Simulated Maneuvers Research Articles

Simulation of Turning Manoeuvre of Planing Craft Taking Into Account the Running Attitude Change in a Simplified Manner

Abstract The modelling and simulation of planing craft manoeuvres requires coupled six degrees of freedom (6 DOF) motion equations. A coupled 6 DOF motion equation needs hundreds of manoeuvring hydrodynamic coefficients (MHCs) that are mostly determined using the planar motion mechanism (PMM) test. The number of test runs is too high, unless a kind of simplification is imposed to the motion equations. This study modifies 6 DOF motion equations to 4+2 DOF motion equations in which heave and pitch equations are replaced by dynamic draught and trim (so-called running attitude), respectively. The method is applicable for a manoeuvre that commences in the planing regime and ends in the same regime. On that basis, the PMM test is conducted and the model is restrained in the vertical plane at a certain running attitude, determined by a resistance test. The 4+2 DOF method, together with MHCs from the PMM test, are employed for the simulation of turning manoeuvres of a 25° prismatic planing hull. The results of the simulation indicate that the 4+2 DOF method reasonably predicts the path of the craft during the turning manoeuvre and cuts the number of PMM tests required at the same time. The PMM test results show that MHCs are highly related to forward speed and wetted surfaces. The turning manoeuvre simulation shows that the non-linear terms of MHCs cannot be ignored. The STD/L (Steady Turning Diameter divided by Length of the craft) for a planing craft is very large, compared to ships.

X타 수중함의 유도･제어시스템 설계

Most submarines use the cross-plane, which is convenient and inexpensive, but the number of submarines equipped with an X-plane is increasing recently. This study focuses on designing the control system of the X-plane submarine with various control methods and analyzing the effect of each controller. First, a maneuvering simulation environment for a subjected submarine is established. The dynamics and the operating range of control surfaces are considered. Second, a depth and heading control system of the submarine, which can be divided into three parts, is designed: guidance, controller, and control allocation. The guidance system generates a smooth desired depth and heading. The controller is designed using Proportional-Integral-Differential (PID), Linear Quadratic Regulator (LQR), and H-infinity (H∞) control methods. A linear control allocation method is used to distribute control moment calculated by the controller to the control surfaces. Finally, the designed control system is applied to a subjected X-plane submarine, and a depth and heading control simulations are performed. Each control method is compared and analyzed under various simulation conditions.

Identification of the safety operating envelope of a novel subsea shuttle tanker

A baseline Subsea Shuttle Tanker (SST) was proposed as a cost-efficient maritime transportation method. It is designed to be a 164 m length, 17 m beam autonomous underwater vessel with a cargo capacity of over 16,000 m3. One of the crucial topics for such underwater vehicles is recoverability during undesired malfunctions. A Safety Operating Envelope (SOE) must be identified for military submarines. It considers the submersibles' malfunctions, including partial flooding, jam-to-rise, and jam-to-dive. This paper aims to identify the SOE to enclose the safety operation zones of the SST. In this work, a planar SST manoeuvring simulation model considering the combined contributions from hydrodynamic loads, compensation tank blowing, propeller thrust, and control planes is derived based on semi-empirical formulas. Second, standard operating procedures of recovery actions are established to cope with each malfunction. After that, free-running simulations are conducted. Three cases are presented to discuss SST recovery responses during each incident. Finally, the SOE of the SST is identified. This established SOE determines the SST's feasible speed and depth excursion ranges from an operational safety perspective. The safety depth is sufficient for the SST to recover from a jam-to-rise failure. Moreover, the study found that the existing safety factor on the structural design suggested by the Norwegian classification society Det Norske Veritas (DNV) naval submarine code is exceedingly conservative and potentially leads to a heavy and complex SST structure. The SOE helps reduce the designed collapse depth from the operational safety perspective and contributes to reduced material cost and considerable payload capacity. Also, this work fills in the blanks of SOE analysis on commercial submersibles.

