Maneuvering Modeling Group Research Articles

Real-time simulation of ship overtake maneuvering at different water depths with a ship motion controller

This study aimed to predict ship trajectories in deep and shallow waters in real-time by properly accounting for the effects of hydrodynamic interactions on ship maneuvering. Ship maneuverability and motion control were investigated under hydrodynamic interactions arising from the effects of water depth, ship speed, and lateral distance between interacting ships on parallel courses. The Maneuvering Modeling Group (MMG) model was used, and the hydrodynamic interaction effect was estimated using an efficient three-dimensional potential-flow code that can run in real time. The influence of water depth on ship maneuverability was analyzed. The ship velocity response to the hydrodynamic interactions and maneuvering motion was simulated during the overtaking process of two ships at a range of water depths, lateral distances, and speeds. The findings suggest that, in shallow waters, changing the heading of the ship becomes more difficult, and the course deviation associated with the overtaking maneuver of two ships also increases. A conventional proportional-integral-derivative (PID) controller was employed for course-keeping. When the ratio of the water depth to ship draft was less than 2.0, the PID controller continued to perform effectively for the overtaking ship. For the overtaken ship, the effectiveness of the controller was diminished owing to the relatively low rudder effect at slow speeds.

Numerical simulation of the maneuvering performance of ships in broken ice area

Maneuverability is a critical aspect of ship navigation performance, particularly during polar navigation, where the presence of ice significantly affects maneuverability compared to open water navigation. By coupling the non-smooth discrete element method (NDEM) with the Maneuvering Modeling Group (MMG) model, this paper proposes a numerical model to simulate the maneuvering motion of full-scale ships in broken ice regions. In the proposed model, the ship-ice interaction was solved through NDEM, while the 3-DOF MMG model was utilized to simulate the autonomous navigation movement of ships. Based on the relationship between ship turning radius and ship speed, the critical relationship between ice moment and ice resistance is derived in this paper, which can be used to verify the rationality of simulation results of maneuvering motion. In addition, the effects of ice concentration, size, thickness, and ship speed and rudder angle on the ship's maneuvering trajectory and steering flexibility are analyzed by simulating turning motion and Zig-Zag maneuvers. This provides an effective numerical model to simulate the maneuvering motion of a ship in a broken ice area with low-medium ice concentration.

Maneuverability Performance of a KRISO Container Ship (KCS) with a Bulb-Type Wavy Twisted Rudder and Asymmetric Pre-Swirl Stator

The maneuverability performance of a KCS with energy-saving devices was investigated. A bulb-type wavy rudder and an asymmetric pre-swirl stator were used as energy-saving devices because their use resulted in considerable efficiency gain. A validated simulation method based on the maneuvering modeling group model was used for the simulation in this study. Turning circle, 10/10 zigzag, and 20/20 zigzag tests were simulated to compare various cases with and without a stator as well as conventional full-spade and bulb-type wavy rudders. Remarkable maneuverability performance was achieved, particularly with a bulb-type wavy rudder, and starboard–port unbalancing due to the one-directional propeller action was almost eliminated using these devices. The findings of this study will be useful in the development of more reliable autonomous maritime surface ships.

Virtual PMM captive tests using OpenFOAM to estimate hydrodynamic derivatives and vessel maneuverability

This study reveals the significance of hydrodynamic derivatives derived at the different Froud number (Fr) in accurately predicting of a vessel's turning-circle maneuvers through solving the maneuvering modeling group (MMG) model. The computed turning-circle diameter showed a good agreement with the model test results, with less than 4% difference observed when using the hydrodynamic derivatives derived at Fr = 0.201. However, at Fr = 0.26, a significant difference was observed, which could be attributed to the use of lower values of maximum sway amplitude ymax and maximum yaw rate rmax′. The hydrodynamic characteristics of a maneuvering vessel may not be fully reflected, with the high displacement of the straight surging motion dominating the results. In this study, a set of virtual planar motion mechanism (PMM) captive tests is numerically conducted on a bare container ship hull model using an open-source code OpenFOAM. The virtual PMM captive test cases involve different maximum sway amplitude, maximum yaw rates, and Fr, achieved by varying sway amplitudes, heading angles, and the carriage speeds, respectively. The obtained numerical results are reconstructed as Fourier series (FS) equations to derive hydrodynamic derivatives employing the single run (SR) method. A system-based method is adopted to predict vessel's turning-circle maneuverability in calm water by employing the MMG mathematical model.

