Ship Motion Parameters Research Articles

Parameter identification algorithm for ship manoeuvrability and wave peak model based multi-innovation stochastic gradient algorithm use data filtering technique

This paper addresses the issue of identifying ship motion parameters and wave peak frequency. Utilising the Euler discretisation principle, we establish a discrete-time auto-regressive moving average model with exogenous input (ARMAX) for the ship-wave system. Furthermore, we develop a filtering-based stochastic gradient algorithm for the system by applying filtering techniques and auxiliary model identification idea. A filtering-based multi-innovation stochastic gradient algorithm, utilizing the multi-innovation identification theory, was developed to enhance the convergence rate and accuracy of parameter identification. This approach was found to be more effective than the filtering-based stochastic gradient algorithm. Simulation results validate the efficacy of the proposed algorithm in parameter identification.

Investigation of the stability of the neu-ronetwork in the surface identification system

The peculiarity of the current moment for modern shipping is that information technologies are intensively used in the fleet and port infrastructure. However, despite the introduction of new technical means of navigation, the problem of taking into account the influence of the human factor remains unsolved. The most promising direction of application of information technologies to solve the above-mentioned problem is the concept of e-Navigation, which is currently a key initiative of the IMO. The concept involves the use of "end-to-end" digital technologies of artificial intelligence and augmented reality in the part of intellectualization of the shipmaster's interface. These technologies are the key to a fundamentally new level of human-operator (master) interaction with navigation data in the digital environment, including for identifying the situation and recognizing situations. According to the results of the conducted research, the conclusion was obtained that the accuracy of the forecast of the ship's motion parameters by a neurocomputer is higher than when using a distributed computing system for this purpose. Thus, in the considered model situations, the neural network showed higher computational reliability compared to the parallel algorithm for solving the differential equation. It should also be noted that the conclusions based on the results of the study of the reliability of the neural network calculation system should be understood in a statistical and not an absolute sense

Reducing wave impacts on high-speed catamarans through deployment of ride control: Analysis of full-scale measurements

Full-scale trials on a 98 m wave piercer catamaran were conducted in the North Sea and North Atlantic region. In order to examine, amongst other things, the effectiveness of the ride control system, the ship was deliberately operated in sea conditions likely to induce a large number of wave impact events. Primary ship motion and structural response parameters, such as angles, rates and accelerations, and strains at various locations were recorded. Slam and minor wave impact events were identified in the data records and analysed to determine the influence of wave headings, vessel speeds, sea states and ride control system activation on their occurrence rates and severity. The Empirical Mode Decomposition technique was used to remove both noise and the rigid body response from the acceleration signals. This was based on prior work by the authors and found to provide more reliable slam identification than traditional methods. A prediction of extreme slam occurrences was modelled using logistic regression. A key outcome of the study was the finding that the activation of ride control significantly reduces the probability of extreme slams occurring.

An interpretable knowledge-based decision support method for ship collision avoidance using AIS data

AIS data include ship spatial-temporal and motion parameters which can be used to excavate the deep-seated information. In this article, an interpretable knowledge-based decision support method is established to guide the ship to make collision avoidance decisions with good seamanship and ordinary practice of seamen using AIS data. First, AIS data is preprocessed and trajectory reconstructed to restore the ship historical navigation state, and a ship encounter identification model is constructed according to the encounter characteristics; Second, a two-stage collision avoidance behavior extraction algorithm is formed to build a behavior knowledge base, and the scenario similarity model is constructed to measure and match similar scenarios based on ship position, motion tendency and collision risk. Then, the Delaunay Triangulation Network is used to fuse ship trajectories of similar scenario to form the collision avoidance path. Finally, a case study is performed using the real AIS data outside Ningbo-Zhoushan Port waters, China, and the effectiveness of the planned path is verified by setting the head-on and crossing situations and comparison between the planned and real paths. Results indicate that the proposed model can extract the ship collision avoidance behavior accurately, and the planned path can ensure navigation safety.

