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The International Maritime Organization aims for net-zero carbon emissions in the maritime industry by 2050. Among various alternatives, route optimization holds an important place as it does not require any additional component-related costs. Especially for wind-assisted ships, the effectiveness of different sailing systems can be improved significantly through route optimization. However, finding the ship's optimal route is computationally expensive when the totality of possible weather conditions is taken into consideration. To determine the optimal route that minimizes energy consumption, an energy model based on the environmental conditions, ship route and ship speed was built using artificial neural networks. The energy consumed for given input data was calculated using a ship dynamics model and a database was generated to train the artificial neural networks, which predict how much energy is consumed depending on the route followed in given environmental conditions. Then, such networks were exploited to derive the optimal routes for all the relevant operational conditions. It was found that route optimization can reduce the overall ship energy consumption depending on the weather conditions of the environment by up to 9.7% without any increase in voyage time and by up to 35% with a 10% delay in voyage time. The proposed methodology can be applied to any ship by training real weather conditions and provides a framework for reducing energy consumption and greenhouse gas emissions during the service life of ships. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the acceleration of a fast boat using a simulation model. Mathematical equations of ship motion dynamics with two types of propeller capabilities are developed using MATLAB and Simulink as simulation tools. The equations are extended to include the acting thrust, resistance, propeller’s performance curves, and the PID governor curve for the acceleration manoeuvre. The application models the dynamic differential equations representing the vessel dynamics in one degree of freedom. MATLAB code was used to develop the ship acceleration as a multibody system. Modules of hydrodynamic forces, resistance, moments, and propeller performances were implemented to simulate the ship manoeuvring process. A comparison of the results for the boat’s propulsion performance with two different propellers and the characteristics of the PID governor, which controls the fuel dose in the gas turbines, was carried out. We present a summary including a comparative analysis of the results for the boat dynamics with and without the PID governor. The results obtained here confirm significant discrepancies between the results of numerical simulations with and without the PID governor.

Ship dynamic models serve as the foundation for designing ship controllers, trajectory planning, and obstacle avoidance. Support vector regression (SVR) is a commonly used nonparametric modelling method for ship dynamics. Achieving high accuracy SVR models requires a substantial amount of training samples. Additionally, as the number of training samples increases, the computational efficiency for solving the quadratic programming problem (QPP) of SVR decreases. Ship controllers demand dynamic models with both high accuracy and computational efficiency. Therefore, to enhance the prediction accuracy and computational efficiency of SVR, this paper proposes a nonparametric modelling method based on twin SVR (TSVR). TSVR replaces a large QPP with a set of smaller QPPs, significantly enhancing generalizability and computational efficiency. To further improve the predictive accuracy of TSVR, the puma optimizer algorithm is employed to determine the optimal hyperparameters. The performance of the proposed method is validated using a Mariner class vessel. Gaussian white noise is introduced into the modelling data to simulate measurement error. The TSVR model accurately predicts various zigzag and turning circle manoeuvring motions under disturbance conditions, demonstrating its robustness and generalizability. Compared to the SVR model, the TSVR model achieves lower root mean square error and computational time, confirming its superior predictive accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

The International Maritime Organization aims for net-zero carbon emissions in the maritime industry by 2050. Among various alternatives, route optimization holds an important place as it does not require any additional component-related costs. Especially for wind-assisted ships, the effectiveness of different sailing systems can be improved significantly through route optimization. However, finding the ship’s optimal route is computationally expensive when the totality of possible weather conditions is taken into consideration. To determine the optimal route that minimizes energy consumption, an energy model based on the environmental conditions, ship route and ship speed was built using artificial neural networks. The energy consumed for given input data was calculated using a ship dynamics model and a database was generated to train the artificial neural networks, which predict how much energy is consumed depending on the route followed in given environmental conditions. Then, such networks were exploited to derive the optimal routes for all the relevant operational conditions. It was found that route optimization can reduce the overall ship energy consumption depending on the weather conditions of the environment by up to 9.7% without any increase in voyage time and by up to 35% with a 10% delay in voyage time. The proposed methodology can be applied to any ship by training real weather conditions and provides a framework for reducing energy consumption and greenhouse gas emissions during the service life of ships.