Turning and zigzag maneuverability investigations on a waterjet-propelled trimaran in calm and wavy water using a direct CFD approach

The evaluation of ship maneuverability characteristics typically involves the mode tests, direct CFD computations, and system-based simulations. The three methods have been widely used in traditional vessels. However, the trimarans, which are appended with the waterjet propulsion systems, have been rarely researched and assessed comprehensively based on the above methods. This paper used a free-running waterjet-propelled trimaran model test to obtain the constant turning and zigzag maneuvering performance in calm water conditions. By embedding the speed and heading controllers in a CFD program, along with the region moving method, a direct free-running maneuvering CFD model was established on a waterjet-propelled trimaran. Compared to the free-running model tests, the simulation results indicated that an empirical hydrodynamic derivative-based Maneuvering Model Group (MMG) method produced the fastest results but lacked accuracy in simulating a constant turning diameter, making it suitable for fast maneuvering estimation and prediction during the design stage. Conversely, a direct force (moment)-based CFD model required more accurate input estimates to acquire acceptable simulated results. Meanwhile, a body force-based CFD model considered more complex nonlinear impacts and was most similar to reality, achieving better agreement with the experimental results. Additionally, the simulations of the direct free-running maneuvering CFD model in calm and wavy water proved advantageous in examining hull-propulsor interaction during physically similar maneuvering processes where the model test was inadequate.

Validation of maneuvering simulations for a KCS at different forward speeds using the 4-DOF MMG method

Ships with a high center of gravity and at relatively fast speed, such as container vessels, may experience significant heel during turning at a rudder angle of 35°. Accurate prediction of the maneuvering motion of such ships requires consideration of roll motion in addition to surge, sway, and yaw motions. This study applies the 4-Degrees of Freedom (4-DOF) Maneuvering Modeling Group (MMG) method, developed by one of the authors, as a practical simulation method that includes the roll-coupling effect, to predict the maneuvering of a Kriso Container Ship (KCS). To validate the accuracy of the maneuvering simulations, the results are compared with those obtained from free-running model tests for turning and zig-zag maneuvers. Furthermore, to capture the effect of speed on maneuvering, the free-running tests are conducted by varying the approach speed of the ship model. The test results reveal that the advance in turning and the overshoot angle in zig-zag maneuvers increase with speed, while the tactical diameter decreases. The simulation results obtained using the 4-DOF MMG method are consistent with the free-running test results with practical accuracy. Therefore, the 4-DOF MMG method proves useful in predicting the maneuvering of ships, such as container ships, at fast speeds.

Research on Maneuverability Prediction of Double Waterjet Propulsion High Speed Planing Craft

A mathematical model for predicting the maneuvering motion of a ship is constructed, using a planing craft with dual waterjet propulsion as the object of study. This model is based on the standard approach of the MMG (Maneuvering Modeling Group) and uses the Runge–Kutta algorithm to solve the differential equations. For the simulation of the turning and Z-shape maneuvering motion, the RANS equation is first solved using the program STAR-CCM + and then the PMM motion of the hull is simulated using the overlapping grid approach to derive the hydrodynamic derivative. The established method for predicting the ship’s maneuverability is feasible, as shown by the calculated results, which agree well with those obtained using data from the sea trials. This method was used to simulate the rudder rotation and Z-shape motion of the planing craft at medium and high speeds to predict the maneuverability index.

