3D-surface reconstruction for partially submerged marine structures using an Autonomous Surface Vehicle

Geological and geophysical surveys, which are the basis for engineering studies on marine structures, pipelines, harbours and marinas, both in offshore and in coastal areas, are customarily carried out using fully equipped research vessels or small craft with appropriate equipment related to this work, and with intensive human labour. This traditional method is very costly, requires extra manpower and equipment and increases the risk to life and property, as well as being dependent on ephemeral weather conditions. A prototype unmanned surface vehicle named JEO-IDA (Marine Autonomous Surface Vehicle) was produced by our team within the scope of a project, which will enable real-time monitoring of the data that are obtained by a side scanning sonar and a single beam echosounder installed on the vehicle for geological and geophysical surveys, from a land-based station. The result of this study is the prototype platform of whose mission is to investigate three-dimensional geological and morphological structures of the seabed with high-resolution and to prepare their maps as well as carrying out coastal and offshore surveys in construction and operation phases. In the scope of this research, studies and hull form selection in the design of the unmanned autonomous surface vehicle are discussed in detail.

Marine structures are inevitably influenced by parametric perturbations as well as multiple external loadings. Among these loadings, earthquake is generally more destructive and unpredictable than others. It is significant to develop effective active control schemes to guarantee the safety, stability, and integrity of marine structures subject to earthquakes and parametric perturbations. In this paper, the problem of networked [Formula: see text] robust damping control is addressed to stabilize a marine structure subject to earthquakes. First, in consideration of perturbations of the structure parameters, an uncertain model of the networked marine structure under earthquakes is presented. Second, a robust networked [Formula: see text] control scheme is presented to suppress seismic responses of the structure. By using stability theory of time-delay systems, several sufficient conditions on robust stability of the networked marine structure system are obtained, and the linear matrix inequality methods are utilized to solve the gain matrix of the controller. Finally, simulation indicates that compared with the traditional robust [Formula: see text] control and the proposed networked [Formula: see text] control, the seismic responses amplitudes of the marine structure under the two controllers are almost the same, while the latter is more economic than the former.

With the development of technologies related to unmanned vehicles, including unmanned aerial vehicle and unmanned surface vehicle, unmanned vehicles play a pivotal role in maritime management and cruise activities. Meanwhile, lots of evidence shows that a single unmanned vehicle is not qualified for operation under complex environment, whereas the unmanned aerial vehicle–unmanned surface vehicle formation consists of multiple unmanned aerial vehicles and unmanned surface vehicles, which can enhance the performance of the single unmanned vehicle significantly. However, the cooperative operation performance of the unmanned aerial vehicle–unmanned surface vehicle formation is constrained by its communication capacity. Consequently, a cooperative communication framework is designed for the unmanned aerial vehicle–unmanned surface vehicle formation. A distributed dynamic network topology is constructed for fulfilling effective communication for the unmanned aerial vehicle–unmanned surface vehicle formation based on ad hoc network. Experiments are carried out by employing the built unmanned aerial vehicle–unmanned surface vehicle formation platform. Results verify the superiority of the designed cooperative communication framework for the unmanned aerial vehicle–unmanned surface vehicle formation.

To evaluate whether a computer vision model can utilize monocular endoscopic images of the middle ear to generate three-dimensional (3D) surface reconstructions that register to ground-truth (GT) imaging with clinically acceptable accuracy for surgical navigation. Eight temporal bone phantoms derived from the publicly available OpenEar data set were 3D-printed. Middle ear endoscopy was performed in each model using a standard monocular otologic endoscope, and a single endoscopic image captured of the mesotympanum. Images were processed with a monocular surface reconstruction model to generate predicted 3D surface reconstructions. Reconstructions were registered to GT meshes using natural anatomic landmarks. Surface reconstruction error (SRE) was quantified using the mean modified Hausdorff distance, and target registration error (TRE) was calculated using withheld test fiducials. Mean SRE across models was 0.58 ± 0.10mm, with 81.6% of points within 1mm of GT surfaces. Mean TRE was 0.96 ± 0.17mm. Simple 2D, monocular endoscopic images can be converted into high-fidelity 3D surface reconstructions of middle ear anatomy, which can be registered to ground-truth imaging with submillimeter registration accuracy. These findings establish the preclinical feasibility of monocular, endoscope-centric navigation for transcanal endoscopic ear surgery.

