共查询到20条相似文献,搜索用时 46 毫秒
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For accurate prediction of the deformation of cable in the towed system, a new finite element model is presented that provides a representation of both the bending and torsional effects. In this paper, the cubic spline interpolation function is applied as the trial solution. By using a weighted residual approach, the discretized motion equations for the new finite element model are developed. The model is calculated with the computation program complier by Matlab. Several numerical examples are presented to illustrate the numerical schemes. The results of numerical simulation are stable and valid, and consistent with the mechanical properties of the cable. The model can be applied to kinematics analysis and the design of ocean cable, such as mooring lines, towing, and ROV umbilical cables. 相似文献
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采用将拖缆直径参数化,可以由 Workbench 一键化建模并由 ICEM 的脚本语言自动生成结构化网格。 采用计算流体力学方法(CFD)计算少量不同攻角时拖缆微元的阻力性能,并由三次样条插值的方法计算拖缆微元在特殊攻角下的阻力性能。 相似文献
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海洋测深中,海底混响信号是测深仪回波信号检测的主要内容。测深仪通常采用信号的相关处理方法对其进行检测,因此在设计测深仪的回波处理单元时,系统地分析海底混响信号的相关特性就显得尤为重要,对混响信号仿真是分析其特性的有效手段。基于单元散射理论,依据海底散射系数的空间相关半径划分散射单元,给出垂直分置海底混响信号的仿真方法。研究结果表明,该模型物理意义明确,计算简单。仿真得到的海底混响信号具有非常好的空间相关性和时间自相关性,与实测的海底混响信号相符,可用于对混响场特性的分析,改善测深仪的设计,从而有效提高测深仪的测量精度。 相似文献
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为了详细了解国外导航卫星反射信号(GNSS-R)新技术在海洋遥感方面的研究进展,在外文文献调研的基础上,详细阐述了GNSS-R的反射率和双基雷达两种方法在海洋监测应用的遥感技术原理,介绍了海面风场遥感、海冰遥感和海面测高等方面的的理论模型和方法。高空间分辨率和高时间分辨率是导航卫星反射信号在海洋中应用的最大优势。虽然GNSS-R的海洋气象要素反演技术只有十几年的发展历史,但是它已经在海洋天气预报和全球气候变化等领域显示出广阔的应用前景和巨大潜力,未来必将成为海洋大气探测的重要技术手段。 相似文献
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利用插值试验分析采样网格对粒度趋势分析的影响 总被引:10,自引:0,他引:10
利用地理信息系统软件ArcView3.2的空间分析功能,采用三次样条插值方法,对采自山东半岛月湖的表层沉积物的粒度参数进行插值。应用“粒度趋势分析”方法,选取一系列的特征距离值进行试验,从原始数据和插值后数据中提取净输运方向的信息。结果显示,原始的不规则采样点所得粒度趋势对于特征距离的选择很敏感,而插值后的规则格网在不同的特征距离下均表现出比较统一的粒度趋势信息。研究表明,规则格网较不规则格网采样点有许多优势,应用插值方法可有效地提高原始数据的信息含量及其质量。 相似文献
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Measurements of the sea surface height (SSH) can be carried out with GNSS aboard ships, but data about the static draft and the hydrodynamic squat effect are necessary. This information is often not available or has an insufficient accuracy. In this study, an alternative method based on the GNSS signal-to-noise ratio observations is presented. Using this method, the distance between the water surface and a GNSS antenna can be estimated directly, if corrections of the heave and the ship’s attitude are considered properly. Suitable segments of a 3-month dataset, gathered aboard a ferry ship operating in the German Bight, were analysed. A global optimization approach based on interval analysis was used and all available observations from a segment were analysed in a common adjustment calculation. The resulting SSH was validated with data from a tide gauge station at Heligoland. The mean difference is 4?mm and a standard deviation of the differences of 5.3?cm was found. The SSH for the same GNSS dataset was also derived from a well-established processing based on the comprehensive consideration of ship dynamics. The mean difference with respect to the tide gauge was 2?mm with a slightly smaller standard deviation of 4.0?cm. 相似文献
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本文介绍用于声呐系统中通道信号模拟器的设计方案,采用PC机进行系统管理和模拟信号的解算,单片机80C31作为其协调处理器用于硬件工作流程的时序控制和信息传送,从而实现模拟多通道声呐信号的效果,该模拟器控制灵活,可靠性高,通用性强,并具有实用价值。 相似文献
