水下碍航物信息三维可视化管理技术研究

研究了水下碍航物信息的获取、处理、显示和管理等一整套技术方法,以水下碍航物数据库为支持,实现水下碍航物数据的获取、海图碍航物信息自动入库、水下碍航物可视化编辑、元数据信息查询和空间定位等功能,并实现以图片库和模型库为支持的海图碍航物要素的三维空间表达,建立水下碍航物三维可视化管理系统平台,为海洋测绘作业人员提供全方位、一体化的技术支持和信息保障。     

Surface perturbations generated by a stratified flow of finite depth over obstacles

We studied the structure of the surface perturbations generated by a stratified flow of an ideal fluid of finite depth around underwater obstacles. We consider a cylinder modeled by a point dipole localized near the density interface both above and below the interface. It is shown that density jumps characteristic of the marine medium significantly influence the formation and variability of the structure of the surface perturbations generated during a fluid??s flowing around an underwater obstacle. The results are compared with the data of the previous model calculations made by the authors for an infinite flow around an obstacle [4]. Significant differences between them are revealed, which should be taken into account in the solution of practical problems, for example, monitoring of coastal marine basins.     

Interaction between submarine landslides and suspended pipelines with a streamlined contour

Recently, the security and stability of submarine pipelines have attracted much attention in ocean engineering. In this paper, pipelines with a streamlined contour (wedge, airfoil, double-ellipse, and arc-angle hexagon) are designed in hopes of defending against the impact of submarine landslides, and the computational fluid dynamics (CFD) approach is used to investigate the interaction between submarine landslides and streamlined pipelines. The results show that the peak interactional force is more representative of the hazard level of pipelines imposed by submarine landslides. It is also found that the streamlined pipelines possess a significant advantage in reducing the drag force and lift force of landslide–pipeline interaction with a maximum lessening percentage of 66.32 and 40.17%, compared with a conventional circular pipeline. In addition, the influence of applying streamlined pipelines to engineering is briefly discussed, and the empirical equation for estimating the drag force and lift force of streamlined pipelines induced by landslides is recommended based on the numerical test results.     

Robust control for an autonomous underwater vehicle that suppresses pitch and yaw coupling

Attitude control systems for autonomous underwater vehicles are often implemented with separate controllers for pitch motion in the vertical plane and yaw motion in the horizontal plane. We propose a novel time-varying model for a streamlined autonomous underwater vehicle that explicitly displays the coupling between yaw and pitch motion due to nonzero roll angle and/or roll rate. The model facilitates the use of a multi-input multi-output H_∞ control design that is robust to yaw-pitch coupling. The efficacy of our approach is demonstrated with field trials.     

Waves at the sea surface generated by a flow over an underwater obstacle

We study wave perturbations appearing at the surface of a two-layer fluid flowing around an underwater obstacle in the lower layer of the fluid. The obstacle is modeled as a point source. A class of asymptotic solutions was obtained that demonstrate that realistic conditions of the open sea and the given parameters of the source in the neighborhood of the source of hydrodynamic perturbations allow for the formation of two types of surface waves. The waves of the first type only slightly depend on the stratification, and, in the conditions of the real sea, they are almost not observed. The characteristics of the second type of waves were repeatedly recorded in field experiments during radar and optical monitoring of the sea surface.     

多光谱遥感水深反演及其水下碍航物探测技术

针对采用传统海洋测量手段难以获取危险及争议海区的水深和水下碍航物信息,提出了基于卫星遥感进行水深反演和水下碍航物探测的新思路。探讨了多光谱遥感水深反演的数据预处理方法、遥感水深反演模型的构建及水下碍航物遥感探测方法,并开展了相应的实验验证。实验表明,采用卫星遥感手段可以快速地获取测量船只不易到达海区的水深和水下碍航物信息,研究成果对海洋测绘技术的发展具有一定的指导意义和应用价值。     

Underwater vehicle obstacle avoidance and path planning using amulti-beam forward looking sonar

This paper describes a new framework for segmentation of sonar images, tracking of underwater objects and motion estimation. This framework is applied to the design of an obstacle avoidance and path planning system for underwater vehicles based on a multi-beam forward looking sonar sensor. The real-time data flow (acoustic images) at the input of the system is first segmented and relevant features are extracted. We also take advantage of the real-time data stream to track the obstacles in following frames to obtain their dynamic characteristics. This allows us to optimize the preprocessing phases in segmenting only the relevant part of the images. Once the static (size and shape) as well as dynamic characteristics (velocity, acceleration,…) of the obstacles have been computed, we create a representation of the vehicle's workspace based on these features. This representation uses constructive solid geometry (CSG) to create a convex set of obstacles defining the workspace. The tracking takes also into account obstacles which are no longer in the field of view of the sonar in the path planning phase. A well-proven nonlinear search (sequential quadratic programming) is then employed, where obstacles are expressed as constraints in the search space. This approach is less affected by local minima than classical methods using potential fields. The proposed system is not only capable of obstacle avoidance but also of path planning in complex environments which include fast moving obstacles. Results obtained on real sonar data are shown and discussed. Possible applications to sonar servoing and real-time motion estimation are also discussed     