Detection of oil spills with aerial or space-born remote sensing resources has been deeply studied and developed over recent years. However, all these technologies still rely on in-situ verification with direct monitoring and sampling for validation. This paper presents the design, fabrication, simulation, and testing of an unmanned surface vehicle (USV), specifically designed for hydrodynamic efficiency and effective oil spill sampling. The USV's design, featuring a customized platform for the oil sampling mechanism, underwent an extensive simulation process using computational fluid dynamics (CFD) to validate its stability and analyze its impact on water flow dynamics. The design and fabrication process involved hull construction, integration of the control and power systems, and testing in a laboratory environment. The CFD analysis and testing revealed exceptional stability in the USV, showing only minimal rocking and pitching, which translates to consistent speed and precise navigation for the USV during operation. Using CFD for the design analysis allowed for the optimization of water flow dynamics between the two hulls, resulting in reduced drag and enhanced maneuverability for the USV. Turbulent flow patterns were observed at higher speeds, which notably provided valuable insights into the USV's hydrodynamic behavior and its possible interaction with any unforeseen marine conditions, such as encounters with marine life or debris. The key findings demonstrate the USV's potential to revolutionize environmental response efforts, especially in the context of oil spill disasters in remote areas. The accuracy of the CFD simulations was pivotal in anticipating the USV's performance in various marine conditions, which demonstrates the importance of collaboration between theoretical models and practical applications. This paper introduces an innovative integration between autonomous technology and environmental responsiveness, which showcases the possibilities of advancements in the field of autonomous maritime solutions. The involvement of this research extends beyond its immediate scope and offers a new prototype for monitoring and protecting marine environments. This advancement significantly contributes to the broader discussion for safer, more sustainable offshore exploration and environmental management.

The use of autonomous marine robots has been rapidly increasing in the development of marine environments. This paper presents the development of an autonomous surface vehicle (ASV) and validation of autonomous navigation technologies. The ASV was developed as a testbed to validate fundamental navigation technologies for autonomous marine robots including both surface and underwater vehicles. The ASV was developed on a catamaran by integrating various sensors and power and electrical propulsion systems, navigation and control systems, and communication devices. As fundamental navigation technologies for ASV, waypoint tracking and obstacle avoidance are developed and tested. Further, using the ASV as a testbed to validate underwater navigation technologies, two types of underwater localization methods were developed. First, an acoustic-based navigation was developed by using acoustic sources as landmarks in underwater environment. The proposed acoustic-based navigation localized both vehicle and source by Kalman filter-based SLAM. Second, terrain-based localization as geophysics-based navigation was developed using a particle filter. Effective resampling can be achieved by using a measurement of terrain roughness. Both acoustic and terrain-based underwater navigation methods are implemented with the developed ASV, and the performance of the navigation methods are evaluated by comparing the estimated localization results to the ground truth acquired by GPS. Several field tests conducted in inland water environments demonstrate the performance of the developed vehicle and navigation algorithms.

Unmanned Surface Vehicles (USVs) can support various maritime applications, such as ocean environment monitoring and target tracking applications. Mobile Edge Computing (MEC) is a promising technology to improve the computing capacities and energy efficiencies of the USVs with latency sensitive computation tasks. In this paper, an OFDM-based maritime broadband MEC system model is developed, where a command surface vehicle provides edge computing service to the surrounding USVs, and the task offloading and resource allocation are formulated as an optimization problem with a goal of minimizing the USVs energy consumption, constrained by the task execution delay requirement and allowable transmit power. First, the optimal transmit power allocation scheme for each USV is obtained based on the water filling algorithm to improve the transmission rate of the OFDM-based wireless link. Second, the sub-problem of the task offloading transmission time allocation is solved by means of the CVX optimization toolbox. Simulation results show that the proposed offloading algorithm can effectively reduce the energy consumption of the maritime MEC system and adapt to a dense USVs MEC environment.