Ship Intention Prediction at Intersections Based on Vision and Bayesian Framework

Due to the high error frequency of the existing methods in identifying a ship’s navigational intention, accidents frequently occur at intersections. Therefore, it is urgent to improve the ability to perceive ship intention at intersections. In this paper, we propose an algorithm based on the fusion of image sequence and radar information to identify the navigation intention of ships at intersections. Some existing algorithms generally use the Automatic Identification System (AIS) to identify ship intentions but ignore the problems of AIS delay and data loss, resulting in unsatisfactory effectiveness and accuracy of intention recognition. Firstly, to obtain the relationship between radar and image, a cooperative target composed of a group of concentric circles and a central positioning radar angle reflector is designed. Secondly, the corresponding relationship of radar and image characteristic matrix is obtained after employing the RANSAC method to fit radar and image detection information; then, the homographic matrix is solved to realize radar and image data matching. Thirdly, the YOLOv5 detector is used to track the ship motion in the image sequence. The visual measurement model based on continuous object tracking is established to extract the ship motion parameters. Finally, the motion intention of the ship is predicted by integrating the extracted ship motion features with the position information of the shallow layer using a Bayesian framework. Many experiments on real data sets show that our proposed method is superior to the most advanced method for ship intention identification at intersections.

Dynamic adaptive intelligent navigation decision making method for multi-object situation in open water

The intelligent navigation system of autonomous ships aims at making fully autonomous navigation decisions to replace the work of seafarers. Realizing intelligent navigation decision-making in open water is the first stage of a fully autonomous navigation system. Through real-time sampling, rapid update of the own ship's motion parameters, and traffic situation information, an open-water intelligent navigation decision-making method that can dynamically adapt to the residual error in the system and the target ship's random manoeuvre is proposed. A digital traffic environment model comprising different target types is built as the basis of navigation decision-making. An optimal feasible plans of the own ship, which will ensure all targets pass safely, is calculated using the velocity obstacle (VO) theory, and dynamic collision avoidance mechanism to construct an autonomous manoeuvring model. The simulation experiments proved that the combined results of this and previous research could realize autonomous navigation in an open water environment having multiple static and dynamic objects under the premise of satisfying the International Regulations for preventing Collisions at Sea, 1972 (COLREGs) and the good seamanship. This research will provide basic theories and methods to realize the autonomous navigation decision-making of ships in an open water environment with multiple targets.

Analysis of ship wake features and extraction of ship motion parameters from SAR images in the Yellow Sea

The identifying features of ship wakes in synthetic aperture radar (SAR) remote sensing images are of great importance for detecting ships and for extracting ship motion parameters. A statistical analysis was conducted on the identifying features of ship wakes in SAR images in the Yellow Sea. In this study, 1091 ship wake sub-images were selected from 327 SAR images in the Yellow Sea near Qingdao. Analysis of the identifying features of ship wakes in SAR images revealed that both turbulent wakes and Kelvin wakes account for the majority of ship wakes, with turbulent wakes occurring approximately four times as frequently as Kelvin wakes. Narrow- V wakes and internal wave wakes were comparatively rare, which is due to the peculiarities of the radar system parameters and marine environments required to observe these wakes. Additionally, we extracted ship motion parameters from four types of ship wakes in the SAR images. Specifically, internal wave wakes in SAR images in the Yellow Sea were also used to extract ship motion parameters. Validation of the extracted parameters indicated that the extraction of these parameters from ship wakes is a viable and accurate approach for the acquisition of ship motion parameters. These results provide a solid foundation for the commercialization of SAR-based technologies for detecting ships and extracting ship motion parameters.

Moving Ship Velocity Estimation Using TanDEM-X Data Based on Subaperture Decomposition

In this letter, a velocity estimation method for moving ships in synthetic aperture radar (SAR) images is proposed based on a subaperture decomposition technique. In contrast to traditional methods, our method needs only a few SAR imaging parameters besides the SAR image itself. The behavior of moving ships in subaperture images is theoretically analyzed, and the ship motion parameters in azimuth direction are accurately estimated. The proposed approach was tested on real SAR stripmap images acquired by TanDEM-X, a twin satellite SAR constellation. The estimated azimuth velocities perfectly fit the data recorded by the international automatic identification system.