Comparative Study on Predicting Ship Maneuvering in Waves Using a Quasi-Steady Method and a Time Domain Approach

_ Numerical prediction of ship maneuvering in waves was considered in this article. The wave drift loads, computed using the potential flow theory, were added into the mathematical modeling group (MMG) equations to account for the effect of waves on the ship maneuvering. Two numerical methods were tested for dealing with the coupled maneuvering-seakeeping problem, namely a time domain approach and a quasi-steady method. For the former approach, a time domain seakeeping computation was conducted that parallels to the maneuvering simulation. For the later one, it is assumed that at each time of the maneuvering process, the wave-ship interaction is in a time harmonic status and, therefore, the wave drift loads could be evaluated using a frequency domain computation. Turning maneuvers of the S-175 container ship in regular waves were numerically tested. The results of the quasi-steady method and the time domain approach show good agreements, which proved the validity of the quasi-steady assumption. The wave drift loads during the turning process were also presented, demonstrating the significant effect of the added resistance on the maneuvering prediction, in contrast to the less remarkable effects of the lateral wave drift force and the wave drift yaw moment. Introduction Ship maneuverability is typically predicted under calm water condition. This provides valuable information at the ship design stage. However, an actual seagoing ship usually maneuvers in waves. To reliably assess a ship’s navigation safety and total performance in a seaway, it is deemed important to understand the maneuvering behavior of a ship in waves. Indeed, ship maneuverability in waves has been increasingly investigated in recent years. Although the physical experiment is still regarded as the most reliable way to investigate ship maneuverability in waves, there are more and more studies providing practical mathematical models of ship maneuvering prediction. Generally, a mathematical model that is suitable for investigating the maneuvering of a ship in waves has to encapsulate the traditional theories of calm water maneuvering and forward-speed seakeeping.

A closed-loop directional dynamics control with LQR active trailer steering for articulated heavy vehicle

To improve the directional performance of articulated heavy vehicles (AHV), three previewed points driver model and LQR active trailer steering (ATS) strategy are proposed and examined using closed-loop driver/vehicle dynamics simulation. Firstly, a simplified linear three-degree-of-freedom (3-DOF) yaw plane model for AHV is established and validated. Secondly, based on the multi-point preview-predictor following strategy, the weighted-average error of three previewed points of the tractor is defined as the final lateral previewed displacement error. According to the assumption of constant yaw rate and the trajectory prediction of AHV, and three previewed points driver model has been configured, it’s path-following performance is verified. Thirdly, instead of using the idea of minimization, a linear quadratic regulator (LQR) controller is proposed based on the linear 3-DOF yaw plane model of AHV to make the control variables to keep following the desired responses. Through joint simulations using MATLAB/Simulink and TruckSim, the effectiveness of the built-in driver model, three-previewed point driver model and three-previewed point driver model + LQR ATS control methods on improving vehicle orientation performance were compared and analyzed through closed-loop driver/vehicle dynamics simulations. The significant effectiveness of the proposed method in improving maneuverability and stability is verified through low-speed 360° trajectory tracking tests and high-speed double lane change maneuver simulations. Finally, a hardware-in-the-loop (HIL) platform is used to further verify the effectiveness of the designed strategy.

Is There Any Difference Between Maneuver Simulation and Scenario Workshop Learning about Radiation Triage?

Background: Very little information on maneuver simulations (MS) effectiveness in radiation triage (RT) training is currently available. Objectives: The present study aimed to compare the effect of MS and scenario workshops (SW) on rescuers' learning of RT. Methods: This quasi-experimental study was conducted on rescuers in July 2020. For this purpose, two military medical centers were randomized into two groups, intervention (MS) and control (SW). The main tool was the researcher-made Radiation Triage Knowledge Questionnaire (RTKQ). In this respect, the pre-test was performed using the RTKQ questionnaire. The first post-test, two weeks following the intervention, was also done through the RTKQ and the objective structured clinical examination (OSCE), and the second post-test was conducted four weeks after the intervention, only via the RTKQ. Results: In total, 30 rescuers with a mean age of 22 participated in this study. During the pre-test, the difference in knowledge between the two study groups (intervention and control) was not significant. In the first post-test, no significant difference was also observed in the levels of knowledge between MS and SW groups respectively (80.0 ± 8.9 vs. 79.3 ± 0.8), but the difference in skills between the study groups was significant (89.3 ± 10.3 vs. 61.3 ± 16.0). In the second post-test, there was a significant difference between the mean value of the levels of knowledge (76.0 ± 9.1 vs. 64.7 ± 10.9) and skills (written scenarios) (71.3 ± 9.9 vs. 54.0 ± 0.14) in two study groups. Conclusions: Both training methods improved RT knowledge and skills, but MT was more effective than SW in boosting and maintaining knowledge and skills up to one month after the intervention. The utilization of MS in RT training was also accompanied by greater effectiveness.

