Algorithm for adaptive correction of the ship's movement along the trajectory in the presence of a sea current

В статье предложен алгоритм адаптивной коррекции движения судна по траектории при наличии морского течения. В основе предлагаемого подхода лежит алгоритм градиента вспомогательных функций. Показаны преимущества предложенного алгоритма адаптивной коррекции движения судна по траектории. Сущность предлагаемого подхода заключается в замене прямолинейного участка маршрута судна, новой виртуальной траекторией и использовании ее во вспомогательной функции и при вычислении соответствующего вектора градиента. Компьютерное моделирование подтвердило эффективность предложенного алгоритма адаптивной коррекции. Адаптивные свойства разработанного алгоритма выражаются в том, что он обеспечивает асимптотически точное движение по участкам запланированной траектории, не используя информации о скорости и направлении морского течения. Предполагается использование предложенного адаптивного алгоритма при разработке систем автоматического управления движением судна по маршруту. The article proposes an algorithm for adaptive correction of the ship's movement along the trajectory in the presence of a sea current. The proposed approach is based on the gradient algorithm of auxiliary functions. The advantages of the proposed algorithm for adaptive correction of the ship's motion along the trajectory are shown. The essence of the proposed approach is to replace the straight-line section of the ship's route with a new virtual trajectory and use it in an auxiliary function and in calculating the corresponding gradient vector. Computer simulation has confirmed the effectiveness of the proposed adaptive correction algorithm. The adaptive properties of the developed algorithm are expressed in the fact that it provides asymptotically accurate movement along sections of the planned trajectory, without using information about the speed and direction of the sea current. It is supposed to use the proposed adaptive algorithm in the development of systems for automatic control of the ship's movement along the route.

Intermittent Beginning to the Formation of Hydrogenous Ferromanganese Nodules in the Vast Field: Insights from Multi-Element Chemostratigraphy Using Microfocus X-ray Fluorescence

Vast ferromanganese nodule fields have been found on the deep-sea floor of all oceans worldwide. They have received attention because they potentially provide high-grade metal resources to develop future high- and green-technology. However, how these vast nodule fields were formed and developed owing to their widespread nature or tendency to be denser with an increasing number of nodules has not yet been established. In this study, the fine-scale inner structure of nodules of various sizes was analyzed on the basis of chemical mapping using microfocus X-ray fluorescence. We found that nodules distributed in the vast field around Minamitorishima (Marcus) Island have several types of innermost layers, which correspond to different chemostratigraphic layers of nodules that have been previously reported by us in this region. As nodules grow in order from the center to the outside, the different types in the innermost layer indicate a difference in the timing of the beginning of their growth. Moreover, because the differences in the chemical features of each layer reflect differences in the composition of the original deep-sea water, our results imply that the beginning of nodule formation occurred intermittently at each time of a water mass replacement due to new deep-sea currents flowing into this region. We recognized that the northern part of the study area was dominated by large nodules that started to grow in relatively earlier times, while the southern part tended to have many nodules that grew in relatively later times. Based on these observations, we hypothesize that the intermittent beginning of nodule formation is governed by the northward inflow of the deep-sea current that originated from the Lower Circumpolar Deep Water for an extended time to form the vast nodule field. Because patterns in the timing of nodule formation were different in the eastern and western regions, we thus further propose that the topographic framework, i.e., the arrangement of individual large seamounts and the cluster of small knolls and petit-spot volcanoes, strongly regulates the flow path of the deep-sea current, even if the position of the entire seamount changes owing to plate motion. The deep-sea current might supply some materials to be nuclei, resulting in the nodule formation at the beginning of the process.

Notes on two rare species of brachyuran crabs (families Matutidae and Parthenopidae) from Indonesian waters with new distribution records

This research aimed to report two species of Brachyuran crabs that were found rarely from Indonesian waters. The latest report was more than one hundred years ago, and the study from Indonesia before was not so clear, both information about specimens and location details. We conducted our study in Southern Aru Island and Malacca Strait using trawl during the cruise research which was held by the Research Institute for Marine Fisheries, Ministry of Marine Affairs and Fisheries. Our findings were Izanami reticulata, New Record (family Matutidae) from Southern Aru Island, and Cryptopodia fornicata (family Parthenopidae) from Malacca Strait. The two locations are located close to the location where the species was found in previous studies, namely the Arafura Sea which is adjacent to the Aru Islands, and the Malacca Strait which is adjacent to Borneo. We suspect that the presence of these two species in western and eastern Indonesia was due to their distribution during the pelagic larval stage through the sea current. This article also provided the specific habitat for both species which has not been stated. In addition, this article will contribute to strengthening Indonesia as a mega biodiversity country with initiate compiling the database of Brachyura in Indonesian waters.

Swarm Of Autonomous Underwater Vehicles – Preliminary Results Of The Control System

A swarm of autonomous underwater vehicles can be a valuable alternative for fully equipped and very expensive super-vehicles. A distributed system of tightly cooperating vehicles can be cheaper, simpler in maintenance, more reliable, more flexible and universal than traditional single-vehicle systems. However, keeping a tight formation of underwater vehicles in the condition of the sea current, unclear environment, and rare inter-vehicle communication is a very challenging problem, which requires an effective vehicle control system. The paper proposes a solution to the above-mentioned problem, which is based on neuro-evolution. Moreover, the paper also presents the first results of the proposed system.