Path planning on satellite images for unmanned surface vehicles

Predicted loads, such as crew, cargo, and structure have been applied as main inputs during ship design and analysis. However, unexpected events on the sea has high possibility to deliver remarkable losses for ship, industry, and environment. Previous oil spill incident by the Exxon Valdez in Alaska is the perfect example which an environmental damage and industry loss are initiated by an impact phenomenon on the ship, i.e. grounding. Even though hull arrangement has adopted double hull system, grounding may threaten ship safety in various scenarios. This situation pushes society to demand sustainable investigation for impact phenomena on water transportation mode to update understanding in the phenomenon and ensure structural safety during ship operation. This work aimed to study structural behaviour of chemical tanker as a marine structure under impact, namely ship grounding. Bottom raking case was considered to be calculated by virtual experiment. The study was performed using nonlinear finite element (FE) method and an idealised geometry of seabed rock would be deployed to be hard obstruction. Observation on the selected crashworthiness criteria, i.e. internal energy and crushing force indicated that as advanced penetration occurred on the ship structure, the absorbed strain energy continued to increase, while major fluctuation appeared during the initial contact between obstruction and ship happened. Damage extent of several structural members during the crushing process was shown, which concluded that the bottom plating had the largest severity in forms of tearing mode among of all members on the bottom structure.

파랑과 해저지반 그리고 해안 해양 구조물과의 상호작용은 지반공학뿐만 아니라 해안공학 분야에서도 중요한 이슈중의 하나이며, 파랑에 의해 해저지반 내부에 발생하는 응력 및 간극수압 거동의 파악은 다양한 해안 해양 구조물의 기초 설계 및 해저 연안 지반의 불안정성 검토에 있어서 중요한 과제이다. 해저지반의 불안정에 대한 문제 중, 파랑에 의한 해저지반의 액상화는 기존의 연구를 통하여, 두개의 메커니즘이 존재한다는 것이 밝혀졌으며, 이는 각각 파랑에 의해 해저지반 내부에 발생하는 과잉간극수압의 변동 특성 및 잔류 특성에 따른 것이다. 본 연구에서는 일본 시코쿠 코치(高知)현에 위치하고 있는 코치항에서 채취한 토사에 대한 동적 특성을 고려하여, 파랑에 의해 해저지반 내부에 발생하는 침투류에 의한 잔류과잉간극수압에 대하여 해석을 하였으며, 더 나아가, 코치항에서 계측된 값과 비교 분석을 하였다. The interaction among wave, seabed and marine structure is an important issue in coastal engineering as well as geotechnical engineering. Understanding variations of stresses and pore water pressures generated in seabed induced by waves is important for civil engineers who have to design the foundation for various marine structures and verify the instability of seabed. In the matters on seabed instability, particularly, in the case of wave-induced liquefaction of seabed, it is turned out there are two different mechanisms through previous studies. These are caused by the transient or oscillatory nature and the residual or progressive nature of excess pore water pressure generated in seabed, respectively. In this study, it is analyzed dynamic characteristics of soils sampled in seabed around the port of Kochi, Japan, through the dynamic triaxial tests and the residual excess pore water pressure in the seabed induced by seepage force of wave. In addition, the calculated residual excess pore water pressures were compared with the field data observed in the port of Kochi.

