Development of an Environmental and Ship Motion Forecasting System

2015 ◽  
Author(s):  
Benjamin S. H. Connell ◽  
Jason P. Rudzinsky ◽  
Christopher S. Brundick ◽  
William M. Milewski ◽  
John G. Kusters ◽  
...  
Keyword(s):  
System Architecture ◽  
Ship Motion ◽  
Retrieval Algorithm ◽  
Ship Motions ◽  
Motion Simulation ◽  
Motion Model ◽  
Key Technologies ◽  
Coherent Forecasts ◽  
Forecasting System ◽  
Better Than

Military sea basing operations include mooring ships together offshore and transferring cargo and equipment between them. A newly developed Environmental and Ship Motion Forecasting (ESMF) System will facilitate these operations by providing predictions of ship motions in waves. Coherent forecasts of the ship motions are provided through remote sensing of the ambient waves and using these waves as input to a predictive ship motion simulation. Key technologies developed in support of the ESMF system include: a custom-built wave sensing radar; a least squares inverse wave retrieval algorithm; a ship motion model for performing rapid seakeeping simulations; and a robust peer-to-peer system architecture. The ESMF system was tested extensively in a demonstration aboard the R/V Melville with very good results, often achieving correlations of forecast-to-realized signals of better than 80% over 30 minute intervals.

Multiple Ship Motion Simulation Code Correlation with Model Test Results

2017 ◽  
Author(s):  
James A. Coller ◽  
Andrew Silver ◽  
Okey Nwogu ◽  
Benjamin S.H. Connell
Keyword(s):  
Real Time ◽  
Model Test ◽  
Three Dimensional ◽  
Angle Measurement ◽  
Ship Motion ◽  
Ship Motions ◽  
Simulation Code ◽  
Forecasting System ◽  
Scale Experiment ◽  
Response Amplitude Operators

The US Nav has developed a real-time multi-ship ship motion forecasting system which combines forecast wave conditions with ship motion simulations to produce a prediction of the relative motions between two ships operating in a skin-to-skin configuration. The system utilizes two different simulation methods for predicting ship motions: MotionSim and Reduced Order Model (ROM) based on AEGIR. MotionSim is a fast three-dimensional panel method that is used to estimate the Response Amplitude Operators (RAOs) necessary for multi-ship motion predictions. The ROM works to maximize the accuracy of high fidelity ship motion prediction methods while maintaining the computational speed required for real-time forecasting. A model scale experiment was performed in 2015 on two Navy ships conventionally moored together. The predicted relative ship motions from MotionSim and ROM were compared to the model data using three different metrics: RMS (root mean square) ratio, correlation coefficient, and average angle measurement (AAM).This paper provides an overview of the two methods for predicting the multi-ship motions, a description of the model test, challenges faced during testing, and a discussion on the methodology of the evaluation and the results of each code correlation.

scholarly journals Prediction of Ship Unsteady Maneuvering in Calm Water by a Fully Nonlinear Ship Motion Model

2012 ◽  
Vol 2012 ◽  
pp. 1-11
Author(s):  
Ray-Qing Lin ◽  
Tim Smith ◽  
Michael Hughes
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Ship Motion ◽  
Ship Motions ◽  
Motion Model ◽  
Forward Speed ◽  
Fully Nonlinear ◽  
Six Degrees Of Freedom ◽  
Calm Water

This is the continuation of our research on development of a fully nonlinear, dynamically consistent, numerical ship motion model (DiSSEL). In this study we will report our results in predicting ship motions in unsteady maneuvering in calm water. During the unsteady maneuvering, both the rudder angle, and ship forward speed vary with time. Therefore, not only surge, sway, and yaw motions occur, but roll, pitch and heave motions will also occur even in calm water as heel, trim, and sinkage, respectively. When the rudder angles and ship forward speed vary rapidly with time, the six degrees-of-freedom ship motions and their interactions become strong. To accurately predict the six degrees-of-freedom ship motions in unsteady maneuvering, a universal method for arbitrary ship hull requires physics-based fully-nonlinear models for ship motion and for rudder forces and moments. The numerical simulations will be benchmarked by experimental data of the Pre-Contract DDG51 design and an Experimental Hull Form. The benchmarking shows a good agreement between numerical simulations by the enhancement DiSSEL and experimental data. No empirical parameterization is used, except for the influence of the propeller slipstream on the rudder, which is included using a flow acceleration factor.