Framework for data-driven propeller and rudder modeling for ship maneuvering

The maneuvering characteristics of a vessel must be understood for safe and efficient operation in the ocean environment. During a maneuver, the propeller and rudder can operate in off-design conditions. Computational Fluid Dynamics is a useful tool to capture flow effects like viscous separation, but it is too costly to perform a large number of maneuvering simulations with a discretized propeller. The propeller has much smaller time and length scales compared to the maneuver, which drives up the computational cost when the propeller is discretized. Body-force propeller models provide a less expensive means of modeling a maneuvering vessel with CFD, but many propeller models can be inaccurate when the propeller operates off-design. This work develops a framework for a data-driven propeller and rudder model which is trained with high-fidelity simulations of the propeller and deflected rudder operating in the wake of the hull. The dimensionless velocity and oblique flow angle are used as features for the propeller and rudder model. The uncertainty of the data-driven model is dependent upon the error inherent in the training and validation data as well as the uncertainty induced by using a surrogate model to determine the response surface. The underlying uncertainties are examined. The calculated propeller and rudder forces from the data-driven model are compared to the experimental forces. The turning circle characteristics of the KRISO Container ship at model scale are examined with the implemented data-driven propeller and rudder model. The accuracy of the method used to train the model is maintained and the computational cost of modeling a maneuvering vessel is dramatically reduced compared to using a discretized propeller.

Ship to Ship Manoeuvring Simulation to Determine Elements of Tugboat Handling

The berthing and unberthing process of a shuttle tanker on the FSO unit has its difficulties if the FSO unit is between several mooring lines. This is an early study to simulate the berthing and unberthing of a 5000 DWT shuttle tanker at the FSO unit without going through the mooring ropes and still comply with the requirements of PIANC berthing speed. The manoeuvring simulation was based on a mathematical manoeuvring group model that used the effects of the propeller and rudder. The model simulated the percentage and direction of force and moment of tugboats to perform the manoeuvring properly. The model assumed the environmental disturbances of wind, current, and wave as the constant values and applied three scenarios of the current direction. As a case study, the berthing and unberthing manoeuvre of a 50000 DWT export tanker need two tugboats with the capacity of at least 2x42 tons bollard pull, exceptional for unberthing in scenario-2.

Development of the Elements of Tugboat Handling for Berthing and Unberthing of Container Ships

This paper provides a study on the procedure of tugboat handling for berthing and unberthing of container ships in the Port of Surabaya Container Terminal. The elements of the tugboat assistance consisted of time series of the percentage of tugboats’ power, the direction of the tug’s force, and the duration. This study developed a manoeuvring simulation program using the mathematical manoeuvring group (MMG) model to determine the handling elements to achieve the intended trajectory properly. The model considered the surging force, swaying force, and yawing moment of tugs, as well as the disturbances of current, wind, and wave. The planning trajectory is determined based on berthing and unberthing passages derived from the automatic identification system (AIS) data. The elements resulting in the berthing speed and berthing angle complied with the Permanent International Association of Navigation Congresses (PIANC).

Inland Navigation as an Opportunity to Increase the Cargo Capacity of the Tri-City Seaports

The aim of the article is to analyse the transport accessibility of the Tri-City seaports as well as to verify the necessity of starting the inland navigation. The proposal to develop inland navigation by creating new and developing existing waterways is supported by the idea of sustainable transport, which emphasizes how important it is to improve the efficiency of transport work and to minimize the harmful impact of transport on the environment. The purpose of the study is to determine the capability to increase the cargo capacity of the Port of Gdansk and the Port of Gdynia. The article presents the results of the operational analysis from the navigation and manoeuvring simulator Navi-Trainer Professional 5000, where scenarios that the barge from Tri-City seaports reaches the planned dry port in Zajączkowo Tczewskie have been made. This concept intends to verify the option of relieving truck traffic in the Tri-City area.

