On the motions of the underwater remotely operated vehicle with the umbilical cable effect

In this paper, a hydrodynamic model is developed to simulate the six degrees of freedom motions of the underwater remotely operated vehicle (ROV) including the umbilical cable effect. The corresponding hydrodynamic forces on the underwater vehicle are obtained by the planar motion mechanism test technique. With the relevant hydrodynamic coefficients, the 4th-order Runge–Kutta numerical method is then adopted to solve the equations of motions of the ROV and the configuration of the umbilical cable. The multi-step shooting method is also suggested to solve the two-end boundary-value problem on the umbilical cable with respect to a set of first-order ordinary differential equation system. All operation simulations for the ROV including forward moving, ascending, descending, sideward moving and turning motions can be analyzed, either with or without umbilical cable effect. The current effect is also taken into consideration. The present results reveal that the umbilical cable indeed significantly affects the motion of the ROV and should not be neglected in the simulation.     

Dynamics of ocean cables with local low-tension regions

A general set of 3-D dynamic field equations for a cable segment is derived based on the classical Euler-Kirchhoff theory of an elastica. The model includes flexural stiffness to remove the potential singularity when cable tension vanishes and can be reduced to the equations for a perfectly flexible cable. A hybrid model and a solution scheme by direct integration are then proposed to solve the oceanic cable/body system with a localized low-tension region. Numerical examples demonstrate the capability and validity of the formulation and the numerical algorithm.     

Investigation on a two-part underwater manoeuvrable towed system

A hydrodynamic model of a two-part underwater manoeuvrable towed system is proposed in which a depressor is equipped with active horizontal and vertical control surfaces, and a towed vehicle is attached to the lower end of a primary cable. In such a system the towed vehicle can be manoeuvred in both vertical and horizontal planes when it is towed at a certain velocity and the coupling effect of excitations at the upper end of the primary cable and disturbances of control manipulations to the towed vehicle can be reduced. In the model the hydrodynamic behavior of an underwater vehicle is described by the six-degrees-of-freedom equations of motion for submarine simulations. The added masses of an underwater vehicle are obtained from the three-dimensional potential theory. The control surface forces of the vehicle are determined by the wing theory. The results indicate that with relative simple control measures a two-part underwater manoeuvrable towed system enables the towed vehicle to travel in a wide range with a stable attitude. The method in this model gives an effective numerical approach for determining hydrodynamic characteristics of an underwater vehicle especially when little or no experimental data are available or when costs prohibit doing experiments for determining these data.     

Simulation studies of the response of deeply towed vehicle to various towing ship maneuvers

The behavior of a long cable towed at slow speeds through the ocean depends in a complex fashion on the path followed by the towing ship relative to the water. A cable simulation program was used to characterize the response of the cable by using idealized towing ship maneuvers as input to the program. The response of the cable was noted and it was found that the behavior of the cable was strongly dependent on the fundamental period of the towing vessel maneuvers. Sinusoidal deviations of the towing ship from a straight towing track resulted in delayed and reduced excursions of the towed vehicle from the tract; the estimated response ratio varied from 0·002 to 0·800, depending both on the period of the deviations (periods ranged from 5·5 to 4·0 hr) and on the towing depth (2 or 6 km). The ship's speed was 3 km/hr. The time lag between ship motion and vehicle response was approximately 0·5 hr for the shallow case and 1·3 hr for the deep case. Simulations runs of a low dragk (faired) cable showed that the behavior of the vehicle when towed at a depth of 6 km was similar to that obtained with a conventional cable at 2 km depth. The response of the towed vehicle to a right-angle turn of the towing ship was investigated and a generalized model of the response developed. The effects of a controllable side force on the towed vehicle were also simulated and it was noted that a deviation (2-hr period) of the towed vehicle from a straight-line track could be reduced from 40 to 2 m by impressing a side force on the vehicle with an average magnitude of 150 newtons (30 lb).     