Modal analysis-based initial axial force recognition method for jacket platform

Marine structures can experience loads coming from steep, non-linear waves. A transient response of the structure can be amplified in some circumstances due to phenomenon known as “ringing”. Exact conditions of the ringing response excitation are not well known and various definitions of what constitutes a ringing event appear in bibliography. This article aims at identification of ringing events for a slender marine structure subjected to the second order nonlinear irregular waves. Loads on the structure are calculated from Morison equation with extensions known as Rainey’s slender body theory. Consistent second order formulation for the flow kinematics above mean water level is employed. The excitation load is non-linear due to wave non-linearity, Morison equation’s drag term and non-linear inertia terms which can be found in Rainey’s formulation. The structure’s dynamic response is obtained by Finite Element calculations in time domain. Overall randomly-excited vibrations are analysed by statistical and spectral methods, and application of Continuous Wavelet Transform (CWT) is presented. The simulations show a number of sudden, high amplitude resonant events which can be classified as ringing.

The eastern Marmara earthquake occurred on 17 August 1999 with an Mw = 7·4 and struck the Izmit Bay and eastern Marmara Sea region, north-west Turkey. The main fault is a single strike-slip fault approximately 140 km long, starting from Sapanca Lake in the east and ending in Izmit Bay in the west. Existing industrial plants and various types of marine structure along the coast of Izmit Bay near this large-magnitude earthquake area provided valuable opportunity to examine the behaviour of marine structures through intensive observations, and to discuss their safety through detailed fieldwork and stability analysis. The active faults were determined from seismic reflection data. The fault itself and associated secondary faults caused severe damage to most of the marine structures in Izmit Bay, and caused settling and sliding of the coastal areas at some locations. On the basis of our field observations, the effects of the earthquake on marine structures and coastal areas are investigated. The tectonic setting and geotechnical properties were analysed, and soil–structure interaction problems are discussed. The effects of the earthquake, including the severity of damage, service losses, and environmental impact at petrochemical facilities, were severe and extensive. The nature of soil and the interactions between structure and ground during the earthquake are very important contributors to the severity of damage. The heavy damage to coastal structures such as refineries, petrochemical plants and ports deserves special attention. In order to identify the distribution of damage and serviceability of marine structures, the scales of damage and serviceability levels are determined, tabulated and discussed. This disaster has shown once again that geotechnical properties such as the nature of soil and soil–structure interactions are very important for construction.

This paper documents recent advances of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach, a method for simulating fully nonlinear wave-body interactions including viscous effects. The methods efficiently combines a fully nonlinear potential flow description of undisturbed wave systems with a modified set of RANS with free surface equations accounting for the interaction with a ship or marine structure. Arbitrary incident wave systems may be described, including regular, irregular waves, multidirectional waves, focused wave events, etc. The model may be fixed or moving with arbitrary speed and 6 degrees of freedom motion. The extension of the SWENSE method to 6 DOF simulations in irregular waves as well as to manoeuvring simulations in waves are discussed in this paper. Different illlustative simulations are presented and discussed. Results of the present approach compare favorably with available reference results.

Although work in ROV (remotely operated vehicles) and AUV (autonomous underwater vehicles) has already led to the development of many vehicles, no surface robots have been designed. The Port of Bordeaux Authority in collaboration with the University of Bordeaux has undertaken the development of such an autonomous surface vehicle. The primary objective of this craft is to serve as a platform for hydrographic data acquisition. The ASV will moreover be an efficient tool destined to serve engineers and researchers involved in the study of sea. The ASV is a completely autonomous small surface craft. Its autonomy and reliability are guaranteed by its state of the art equipment. Navigation itself is monitored by a DGPS positioning system. The progress of the ASV is tracked by a mobile control station (MCS) which can either remain on-shore or be placed on-board a mother ship. The mobile control station is needed to define and preprogram the mission of the ASV before its departure, launch the ASV, monitor its progress (the MCS can retake control of the ASV at any moment) and recover it at the end of its mission. This paper describes the general architecture of the ASV and the technological choices made. It then focuses on the identification process and on the development of the control system. >