Motion Simulation of Underwater Mooring Platform with Ocean Current

2013 ◽  
Vol 321-324 ◽  
pp. 815-818
Author(s):  
Fang Ze Zhao ◽  
Bao Wei Song ◽  
Xiao Xu Du
Keyword(s):  
Ocean Current ◽  
Mooring System ◽  
Motion Simulation ◽  
Motion Model ◽  
Motion Characteristics

Underwater mooring platforms which anchored by the anchor and cable have a certain function of the platform mooring at a certain depth. In this paper, the motion model of underwater mooring system was built through analyseing the motion characteristics of the cable geometry and the force of the cable. And the motion simulation of underwater mooring platform with ocean current was done. The results show that the motion of underwater mooring platform is stable.

SHIP MOTIONS DURING REPLENISHMENT AT SEA OPERATIONS IN HEAD SEAS

2021 ◽  
Vol 152 (A4) ◽  
Author(s):  
G Thomas ◽  
T Turner ◽  
T Andrewartha ◽  
B Morris
Keyword(s):  
Experimental Study ◽  
Green Function ◽  
Prediction Method ◽  
Ship Motion ◽  
Motion Prediction ◽  
Ship Motions ◽  
Forward Speed ◽  
Theoretical Predictions ◽  
Relative Separation ◽  
Replenishment At Sea

During replenishment at sea operations the interaction between the two vessels travelling side by side can cause significant motions in the smaller vessel and affect the relative separation between their replenishment points. A study into these motions has been conducted including theoretical predictions and model experiments. The model tests investigated the influence of supply ship displacement and longitudinal separation on the ships’ motions. The data obtained from the experimental study has been used to validate a theoretical ship motion prediction method based on a 3-D zero-speed Green function with a forward speed correction in the frequency domain. The results were also used to estimate the expected extreme roll angle of the receiving vessel, and the relative motion between the vessels, during replenishment at sea operations in a typical irregular seaway. A significant increase in the frigate’s roll response was found to occur with an increase of the supply ship displacement, whilst a reduction in motion for the receiving vessel resulted from an increase in longitudinal separation between the vessels. It is proposed that to determine the optimal vessel separation it is vital that the motions of the vessels are not considered in isolation and all motions need to be considered for both vessels simultaneously.

On the Nature of Logic Trees in Probabilistic Seismic Hazard Assessment

2012 ◽  
Vol 28 (3) ◽  
pp. 1291-1296 ◽  
Author(s):  
Roger Musson
Keyword(s):  
Seismic Hazard Assessment ◽  
Seismic Source ◽  
Source Model ◽  
Probabilistic Seismic Hazard Assessment ◽  
Motion Model ◽  
Logic Tree ◽  
Ground Motion Model ◽  
Seismic Source Model ◽  
Kolmogorov Axioms ◽  
Better Than

An objection sometimes made against treating the weights of logic tree branches as probabilities relates to the Kolmogorov axioms, but these are only an obstacle if one believes that logic tree branches represent a seismic source model or ground motion model as being “true.” Models are never true, but some models are better than others. It is argued here that a logic tree weight represents the probability that the model in question is better than the others considered. Only one branch can be the best one, and one branch must be the best one. It is also argued that there are situations in PSHA where uncertainty exists but the analyst lacks the means to express it. Therefore it is not necessarily the case that more information increases uncertainty; it may be that more information increases the possibility of expressing uncertainty that was previously unmanageable.

Advanced Bridge Automation

1993 ◽  
Vol 30 (04) ◽  
pp. 276-285
Author(s):  
Edward Denham
Keyword(s):  
Human Error ◽  
Environmental Data ◽  
Management Systems ◽  
Propulsion Systems ◽  
The Past ◽  
Key Technologies ◽  
Routine Tasks ◽  
Information Management Systems ◽  
Better Than ◽  
Do So

The past thirty years have seen great advances in many areas of the technologies used in naval vessels. Propulsion systems, machinery automation, and information management systems have all undergone revolutionary changes. The bridges of these ships have similarly seen the advent of many new sources of navigational and environmental data. The process of correlating and interpreting all of this information has until now remained very labor-intensive, subject to human error at many stages of the process. In response to this challenge, a suite of new equipment has been developed for distributing, displaying, correlating, and logging shipboard data. This equipment automates most of the low-level, routine tasks involved in navigating a vessel at sea, significantly reducing the stress and workload of bridge personnel. This gives the humans on the bridge more time for doing the job that they do so much better than machines: making decisions. This paper focuses on the key technologies that are used in these new products and the advances in bridge design and automation they make possible. The benefits of these new capabilities to system designers, to shipbuilders, and to ship operators are also explored.