主动式声纳列阵拖曳系统姿态数值计算

主动式声纳列阵拖曳系统是用于探测潜艇的新型声纳系统，为了准确探测潜艇的位置，必须首先预报声纳列阵的瓷态，本文通过对其三维力学模型的分析，得到该系统的运动微分方程，其中缆索的力学方程是基于Ablow和Milinazzo的模型，而对于拖体则运用六自由度空间运动方程模拟，结合边界条件，用有限差分法求解，通过对拖船的不同运动状态如匀速，变速和回转的计算，证明本文的方法对于预报声纳列阵的姿态是有效的。     

A Geometrically Exact Formulation for Three-Dimensional Numerical Simulation of the Umbilical Cable in A Deep-Sea ROV System

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle(ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized-a implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.     

A Geometrically Exact Formulation for Three-Dimensional Numerical Simulation of the Umbilical Cable in A Deep-Sea ROV System

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle (ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized- implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.     

Dynamic motion and tension of marine cables being laid during velocity change of mother vessels

Flexible segment model （FSM） is adopted for the dynamics calculation of marine cable being laid. In FSM, the cable is divided into a number of flexible segments, and nonlinear governing equations are listed according to the moment equilibriums of the segments. Linearization iteration scheme is employed to obtain the numerical solution for the governing equations. For the cable being laid, the payout rate is calculated from the velocities of all segments. The numerical results are shown of the dynamic motion and tension of marine cables being laid during velocity change of the mother vessels.     

Nonlinear Finite Element Analysis of Ocean Cables

This study has focused on developing numerical procedures for the dynamic nonlinear analysis of cable structures subjected to wave forces and ground motions in the ocean. A geometrically nonlinear finite element procedure using the isoparamnetrie curved cable element based on the Lagrangian folmulation is briefly summarized. A simple and accurate method to determine the initial equilibrium state of cable systems associated with self-weights, buoyancy and the motion of end points is presented using the load incremental method combined with penalty method. Also the Newmark method is used for dynamic nonlinear analysis of ocean cables. Numerical examples are presented to validate the present numerical method.     

中韩海底光缆(西段)弃置方案可行性研究

中韩海底光缆已于2005年7月宣布废弃.中韩海底光缆是我国宣布废弃的第一条国际海底光缆.通过对中韩海底光缆多种可能的弃置方案进行分析,对比研究了各种弃置方案的利弊及可行性.通过比选,提出了全线打捞回收方案是最佳方案;领海以内打捞回收方案次之,是具有现实性和可操作性的方案;原地弃置方案是最不适合中韩光缆弃置的方案.     

A finite element cable model and its applications based on the cubic spline curve

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.     

Dynamic Analysis of Towed and Variable Length Cable Systems

Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.     

Transient behavior of towed cable systems during ship turning maneuvers

The dynamic behavior of a towed cable system that results from the tow ship changing course from a straight-tow trajectory to one involving steady circular turning at a constant radius is examined. For large-radius ship turns, the vehicle trajectory and vehicle depth assumed, monotonically and exponentially, the large-radius steady-state turning solution of Chapman [Chapman, D.A., 1984. The towed cable behavior during ship turning manoeuvers. Ocean Engineering 11, 327–361]. For small-radius ship turns, the vehicle trajectory initially followed a corkscrew pattern with the vehicle depth oscillating about and eventually decaying to the steady-state turning solution of Chapman (1984). The change between monotonic and oscillatory behavior in the time history of the vehicle depth was well defined and offered an alternate measure to Chapman's (1984) critical radius for the transition point between large-radius and small-radius behavior. For steady circular turning in the presence of current, there was no longer a steady-state turning solution. Instead, the vehicle depth oscillated with amplitude that was a function of the ship-turning radius and the ship speed. The dynamics of a single 360° turn and a 180° U-turn are discussed in terms of the transients of the steady turning maneuver. For a single 360° large-radius ship turn, the behavior was marked by the vehicle dropping to the steady-state turning depth predicted by Chapman (1984) and then rising back to the initial, straight-tow equilibrium depth once the turn was completed. For small ship-turning radius, the vehicle dropped to a depth corresponding to the first trough of the oscillatory time series of the steady turning maneuver before returning to the straight-tow equilibrium depth once the turn was completed. For some ship-turning radii, this resulted in a maximum vehicle depth that was greater than the steady-state turning depth. For a 180° turn and ship-turning radius less than the length of the tow cable, the vehicle never reached the steady-state turning depth.     