Design optimization of an AUV for performing depth control maneuver

A methodology for optimizing the inertial characteristics, propeller, battery capacity and PID (Proportional Integral Derivative) controller for propeller of an Autonomous Underwater Vehicle (AUV) is proposed in this paper. The AUV is launched at high speed in horizontal orientation, thereafter it pitches bow down and finally hovers at a particular desired water depth. The study involves both positively and negatively buoyant AUV. Four quadrant propeller open water model and quaternion are incorporated in the Maneuvering Modeling Group (MMG) type maneuvering model to make it suitable for 7 degree of freedom (DoF) dynamics. The bow down orientation is performed due to the inertial characteristics of the AUV, while the depth control maneuvering of the AUV is carried out by using PID controller for propeller revolutions. A cost function is proposed in terms of energy consumed and the distance traveled by AUV during the desired maneuver. The numeral value of cost function can be computed by carrying out numerical simulations. The numerical simulations can estimate when the AUV's propeller works in turbine mode. This information is useful for protecting the electric/electronic components of the AUV.

Timing of stand-on ship actions for cooperative collision avoidance under calm water condition

Rule 17 of the COLREGS states that a stand-on ship should take cooperative action to avoid a collision when the action of the give-way ship will not be sufficient to avoid a collision. However, most studies on collision avoidance have focused on the action of the give-way ship and not on what the stand-on ship should do. In this study, a novel criterion was developed for assessing when a stand-on ship should take action for collision avoidance that is called the computed distance at collision (CDC). Simulations were performed of the maneuvering motions of two ships in various situations to assess whether or not a collision would occur. The results of the collision assessment were assessed by the CDC, which is calculated from the ship's parameters such as the ship's heading, length, and collision angle between the two ships. Meanwhile, the actual distance (AD) between the two ships can be calculated according to their coordinates. When the CDC is greater than the AD, this means that a collision is inevitable. In other words, the stand-on ship should take action to avoid a collision while the CDC is still less than the AD. Of course, this study may have the following limitations: The study was conducted on the same model ship under calm water conditions. The interactions of hull-propeller-rudder-engine of ship and interaction of hull-hull between the two ships was not considered, and uncertainty of MMG (Maneuvering Modeling Group) model may exist. However, this study should help determine the timing of actions by the stand-on ship for collision avoidance, whether manned or unmanned.

Assessment of CFD-Based Ship Maneuvering Predictions Using Different Propeller Modeling Methods

Propeller modeling in virtual captive model tests is crucial to the prediction accuracy of ship maneuvering motion. In the present study, the Computational Fluid Dynamics (CFD) method with two propeller modeling methods, Sliding Mesh (SM) and Multiple Reference Frames (MRF), was used to simulate the captive model tests for a KVLCC2 tanker model. The virtual captive model tests, including for resistance, self-propulsion, rudder force, oblique towing, circular motion, oblique towing and steady turning tests with rudder angle, were conducted by solving the Reynolds-averaged Navier–Stokes (RANS) equations. The computed hydrodynamic forces, hydrodynamic derivatives, and hull-propeller-rudder interaction coefficients were validated against the available captive model test data and the CFD results obtained by a Body Force (BF) method in the literature. Then the standard turning circle and zig-zag maneuvers were simulated by using the MMG (Maneuvering Modeling Group) model with the computed hydrodynamic derivatives and hull-propeller-rudder interaction coefficients, and the results were validated against available free-running model test data. The most satisfactory agreement in terms of the ship hydrodynamic forces and maneuvering parameters and the most accurate rudder normal force were obtained by the SM method rather than by the MRF or the BF methods, while the lateral forces and yaw moments obtained by the SM and the MRF methods were all in good agreement with the model test data.

