Surface Craft Research Articles

Efficiency Improvement of Friction Stir Welding Parameters on AZ91 Magnesium Alloy Joints

Abstract: Friction Stir Welding (FSW) is a solid-state welding that permits an intensive formof parts and geometries to be welded with great nature of joints. The use of high-quality Magnesium alloys is extending in shipbuilding industry, particularly for the advancementof naval warships, cruise ships, littoral surface craft and merchant ships. FSW advancementhas been seemed to have various focal points for the exploitation of Magnesium alloys structures, as it is a minimal effort welding process. The objective is to come across the optimum levels of the process parameters in which it yields maximum tensile strength andbetter hardness. A three-factor, three-level design is utilized for optimizing the FSW process parameters and a Taguchi L9 orthogonal array experimental set up is used to anticipate the responses. The system parameters considered are Rotational speed, Transverse speed and the Tool tilt angle. The Friction stir welding is processed for butt joining of Magnesium alloys (AZ91) plates with 6 mm thickness. Tensile testing is attempted on dog-bone kind test specimen for Magnesium alloys. Analysis of Variance (ANOVA) has been used to analyze the effect of different parameters regarding the responses. The microstructural attributes of the welded segments, including base metal, heat affected zone (HAZ), Thermo Mechanically Affected Zone (TMAZ) and Stir Zone (SZ) are examined through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis carried out to quantify the chemical element allocation at the weld interface. The observed optimum condition for Magnesium alloys (AZ91) is 560 rpm, 60 mm/min and 1 degree.

Optimization study of unmanned surface craft formation control by fusing BSM and ANN

Optimization study of unmanned surface craft formation control by fusing BSM and ANN

Numerical Validation of the Hydrodynamic Drag of a Surfaced and Fully Appended Underwater Vehicle

Underwater Vehicles (UV) are required to travel on the surface for periods of time to complete mission requirements. However, knowledge on the drag of a surfaced UV is scarce in the public domain and the knowledge on the behaviour of surface craft is generally not applicable due to substantial differences in hull form. This paper presents a numerical study on the drag coefficient of a surfaced and fully appended BB2 UV in calm water. The results were firstly validated with the available experimental drag data for a range of speeds. Secondly, the free surface elevation along the length of the UV photographed during physical model scale experiments is compared to the free surface elevation predicted by CFD. This research has shown that a multiphase CFD model can accurately predict the drag due to the forward motion of a surfaced UV in calm water.

Vision-based Autonomous Landing Control of a Multi-rotor Aerial Vehicle on a Moving Platform with Experimental Validations

This paper studies the problem of landing a multi-rotor unmanned aerial vehicle (UAV) on a moving platform (i.e., surface craft, car) based on visual servo. An efficient method is proposed to get the landmark position, in which the camera can follow the moving landmark to supply the relative position information between UAV and the platform. To avoid the divergence of the collected image caused by the swinging camera, an inertial measurement unit (IMU) is used to get the attitude of camera, which will provide the rectification information for the collected image. By using the collected image and the compensation information, we could obtain the proper image and then the relative position can be expressed through the principle of monocular ranging. To demonstrate the effectiveness of the proposed landing method, we present and analyze the experimental results, showing that the landing procedure is steady with a high accuracy.

Research on YOLOv3 target detection model in the field of remote sensing

The target recognition problem of high-resolution remote sensing images is marine traffic monitoring, disaster reduction emergency search and rescue, unmanned autonomous systems (UAS) (such as unmanned aerial vehicles, unmanned vehicles, unmanned submersibles, unmanned surface craft and other autonomous robots) and other civilian applications. The core technology of the system is also the key technology of military automatic target recognition (ATR) systems such as military reconnaissance, precision guidance, and maritime monitoring. With the development of high-resolution earth observation systems, more and more industrial applications require the extraction of more valuable target details from high-resolution remote sensing images. Then, due to the complex background of high-resolution remote sensing images and the difference in image quality (factors such as size, resolution, noise, etc.), low target detection accuracy and slow speed are the main bottlenecks that affect the combination of artificial intelligence and remote sensing. In order to solve the technical bottleneck of target detection, this paper focuses on exploring the detection performance of the channel attention module SElayer and YOLOv3 model in the field of high-resolution remote sensing images, providing basic technical support for related research.