基于有限差分法的复合系泊链缆动力模型及其验证

具有链—缆—链结构的复合系泊链缆因其相对于全钢链质量和成本上的优势而在深水系泊中得以广泛应用。基于细长杆理论采用有限差分法建立了可以考虑链—缆—链结构的复合系泊缆数值模型,将其应用于不同工况下全钢链和复合链缆运动的数值模拟中,并开展了验证。首先,将单根钢链顶张力数值模拟结果与不同工况下的模型试验结果进行了对比,验证了数值预报程序应用于全钢链的准确性。然后,对于复合系泊链缆开展了静刚度和动刚度迭代数值模拟,并将模拟结果同已发表文章中的算例结果进行比较,验证了该数值模型在复合链缆模拟上的准确性。发现对于单根钢锚链的验证,激励半径越大,激励周期越小,一个周期内顶张力幅值及其极差越大,钢链运动就越剧烈。对于链—缆—链式复合系泊链缆的验证,发现静刚度迭代中数值模拟结果与算例结果差异较小;对于动刚度迭代,除个别大幅慢漂工况外,两者有较高的吻合;且激励周期越小,激励半径越大,复合系泊链缆顶张力越大,弹性模量越小,运动越剧烈。对于聚酯缆刚度的敏感性分析,发现改变动刚度经验公式参数的情况下,杨氏模量的静刚度迭代和动刚度迭代结果误差分别最大达到了60.81%和68.21%,因此合成纤维材料特性对复合系泊链...     

海底有缆在线观测系统研究与应用综述

获取高质量海洋观测数据是维护国家安全和权益、保障人类生存与可持续发展、应对全球气候变化、开发利用海洋资源、防灾减灾等的重要基础。随着海底观测技术的发展，海底有缆观测已成为地球观测的第三个平台。通过借鉴国内外海底观测网的成熟技术，设计研发单节点海底有缆在线观测系统，主要包含海底观测、电力信息传输和陆上人机交互信息管理等三个子系统，具有高度可扩展性，可根据监测需求集成安装常用的各类海洋观测仪器和水下高清摄像头，从而实现海洋环境和水下生物资源的原位、长期、连续、稳定的在线观测。研发的海底有缆在线观测系统构造简单、扩展性强、经济成本低，已广泛应用于山东省海洋牧场观测网的海洋生态环境和渔业资源、辽东湾的冬季海冰、海洋牧场与海上风电的融合效应、河流入海口水质、海上溢油等不同领域的业务化监测中，为我国海洋生态环境保护与修复、海洋资源开发利用、海洋防灾减灾等提供了高质量的科学数据支撑。海底有缆在线观测系统是业务化海洋在线观测技术领域里的创新研究，具有重要科学意义和广泛应用前景。     

A new approach for mobile and expandable real-time deep seafloorobservation - adaptable observation system

Although submarine cable in-line seafloor observation systems are very effective tools for real-time/long-term geo-scientific measurements,, there are technological difficulties for deploying as many sensors as on land. To solve this problem, JAM-STEC developed an expandable and replaceable satellite measurement station called the adaptable observation system (AOS). The AOS is a battery operated mobile observatory connected to the backbone cable system by a 10 km long thin fiber cable to ensure real-time data recovery. The system consists of a branching system, a junction box, a fiber cable, and a battery system for a six-month operation. Installation and construction of the AOS will be conducted by a towed vehicle and an ROV. A thin fiber cable-laying system was developed and tested for practical operation. This observation system provides a chance to extend existing seafloor networks from an in-line area to a wider area     