Numerical investigation of the hydrodynamic interaction between two underwater bodies in relative motion

The hydrodynamic interaction between an Autonomous Underwater Vehicle (AUV) manoeuvring in close proximity to a larger underwater vehicle can cause rapid changes in the motion of the AUV. This interaction can lead to mission failure and possible vehicle collision. Being self-piloted and comparatively small, an AUV is more susceptible to these interaction effects than the larger body. In an aim to predict the manoeuvring performance of an AUV under the effects of the interaction, the Australian Maritime College (AMC) has conducted a series of computer simulations and captive model experiments. A numerical model was developed to simulate pure sway motion of an AUV at different lateral and longitudinal positions relative to a larger underwater vehicle using Computational Fluid Dynamics (CFDs). The variables investigated include the surge force, sway force and the yaw moment coefficients acting on the AUV due to interaction effects, which were in turn validated against experimental results. A simplified method is presented to obtain the hydrodynamic coefficients of an AUV when operating close to a larger underwater body by transforming the single body hydrodynamic coefficients of the AUV using the steady-state interaction forces. This method is considerably less time consuming than traditional methods. Furthermore, the inverse of this method (i.e. to obtain the steady state interaction force) is also presented to obtain the steady-state interaction force at multiple lateral separations efficiently. Both the CFD model and the simplified methods have been validated against the experimental data and are capable of providing adequate interaction predictions. Such methods are critical for accurate prediction of vehicle performance under varying conditions present in real life.     

Performance analysis of digital acoustic communication in a shallowwater channel

The major obstacle to underwater acoustic communication is the interference of multi-path signals due to surface and bottom reflections. High speed acoustic transmission over a shallow water channel characterized by small grazing angles presents formidable difficulties. The reflection losses associated with such small angles are low, causing large amplitudes in multi-path signals. In this paper we propose a simple but effective model for multi-path interference, which is then used to assess the performance of a digital communication system operating in a shallow water channel. The results indicate that transmission rates in excess of 8 kbits/s are possible over a distance of 13 km and channel depth of only 20 meters. Such a system offers improved performance in applications such as data collection from underwater sensors     

深海采矿转场工况平台—水下系统耦合动力响应特性研究

针对水深6.0 km深海采矿装备,研究其转场工况平台—水下系统耦合动力响应特性。建立深海采矿平台—输浆管—中继站一体化耦合动力模型,其中采用有限元方法离散输浆管,采用势流理论计算平台水动力,基于Kalman滤波对动力定位系统进行参数整定,优化动力定位系统推力。考虑动力定位系统,计算水动力和采矿平台—输浆管—中继站的频域响应和平台—水下系统耦合时域运动响应,计算得到了平台时域运动响应、水下系统动力响应及动力定位系统推力响应。结果表明：建立的一体化耦合动力分析模型是可行的,可以有效预报平台及水下系统响应;转场0°浪向动力定位系统可以有效控制平台运动;中继站运动较小,输浆管轴力较大,建议将输浆管的浮力材料移动到流速较小的水下范围,可降低拖曳力,有利于输浆管的强度性能。     

被动声呐的高分辨率目标方位估计

本文讨论应用高分辨率非线性谱分析技术进行水声目标方位的估计。文中针对水声信号特点，通过主值频谱抽取方法克服宽频带非线性方位估计的大运算量难题，大大简化了计算复杂性，同时还保证了较高的信噪比。经模拟计算表明，该方法实现简单，有较常规波束形成法为高的方位分辨率     

Numerical Study on Characteristics of Supercavitating Flow Around the Variable-Lateral-Force Cavitator

A control scheme named the variable-lateral-force cavitator, which is focused on the control of lift force, drag force and lateral forces for underwater supercavity vehicles was proposed, and the supercavitating flow around the cavitator was investigated numerically using the mixture multiphase flow model. It is verified that the forces of pitching, yawing, drag and lift, as well as the supercavity size of the underwater vehicle can be effectively regulated through the movements of the control element of the variable-lateral-force cavitator in the radial and circumferential directions. In addition, if the control element on either side protrudes to a height of 5% of the diameter of the front cavitator, an amount of forces of pitching and yawing equivalent to 30% of the drag force will be produced, and the supercavity section appears concave inwards simultaneously. It is also found that both the drag force and lift force of the variable-lateral-force cavitator decline as the angle of attack increases.     

Model simplification for AUV pitch-axis control design

Although the use of low-order equivalent models is common and extensively studied for control of aircraft systems, similar analysis has not been performed for submersible systems. Toward an improved understanding of the utility of low-order equivalent models for submersible systems, we examine control design for pitch-axis motion of an autonomous underwater vehicle (AUV). Derived from first principles, the pitch-axis motion of a streamlined AUV is described by third-order dynamics. However, second-order approximate models are common for system identification and control design. In this work, we provide theoretical justification for both the use of and limitations of a second-order model, and we verify our results in practice via a series of case studies. We conclude that a second-order pitch-axis model should often be sufficient for system identification and control design.     