Enhanced body-force propeller model for non-uniform inflow flow and application to turning circle test of KCS in calm water

An enhanced body-force propeller model is developed to consider propulsion effects without solving the actual propeller geometry in ship maneuvering problems. Application to the KCS turning circle test in calm water (starting at the self-propulsion point) is conducted using the computational fluid dynamics solver, snuMHLFoam, which was developed on OpenFOAM-plus. Based on the original Hough and Ordway model, the non-uniform advance velocity of the propeller is considered using the local velocity on the inflow plane, to compute the local advance coefficient for different parts of the propeller disk when the propeller works behind a hull. The original overset algorithm is revised by introducing more flexible hole-patch definitions for the hole-cutting procedure and an iterative procedure for the donor-searching procedure to remove invalid donors. The motion decomposition of ship and rudder motions with the revised overset is implemented in order to handle body motions effectively. Self-propulsion and turning circle tests for KCS ships are successfully conducted in calm water. The predicted results, including the PI control results, turning trajectory and parameters, ship motions and velocities, forces and moments, and flow and vortical structures are illustrated and compared with the benchmark experimental data, as well as the numerical results obtained using the Maneuvering Modeling Group (MMG) model. The results indicate that the developed body-force propeller model can provide more reasonable predictions of the propulsive performance when the propeller works behind a hull. The snuMHLFoam solver, which is coupled with motion decomposition using the revised overset grid methodology, is validated to be effective and reliable.

Collision-Avoidance Decision System for Inland Ships Based on Velocity Obstacle Algorithms

Due to the complex hydrology and narrow channels of inland rivers, ship collision accidents occur frequently. The traditional collision-avoidance algorithms are often aimed at sea areas, and not often at inland rivers. To solve the problem of inland-ship collision avoidance, this paper proposes an inland-ship collision-avoidance decision system based on the velocity obstacle algorithm. The system is designed to assist ships in achieving independent collision-avoidance operations under the limitation of maneuverability while meeting inland-ship collision-avoidance regulations. First, the paper improves the Maneuvering Modeling Group (MMG) model suitable for inland rivers. Then, it improves velocity obstacle algorithms based on the dynamic ship domain, which can deal with different obstacles and three encounter situations (head-on, crossing, and overtaking situations). In addition, this paper proposes a method to deal with close-quarters situations. Finally, the simulation environment built by MATLAB software is used to simulate the collision avoidance of inland ships against different obstacles under different situations with a decision-making time of less than 0.1 s. Through the analysis of the simulation results, the effectiveness and practicability of the system are verified, which can provide reasonable collision-avoidance decisions for inland ships.

A novel ship collision risk evaluation algorithm based on the maximum interval of two ship domains and the violation degree of two ship domains

In the research of ship collision avoidance, the evaluation of ship collision risk is an important part to determine whether there is a potential collision risk. In the field of ship collision avoidance, using an appropriate method to calculate the ship collision risk has always been a hot topic. To address the issues that only qualitative evaluation using the ship domain and the distance to the closest point of approach (DCPA) does not reflect the true distance between the two ships when the closest point of approach (CPA) parameters are used, a novel ship collision risk evaluation model is proposed. (1) A fuzzy quaternion ship domain (FQSD) model is established for the own ship (OS) and the target ship (TS) at the same time. (2) The two parameters the maximum interval of two ship domains (MISD) and the violation degree of two ship domains (VDSD) are introduced, which are solved based on Support Vector Machine for Classification (SVC) and geometric methods, respectively, and the ship collision probability model is established based on these two parameters. (3) Based on the momentum conservation theorem, considering the mass ratio of two ships, ship type, collision velocity and the location of the collision damage, the consequences of ship collision are calculated. (4) Based on the ship collision probability and ship collision consequences, a ship collision risk evaluation model is proposed. The simulation verification is performed under the three encounter situations of head-on, crossing, and overtaking, based on Maneuvering Model Group using the basic ship parameters of Dalian Maritime University's teaching-training ships “YUKUN” and “YUUPENG” to establish the model proposed in this paper. Simultaneously, it is compared to the ship collision risk evaluation method based on ship domain, CPA parameters, and spatial collision risk model. The simulation results demonstrate the superiority and efficacy of the ship collision risk evaluation algorithm proposed in this paper, which is an effective method for assessing ship collision risk.