Stabilization of the Ship Motion by Restricted Control

2020 ◽  
Vol 28 (4) ◽  
pp. 106-123
Author(s):  
G.M. Dovgobrod ◽  
Keyword(s):  
Feedback Linearization ◽  
Control Algorithm ◽  
Linearization Method ◽  
Ship Motion ◽  
Control Law ◽  
Motion Model ◽  
Lateral Deviation ◽  
Bounded Curvature ◽  
Trajectory Attractor ◽  
Singularity Point

. The article presents an algorithm for controlling the motion of an insufficiently controlled ship along a trajectory with a continuous bounded curvature, based on the feedback linearization method. The algorithm allows restricting the control signal, while the state vector of the ship motion model does not approach the singularity point of the control law. The control algorithm returns the ship to the specified trajectory-attractor at any lateral deviation of the ship from the specified trajectory.

Research on the Ship Motion Simulation Platform for Three Degrees Based on Seasickness Test and Kinematics Analysis

2012 ◽  
Vol 252 ◽  
pp. 89-92
Author(s):  
Zhi Wei Zhang ◽  
Song Li ◽  
Kai Cong ◽  
Jin Chun Song
Keyword(s):  
Control System ◽  
Virtual Prototype ◽  
Ship Motion ◽  
Simulation Platform ◽  
Motion Simulation ◽  
Hydraulic Control ◽  
Kinematics Analysis ◽  
Matlab Simulink ◽  
Hydraulic Control System

A new structure of ship motion simulation platform and its hydraulic control system were designed. Matlab/Simulink was used for the analyses of hydraulic control system. Virtual prototype of the ship motion simulation platform was built up by ADAMS under the seasickness test condition, and the kinematics analysis was also carried on. The results show the effectiveness on the model of platform.

Research on Moment Coupling and Compensation Control of Three-Axis Ship Motion Simulation Turntable

2009 ◽  
Vol 419-420 ◽  
pp. 625-628 ◽  
Author(s):  
Li Hua Liang ◽  
Dong Liang Cui ◽  
Song Tao Zhang ◽  
Dong Hai Cui
Keyword(s):  
Pid Control ◽  
Ship Motion ◽  
Decoupling Control ◽  
Motion Simulation ◽  
Velocity Feedback ◽  
Compensation Control ◽  
Compound Control ◽  
Dynamic Tracking ◽  
The Moment ◽  
Robust Compensation

With regard to the high precise three-axis ship motion simulation turntable, the precision is influenced by strong dynamics coupling, such as the moment coupling when three frames rotating at the same time. Therefore, the coupling problem of three-axis ship motion simulation turntable was analyzed profoundly. Then, on the basis of the analysis, in order to restrain the disturbance of coupling torque, the method of dynamic robust compensation based on decoupling control was given. Finally, the compound control strategy including PID control, velocity feedback, position feedback ,input signal differential feedforward and dynamic robust compensation was employed, and a electromechanical Co-simulation of three-axis turntable based on ADAMS and MATLAB was completed. The results of the Co-simulation prove that the method given in this paper can restrain coupling disturbance and improve dynamic tracking performance of three-axis simulation turntable

On the Effect of Water on Deck on Ship Motion

2002 ◽  
Author(s):  
Dimitris Spanos ◽  
Apostolos Papanikolaou ◽  
George Tzabiras
Keyword(s):  
Numerical Simulation ◽  
Satisfactory Agreement ◽  
Simulation Method ◽  
Interaction Force ◽  
Ship Motion ◽  
Simplified Model ◽  
Ship Motions ◽  
Efficient Simulation ◽  
Water On Deck ◽  
Present Simulation

The effect of trapped water on deck or the interior compartments of ships on ship motions is closely investigated by use of a non-linear numerical simulation method. The employed method enables the efficient simulation of the wave excited, coupled ship – trapped water motions and proves to be a very valuable tool for the assessment of the survivability of flooded ships in waves. A detailed study has been carried out to more carefully investigate the coupling effects between the ship and the floodwater mass that can be expressed through a resultant interaction force. This interaction force has been approximated both by a simplified model employed by the present simulation method and also by a more accurate CFD code and satisfactory agreement between the results of both approaches has been obtained.

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