A practical criterion which can be used for assessing the course-keeping capability of a ship in following waves, is proposed and evaluated. Presently, it accounts for regular waves and it accrued from an analytical estimation of the course instability region's boundary by applying the method of harmonic balance. The calculation is performed with regard to the third-order yaw equation, derived from a classic sway--yaw-rudder model of ship maneuvering motions, with time-dependent coefficients at two places, which is like a Mathieu-type equation extended to third order. The proposed analytical criterion was evaluated thoroughly against simulations with regard to this sway--yaw model and it was found to be adequately accurate. A supplementary quasi-static yaw stability criterion (fitting to ship operation with frequency of encounter, with respect to the waves, close to zero) was also considered in order to determine which one yields more stringent requirements, for various operating conditions. The proposed criterion could be an extra vulnerability check for broaching-to, in the context of the Second Generation Intact Stability Criteria. [ABSTRACT FROM AUTHOR]

Ship dynamic models serve as the foundation for designing ship controllers, trajectory planning, and obstacle avoidance. Support vector regression (SVR) is a commonly used nonparametric modelling method for ship dynamics. Achieving high accuracy SVR models requires a substantial amount of training samples. Additionally, as the number of training samples increases, the computational efficiency for solving the quadratic programming problem (QPP) of SVR decreases. Ship controllers demand dynamic models with both high accuracy and computational efficiency. Therefore, to enhance the prediction accuracy and computational efficiency of SVR, this paper proposes a nonparametric modelling method based on twin SVR (TSVR). TSVR replaces a large QPP with a set of smaller QPPs, significantly enhancing generalizability and computational efficiency. To further improve the predictive accuracy of TSVR, the puma optimizer algorithm is employed to determine the optimal hyperparameters. The performance of the proposed method is validated using a Mariner class vessel. Gaussian white noise is introduced into the modelling data to simulate measurement error. The TSVR model accurately predicts various zigzag and turning circle manoeuvring motions under disturbance conditions, demonstrating its robustness and generalizability. Compared to the SVR model, the TSVR model achieves lower root mean square error and computational time, confirming its superior predictive accuracy and computational efficiency.

In this study, the impact of propeller emergence on the performance of a ship (speed), propeller (thrust, torque, and RPM), a diesel engine (torque and RPM) and fuel consumption are analysed under severe sea conditions. The goal is to describe the variation in the system variables and fuel consumption rather than analysing the motion of the ship or the phenomenon of propeller ventilation in itself. A mathematical model of the hull, propeller, and engine interactions is developed in which the propeller emergence is included. The system parameters are set using model experiments, empirical formulae, and available data for the engine. The dynamic response of the system is examined in regular head waves under submerged and emerged conditions of the propeller. The pulsatility and the extent of variation of 20 selected variables for the coupled system of hull, propeller, and engine are elaborated using quantitative and qualitative terms and absolute and relative scales. The simulation begins with a ship moving on a straight path, in calm water, with a constant speed for the ship, propeller and engine under steady conditions. The ship then encounters regular head waves with a known time series of the total resistance of the ship in waves. Large motions of the ship create propeller emergence, which in turn reduces the propeller thrust and torque. This study shows that for a specific ship, the mean ship speed, shaft angular velocity, and engine power were slightly reduced in submerged conditions with respect to calm water. We compared the mean values of the variables to those in the emerged condition, and found that the shaft angular velocity was almost the same, the ship speed was considerably reduced, and the engine power significantly dropped with respect to calm water. The ratios of the amplitude of fluctuation to the mean (Amp/Mean) for the ship speed and angular velocity of the shaft under both conditions were considerable, while the Amp/Mean for the power delivered by the engine was extremely high. The outcomes of the study show the degree of influence of propeller emergence on these variables. We identify the extent of each change and categorise the variables into three main groups based on the results.

Autonomous trajectory generation plays an essential role in the navigation of vehicles in space as well as in terrestrial scenarios, i.e. in the air, on solid ground, or water. For the latter, the navigation of ships in ports has specific challenges since ship dynamics are highly nonlinear with limited agility, while the manoeuvre space in ports is limited. Nevertheless, for providing support to humanly designed control strategies, autonomously generated trajectories have not only to be feasible, i.e. collision-free but shall also be optimal with respect to manoeuvre time and control effort. This article presents a novel approach to autonomous trajectory planning on the basis of precomputed and connectable trajectory segments, the so-called motion primitives, and an A*-search algorithm. Sequences of motion primitives provide an initial guess for a subsequent optimization by which optimal trajectories are found even in terrains with many obstacles. We illustrate the approach with different navigation scenarios.