On neural network identification for low-speed ship maneuvering model

Several studies on ship maneuvering models have been conducted using captive model tests or computational fluid dynamics (CFD) and physical models, such as the maneuvering modeling group (MMG) model. A new system identification method for generating a low-speed maneuvering model using recurrent neural networks (RNNs) and free running model tests is proposed in this study. We especially focus on a low-speed maneuver such as the final phase in berthing to achieve automatic berthing control. Accurate dynamic modeling with minimum modeling error is highly desired to establish a model-based control system. We propose a new loss function that reduces the effect of the noise included in the training data. Besides, we revealed the following facts—an RNN that ignores the memory before a certain time improved the prediction accuracy compared with the “standard” RNN, and the manual random maneuver test was effective in obtaining an accurate berthing maneuver model. In addition, several low-speed free running model tests were performed for the scale model of the M.V. Esso Osaka. As a result, this paper showed that the proposed method using a neural network model could accurately represent low-speed maneuvering motions.

EXPERIMENTAL AND NUMERICAL INVESTIGATION ON MANEUVERING PERFORMANCE OF SMALL WATERPLANE AREA TWIN HULL

Free running model tests and a system-based method are employed to evaluate maneuvering performance for a Small Waterplane Area Twin Hull (SWATH) ship in this paper. A 3 degrees of freedom Maneuvering Modeling Group (MMG) model is implemented to numerically simulate the maneuvering motions in calm water. Virtual captive model tests are performed by using a Reynolds-averaged Navier-Stokes (RANS) method to acquire hydrodynamic derivatives, after a convergence study to check the numerical accuracy. The turning and zigzag maneuvers are simulated by solving the maneuvering motion model and the predicted results agree well with the experimental data. Moreover, free running model tests are carried out for three lateral separations and the influence of the lateral separations on maneuvering performance is investigated. The research results of this paper will be helpful for the maneuvering prediction of the small waterplane area twin hull ship.

Dynamic Effect of Rudder Rotary Response on Ship Manoeuvrability

Simulation mathematical model of maneuverability such as zig-zag and turning circle test under different rudder and speed is built and the rudder rotary response effect on ship maneuverability parameters is analyzed extensively. In the paper, MMG (maneuvering model group) model is adopted to set up the 3 degrees of freedom governing equations of ships, in which the rudder rotary response is approximated by the assumption of uniform rotary speed. A sea-going vessel of 10 thousand deadweight tonnages is selected as the numerical simulation target to investigate the rudder rotary response effect on ship maneuverability parameters, such as the zig-zag and turning circle test. Some meaningful conclusions are concluded through comparative analysis, the conclusions indicate that rudder rotary response has remarkable effect on ship maneuverability, and it is a significant factor which needs to be taken into consideration for actual ships.

Investigation on the rudder force of a ship in large drifting conditions with the MMG model

The rudder force, including interference with a ship hull in large drifting conditions, is investigated in this study by captive model tests using a ship model with steering. In the tests, hydrodynamic forces acting on the ship, the rudder normal force, and propeller thrust are measured while changing the hull drift angle $$\beta $$ in the range of $$-180^{\circ } \sim 180^{\circ }$$ , which encompasses forward, lateral, and astern motion. The hull and rudder interaction coefficients, thrust deduction factor, inflow velocity to propeller, and inflow velocity to rudder are obtained in large drifting conditions using the measured hydrodynamic force data. The Maneuvering Model Group (MMG) model (Yasukawa and Yoshimura, 2015) is applicable for estimating the rudder force when the absolute value of $$\beta $$ is smaller than $$45^\circ $$ . In this region, the hydrodynamic force parameters for the inflow velocity to the rudder are nearly constant for any hull drift angle. However, in the region where the absolute value of $$\beta $$ is greater than nearly $$45^\circ $$ , the MMG model cannot be applied. For improving the formula for the longitudinal inflow velocity component to the rudder ( $$u_R$$ ), we propose a new formula that is applicable to any hull drift angle.

