动能有关,还受船只与结构间的接触刚度及结构的自身刚度影响,这两种刚度越大,则最大撞击力也越大,撞击持续时间则越短,而撞击力时程曲线的振荡越明显,甚至在船只撞击结构后的很短时间内就可能产生较大的撞击力峰值。  相似文献   

18.
A method to evaluate the use of actively controlled moving weights on board ships to reduce roll motion is developed. The weights can simulate in principle anti-roll-tank systems, or they can be considered a possible anti-roll device in their own right. The ship, the moving weight, and the control device are considered components of a single dynamic system. The full eight-degree-of-freedom set of coupled governing equations for the complete dynamic system is derived. And a three-degree-of-freedom non-linear approximation for the roll motion only (MOTSIM) is derived from these eight equations. The reduced set of equations is used to determine the influence of various parameters and to evaluate control strategies. A PID controller is developed to command the position of the weight and a servomechanism model is used to predict its actual position. Then, the moving-weight system is incorporated into LAMP (Large–Amplitude–Motion Program), a computer code that integrates the governing equations of the sea and the motion of the ship interactively and simultaneously and predicts the motion of the ship in the time domain. A comparison of the results from the two simulations shows that there is fairly good correlation between the simple and complex models, but the simple model is a little optimistic in predicting the effectiveness of the moving-weight system. The results predict that the moving-weight system can be an excellent roll-suppressing device when the moving weight is as small as 1% of the displacement of the ship and the maximum distance the weight moves is as small as 15% of the half-beam.  相似文献   

19.
This paper presents an on-line trained neural net work controller for ship track-keeping problems. Following a brief review of the ship track-keeping control development since the 1980's, an analysis of various existing backpropagation-based neural controllers is provided. We then propose a single-input multioutput (SIMO) neural control strategy for situations where the exact mathematical dynamics of the ship are not available. The aim of this study is to build an autonomous neural controller which uses rudder to regulate both the tracking error and heading error. During the whole control process, the proposed SIMO neural controller adapts itself on-line from a direct evaluation of the control accuracy, and hence the need for a “teacher” or an off-line training process can be removed. With a relatively modest amount of quantitative knowledge of the ship behavior, the design philosophy enables real time control of a nonlinear ship model under random wind disturbances and measurement noise. Three different track-keeping tasks have been simulated to demonstrate the effectiveness of the training method and the robust performance of the proposed neural control strategy  相似文献   

20.
Among the fastest‐growing applications of high‐precision GPS positioning are those which are kinematic in nature. Carrier phase‐based GPS positioning of a moving antenna—for example, attached to a ship, an aircraft, or a land vehicle—is now commonplace. Recent software innovations make use of advanced ambiguity resolution “on the fly” and real‐time kinematic data processing algorithms to emulate the ease of operation of conventional differential GPS (DGPS) based on transmitted pseudo‐range corrections. However, as much higher accuracy must now be assured compared to DGPS, greater attention must be focused on the quality control aspects of GPS positioning. This study describes two methods for detecting failures or changes of small magnitude in real time in GPS measurements. Examination of the overlap or disjointedness of robust and conventional confidence intervals and studentized normal variates have been used as failure detection tools. These methods are based on testing the performance of the differences between the conventional (nonrobust) Kalman state estimates and the robust Kalman filler estimates. Detection of cycle slips in carrier phase data, outliers in phase rate or in code ranges, or any other type of disorder in the measurements of the GPS system can be addressed with these failure detection methods. Application and evaluation of the algorithms has been carried out using raw carrier‐phase and phase‐rate GPS measurements. It has been demonstrated that these failure detection tools provide powerful and efficient diagnostics for detecting small changes in the measurements of the GPS system.  相似文献   

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