An adaptable walking-skid for seabed ROV under strong current disturbance

This paper proposed a new concept of an adaptable multi-legged skid design for retro-fitting to a remotely-operated vehicle （ROV） during high tidal current underwater pipeline inspection. The sole reliance on propeller-driven propulsion for ROV is replaced with a proposed low cost biomimetic solution in the form of an attachable hexapod walking skid. The advantage of this adaptable walking skid is the high stability in positioning and endurances to strong current on the seabed environment. The computer simulation flow studies using Solidworks Flow Simulation shown that the skid attachment in different compensation postures caused at least four times increase in overall drag, and negative lift forces on the seabed ROV to achieve a better maneuvering and station keeping under the high current condition （from 0.5 m/s to 5.0 m/s）. A graphical user interface is designed to interact with the user during robot-in-the-loop testing and kinematics simulation in the pool.     

Calculation of hydrodynamics for semi-submersibles based on NURBS

Accurate hydrodynamic calculations for semi-submersibles are critical to support modern rapid exploration and extraction of ocean resources. In order to speed hydrodynamic calculations, lines modeling structures were separated into structural parts and then fitted to Non-uniform Rational B-spline （NURBS）. In this way, the bow and stern section lines were generated. Modeling of the intersections of the parts was then done with the universal modeling tool MSC.Patran. Mesh was gererated on the model in order to obtain points of intersection on the joints, and then these points were fitted to NURBS. Next, the patch representation method was adopted to generate the meshes of wetted surfaces and interior free surfaces. Velocity potentials on the surfaces were calculated separately, on basis of which the irregular frequency effect was dealt with in the calculation of hydrodynamic coefficients. Finally, the motion response of the semi-submersible was calculated, and in order to improve calculations of vertical motion, a damping term was affixed in the vertical direction. The results show that the above methods can generate fine mesh accurately representing the wetted surface of a semi-submersible and thus improve the accuracy of hydrodynamic calculations.     

Mathematical modelling of response amplitude operator for roll motion of a floating body: Analysis in frequency domain with numerical validation

This paper investigates mathematical modelling of response amplitude operator （RAO） or transfer function using the frequency-based analysis for uncoupled roll motion of a floating body under the influence of small amplitude regular waves. The hydrodynamic coefficients are computed using strip theory formulation by integrating over the length of the floating body. Considering sinusoidal wave with frequency （ω ） varying between 0.3 rad/s and 1.2 rad/s acts on beam to the floating body for zero forward speed, analytical expressions of RAO in frequency domain is obtained. Using the normalization procedure and frequency based analysis, group based classifications are obtained and accordingly governing equations are formulated for each case. After applying the fourth order Runge-Kutta method numerical solutions are obtained and relative importance of the hydrodynamic coefficients is analyzed. To illustrate the roll amplitude effects numerical experiments have been carried out for a Panamax container ship under the action of sinusoidal wave with a fixed wave height. The effect of viscous damping on RAO is evaluated and the model is validated using convergence, consistency and stability analysis. This modelling approach could be useful to model floating body dynamics for higher degrees of freedom and to validate the result.     

浮体横摇运动传递函数数学建模的频域分析研究及相关数值验证(英文)

This paper investigates mathematical modelling of response amplitude operator(RAO) or transfer function using the frequency-based analysis for uncoupled roll motion of a floating body under the influence of small amplitude regular waves. The hydrodynamic coefficients are computed using strip theory formulation by integrating over the length of the floating body. Considering sinusoidal wave with frequency( ω) varying between 0.3 rad/s and 1.2 rad/s acts on beam to the floating body for zero forward speed, analytical expressions of RAO in frequency domain is obtained. Using the normalization procedure and frequency based analysis, group based classifications are obtained and accordingly governing equations are formulated for each case. After applying the fourth order Runge-Kutta method numerical solutions are obtained and relative importance of the hydrodynamic coefficients is analyzed. To illustrate the roll amplitude effects numerical experiments have been carried out for a Panamax container ship under the action of sinusoidal wave with a fixed wave height. The effect of viscous damping on RAO is evaluated and the model is validated using convergence, consistency and stability analysis. This modelling approach could be useful to model floating body dynamics for higher degrees of freedom and to validate the result.     