Modular, Flexible, Low-Cost Microstructure Measurements: The Epsilometer

AbstractThe Epsilometer (“epsi”) is a small (7 cm diameter × 30 cm long), low-power (0.15 W), and extremely modular microstructure package measuring thermal and kinetic energy dissipation rates, χ and ε. Both the shear probes and FP07 temperature sensors are fabricated in house following techniques developed by Michael Gregg at the Applied Physics Laboratory/University of Washington (APL/UW). Sampling eight channels (two shear, two temperature, three-axis accelerometer, and a spare for future sensors) at 24 bit precision and 325 Hz, the system can be deployed in standalone mode (battery power and recording to microSD cards) for deployment on autonomous vehicles, wave powered profilers, or it can be used with dropping body termed the “epsi-fish” for profiling from boats, autonomous surface craft or ships with electric fishing reels or other simple winches. The epsi-fish can also be used in real-time mode with the Scripps “fast CTD” winch for fully streaming, altimeter-equipped, line-powered, rapid-repeating, near-bottom shipboard profiles to 2200 m. Because this winch has a 25 ft (~7.6 m) boom deployable outboard from the ship, contamination by ship wake is reduced one to two orders of magnitude in the upper 10–15 m. The noise floor of ε profiles from the epsi-fish is ~10−10 W kg−1. This paper describes the fabrication, electronics, and characteristics of the system, and documents its performance compared to its predecessor, the APL/UW Modular Microstructure Profiler (MMP).

Algorithms for Functioning of the Magneto-Metric System to Provide Search and Rescue Operations Using Unmanned Flying Vehicles

Purpose of research. Reducing the time and increasing the efficiency of search and rescue of crews of land vehicles, air, surface and underwater craft. Combining physical, informational, and geometric parameters allows reliable detection of single ferromagnetic bodies by analyzing additional information in working algorithms.Methods. The paper contains a practically significant variant of building a search engine that is implemented on two or more unmanned flying vehicles moving in the search area in a coordinated formation at the basic distance. The solution system is based on using magnetic field components as magnetometric information without using primary gradient information. This feature allows us to get compact and functionally complete algorithms. Calculations using such algorithms ensure the stability of an unmanned flying vehicle in various combinations of vector, roll and pitch.Results. Algorithms for the functioning of the magnetometric system for searching ferromagnetic bodies based on the magnetostatic equations have been constructed in the article,. The intelligent system is based on the scheme of a measuring and computing circuit with staggered vector three-axis blocks of magnetometers in space. The system is able to solve the whole range of problems of search, detection, direction finding, localization, positioning and identification of metal objects that have their own magnetic field.Conclusion. The main result of the study is that the working algorithms for detecting ferromagnetic bodies take into account the characteristics of the air environment, the instrumental error of measurement units of physical quantities and the geometric proportions of measuring equipment location on board the unmanned and manned search and rescue helicopters. The obtained research results have been used in the development of a hardware and software complex with helicopter-type unmanned flying vehicles designed to support search and rescue operations in the Arctic.

Parameter Estimation of the ALBA Autonomous Surface Craft

Arequipa region holds the largest extension of the Peruvian littoral at the Pacific sea, has also fresh water resources composed of rivers and lagoons from the coast to the Andes highland. The ALBA vehicle is a low-cost autonomous surface vessel with open source architecture that is being developed to support water monitoring tasks in the region. This article deals with the nonlinear identification problem for an autonomous surface craft and the maximum likelihood estimation approach is used to estimate its parameters. The parametric nonlinear model is considered with simulated and experimental data. The results shows good fitting values when two, three and a maximum four parameters are estimated.

