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准确模拟舵叶承受的负载是舵机试验系统的一项关键技术.将流体动力基本方程应用于船舶液压舵机系统的稳态和动态特性的研究.建立了系统在变频电机转速一定时的稳定工作方程,计算的稳态特性与实验结果吻合.建立系统的动态数学模型,推导出系统的传递函数.研究提高系统的响应速度的方法,以及系统抗外界干扰的刚度问题,为液压舵机系统准确设计提供了指导. 相似文献
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通过引入动态面控制思想对扩张状态观测器及非线性状态误差反馈控制律进行改造,设计一种动态面自抗扰控制器,并将其用于海洋平台动力定位系统的控制问题上.动态面扩张状态观测器的设计是为了提高系统的扰动估计能力,动态面非线性状态误差反馈控制律的设计是为了提高系统的稳定性与控制效率.仿真实验表明,改进后的动态面自抗扰动力定位控制系统对扰动的估计能力明显提升,系统的抗扰能力与鲁棒性得到增强,同时其具有较好的控制品质和响应特性,进而提高了海洋平台的定位精度. 相似文献
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YAO Xiong-liang FENG Lin-han ZHANG A-man ZHOU Qi-xin 《船舶与海洋工程学报》2007,6(4):18-26
The non-linear finite element software ABAQUS was used to simulate the dynamic response of a marine supercharged boiler when subjected to impact loading. Shock resistance was analyzed by the time-domain simulation method. After exhaustive simulations,the effect of air pressure induced by different working conditions on the shock response of a supercharged boiler was reviewed,leading to conclusions about the variability of structural response with different loading parameters. In order to simulate the real impulsive environments of supercharged boilers,the integration of equipment and ship structure was then primarily used to analyze shock response. These distinctly different equipment shock test methods,run under equivalent work conditions,were compared and the causes of discrepancy were analyzed. The main purpose of this paper is to present references for the anti-shock design of marine supercharged boilers. 相似文献
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ZHENG Ke-wei BIAN Xin-qian SHI Xiao-cheng 《船舶与海洋工程学报》2007,6(1):15-20
It is an important control process to operate motion of an submergence rescue vehicle(SRV). Seeing that the motion of the submergence rescue vehicle is special, it is necessary to employ non-linear predictive control system. For this reason, continuous dynamic performance of the system, the logical components and the operative restraints are expressed as the non-linear equations of state with the inequality restraints, and the model principle of hybrid system is introduced. The conclusion shows that it comes true to exactly control position and attitude of the SRV by means of non-linear model predictive control. The test in a model basin has also proved that the above methods are efficient. 相似文献
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In the IACS Polar Class Rules, primary structures are required to be assessed with direct calculation methods, which in most cases is either linear or non-linear finite element analysis. For linear analysis a clear set of requirements and acceptance criteria are provided in the rules. This approach is currently the most widely used assessment method although non-linear analysis would provide better insight into the behavior of the structure, giving designers tools to reduce weight and/or improve safety. The current rule requirements for non-linear analysis are high-level in nature and not easily applicable to practical design work. In order to implement non-linear analysis practically, a simple-to-use acceptance criteria is be needed. In this paper, a robust and simple-to-use assessment methodology and acceptance criteria is proposed. The proposed method provides means to ensure proper structural hierarchy. Appropriate safety margins are described through the plastic response of the local frame and the primary structural member. Allowable plastic deformation caused by the design ice load is determined by relating the permanent set of the structure to newbuild vessel production tolerances. An example analysis comparing the proposed method to existing linear and non-linear methods is presented. The proposed method ensures that the structure remains serviceable throughout the lifetime of the vessel. 相似文献