Adaptive Neural Tracking Control for an Autonomous Azimuthing Stern Drive (ASD) Tug

The ASD tug is considered the modern habour tug due to its versatility in performing a wide variety of tugging/towing operations. With the advent of autonomous systems and desire to improve operations, there are benefits to automating the tug operations. Under different operating environments, there could be uncertainties in the model and the disturbance from the environment significant enough to affect the performance and control of the tug. In this paper, we consider the problem of tracking a desired trajectory for an autonomous ASD tug in the presence of uncertainties and unknown disturbances. The numerical modelling of an ASD tug based on a modified 4-DoF MMG model is first presented. The modified Maneuvering Modeling Group (MMG) model is then used to design a model based backstepping control. Thereafter, a adaptive neural network approximator is introduced which has the capability to account for uncertainties and unknown disturbance. The combination of approximation-based and backstepping design techniques allows us to handle time-varying model uncertainties. Stability analysis is carried out for the control design via Lyapunov analysis. Simulation are carried out for the tracking of maneuvering motion paths to demonstrate the performance of proposed approach.

Study on ship operation performance in actual seaways using time-domain free-running simulation

This study considers the evaluation of ship operational performance in real sea states using a time-domain approach. The current seakeeping-maneuvering coupling approach consists of two modules. First, in the seakeeping module, the time-domain three-dimensional Rankine panel method is applied to compute wave-induced forces and resultant ship motion. To validate this module, the computational results for wave drift force are compared with the existing experimental data for various forward speeds and regular wave conditions. Second, in the maneuvering module, the equations of motion with 4 degrees of freedom that are based on the Maneuvering Modeling Group are solved to simulate the ship navigation. The computed seakeeping and maneuvering values are immediately transferred between the two modules in the time domain, and so they are directly integrated. By applying this coupling method, a free-running simulation for a ship navigating along a given route is performed. The trajectory tracking method based on a proportional–derivative-based rudder control is adopted for straight course-keeping. Not only the speed loss but also the attitude for route maintenance is evaluated for various environmental load conditions. The simulation results are validated by a comparison with those of the existing free-running model test. Based on comparisons, environmental load effects and resultant quantities on operational performance are discussed.

Numerical Evaluation of Ship Turning Performance in Regular and Irregular Waves

AbstractIn this study, ship's maneuvering performance in waves is evaluated using numerical computation. To this end, three degrees-of-freedom (3DOF) planar motions are considered, and modular-type maneuvering model (maneuvering modeling group model (MMG model)) is applied. As external force of the equation of motion, hull force, propulsion force, rudder force, and wave drift force are adopted. In order to calculate wave drift force, seakeeping program which is based on a higher-order Rankine panel method is used by considering wave frequency, wave heading, ship's forward speed, and ship's lateral speed. This wave drift force is pre-calculated, made into database, and used in time domain simulation. The developed simulation program is validated by comparing the computation results of a turning test in regular waves with experimental data. Using this program, turning performance in irregular waves is evaluated and sensitivities for time signal of wave elevation are investigated. Through this study, it is confirmed that the simplified method based on the MMG model including wave drift force can provide good agreement with experimental data in a practical point of view. It can be observed that the simulation results considering the lateral speed show better agreement with the experimental data than those without consideration. In the case of irregular wave condition, the turning performance can be affected by wave random phases. When the ship encounters the beam sea during the turning operation, the wave elevations at that time play an essential role in the change of ship speed and turning trajectory.