Design and Experimental Testing of a Free-Running Ship Motion Control Platform

In recent years, ship motion control has been used in unmanned merchant ships. It is a key issue in the sailing performance and navigation cost of unmanned vessels. The merchant ship trajectory and attitude are always generated from the response mechanism for ship motion, which uses one rudder and one propeller as the actuator. Therefore, it is a typical underactuated ship. However, there is not a specialized control test platform for unmanned merchant ships, in particular container ships. A precise merchant ship motion control platform is crucial; its computing power and motion attitude monitoring are difficult to solve by ship-borne computers. To solve this problem, a new free-running ship motion control platform is proposed, which realizes ship attitude monitoring and various motion control experiments. The proposed platform is novel as it embeds ship motion parameters and control parameters in the ship motion model, which successfully solves the precise control of the ship motion control experiment with linear or nonlinear dynamics. In this paper, the design scheme of the ship motion control platform is first presented. Then, the operating principle of the platform is shown, and the adaptive model of the ship plane motion is selected. A series of free-running model experiments and simulations is conducted to test performance of the new platform. To this end, the proposed platform can meet the requirements.

Searching for Critical Conditions During Lifeboat Launching – Simulations

Abstract The article describes numerical simulations of the process of lifeboat launching at the ship’s side. The research aimed at finding the values of ship motion parameters which appear to be most dangerous for people in the lowered lifeboat due to the generated accelerations. The simplified model of ship hull motion adopted at this research stage bases on a superposition of harmonic motions with given amplitudes and periods in six degrees of freedom. The range of the amplitude of motion for each degree of freedom corresponds approximately to that of possible motion of the PANAMAX type ship on the Baltic sea. In total, 120 960 cases of ship hull motion were examined.

Radiation and Diffraction Velocity Potentials for Multi-hulled Vessels in 2-D

The blended approach has the potential to provide the engineering solutions for design optimization keeping in view the current demand of the extensive computer resources for fully nonlinear computations. This study investigates two-dimensional boundary value problem for multi-bodies radiation and diffraction velocity of multi-hulled vessels using blended method. In blended scheme, fully nonlinear Euler equations of motion are solved with nonlinear hydrodynamic forces acting on multi-hulled vessels. Lid is employed over the body segment to suppress the eigenvalue mode, thus eliminating singularities in source strength being used on multi-hull bodies presenting geometrical discontinuities. Comparison between the blended technique and its validation against analytical calculations and experimental work are presented and found in good agreement. It is concluded that blended technique is an efficient and accurate alternate method to provide time simulations of ship motion and other essential parameters for design optimization.

Comprehensive Assessment of Automatic Identification System (AIS) Data Application to Anti-collision Manoeuvring

The use of radar information for collision avoidance is common, however it is effective only for constant values of ship motion parameters. As information delays or information errors occur, it is reasonable to supplement the information derived from radar with another information system. An ideal system should operate automatically and continuously. A system that appears to be suitable to provide this kind of information is the Automatic Identification System (AIS), which may be classified as a radio communication system that uses radio waves to transmit data with regard to ship motion parameters. In this paper the topic of integrity and completeness of AIS information is discussed and the research results for the completeness and integrity of dynamic information are presented. In addition, the outcomes of AIS information correctness from the Gulf of Gdańsk were compared with studies carried out in the Baltic Sea, east of Bornholm, between Trelleborg and Arkona. The results of research for AIS dynamic information with the highest completeness (Position, Course over Ground and Speed over Ground) are presented. The research outcomes presented in the paper lead to the conclusion that AIS could deliver useful supplementary information in the process of collision avoidance.