An efficient and accurate approach for zero-frequency added mass for maneuvering simulations in deep and shallow water

An overall increase in ship sizes in conjunction with a general decrease in ship powering has increased the relevance of reliably predicting a ship’s maneuvering performance. These predictions rely often on mathematical models based on modified Taylor series expansion, where nonlinear multivariate algebraic polynomials that require hydrodynamic coefficients are determined from physical or numerical planar motion mechanism (PMM) tests. The added mass coefficients are needed for a fast and accurate simulation. For maneuvering simulations, these added mass coefficients should be obtained for zero frequency. Despite the advance of high-performance computing, numerical PMM tests based on solving the unsteady Reynolds-averaged Navier–Stokes equations is time-consuming and often not suitable for practical design-related investigations. Furthermore, hydrodynamic coefficients obtained from PMM tests are frequency-dependent. An alternative to numerical PMM tests consists of steady numerical tests. This kind of analysis requires much less computing time and effort for the users. However, the acceleration-dependent hydrodynamic forces and moments cannot be derived from these steady computations. Here we introduced a fast and accurate procedure to obtain water depth-dependent zero-frequency added mass and added moment of inertia. Using Euler Equations, we impulsively accelerated the ship hull over only one time step. We validated our method against an analytical solution for an ellipsoid. We performed systematic computations of added mass and added moment of inertia for two benchmark containerships, a benchmark tanker, and a cruise ship, thereby demonstrating the effects of water depth on added mass for different hull shapes.

Z-Drive Escort Tug manoeuvrability model and simulation, Part II: A full-scale validation

A deep insight into the manoeuvring characterisation of a wider class of Azimuthal Stern Drive Escort tugs (ASD) is undertaken with the scope of defining a real-time parametric manoeuvring simulation code for the free-sailing and towing operations. In the part I of the work a physics-based 4-DOF prediction parametric tool for the dynamic behaviour of the ASD tug has been developed, and a validation with model-scale Escort-towing tests has been presented. In the present paper a second validation methodology, based on full-scale measurements, is discussed. This verification envisages simulator’s capability of describing the free-sailing performance of a different but compatible hull, having dimensions, propulsion, skeg characteristics significantly different with respect to the “parent design” used to develop the tool. The experimental campaign involves the measurements purposely performed during sea trials onto two sister-ship ASD new-buildings (RM3213). Turning circle, zig-zag manoeuvres, and Dieudonne’ spiral tests are deeply analysed and the results used for validation purpose. The simulation results showed a satisfactory agreement with the full scale manoeuvres, positively demonstrating the ability of the parametric mathematical formulations to forecast customised tug manoeuvrability for tug design purposes.

Moving Spatial Turbulence Model for High-Fidelity Rotorcraft Maneuvering Simulation

A moving spatial turbulence model is developed for rotorcraft maneuvering simulation under different flight conditions. The recursive algorithms are adopted to model its distributed longitudinal turbulence components, which are correlated with the lateral and vertical axes to form a local spatial turbulence field. The flow field is constrained around the rotorcraft by following its movement, and the corresponding turbulence components are updated at a constant spatial interval. The statistical properties along the longitudinal, lateral, and vertical directions have been validated against the von Kármán theory. A synthetic simulation environment consisting of a flight dynamics model and a pilot model is constructed to demonstrate the effectiveness of the turbulence model. Its performance is validated by comparing the power spectral densities of both rotorcraft responses and pilot controls in turbulence against flight test data. The piloted simulation results on an Approach-to-Hovering task show that the handling qualities ratings are susceptive to the level of turbulence and significantly increase when performing aggressive controls. The simulation also accurately predicts the expected effect of varied aircraft speed, wind speed, turbulence intensity, and stability augmentation system on piloted handling qualities rating for rotorcraft flight in turbulence.

Development and assessment of CFD methods to calculate propeller and hull impact on the rudder inflow for a twin-screw ship

The purpose of this study is to investigate the feasibility of a simple but robust approach for the identification of the main interaction effect of hull and propeller on the rudder inflow in a conventional manoeuvring simulator. The manoeuvring simulator adopts a modular/MMG based approach in which the hull, the rudders and the propellers are described by separate mathematical models which take into account the interaction phenomena. The propeller–rudder interaction factor is examined by means of a numerical model developed in OpenFOAM for the prediction of the performance of a rudder in behind propeller condition. Differently the hull–rudder interaction factor is numerically obtained by means of two different approaches. The proposed kinematic method shows the minimum additional computational cost without loss of accuracy. It is based on the analysis of rudder inflow fields (in a PIV fashioned), therefore It can be carried out in a post-processing phase of CFD simulations adopted to extract the hydrodynamic coefficients. This study validates the method by comparing it with the classical approach also used in the experimental campaign, based on the analysis of rudder forces from virtual captive tests. The approaches demonstrate to improve the overall accuracy of the main manoeuvring parameters with respect to the ones obtained by means of a calibrated semi-empirical model.