模糊多属性决策法在海底电缆路由方案比选中的应用

海底电缆预选路由方案的比选需要参考多种指标,这些指标包含定量和定性两种,但各指标间的不可公度性,给路由方案的选择提出挑战。文章提出了一种基于离差思想和模糊向量投影的多属性决策法。首先引入三角模糊数,将定性指标合理量化,构建决策矩阵,规范化后运用离差思想求解各指标权重,然后计算各方案在正理想方案和负理想方案上的投影,最后求出相对贴近度,依据其大小比选出最佳方案。     

New Numerical Scheme for Simulation of Hyperbolic Mild-Slope Equation

The original hyperbolic mild-slope equation can effectively take into account the combined effects of wave shoaling, refraction, diffraction and reflection, but does not consider the nonlinear effect of waves, and the existing numerical schemes for it show some deficiencies. Based on the original hyperbolic mild-slope equation, a nonlinear dispersion relation is introduced in present paper to effectively take the nonlinear effect of waves into account and a new numerical scheme is proposed. The weakly nonlinear dispersion relation and the improved numerical scheme are applied to the simulation of wave transformation over an elliptic shoal. Numerical tests show that the improvement of the numerical scheme makes efficient the solution to the hyperbolic mild-slope equation. A comparison of numerical results with experimental data indicates that the results obtained by use of the new scheme are satisfactory.     

Nonlinear adaptive control of an underwater towed vehicle

This paper addresses the problem of simultaneous depth tracking and attitude control of an underwater towed vehicle. The system proposed uses a two-stage towing arrangement that includes a long primary cable, a gravitic depressor, and a secondary cable. The towfish motion induced by wave driven disturbances in both the vertical and horizontal planes is described using an empirical model of the depressor motion and a spring-damper model of the secondary cable. A nonlinear, Lyapunov-based, adaptive output feedback control law is designed and shown to regulate pitch, yaw, and depth tracking errors to zero. The controller is designed to operate in the presence of plant parameter uncertainty. When subjected to bounded external disturbances, the tracking errors converge to a neighbourhood of the origin that can be made arbitrarily small. In the implementation proposed, a nonlinear observer is used to estimate the linear velocities used by the controller thus dispensing with the need for costly sensor suites. The results obtained with computer simulations show that the controlled system exhibits good performance about different operating conditions when subjected to sea-wave driven disturbances and in the presence of sensor noise. The system holds promise for application in oceanographic missions that require depth tracking or bottom-following combined with precise vehicle attitude control.     

近岸波浪和波生流环境中泥沙输运的数值模拟

Owing to lack of observational data and accurate definition,it is difficult to distinguish the Kuroshio intrusion water from the Pacific Ocean into the South China Sea(SCS).By using a passive tracer to identify the Kuroshio water based on an observation-validated three-dimensional numerical model MITgcm,the spatio-temporal variation of the Kuroshio intrusion water into the SCS has been investigated.Our result shows the Kuroshio intrusion is of distinct seasonal variation in both horizontal and vertical directions.In winter,the intruding Kuroshio water reaches the farthest,almost occupying the area from 18°N to 23°N and 114°E to 121°E,with a small branch flowing towards the Taiwan Strait.The intrusion region of the Kuroshio water decreases with depth gradually.However,in summer,the Kuroshio water is confined to the east of 118°E without any branch reaching the Taiwan Strait;meanwhile the intrusion region of the Kuroshio water increases from the surface to the depth about 205 m,then it decreases with depth.The estimated annual mean of Kuroshio Intrusion Transport(KIT) via the Luzon Strait is westward to the SCS in an amount of –3.86×106 m3/s,which is larger than the annual mean of Luzon Strait Transport(LST) of –3.15×106 m3/s.The KIT above 250 m accounts for 60%–80% of the LST throughout the entire water column.By analyzing interannual variation of the Kuroshio intrusion from the year 2003 to 2012,we find that the Kuroshio branch flowing into the Taiwan Strait is the weaker in winter of La Ni?a years than those in El Ni?o and normal years,which may be attributed to the wind stress curl off the southeast China then.Furthermore,the KIT correlates the Ni?o 3.4 index from 2003 to 2012 with a correlation coefficient of 0.41,which is lower than that of the LST with the Ni?o 3.4 index,i.e.,0.78.