船体運動パラメータの包括的同定手法

This paper proposes a method that identifies ship motion parameters needed to a control system for an autopilot. The autopilot has the function of heading control and tracking control. In order to realize the function by automatic control, it is essential to identify parameters of dynamics of yaw and sway. The proposed method consists of ship motion models, identification models, evaluations of identified values, and identification algorithm. The ship motion models adopt first-order models that approximated second-order models derived from coupled motion between the yaw and the sway. The identification models have constructions based on the ship motion models and can apply practically. The identification algorithm uses a method that focused on minimum problem of multivariate function. Because the ship models have model error explicitly, the identified values are evaluated by the following response errors and the closed-loop stability. Finally, the proposed method verifies the validity by simulatins and full-scale experimental data.

A fully coupled ship motion and sloshing analysis in various container geometries

In the present study a novel modeling approach is presented to solve the combined internal sloshing and sea-keeping problem. The model deals with interesting effects arising due to the coupled interaction between the sloshing in partially filled containers of several geometries and the ship motion. The study is very important for the liquid cargo carrier operating in rough sea or under different environmental conditions. The resulting slosh characteristics that include transient pressure variation, free surface profiles and hydrodynamic pressure over the container walls have been reported in this study. In addition, the effects of coupled ship response and sloshing on ship motion parameters have also been investigated. The equations of motion of fluid, considered inviscid, irrotational, and partially compressible, are expressed in terms of the pressure variable alone. A finite difference-based iterative time-stepping technique is employed to advance the coupled solution in the time domain. Several parameters of interest, including the container parameters, level of liquid, thrusters modeling and some important environmental factors are investigated.

Modelling of seakeeping qualities of open-top container carriers in the preliminary design phase

Modelling of seakeeping qualities of open-top container carriers in the preliminary design phaseIn this paper are presented problems of modelling seakeeping qualities of open-top container carriers in the preliminary design phase. Approximations of accelerations and occurrence rate of green water ingress to holds are presented in function of main ship design and wave parameters. The approximations have been elaborated by applying theory of artificial neural networks in the wide range of ship hull dimensions and forms, while ship motion and wave parameters have been limited to real operational conditions described by means of the so called operational scenario. Such approach has made it possible to reach high accuracy of approximation and simple structure of mathematical model simulatneously.

時系列解析による動揺パラメータの直接推定法

In this paper, a statistical estimation procedure for parameters in an equation of ship's oscillation, such as a damping coefficient and a natural frequency, is proposed. It is important that a mariner grasps the performance of the ship, when carrying out safe operation of the ship. From a viewpoint of avoiding a resonance with a wave, it is especially important for the mariner to grasp the natural frequency of the ship. Using the procedure, the parameters can be estimated by using an observed data on board. Therefore,the mariner can always grasp the parameters of the ship under navigation.In this procedure, two kinds of stochastic techniques are adopted. The first one is a CAR (Continuous AutoRegressive) model that can gain precise parameters of ship's oscillating equation. In general, the ship motions in waves are regarded as a stochastic process.However, it has the problem that the noise process can not regard as a white noise. In the CAR model, it can be coped with by considering that the noise is an auto regressive process. The second one is a self-organizing state space modeling that can evaluate both the state estimation and the identification of unknown parameters in a general nonlinear non-Gaussian system. In this estimation calculation, Monte Carlo Filter which is a kind of Particle Filter is adopted. The goodness of the model is evaluated by using AIC (Akaike Information Criterion) with respect to the model.To examine the reliability of the proposed procedure, the numerical experiments are carried out by using the reproduced data under the condition which the unknown parameters are a fixed value. The estimated ship motion parameters based on the proposed method shows good agreement with the input data. Moreover, to examine the proposed procedure, the onboard experiments are carried out.Although some future problems became clear, we conclude that the proposed method is a powerful tool for the estimation of the ship motion parameters.

Application of artificial neural networks to approximation and identification of sea-keeping performance of a bulk carrier in ballast loading condition

Application of artificial neural networks to approximation and identification of sea-keeping performance of a bulk carrier in ballast loading condition This paper presents an application of artificial neural networks to approximation and identification of additional wave-generated resistance, slamming and internal forces depending on ship motion and wave parameters. The analysis was performed for a typical bulk carrier in ballast loading conditions. The investigations were carried out on the basis of ship response data calculated by means of exact numerical methods. Analytical functions presented in the form of artificial neural networks were analyzed with a view of their accuracy against standard values. Possible ways of application of the artificial neural networks were examined from the point of view of accuracy of approximation and identification of the assumed ship response parameters.