Experimental investigation of TARMAX model for modeling of hydrodynamic forces on cylinder-like structures

A new approach that models lift and drag hydrodynamic force signals operating over cylindrical structures was developed and validated. This approach is based on stochastic auto regressive moving average with exogenous (ARMAX) input and its time-varying form, TARMAX. Model structure selection and parameter estimation were discussed while considering the validation stage. In this paper, the cylindrical structure was considered as a dynamic system with an incoming water wave and resulting forces as the input and outputs, respectively. The experimental data, used in this study, were collected from a full-scale rough vertical cylinder at the Delft Hydraulics Laboratory. The practicality of the proposed method and also its efficiency in structural modeling were demonstrated through applying two hydrodynamic force components. For this purpose, an ARMAX model is first used to capture the dynamics of the process, relating in-line forces provided by water waves;secondly, the TARMAX model was applied to modeling and analysis of the lift forces on the cylinder. The evaluation of the lift force by the TARMAX model shows the model is successful in modeling the force from the surface elevation.     

The method of imbedded Lagrangian element to estimate wave power absorption by some submerged devices

A simple approach is described to estimate the wave power absorption potential of submerged devices known to cause wave focusing and flow enhancement. In particular, the presence of a flow-through power take-off （PTO） system, such as low-head turbines, can be accounted for. The wave radiation characteristics of an appropriately selected Lagrangian element （LE） in the fluid domain are first determined. In the limit of a vanishing mass, the LE reduces to a patch of distributed normal dipoles. The hydrodynamic coefficients of this virtual object are then input in a standard equation of motion where the effect of the PTO can be represented, for example, as a dashpot damping term. The process is illustrated for a class of devices recently proposed by Carter and Ertekin （2011）, although in a simplified form. Favorable wave power absorption is shown for large ratios of the LE wave radiation coefficient over the LE added mass coefficient. Under optimal conditions, the relative flow reduction from the PTO theoretically lies between 0.50 and 1 2 ≈ 0.71, with lower values corresponding to better configurations. Wave power capture widths, the sensitivity of results to PTO damping and sample spectral calculations at a typical site in Hawaiian waters are proposed to further illustrate the versatility of the method.     

嵌入拉格朗日元法估算某些水下装置吸收波浪能研究(英文)

A simple approach is described to estimate the wave power absorption potential of submerged devices known to cause wave focusing and flow enhancement.In particular,the presence of a flow-through power take-off(PTO)system,such as low-head turbines,can be accounted for.The wave radiation characteristics of an appropriately selected Lagrangian element(LE)in the fluid domain are first determined.In the limit of a vanishing mass,the LE reduces to a patch of distributed normal dipoles.The hydrodynamic coefficients of this virtual object are then input in a standard equation of motion where the effect of the PTO can be represented,for example,as a dashpot damping term.The process is illustrated for a class of devices recently proposed by Carter and Ertekin(2011),although in a simplified form.Favorable wave power absorption is shown for large ratios of the LE wave radiation coefficient over the LE added mass coefficient.Under optimal conditions,the relative flow reduction from the PTO theoretically lies between 0.50 and 1 2≈0.71,with lower values corresponding to better configurations.Wave power capture widths,the sensitivity of results to PTO damping and sample spectral calculations at a typical site in Hawaiian waters are proposed to further illustrate the versatility of the method.     

