Active control for installation of underwater structures

The trend towards deepwater development requires a new approach to underwater installation of offshore structures. The present method using crane vessels has some drawbacks in operations at more than 2000 m depth. The natural period of the coupled system of the rigged structure and the crane vessel becomes longer, so that it is no longer possible to manipulate the cranes to achieve the desired positioning accuracy. This paper examines the application of an active control technique for underwater installations as one of the solutions to the present problems. An active control technique also has the advantage that it can deal with the structural flexibility which allows the structure to be large and light-weight. This structural flexibility imposes problems of suppressing the elastic responses and securing the stability of the control system. In this paper, anH _∞ controller combined with a low authority control/high authority control (LAC/HAC) feedback controller is designed for cases where structural flexibility cannot be ignored. A robust model-following controller is examined for cases where the structure can be treated as rigid. In order to confirm the control algorithm and verify the possibility of the active control installation method, basin tests are executed using two types of neutrally buoyant flexible models with ultrasound ranging systems and thrusters.     

常规起重船外海无掩护安装大型沉箱施工组织与控制

在常规情况下,大型沉箱外海无掩护安装须采用大型起重船组,才能克服恶劣海况,确保施工安全,但是,大型起重船组台班费高,船源少,进度与成本难于控制。以福建鸿山热电厂煤码头及引堤工程沉箱安装为实例,总结常规起重船在外海无掩护条件下成功完成大型沉箱安装的施工组织与措施,对类似外海工程沉箱安装具有一定的借鉴作用。     

Effects of structural flexibility on the dynamic responses of low-height lifting mechanism for offshore wind turbine installation

Installation complexities are one of the major challenges in the floating offshore wind turbine (OWT) industry. The modern concept introduced by the SFI-MOVE project is an effort to overcome the complexities by utilizing a low-height lifting mechanism. It is common to idealize a crane in the lifting mechanism as a rigid body since the structural deflections are smaller than the responses introduced by the other system components. However, structural flexibility can play an essential role in demanding offshore operations with smaller acceptable tolerances. In this study, lifting cranes are modeled using the finite element method and simplified by implementing equivalent 3D beam elements. Dynamic analysis is performed for various environmental conditions, and the responses of the crane structure and the OWT are calculated for each load case. This research reveals that crane structure flexibility influences the relative motion between a floating spar buoy and an OWT during mating operations. Crane structural flexibility contributes significantly to the OWT rotations. In addition, the response deviation between using rigid and flexible cranes increases as the excitation force increases. Therefore, it is recommended to consider the crane structural flexibility in the calculation when strict installation tolerances are needed.     

中型沉箱出运、安装方案

人们普遍认为采用半潜驳出运、安装超过2000 t的大型沉箱,采用浮吊船出运、安装低于500 t小沉箱较为适宜,而对500~2000 t之间的中型沉箱采用何种方案出运、安装并未有统一意见。通过广西北海LNG接收站陆域形成工程,从环境、经济、技术方面进行分析比较,提出采用大型浮吊船（起重船）配合平板方驳出运、安装中型沉箱的优越性,并探讨施工措施。     

海洋石油平台吊机非常规安装设计分析

海洋石油平台一般在陆地建造期间就已完成平台吊机安装和相关功能的试验,出海后对吊机进行简单调试就能投入使用。渤海油田某项目WHPA平台因吊机安装位置与平台钻修机橇块位置较近,吊机安装后会增加平台海上吊装的难度且风险极高。为解决该问题,经过多次讨论分析,将设计方案确定为平台出海安装固定后再对吊机进行安装。这种方案虽然在施工中受到地域限制和海洋环境影响,施工难度和风险大,对安装技术要求较高,但通过该设计方案安全有效的完成了吊机安装工作。     

Active heave compensation of floating wind turbine installation using a catamaran construction vessel

The application of floating wind turbines is limited by the high cost that increases with the water depth. Offshore installation and maintenance continue to consume a high percentage of the project budget. To improve the installation efficiency of the floating offshore wind turbine, a novel concept is proposed by the SFI MOVE project. Several wind turbine superstructure components are preassembled onshore and carried to the installation site by a catamaran construction vessel. Each assembly can then be installed using only one lift, and the concept is less sensitive to weather conditions. In this paper, a control algorithm of the proposed hydraulic active heave compensator system is developed using singular perturbation theory to cancel the relative motion between the spar top and gripped preassembly bottom. Closed-loop stability is proven, and the simulation results show that the installation efficiency is improved with an increase in the acceptable weather conditions.     