A numerical and experimental study on the obstacle collision avoidance system using a 2D LiDAR sensor for an autonomous surface vehicle

In recent years, great efforts have been made to develop unmanned navigation systems for Autonomous Surface Vehicles (ASVs), while further improvements are still required for ASVs operating around obstacles. In this circumstance, this paper presents an Obstacle Collision Avoidance Guidance (OCAG) using obstacle detection with a two-dimensional (2D) LiDAR sensor. After verifying the algorithm of the OCAG in a numerical manoeuvring simulation, the OCAS was embedded in a physical model of a Catamaran-type ASV with a 2D LiDAR sensor. When the ASV sails along with a predefined global path, the LiDAR sensor detects the obstacles, the collision-avoidance actions are determined based on multiple factors including the motion and orientation information of the vehicle, the measured distance and direction information of the obstacles, as well as the types of the obstacles. The proposed OCAG showed good collision-avoidance performances with different obstacle types along the path.

Assessment of ship maneuvering simulation with different propeller models

Assessment of ship maneuvering simulation with different propeller models

A high-fidelity CFD-based model for the prediction of ship manoeuvrability in currents

The manoeuvring behaviour of a vessel in currents differs remarkably from its behaviour in water without a current, stemming from hydrodynamic effects caused by the presence of the current. Given that vessels operating in open seas and coastal waters are mostly exposed to ocean currents, it is important to have an understanding of the influence of currents on ship manoeuvrability. In the present paper, by means of an unsteady Reynolds-Averaged Naiver-Stokes solver, a numerical study of ship manoeuvrability in different currents was performed. Firstly, a model-scale container ship (the KRISO Container Ship) was used to develop the Computational Fluid Dynamics (CFD) model capable of performing a self-propelled free manoeuvre. Then, a validation study was carried out to assess the validity of the CFD model by comparison with the available experimental results from a free-running test. Following this, a series of manoeuvring simulations (i.e., standard turning manoeuvres) in deep waters with current speed to ship speed ratios varying between −0.552 and −0.138/+0.138 and + 0.552 were conducted using the present CFD model. The numerical results demonstrated that the inclusion of the current has a remarkable influence on the turning performance of the ship, leading to significant changes in the ship trajectory and its turning parameters when compared to the inherent ship manoeuvrability in deep water without a current.

A comparison of ship manoeuvrability models to approximate ship navigation trajectories

ABSTRACT It is essential to describe a ship’s manoeuvrability for various applications, e.g. optimal control of unmanned surface vehicles (USVs). In this study, the capability of two recognised manoeuvrability models to predict ships’ trajectories is investigated based on both simulation and open-water experiment test data. The parameters of these models are estimated by a statistical learning method. The goodness of the two estimated models for describing a merchant ship’s manoeuvrability is first studied using her manoeuvring simulation data. Then, experimental manoeuvring tests to use a USV in open water with wind and drifting effects are used to check the conventional model identification procedures. Finally, some modifications and adjustments are proposed to improve the conventional procedures. It shows that the proposed procedures can accurately derive the ship’s manoeuvrability based on experimental data.

Numerical simulation of turn and zigzag Maneuvres of trimaran in calm water and waves by a hybrid method

As one of the widely used high-performance ships, the hydrodynamic characteristics of the trimaran ships have been widely investigated in recent years. But, the study on the maneuverability and the skill of the maneuvering simulation are still limited. In this paper, a hybrid method coupling the FNPT-based (fully nonlinear potential flow theory) QALE-FEM (quasi arbitrary Lagrangian-Eulerian finite element method) with the viscous flow method is applied to simulate the turn and zigzag maneuvers of the trimaran in both calm water and waves. The environment of calm water and incident waves is simulated by the numerical tank of QALE-FEM. The maneuvering of the trimaran is carried out in the scope of the numerical tank by the viscous flow method. The grid convergence test is carried out first, and the computed results are compared with the experimental results. Then, the turn and zigzag maneuvers of a trimaran model in both calm water and waves are simulated to study the trimaran's maneuvering characteristics.

Suitability Evaluation for Simulated Maneuvering of Autonomous Vehicles

Suitability Evaluation for Simulated Maneuvering of Autonomous Vehicles