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A common approach to investigate the response of a structural detail such as a hatch corner is to compute the seakeeping loads using a linear 3D Boundary Element Method (BEM) and transfer the seakeeping loads to a Finite Element (FE) model of the ship structure. This approach is suitable for computations of the fatigue loading of structural details near amidships because a majority of the fatigue loading will occur in mild sea-states where the loading may be assumed linear. However, the linear seakeeping model may not hold when one investigates the ultimate response of the local bow structure of a ship which is designed to remain operational in severe conditions, for example, a frigate. A linear seakeeping analysis will significantly underpredict the loading at the bow because both the impulsive slamming loads and the non-linearities in the non-impulsive wave loads will contribute significant to the structural loading.The non-linear loads require one to first derive a short-term distribution of the local structural response before the ultimate value of the response can be derived. A method to compute the short-term distribution of a structural detail is presented in this paper. The first step is to perform seakeeping analyses which includes slamming, non-linear Froude-Kryloff and hydrostatic loads. The short-term distribution of the total hydrodynamic loading at the structural detail is obtained by simulating the seakeeping response for several hours. The response of the local structure is computed for the most severe impacts found in the seakeeping simulation. The hydrodynamic loading, including the non-linear contributions, is transfer to the structural model and the structural response is computed using the FE-method. The results of the structural analyses allow one to transform the short-term distribution of the structural loading to a short-term distribution of the response of the structural detail. A designer can obtain the ultimate structural response by entering the probability at which one accepts overloading of the structure in the short-term distribution of the response of the structural detail. 相似文献
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The complexity of the dynamic response of offshore marine structures requires advanced simulations tools for the accurate assessment of the seakeeping behaviour of these devices. The aim of this work is to present a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads. The paper first introduces the formulation of the second-order wave radiation-diffraction solver, designed for calculating the wave-floater interaction. Then, the solver of the mooring dynamics, based on a non-linear Finite Element Method (FEM) approach, is presented. Next, the procedure developed for coupling the floater dynamics model with the mooring model is described. Some validation examples of the developed models, and comparisons among different mooring approaches, are presented. Finally, a study of the OC3 floating wind turbine concept is performed to analyze the influence of the mooring model in the dynamics of the platform and the tension in the mooring lines. The work comes to the conclusion that the coupling of a dynamic mooring model along with a second-order wave radiation-diffraction solver can offer realistic predictions of the floating wind turbine performance. 相似文献
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A jack-up platform,with its particular structure,showed obvious dynamic characteristics under complex environmental loads in extreme conditions.In this paper,taking a simplified 3-D finite element dynamic model in extreme storm conditions as research object,a transient dynamic analysis method was proposed,which was under both regular and irregular wave loads.The steps of dynamic analysis under extreme conditions were illustrated with an applied case,and the dynamic amplification factor(DAF) was calculated for each response parameter of base shear,overturning moment and hull sway.Finally,the structural response results of dynamic and static were compared and analyzed.The results indicated that the static strength analysis of the Jack-up Platforms was not enough under the dynamic loads including wave and current,further dynamic response analysis considering both computational efficiency and accuracy was necessary. 相似文献
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This paper describes the development of a non-linear, dynamic jack-up analysis method in the time domain. It provides background as to why and when such analysis is required.