On-line Identification of the Ship Motion Parameters

The direct parameter estimation algorithm is applied to the simple equation of rolling motions. The algorithm is composed of the IIR (Infinite Impulse Response) digital filters and RLS (Recursive Least Squares) algorithm. The IIR digital filters are introduced to avoid taking direct derivatives and to reduce the effects of measurement noise. Furthermore, the digital filters are free from the initial condition problem and the accumulation problem of integration error.In order to discuss the quantitative accuracy, the authors carried out model experiments. At the first, the present method is applied to the time history data of free rolling motion tests in the still water. Next, the method is applied to the random rolling motion data in irregular waves. In both cases, there is satisfactory agreement of the dynamic rolling motion parameters identified by the present method and the previously measured parameters. This concludes that the present method is a powerful tool for on-line identification of dynamic rolling motion parameters. Finally, in order to verify the practical usefulness, we also carried out on board tests. The results of these tests are shown and problems encountered on applying are reported.

Estimating the extent of the spraying zone on a sea-going ship

The maximum extent of ship spraying for a medium-sized fishing trawler (MFV) of Soviet type has been considered. A simple geometrical model for generating the spray due to ship-wave collisions has been applied to determine the maximum height of the spray source above the ship deck. The maximum height of the spray source has been assumed to depend on the ship speed relative to the moving waves and an empirical constant specific to a given type of ship. A unique field data set (Kuzniecov et al., 1971) of the height of the upper limit of ice accretion on the foremast of an MFV has been used to determine the value of the empirical constant for this vessel. For documented air-sea and ship motion parameters, the trajectories of droplets hitting the upper parts of the accretion on the foremast have been calculated using the equation of droplet motion for each reported icing event. The heights of the spray source computed by the trajectory method for each case of icing were compared with the heights of the spray source determined by a correlation involving the ship speed relative to the waves and the vertical extent of spray. The best fit was obtained for an empirical constant value of 0.535. The model performance was tested using an independent data set (Sharapov, 1971) on the spraying zone of an MFV. The tests showed that this model predicts the extent of the spraying zone over the ship with satisfactory accuracy and suggest that it should be incorporated into an integrated ship icing model. Finally, the model was run for several ship speeds, headings and wind speeds to examine the effect of these parameters on the maximum height of the spray hitting the ship's foremast. It was found that this height increases with wind speed and ship speed and is maximum for ship headings of 120–130°.

A Review of Research to Aid the Development of Commercial Arctic Marine Transportation: 1982 Trafficability Tests on the USCGC Polar Star

A multi-year "trafficability" research program was begun in 1978 to demonstrate that year-round commercial marine transportation in Arctic waters is feasible and to collect data necessary to begin developing the criteria to design and operate marine vehicles for that environment. Using U.S. Coast Guard Polar Class icebreakers, annual winter deployments had been made in 1979, 1980, and 1981 into the Bering and Chukchi Seas to collect environmental and ship performance data. Early in 1982, the fourth phase of these research activities was conducted on the USCGC Polar Star in western Alaskan waters as far north as the Arctic Circle. Participants in the research were the Maritime Administration, the U.S. Coast Guard, the State of Alaska, the Canadian Ministry of Transport, twelve participating companies of the Alaskan Oil and Gas Association, and the Newport News Shipbuilding Company. This paper reviews the results of this voyage and the data collected. The Polar Star was instrumented to continuously monitor and record propulsion and ship motion parameters and speed. Video recording equipment was used to document ice conditions. Extensive on-ice equipment was used to profile ice features and to measure other ice parameters. Numerous pressure ridges were profiled and ice cores taken to improve the understanding of Bering and Chukchi Sea winter ice conditions and ice strength. Level ice resistance tests were conducted. However, heavy level ice conditions were not encountered and it is planned to complete the level ice resistance tests in 1984. Other research tasks included an ice edge analysis, hull friction experiments, and an ice drift study.