Design,modelling, and analysis of a large floating dock for spar floating wind turbine installation

Installation of floating wind turbines at the offshore site is a challenging task. A significant part of the time efficiency and costs are related to the installation methods which are sensitive to weather conditions. This study investigates a large floating dock concept, which can be used to shield a floating wind turbine during installation of tower, nacelle, and rotor onto a spar foundation. In this paper, the concept is described in detail, and a design optimisation is carried out using simple design constraints. Hydrodynamic analysis and dynamic response analysis of the coupled system of the optimum dock and spar are conducted. Two spars of different sizes are considered, and the motion responses of the spars with and without the dock in irregular waves are compared. Through analysis of the motion spectra and response statistics, dynamic characteristics of the coupled system is revealed. The present design of the dock reduces the platform-pitch responses of the spars and potentially facilitates blade mating, but may deteriorate the heave velocity of the spars in swell conditions. Finally, future design aspects of the floating dock are discussed.     

海上风力机安装技术研究(英文)

Wind power has made rapid progress and should gain significance as an energy resource, given growing interest in renewable energy and clean energy. Offshore wind energy resources have attracted significant attention, as, compared with land-based wind energy resources, offshore wind energy resources are more promising candidates for development. Sea winds are generally stronger and more reliable and with improvements in technology, the sea has become a hot spot for new designs and installation methods for wind turbines. In the present paper, based on experience building offshore wind farms, recommended foundation styles have been examined. Furthermore, wave effects have been investigated. The split installation and overall installation have been illustrated. Methods appropriate when installing a small number of turbines as well as those useful when installing large numbers of turbines were analyzed. This investigation of installation methods for wind turbines should provide practical technical guidance for their installation.     

高桩码头构件吊装新技术

在高桩码头预制构件安装中,传统工艺一般都采用起重船施工。在某些工程中,天气恶劣、海况复杂,在利用起重船安装时,受风浪等因素的影响,施工进度缓慢,配套船机投入大、利用率低、成本大,安全风险高。主要介绍一种码头预制构件吊装技术,转水上施工为陆上施工。采用该技术安装码头预制构件,作业时间长,安装速度快,风险小,精度高,造价低,在外海无掩护海域作业时尤为明显。     

弧形岛式防波堤半圆体高基床安装施工工艺

为解决传统的起重船高基床安装半圆体遇到的角度问题,在目前半圆体安装施工经验不多、施工设备还不具备专门性的情况下,对起重船安装半圆体工艺进行了技术创新.提出采用传统的起重船经过双构转换单钩装置的改造来适应半圆体的安装,采用缝板控制半圆体的安装间距,相邻半圆体之间以偏差a/4控制纵轴线纠偏等措施,保证了施工进度和施工质量,可为类似工程提供参考.     

船舶起重作业时定位控制方法研究

近海建筑的建造和安装,需要起重船定点作业,所以要求对起重船动力定位控制方法进行研究。在建立海洋环境模型(风、浪、流)的基础上,建立船舶起重作业模型。设计带有风前馈的反步控制方法,降低系统对环境扰动的敏感性。通过设计估计器,给出船舶运动低频位置、艏向和速度量的估计值,并且使用估计器所得出的低频估计值作为反馈值来减少控制输出的高频振荡。仿真结果表明对于建立的船舶起重模型,所设计的控制方法和估计器,可以较好地完成定位作业。     

海上风电浮船分体安装运动响应数值仿真分析

本文采用数值仿真手段分析浮吊船的运动响应以确定采用浮吊船进行风电机组分体安装的可行性。利用基于边界元法的水动力学数值仿真的手段，计算强峰1800和苏连海起重08两艘起重船的浮体运动响应RAO。采用频域谱分析的方法，计算随机波条件下两船吊钩位置的垂荡运动响应谱，并通过波浪谱统计规律确定船舶的最大运动响应以及加速度响应，以确定风电机组分体安装的可行性。     

Dynamic response analysis of load transfer of topsides from T-barge onto twin-barge in floatover installation

The twin-barge floatover method is a promising approach in the topsides installation of the offshore platform. However, the topsides transfer onto the twin-barge is a challenging task and is seldom investigated. This study focuses on the floatover load transfer operation of the topsides onto the twin-barge by a T-shaped barge and investigates the dynamic responses of the three proximate barges in the operation. The floatover mating process was experimentally simulated by three representative intermediate stages, including 0%, 50%, and 100% stages. The barge and topsides motions, the relative motions of mating points, the contact loads on mating units, tether forces, and mooring forces at various environmental conditions were analyzed. The three floating barges experienced large surge drift motions as well as the sway and yaw drift motions in head seas because of the unsymmetrical configurations. Although a relative radial distance between mating points occurred and exceeded the capture radius of the mating unit at limited instants, the relative motions were to a great extent within the capture radius, indicating the feasibility of the twin-barge floatover method. Comparisons of the loads at the three stages show that the mating units and the tether lines were subjected to larger impact impulse loads at the 0% stage than the 100% stage.     