The theoretical background of the methods applied are discussed and the main features of the programme are described. 相似文献
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《Marine Structures》2002,15(1):15-34
Many important technical issues in the design of deep water jackup rigs stem from the prediction of extreme values of global design parameters such as platform sway, base shear, and overturning moment. Several analytical methods primarily based on time-domain dynamic simulation have been recommended in SNAME T&R Bulletin 5–5A (hereafter referred to as “the Bulletin”) in the realm of the so-called most probable maximum extreme. This paper compares the four major dynamic, time-domain methods recommended in the Bulletin, investigates the random seed effect on each method, exams the convergence of the statistical properties within the recommended time simulation, and presents the impact on the dynamic response due to various parameters, e.g. leg-to-hull flexibility, P-delta effect and foundation fixity. Comparison among the four methods is presented in terms of the calculated extreme values and the corresponding dynamic amplification factors. The structural models employed in this investigation were constructed to reflect the behavior of two jackup rigs in service. These rigs were purposely selected to represent two of the most widely used jackup designs, which are of different leg types, different chord types, and designed for different water depth. 相似文献
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海上极端波因其巨大的波高常常导致船体的极限破坏。该文提出了一个二维的修正水弹性方法来研究一个集装箱船船体梁在极端波中的动态前极限强度。传统的极限强度评估基于准静态方法,没有动态效应被考虑。而船体在波浪下的动态结构响应是基于水弹性方法,传统的水弹性方法并不能计算船体梁的动态非线性强度。该二维修正的水弹性方法考虑时域波浪和非线性船体梁之间的耦合,将水弹性方法和Smith方法结合,用Smith方法计算船体梁的刚度,而其刚度与船体梁的强度和变形曲率有关。所以该时域的非线性刚度被用于修改水弹性方法里的常数项的结构梁刚度。几组极端波模型被用以产生船体梁的大变形和非线性动态垂向弯矩。文中分别采用修正水弹性方法和普通水弹性方法,通过改变四个重要的极端波参数如极端波最大波高、规则波的波高、波速和波长等来研究其对船体梁船中处的大变形转角和非线性垂向弯矩的影响,通过采用修正的水弹性方法计算得来的结果与水弹性方法计算得来的结果相比较,得到了一些差异和结论。 相似文献
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Patar Ebenezer Sitorus Tuyen Quang Le Jin Hwan Ko Tri Quang Truong Hoon Cheol Park 《Journal of Marine Science and Technology》2016,21(1):115-128
A lab-scale flapping-type turbine with a semi-passive activation mode has been designed and implemented. A non-linear dynamic model, developed in our previous work, is validated by a series of experiments along with computational fluid dynamics (CFD) simulations. Previously, the dynamic model was used only to estimate the dynamic response of a flapping-type turbine. In this work, the applicability of the dynamic model is extended to estimate the hydrodynamic forces, extracted power, and efficiency. It was demonstrated from a comparison of the CFD results and measured values that the dynamic model based on a quasi-steady approach estimates the aforementioned performance parameters of measurements well in cases particularly with a low effective angle of attack, thus demonstrating the usefulness of the dynamic model for a flapping-type turbine at an early stage. 相似文献
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基于滑模自抗扰的半潜式海洋平台动力定位控制方法研究 总被引:1,自引:1,他引:0
针对海洋平台动力定位系统,通过构造连续光滑函数并将其用于扩张状态观测器以及引入非奇异终端滑模控制来代替非线性状态误差反馈控制律,设计了一种滑模自抗扰动力定位控制器。连续光滑函数的设计可避免控制器应用过程中的高频颤振现象,非奇异终端滑模控制的引入是为了提高系统的快速响应性与稳定性。通过仿真实验,改进后的滑模自抗扰动力定位控制系统具有较好的控制品质和响应特性,系统的抗扰能力与鲁棒性得到提升,同时其对扰动的估计能力明显增强,实现了海洋平台定位精度的提高。 相似文献
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基于N-S方程和连续性方程建立了三维数值波浪水池,并在该水池内对固定直立柱在不同浪向下的波浪爬升和绕射问题进行了数值模拟。为了验证数值计算的准确性,对立柱近壁面处的波浪爬升效应展开了模型试验研究,计算值与试验值吻合较好,证明了该方法的可行性。研究了入射角度的变化对立柱周围波浪爬升幅度和非线性特征的影响,同时从垂直浪向的投影面积和相对浪向的投影面形状这两个因素出发,探讨了不同浪向角下立柱周围的波浪叠加、波面放大率以及二次波峰效应,并对自由面漩涡生成特性进行了较为深入的机理性研究,可为今后进一步研究不同的入射角度下,复杂的海洋结构物周围的波浪非线性效应提供有价值的参考。 相似文献