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GNSS/声纳定位精度主要取决于GNSS浮标阵列构型和测距精度。优化水面GNSS浮标阵列对提高定位精度和可靠性有重要意义。本文提出了基于高度角约束条件的GNSS浮标阵列优化搜索算法。基于GNSS浮标位于海平面和高度角约束条件,本文提出了优化PDOP算法。我们以5个浮标为例对该算法进行了验证,并且获得了完整解。最后,为了在PDOP最小的解中搜索到最优构型,我们提出了一个用来获取最小GDOP解的搜索算法。算法表明:在区域范围内,区域中心点处GDOP最小与区域PDOP均值最小是等价的。我们用中国南海实测数据阐明了5枚浮标情况下定位图形与定位精度的关系。 相似文献
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研究非完整移动机器人的轨迹跟踪控制问题。首先根据移动机器人侧向误差和角度误差的几何关系,提出了一种基于引导角的轨迹跟踪控制方法。然后利用Lyapunov直接法和积分Backstepping方法设计了基于引导角的轨迹跟踪控制器,并证明了移动机器人轨迹跟踪误差收敛性。最后通过仿真结果验证了本文方法的有效性。 相似文献
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This study presents a piecewise model for determining the vertical distance and velocity evolution with time for a sphere impacting a water surface and submerging to depths beyond deep-seal cavity pinch-off. Experimental data taken with a high-speed camera are presented for varying sphere mass ratios and impact velocities. The semi-empirical model incorporates results from previously published research and is shown to be in good agreement with experiments for heavier spheres but deviates when the sphere is only slightly denser than water. Two causes for the deviation are presented which relate to the dynamics of the cavity pinch-off event and the inception of a trailing vortex ring after the trailing cavity sloughs from the sphere. A model for predicting cavity pinch-off time and sphere position and velocity at the moment of cavity pinch-off is shown to agree well with experimental results for varying sphere mass ratios and impact velocities. The key experimental values are provided for comparison with current and future modeling efforts. 相似文献
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A global trajectory tracking controller is presented for underactuated AUVs with only surge force and yaw moment in the horizontal plane. A transformation is introduced to represent the tracking error system into a cascade form. The global and uniform asymptotic stabilization problem of the resulting cascade system is reduced to the stabilization problem of two subsystems by use of the cascade approach. For the stabilization of the subsystem involving the yaw moment, a control law is proposed based on the feedback linearization method. Another subsystem is stabilized by designing a fuzzy sliding mode controller which can offer a systematical means of constructing a set of shrinking-span and dilating-span membership functions. In order to demonstrate the practicability of the proposed controller, control constraints, parameter uncertainties, and external disturbances are considered according to practical situation of AUVs. Simulation results show very good tracking performance and robustness of the proposed control schemes. 相似文献
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A robust neural network controller (NNC) is presented for tracking control of underwater vehicles with uncertainties. The controller is obtained by using backstepping technique and Lyapunov function design in combination with neural network identification. Modeling errors and environmental disturbances are considered in the mathematical model. A two-layer neural network is introduced to compensate the modeling errors, while H∞ control strategy is used to achieve the L2-gain performance. The uniformly ultimately bounded (UUB) stabilities of tracking errors and NN weights are guaranteed through the proposed controller. An on-line NN weights tuning algorithm is also proposed. Good performances of the tracking control system are illustrated by the results of numerical simulations. 相似文献