一种新船型——海上风电设备安装船的开发

风电是一种理想的绿色能源，目前对风电的开发利用已从陆地延伸到海上，由此，海上风电场应运而生并迅速发展。风电设备安装船作为建设海上风电场的关键装备，其开发利用也引起关注与重视。阐述了国内外海上风力发电现状以及风电设备安装船的需求，并提出一型风电设备安装船供参考。     

三维竖轴潮流水轮机水动力性能研究

竖轴水轮机作为潮流能转换为电能的核心装置,其水动力性能的优劣将会直接影响到整体发电系统的效率。为了研究大型竖轴水轮机叶片安装角对水轮机水动力性能的影响,基于多参考系模型(MRF),采用Fluent软件对流场中的模型进行3D数值模拟。在转速和来流速度保持不变,改变安装角时,分析同种翼型5个不同安装角叶片对潮流能水轮机的水动力性能的影响。同时分析在同一安装角和旋转速度条件下,不同来流速度对水轮机水动力性能的影响。结果表明,叶片安装角对竖轴潮流水轮机的能量利用率影响较大,来流速度对水轮机叶片表面的静压力和输出功率具有一定的影响。研究结果对今后竖轴水轮机的设计和生产具有借鉴意义。     

海上风电安装船的发展趋势研究

随着海上风力发电产业的迅速发展,风电安装船需求越来越大,并且风电安装船是高附加值工程船,因此这一市场的吸引力将越来越受到造船界重视,竞争将越来越激烈,但海上风电场施工成本高、海上作业时间长及工期长等问题的存在延缓了海力发电产业的发展。因此,本文将着重对海上风电结构物施工、安装过程的单一海工设备发展进行浅析,为探索深水化、大型化、专业化、集成化的海上风电安装船来完成深海域基础施工及风机安装问题提供设计参考。     

强浪条件下高桩码头桩间大棱体抛石及块体安装施工技术

针对在建的以色列阿什杜德港项目28号码头桩间抛石及块体安装施工工期紧张且窗口期有限、工程量大且作业面有限,以及抛填安装棱体大且验收标准高的难点,采用将组合钢板架设在夹桩结构上作为施工平台并由履带吊搭配特定抛填安装工具的施工方案。介绍现场实施进度情况及越冬防护结构的设计,为类似海况条件下的高桩码头桩间抛石及块体安装施工提供借鉴。     

某型舰载惯导平台安装与对准精度控制

舰载惯性系统的精度与船台（坞）的安装与对准密切相关。传统的激光经纬仪采用惯性平台基座零方位刻线与舰船首尾线重合的安装标校方法,但其精度较难满足惯性平台航向的对准要求。文中给出一种基于电子陀螺经纬仪、差分水准仪和方位基准镜进行惯性平台安装与对准的有效控制精度方法,并在后期的实船应用中取得了良好效果。     

自锁原理在混凝土块体安装机械中的应用

孟加拉Mirsarai海岸防护项目工程护底块体采用100 cm×80 cm×60 cm长方体混凝土块体。在块体生产堆放过程中,须采用夹块机运输,但在安装时由于该护底块未设计吊钩,故无法采用吊车安装,只能用长臂挖机安装液压夹进行夹块安装。液压夹故障率较高,且夹块困难,安放时力度不好控制,容易造成块体间的碰撞损伤。为此,对现有的机械设备做出改进,根据物理学中的静摩擦自锁现象,制作出自锁型夹子。该夹子在夹块时仅仅依靠夹子橡胶复合结构和混凝土块自身重力产生的摩擦力夹紧块体,而安放时仅须旋转挖机斗改变受力钢丝绳来松开块体,无须人员辅助,有效地解决了块体安装过程中机械伤的问题。同时,由于自锁型夹子制作简单、维修方便,因此提高了生产效率、降低了成本。     

基于Modelica的主动波浪补偿起重机建模与仿真

为研究主动波浪补偿起重机的动态特性和起吊重物质量等关键参数对主动波浪补偿起重机性能的影响,采用多领域统一建模语言Modelica,在MWorks仿真软件中构建二次马达、恒压变量泵、蓄能器、溢流阀和钢丝绳等模型,以构造出完整的主动波浪补偿起重机模型.对该模型进行仿真分析,结果表明:当起吊重物的质量为20t～160t时,主动波浪补偿起重机的控制效果较好;当起吊重物的质量达到200 t时,重物的补偿位移控制效果相对较差;通过调整PID控制参数可提高起重机起吊重物的质量.