Quantifying cold front induced water transport of a bay with in situ observations using manned and unmanned boats

The generation of high-resolution data is increasingly important in understanding the complexities of coastal ocean and developing sound management strategies, especially in view of the long-term impact of severe weather systems. The impact of severe weather systems, when integrated over time, can be significant when compared with tidal oscillations. This paper presents a study of water transport out of Vermilion Bay in response to a short, intense event associated with a passing atmospheric cold front, and reports the application of an Acoustic Doppler Current Profiler (ADCP) mounted on an Automated Surface Craft (ASC), known as the auto-boat or unmanned boat, developed in our lab at the Louisiana State University, to generate high resolution data accurately at a fraction of the cost of a manned boat. In our study, we used a manned boat and an unmanned boat, each for over 24 h to cover an entire diurnal tidal cycle, to measure flow velocity profiles to calculate the total transport. A stationary ADCP was deployed in the Southwest Pass of the Vermilion Bay from May 2009 to April 2012, providing data almost continuously (with only one major gap), with a 717-day record of water transport between the northern Gulf of Mexico and Vermilion Bay, and demonstrates the importance of the pass in water transport.

ISME activity on the use of Autonomous Surface and Underwater Vehicles for acoustic surveys at sea

<p class="Abstract"><span lang="EN-US">The paper presents an overview of the recent and ongoing research activities of the Italian Interuniversity Center on Integrated Systems for the Marine Environment (ISME) in the field of geotechnical seismic surveying. Such activities, performed in the framework of the H2020 European project WiMUST, include the development of technologies and algorithms for Autonomous Surface Crafts and Autonomous Underwater Vehicles to perform geotechnical seismic surveying by means of a team of robots towing streamers equipped with acoustic sensors.</span></p>

Experimental Evaluation of an Autonomous Surface Craft for Shallow-Water Bathymetry

AbstractVast coastal water bodies such as mangroves and wetlands, despite their enormous importance, are inaccessible to even the smallest aquatic vehicles, which are not capable of navigating the extremely shallow environments. To understand their behavior and the transport and exchange processes with both sea and land, it is crucial to study local hydrodynamics, which are highly dependent on bathymetric configuration. In order to obtain accurate and high spatial resolution bathymetric samples, an existing small surface vehicle instrumented with GPS and echosounder was implemented with an autopilot system to achieve autonomy. A description of the autonomous system together with the evaluation of the whole vehicle's performance in a natural coastal environment (e.g., affected by the wind, waves, and currents that exist in coastal regions) is presented. The navigation system is based on an autopilot system, which follows a set of user-selected waypoints to drive the vehicle through a previously designed path. The trajectory is self-corrected to achieve sufficient accuracy (the limits are also defined by the user) using real-time kinematics. The tracking is performed by two independent proportional-integral-derivative (PID) control systems: the boat's displacement speed and the bearing control. A simple experimental procedure to tune the low-level PID control parameters is presented. Comparisons between the bathymetric maps obtained with the system and with other standard bathymetric surveys from a selected coastal site (ship-towed echosounder) are presented to test both the precision of the boat's navigation and the fine structure of the bottom topography. The results confirm the system's capability as a valuable tool for surveying large and very shallow environments.

Lift-Off Velocity on Solar-System Small Bodies

The lift-off velocity is defined as the velocity at which a particle, moving tangentially on the surface of some arbitrary body, will lift off from that surface and enter orbit. A vectorial expression for this velocity was previously derived for dimensionless particles. This theory is extended to be applicable to surface exploration craft with some finite size that are envisioned for missions to the small bodies of our solar system. For realistic mission scenarios, the lift-off velocity is shown to be independent of the craft size, and to depend strongly on the radius of curvature of the target body; this velocity is useful in the operational design of surface craft. A similar expression is derived for the case of motion on a ridge or asperity, in which the lift-off velocity becomes independent of the surface curvature. This second case has implications to the friction force experienced by a surface vehicle or rock. A methodology is developed to compute the curvature of a spherical-harmonic shape model; an established method that yields the curvature of a vertex-facet model is reviewed. The two methods are then applied to compute the lift-off-velocity distributions on the surfaces of asteroids Alpha, Bennu, and Eros.