Influence Of Hydro-Meteorological Elements On The Ship Manoeuvring In The City Port Of Split

The Port of Split is located in the central part of the eastern Adriatic and is the largest Croatian passenger port. The Port of Split consists of the North Port, for the reception of mainly cargo ships, and the City Port for the reception of passenger ships. Although the port is protected from the open part of the Adriatic by a number of islands, its specific spatial position as well as local hydro-meteorological factors, primarily wind, can significantly affect the safety of navigation, and ultimately close all traffic. The entrance to the City Port is facing to the south; accordingly, the effect of southerly winds and waves will be one of the primary factors influencing the safety of manoeuvring. Also, the wider area of Split is characterized by the strong local, approximately NE wind with sudden gusts (‘’Bura’’) which is especially dangerous for navigation. This paper analyses the effect of significant hydro-meteorological factors on the safety of manoeuvring at the approach and within the City Port of Split. The influence of wind, waves, sea current, tides and visibility will be analysed. Also, these factors will be classified in order of importance with respect to those parts of the port where they predominate as a threat to manoeuvring safety. The obtained results should serve as a basis for future defining of limiting working/manoeuvring conditions.

Testing a Novel Aggregated Methodology to Assess Hydrodynamic Impacts on a High-Resolution Marine Turtle Trajectory

We designed a novel aggregated methodology to infer the impact of ocean motions on the movements of satellite-tracked marine turtles adopting available oceanographic observations and validated products of a numerical oceanographic forecasting system. The method was tested on an 11-months trajectory of a juvenile loggerhead turtle (LT) wandering in the Tyrrhenian Sea (Mediterranean Sea) that was reconstructed with a high-resolution GPS tracking system. The application of ad-hoc designed metrics revealed that the turtle’s route shape, ground speed and periodicities of its explained variance mimic the inertial motions of the sea, showing that this methodology is able to reveal important details on the relation between turtle movements and oceanographic features. Inertial motions were also identified in the observed trajectory of a surface drifting buoy sampling the Tyrrhenian Sea in a common period. At each sampling point of the turtle trajectory, the sea current eddy kinetic energy (EKE) and a Sea Current Impact index were computed from a validated set of high-resolution ocean modeling products and their analysis showed the relevant effects of the highly variable local sea currents mechanical action. Specifically, the metric we adopted revealed that the turtle trajectory was favorably impacted by the encountered sea current advection for about 70% of its length. The presented oceanographic techniques in conjunction with high-resolution tracking system provide a practicable approach to study marine turtle movements, leading the way to discover further insights on turtle behavior in the ocean.

The Potential of DAS on Underwater Fiber Optic Cables for Deep-Sea Current Monitoring

<p><span>Distributed Acoustic Sensing (DAS) </span>enables<span> the </span>use of <span>existing </span>underwater <span>telecommunication </span>cables <span>as multi-sensor arrays</span>, allowing for detailed<span> study of the seismic wavefield. </span>Since <span>underwater </span>telecommunication <span>cables </span>were not deployed for seismological investigations, <span>the coupling between the </span>cable and the seafloor varies<span>, dramatically reducing the usefulness of </span>poorly coupled<span> cable segments</span> for<span> seismological research. In particular, underwater cables include segments that are suspended </span>in the water column across seafloor valleys or other bathymetry irregularities. Here, we propose that <span>ocean bottom currents may be studied by monitor</span>ing the vibrations of suspended cable <span>segments</span>. We analyze <span>DAS-strain recordings</span> on <span>three dark fibers deployed in the Mediterranean </span>S<span>ea. </span>Several cable segments, presumably suspended, feature h<span>igh-amplitude signals with harmonic spectra</span> as expected from<span> a </span>theoretical <span>model of in-plane vibration of hanging cables. The spatial shape of the vibration modes are determined by filtering and stacking. Their comparison to theory allows constraining the attenuation of longitudinal waves propagating along the cable in the non-suspended sections. The vibration frequencies change over time scales of tens of minutes. </span>Assuming that<span> oscillations of </span>suspended<span> sections are driven by deep sea currents, the temporal fluctuations of the vibration frequencies</span> <span>are related to changes of the cable</span>s<span> tension which, in turn, are related to the drag force induced on the suspended cable by </span><span>the shedding of </span><span>Karman </span><span>vortex</span>.<span> On this basis, we propose a method to infer changes of deep sea current speeds from the changes of fundamental frequency of cable vibrations</span>. Submarine optical reconnaissance campaigns and controlled smaller-scale experiments are planned to validate the approach. <span>The work aims at </span>demonstrating the potential of using suspended telecommunication <span>cable</span>s<span> to </span>monitor and investigate <span>marine currents in </span>deep <span>ocean environments. </span></p>

Modelling and simulation of ship collisions in port and coastal waters

Navigational safety is an important issue in maritime transportation. The most frequent type of maritime accident in the port and coastal waters is the ship collision. Although some ship collision models have been developed in the past, few have taken account of wind and sea current effects. However, wind and sea current are critical factors in ship maneuvering. Therefore, based on the previous collision model without wind and sea current effects, this study further develops a ship collision model with wind and sea current effects. Finally, a comparison of the results for the proposed collision model in this study and the ship maneuvering simulator is shown to illustrate the effectiveness of the proposed mathematical model in this paper, followed by the conclusions and suggestions given to navigators, port managers, and governmental maritime departments to improve navigational safety in port and coastal waters.