水下机器人动力定位模糊逻辑控制的虚拟现实仿真（英文）

In this paper, graphical-user-interface(GUI) software for simulation and fuzzy-logic control of a remotely operated vehicle(ROV) using MATLAB TM GUI Designing Environment is proposed. The proposed ROV’s GUI platform allows the controller such as fuzzy-logic control systems design to be compared with other controllers such as proportional-integral-derivative(PID) and sliding-mode controller(SMC) systematically and interactively. External disturbance such as sea current can be added to improve the modelling in actual underwater environment. The simulated results showed the position responses of the fuzzy-logic control exhibit reasonable performance under the sea current disturbance.     

低阻通风船体的远程控制测试平台开发（英文）

This paper addresses the development and testing of a remotely controlled boat platform with an innovative air-ventilated hull. The application of air cavities on the underside of ship hulls is a promising means for reducing hydrodynamic drag and pollutant emissions and increasing marine transportation efficiency. Despite this concept’s potential, design optimization and high-performance operation of novel air-cavity ships remain a challenging problem. Hull construction and sensor instrumentation of the model-scale air-cavity boat is described in the paper. The modular structure of the hull allows for easy modifications, and an electric propulsion unit enables self-propelled operation. The boat is controlled remotely via a radio transmission system. Results of initial tests are reported, including thrust, speed, and airflow rate in several loading conditions. The constructed platform can be used for optimizing air-cavity systems and testing other innovative hull designs. This system can be also developed into a high-performance unmanned boat.     

ROV空间运动仿真研究(英文)

In order to analyze the spatial maneuverability of the remotely operated underwater vehicle(ROV),the 6-DOF motion mathematic model of the ROV was founded.Hydrodynamics were analyzed by using the Taylor series.The thrusters on the ROV were discussed.This paper considers three cases of motion simulation:vertical motion,rotational motion and Z-shape motion.A series of simulation experiments showed that the 6-DOF motion mathematic model was correct and reliable,and also fit with the scene simulation.     

复杂外形潜水器的动力学建模

为建立复杂外形潜水器精确的动力学模型,并基于模型设计控制算法,本文以DOE HD2+2无人遥控潜水器(ROV)为对象,应用计算流体力学(CFD)粘流方法与面元法预测水动力系数.为提高计算速度,在保证计算精度的前提下,采用多面体网格,进行网格优化,减少了流体域的网格总数.由于ROV几何外形不对称,基于最小二乘法分段拟合了阻尼力/力矩与速度的曲线,建立了耦合的阻尼矩阵和附加质量矩阵.最后,基于CFD计算的水动力系数建立了Matlab Simulink动力学仿真模型,并通过水池操控实验对所建动力学模型进行了有效性验证.     

参数不确定及有扰动的情况下欠驱动遥控无人潜水器鲁棒性建模、滑模控制及仿真研究（英文）

A dynamic model of a remotely operated vehicle(ROV) is developed. The hydrodynamic damping coefficients are estimated using a semi-predictive approach and computational fluid dynamic software ANSYS-CFX~(?) and WAMIT~(?). A sliding-mode controller(SMC) is then designed for the ROV model. The controller is subsequently robustified against modeling uncertainties,disturbances, and measurement errors. It is shown that when the system is subjected to bounded uncertainties, the SMC will preserve stability and tracking response. The paper ends with simulation results for a variety of conditions such as disturbances and parametric uncertainties.     

考虑螺旋桨体积力的水下机器人水动力特性仿真

为在初步设计时预测ROV的水动力性能,使用CFD技术进行分析,以ROV模型为例,最大程度地保留ROV内部的构件,使模型更加接近真实状况。分别计算ROV在不同工况下的阻力、不同漂角下的横向力和转艏力矩以及添加体积力模型之后的螺旋桨流场状况,很好地模拟出ROV周围的流场,并与已有的试验数据进行对比。结果验证了CFD水动力仿真的可行性和准确性,并还可预测ROV在螺旋桨作用下的进速等,对ROV设计具有实际的参考价值和指导意义。     