Cost and weight of composite ship structures: A parametric study based on Det Norske Veritas rules

A wider use of composites in larger, commercial vessels has been limited by initial costs and fire regulations, but both of these obstacles are diminishing. Increasing fuel costs and more stringent emission requirements have heightened the value of lightweight structures. Due to the higher acquisition costs and other entry barriers, composite designs must be as cost efficient as possible in order to compete with traditional steel or aluminium designs. The purpose of this article is to investigate which fibre-reinforced polymer materials and types of structures are most suitable for different parts of a ship design in order to minimize weight or cost. This is done by designing and comparing individual composite panels while varying a wide range of input parameters and strictly following the ‘Det Norske Veritas (DNV) Rules for Classification of High Speed, Light Craft and Naval Surface Craft’. The results are presented as weight and cost comparisons between materials and structures and also degree of utilization for the different design criteria; carbon fibre structures are on the average 20%–30% lighter than glass fibre structures but are consistently more expensive. The results also indicate that sandwich panels in most cases are lighter than single-skin panels, and that for sandwich structures, the mechanical properties of the core material are commonly the critical design criterion. The minimum amount of reinforcement stipulated by the rules is also found to be a critical factor.

An AIS-Based Site Planning Method to Help Minimize Collision Risk during Marine Autonomous Surface Craft Deployments

AbstractMarine autonomous surface crafts (MASCs), or unmanned surface vehicles as their precursors have traditionally been known, could cost effectively advance spatiotemporal coverage and resolution capabilities for oceanographic sampling in coastal and estuarine settings, if deployed for long durations (from days to weeks). Site planning for such deployments balances scientific goals against operational risk of collision avoidance (CA) maneuvers required by the MASC during encounters with other vessels. A method is developed and demonstrated in this paper, using archived Automatic Identification System (AIS) vessel tracking data, to quantify such potential encounters of a MASC on a repeat-transect survey. The demonstration site is Rhode Island Sound, where average vessel track frequencies are shown to range from about 8 to 0.01 or less per day, from inshore shipping lanes to areas farther offshore, respectively. Encounters per month ranged from 24 to 1 for increasingly offshore locations, based on a MASC repeatedly traversing an 18-km transect at an average speed of 2.5 m s−1 (~5 kt) over a one-month summer period and stopping at each of 10 equispaced stations in one direction to sample for 10 min. Crude estimates of non-AIS vessel traffic suggest total encounters (with vessels equipped by AIS or not) up to 3–4 times higher. The method can be applied anywhere AIS data are available and is generalizable to any survey configuration. It facilitates investigating sensitivity to choices of transect location and sampling configuration parameters, providing crucial information to guide deployment planning for a given level of confidence in CA capabilities of the MASC.

Multipurpose stabilization of the advanced marine surface crafts

Advanced marine surface crafts, such as SWATHs, catamarans or hovercrafts become more and more popular for a great range of various tasks. They usually operate at much higher speed than conventional ships. Moreover, in the open sea there are a lot of requirements and restrictions concerning the quality of such crafts’ dynamics, especially in case of the wind or waves. This paper considers application of the control law with a special multipurpose structure for autopilot design for amphibious air cushion vehicles. Such control law allows to decompose the autopilot task into simpler optimization subtasks. Efficiency of this approach is shown in the task of stabilizing yaw angle of the air cushion vehicle in the different weather conditions.

Robust system of dynamic positioning for robotized model of surface craft

Robust system of dynamic positioning for robotized model of surface craft

Неразрушающий контроль на «Северном машиностроительном предприятии»

“Sevmash” is one of the biggest Russian shipbuilding enterprises. Its capacity enables high-tech and knowledge-intensive projects to be fulfilled, such as manufacturing of spent nuclear fuel containers, building of modern nuclear-powered submarines (NPS) and marine engineering structures. The enterprise has mastered manufacturing of offshore platforms for oil and gas field development in the Arctic. Now “Sevmash” continues construction of nuclear strategic and multi-purpose submarines of the fourth generation “Borey” and “Yasen”.
 The article deals with the formation and development of non-destructive testing services from its beginning to the present day. Since 1950s, the radiography of hull structures welded seams and pipelines joints was the main testing method. In 1970s construction of new generation nuclear submarines began; it was necessary to create gamma flaw detectors of new design and they were created within 15 years. Besides in 1970s the active period began for development of ultrasonic testing instruments. In 1970s–1990s, concurrently with radiographic and ultrasonic techniques, testing of welds during the welding process with an acoustic emission method was carried out.
 In 1990s magnetic particle inspection of welded joints, radiation monitoring, leakage testing with the use of helium leak detectors and vacuum chambers had been extensively developed. The bubble vacuum method of welded connections testing was widely used in the process of repair and re-equipment of surface crafts. 
 Today “Sevmash” actively re-equips its production facilities. It gives “Sevmash” the opportunity to built ships that meet the highest demands.