Investigation of a method for predicting AUV derivatives

The paper addresses the problem of autonomous underwater vehicle (AUV) modelling and parameter estimation as a means to predict the dynamic performance of underwater vehicles and thus provide solid guidelines during their design phase. The use of analytical and semi-empirical (ASE) methods to estimate the hydrodynamic derivatives of a popular class of AUVs is discussed. A comparison is done with the results obtained by using computational fluid dynamics to evaluate the bare hull lift force distribution around a fully submerged body. An application is made to the estimation of the hydrodynamic derivatives of the MAYA AUV, an autonomous underwater vehicle developed under a joint Indian-Portuguese project. The estimates obtained were used to predict the turning diameter of the vehicle during sea trials.     

Underwater autonomous manipulation for intervention missions AUVs

Many underwater intervention tasks are today performed using manned submersibles or remotely operated vehicles in teleoperation mode. Autonomous underwater vehicles are mostly employed in survey applications. In fact, the low bandwidth and significant time delay inherent in acoustic subsea communications represent a considerable obstacle to remotely operate a manipulation system, making it impossible for remote controllers to react to problems in a timely manner.Nevertheless, vehicles with no physical link and with no human occupants permit intervention in dangerous areas, such as in deep ocean, under ice, in missions to retrieve hazardous objects, or in classified areas. The key element in underwater intervention performed with autonomous vehicles is autonomous manipulation. This is a challenging technology milestone, which refers to the capability of a robot system that performs intervention tasks requiring physical contacts with unstructured environments without continuous human supervision.Today, only few AUVs are equipped with manipulators. SAUVIM (Semi Autonomous Underwater Vehicle for Intervention Mission, University of Hawaii) is one of the first underwater vehicle capable of autonomous manipulation.This paper presents the solutions chosen within the development of the system in order to address the problems intrinsic to autonomous underwater manipulation. In the proposed approach, the most noticeable aspect is the increase in the level of information transferred between the system and the human supervisor.We describe one of the first trials of autonomous intervention performed by SAUVIM in the oceanic environment. To the best knowledge of the authors, no sea trials in underwater autonomous manipulation have been presented in the literature. The presented operation is an underwater recovery mission, which consists in a sequence of autonomous tasks finalized to search for the target and to securely hook a cable to it in order to bring the target to the surface.     

智能潜器控制系统的实航验证

本文介绍了某智能潜器的系统概要及其使命规划系统和使命控制系统的结构,并通过对其实航试验结果的分析,证明了本系统能够实现自主导航、自主避障等功能。特别是,本系统对潜器的位置和艏向具有优良的控制特性,达到了预定的研究目标。     

Transformation of a diurnal tide climbing an extensive bottom irregularity

Diffraction of a diurnal barotropic tide above a solitary bottom elevation is studied on the basis of a linear model. The relationships between the structure of the wave disturbance field, the extent of the underwater obstacle, its latitude, and the angle of climb of the tidal wave are obtained.Translated by Mikhail M. Trufanov.     

Application of a panel method to hydrodynamics of underwater vehicles

A low-order singularity panel method based on Green's formulation is used to predict the hydrodynamics characteristics of underwater vehicles. The low-order modeling employs constant strength sources and doublets, and the body surface is modeled by quadrilaterals. The method is first applied to predicting the force and moment coefficients of underwater vehicles for the body-alone and finned configurations. Hydrodynamic coefficients of added mass and added moment of inertia are also calculated by modifying the code. Results for several two and three-dimensional bodies show the usefulness of the method for predicting the added mass and added moment of inertia.     

Hydrodynamic Modeling with Grey-Box Method of A Foil-Like Underwater Vehicle

In this study, a dynamic modeling method for foil-like underwater vehicles is introduced and experimentally verified in different sea tests of the Hadal ARV. The dumping force of a foil-like underwater vehicle is sensitive to swing motion. Some foil-like underwater vehicles swing periodically when performing a free-fall dive task in experiments. Models using conventional modeling methods yield solutions with asymptotic stability, which cannot simulate the self-sustained swing motion. By improving the ridge regression optimization algorithm, a grey-box modeling method based on 378 viscous drag coefficients using the Taylor series expansion is proposed in this study. The method is optimized for over-fitting and convergence problems caused by large parameter matrices. Instead of the PMM test data, the unsteady computational fluid dynamics calculation results are used in modeling. The obtained model can better simulate the swing motion of the underwater vehicle. Simulation and experimental results show a good consistency in free-fall tests during sea trials, as well as a prediction of the dive speed in the swing state.     

便携式AUV水下对接过程中的碰撞分析与罩式对接平台优化设计

以便携式自主水下机器人(AUV)和罩式导向对接平台的水下对接过程为研究对象,将碰撞力大小和对接时间作为评价指标,研究导向罩形状、对接管尺度以及AUV与对接管的偏心距对整个对接过程的影响。在三维建模的基础上,使用ADAMS软件进行动力学仿真分析,结果表明,减小导向罩开口角度、增大对接管直径、减小偏心距可以适当减小碰撞力和对接时间。通过对上述影响因素与评价指标建立函数关系,利用多目标优化设计的方法并结合实际情况对参数做出合理的分析和筛选,为水下机器人对接平台提供设计依据。