无模型自适应控制算法在ROV定深控制中的仿真

将无模型自适应控制方法应用于ROV(Remote Operated Vehicle)定深控制当中。该控制方案的设计仅利用ROV的垂向推力输入数据和深度输出数据，用动态线性化时变模型替代ROV非线性系统模型，算法中不包含ROV模型及水动力参数信息。因此，解决了ROV因系统复杂，水动力参数难以确定所导致的控制器设计复杂度高，控制效果不理想的问题。为了便于仿真，本文建立含有补偿参数的ROV简化模型，模型仅用于产生系统的I/O数据，不参与控制器的设计。仿真结果表明，在ROV定深控制当中，无模型自适应控制(Model-free adaptive control，MFAC)比PID控制具有更强的抗扰能力。此外，在欠阻尼ROV系统中，基于偏格式动态线性化的无模型自适应控制(partial form dynamic linearization based Model-free adaptive control，PFDL-MFAC)方案相比于基于紧格式动态线性化的无模型自适应控制(compact form dynamic linearization based Model-free adaptive control，CFDL-MFAC)方案具有更好的控制效果。     

用于海底ROV在强流干扰下的一种自适应防走滑装置（英文）

This paper proposed a new concept of an adaptable multi-legged skid design for retro-fitting to a remotely-operated vehicle(ROV) during high tidal current underwater pipeline inspection. The sole reliance on propeller-driven propulsion for ROV is replaced with a proposed low cost biomimetic solution in the form of an attachable hexapod walking skid. The advantage of this adaptable walking skid is the high stability in positioning and endurances to strong current on the seabed environment. The computer simulation flow studies using Solidworks Flow Simulation shown that the skid attachment in different compensation postures caused at least four times increase in overall drag, and negative lift forces on the seabed ROV to achieve a better maneuvering and station keeping under the high current condition(from 0.5 m/s to 5.0 m/s). A graphical user interface is designed to interact with the user during robot-in-the-loop testing and kinematics simulation in the pool.     

微型开架式水下机器人水动力系数测定

水下机器人水动力系数的准确测定,是对机器人运动进行仿真和控制的前提。以形状复杂的开架式有缆水下机器人(ROV)作为研究对象,通过一系列水动力试验,计算出适用于开架式水下机器人模型的几个重要的实时水动力系数,为自主遥控水下机器人(ARV)的运动仿真提供了数据支撑,进而为ARV的控制奠定了基础。     

ROV近底行走装置水平面动力学建模及稳定性分析

针对深海管线埋设ROV底部行走装置——滑撬进行动力学建模与分析。分析滑撬运动过程中的受力,建立动力学模型,通过实验验证模型的适用性。根据5种典型的滑橇外形,制作缩尺度模型,进行泥池中的拖动实验,对实验数据进行分析和对比,选出最优滑橇外形。在ROV近底滑行状态下的三自由度动力学模型基础上,对稳定性进行分析,得出稳定性判据,结果表明合理的滑橇设计能够提高系统的运动稳定性。     

无航速三体浮驳水动力特性频域分析

为了研究不同工作条件下无航速三体浮驳的水动力特性的变化规律,根据势流理论和波浪的辐射/衍射理论对无航速三体浮驳的水动力特性进行了分析,并以某三体浮驳为例应用水动力计算软件AQWA对其在不同工况下进行了水动力计算。分别求得了该三体浮驳在不同水深、不同吃水深度时的附加质量、附加阻尼、不同波向下的波浪激励力和幅值响应算子随波频的变化曲线,并对其进行了对比分析。结果表明,水深对三体浮驳附加质量、附加阻尼、波浪激励力和幅值响应算子均有较大的影响,特别是在低波频时影响较为显著;水深大于20倍吃水深度后三体浮驳的水动力系数可按照无限水深进行近似计算。吃水深度对三体浮驳纵荡和横荡幅值响应算子几乎无影响,对垂荡和纵摇幅值响应算子的影响较小,对横摇和艏摇幅值响应算子的影响较大。