A dynamic interface compression method for VOF simulations of high-speed planing watercraft

A high speed surface craft is mostly supported by hydrodynamic lift force rather than by buoyancy force. The lift force directly influences the running attitude of the surface craft such as trim and sinkage. The pressure distribution is caused by a solution of free-surface flow around the surface craft. To deal with the free-surface flow, volume-of-fluid (VOF) method has been widely used even with its disadvantages including interface smearing. In the present study, a new dynamic interface compression method is introduced to reduce interface smearing and to avoid unphysical solutions. The method was validated by the volume fraction advection test and prismatic body problem. Finally, the method was applied to simulate the running attitude and resistance of several high speed planing vessels.

A Marine Autonomous Surface Craft for Long-Duration, Spatially Explicit, Multidisciplinary Water Column Sampling in Coastal and Estuarine Systems

AbstractThe Surveying Coastal Ocean Autonomous Profiler (SCOAP) is a large catamaran marine autonomous surface craft (MASC) for unattended weeks-long, spatially explicit, multidisciplinary oceanographic water column profile sampling in coastal/estuarine waterbodies. Material transport rates/pathways, crucial to understanding these ecosystems, are typically poorly known. SCOAP addresses demanding spatiotemporal sampling needs and operational challenges (strong currents, open coastal sea states, complex bathymetry, heavy vessel traffic). Its large size (11-m length, 5-m beam) provides seaworthiness/stability. The average speed of 2.5 m s−1 meets the representative goal to traverse an 18-km transect, sampling 10 min at each of 10 stations 2 km apart, nominally 4 times daily. Efficient hulls and a diesel–electric energy system can provide the needed endurance. The U.S. Coast Guard guidelines are followed: lighting, code flags, the Automatic Identification System (AIS), and collision avoidance regulations (COLREGs)-based collision avoidance (CA) by onboard autonomy software. Large energy reserves obviate low-power optimization of sensors, enabling truly multidisciplinary sampling, and provide on-demand propulsion for effective CA. Vessel stability facilitates high-quality current profile observations and will aid engineering/operation of the planned winched profiling system, performance of an anticipated radar system to detect/track non-AIS vessels, and potential research-quality meteorological sensor operation. A Narragansett Bay test deployment, attended by an escort vessel, met design goals; an unattended open coastal deployment is planned for Rhode Island Sound. Scientific and operational strengths of large catamaran MASCs suggest they could be an important cost-effective complement to other sampling platforms (e.g., improved spatiotemporal coverage and resolution, extending farther inshore, with a broader range of sensors, compared to underwater gliders) in coastal/estuarine waters.

Capability-oriented robot architecture for maritime autonomy

Advanced ocean systems are increasing their capabilities and the degree of autonomy more and more in order to perform more sophisticated maritime missions. Remotely operated vehicles are no longer cost-effective since they are limited by economic support costs, and the presence and skills of the human operator. Alternatively, autonomous surface and underwater vehicles have the potential to operate with greatly reduced overhead costs and level of operator intervention. This paper proposes an Intelligent Control Architecture (ICA) to enable multiple collaborating marine vehicles to autonomously carry out underwater intervention missions. The ICA is generic in nature but aimed at a case study where a marine surface craft and an underwater vehicle are required to work cooperatively. They are capable of cooperating autonomously towards the execution of complex activities since they have different but complementary capabilities. The architectural foundation to achieve the ICA lays on the flexibility of service-oriented computing and agent technology. An ontological database captures the operator skills, platform capabilities and, changes in the environment. The information captured, stored as knowledge, enables reasoning agents to plan missions based on the current situation. The ICA implementation is verified and early validated in simulations by means of a team of two above autonomous marine robots. This paper also presents architectural details and evaluation scenarios of the ICA, results of simulations from different maritime operations, and future research directions.