According to the International Maritime Organization (IMO)'s Greenhouse Gas (GHG) strategy whose aim is to reduce the shipping industry's total carbon emissions by 50% by the year 2050, it is desirable to increase ships energy efficiency to reduce GHG emissions and fuel costs. To do so, a short-term measure is to develop innovative engine control strategies in waves that will reduce ship's GHG emissions. In this study, a mathematical model is developed to assess two engine control strategies: the standard constant rotational speed mode and an innovative constant fuel rack approach. The coupled model is made of a mean value engine, propeller curves and a ship behavior simulator. Emphasis is placed on the presentation of the engine model and references are given for further details on the ship simulator. After verifying the coupling between the engine model and the ship simulator, the fuel consumption is compared, for the two strategies, at the same average speed and for three head regular waves. This paper presents the basics of a further long time research project and shows that coupling ship simulators with engine simulators leads to promising simulation tools for a ship's GHG emissions reduction. Results from a first application case show that the constant fuel rack approach reduces fuel consumption (up to 1.6%). [ABSTRACT FROM AUTHOR]

Autonomous trajectory generation plays an essential role in the navigation of vehicles in space as well as in terrestrial scenarios, i.e. in the air, on solid ground, or water. For the latter, the navigation of ships in ports has specific challenges since ship dynamics are highly nonlinear with limited agility, while the manoeuvre space in ports is limited. Nevertheless, for providing support to humanly designed control strategies, autonomously generated trajectories have not only to be feasible, i.e. collision-free but shall also be optimal with respect to manoeuvre time and control effort. This article presents a novel approach to autonomous trajectory planning on the basis of precomputed and connectable trajectory segments, the so-called motion primitives, and an A*-search algorithm. Sequences of motion primitives provide an initial guess for a subsequent optimization by which optimal trajectories are found even in terrains with many obstacles. We illustrate the approach with different navigation scenarios. [ABSTRACT FROM AUTHOR]

Two nonlinear models of the roll motion of ships are discussed and analytically solved. Both models are second-order differential equations with nonlinear restoring and damping moments. A new approach to the homotopy perturbation method is applied to derive analytical expressions for the roll angle, velocity, acceleration and restoring and damping moments. The analytical results are validated by direct comparison with the fourth-order Runge-Kutta method. The analytical approach of this paper can be efficiently extended to various vibrating dynamical models arising in mechanical systems. [ABSTRACT FROM AUTHOR]

This article introduces a novel nonlinear control approach for quadrotor landing on a moving ship. The dynamics of the relative position and attitude dynamics with uncertainties, unmodeled dynamics, external disturbances, and control input saturation is derived. Then, a novel robust adaptive constrained backstepping control law for the propeller and torques of the quadrotor is designed. To deal with uncertainties and un-modeled dynamics, radial basis function is employed. The bounded-in-probability stability is used to alleviate the destructive influence of the stochastic Wiener process on the system positions and attitudes. Whereas the quadrotor is under-actuated, a redundant control input technique, which affects the attitude commands, is presented. The actual control input saturation limits are turned into unknown saturation limits of the redundant control inputs. Also, since two phases for the landing problem are considered, a smooth switching mechanism between the control inputs is developed. Simulation results show the merits and applicability of the developed robust adaptive nonlinear controller. [ABSTRACT FROM AUTHOR]

Survivability of ships in damaged condition is an issue of paramount importance. Therefore, the regulatory framework is constantly updated, in response to the societal aversion towards accidents with severe impact on human life and on the environment. The introduction of the probabilistic damage stability framework was a major step towards the rationalization of the procedure for the assessment of survivability of ships in damaged condition. Subsequent revisions of SOLAS 2009 included the increase of the safety standard via the new formulations for the R-Index and for the calculation of the probability of survival (s-factor), which however is still performed by a hydrostatic approach. Flooding simulation tools can be used for an in-depth investigation of the transient response of a damaged ship, aiming to identify conditions that could jeopardize her survivability during the initial phases of flooding, or to assist in the improvement of the s-factor formulation. In this work, a newly developed flooding simulation tool, employing the Smoothed Particles Hydrodynamics (SPH) method coupled with a ship motions solver, is presented. The developed methodology predicts the dynamic response of the ship during the flooding process, primarily focusing on the initial stages, when particularly violent flow phenomena may be observed. • Application of SPH in damage stability flooding simulations. • SPH modeling of water inflow (and outflow) in a damaged compartment. • Simulation of box-shaped barge dynamics in symmetric and non-symmetric damages. • Comparison between non-linear dynamic SPH method and quasi-static method. [ABSTRACT FROM AUTHOR]

This paper focuses on the design stage of an electrical energy storage system which is intended to be used to level the power required by ships for propulsion when sailing in irregular seas. Particularly, a preliminary analysis has been carried out aimed at choosing, between two storage technologies namely battery and ultracapacitor, the more adequate storage system for the levelling action with respect to the period of the sea waves. A sizing procedure based upon a Hilbert transform decomposition of load demand is used. More specifically, a specified threshold frequency has been identified such that, power fluctuations related to irregular seas which are characterized by frequencies higher than the specified threshold, indicate the ultracapacitor as the more appropriate device for load levelling. For sizing the storage device, the load demand has been decomposed into two signals without overlapping frequencies. An optimal control strategy is proposed, by exploiting the decomposition of the load power, which allows simulating ultracapacitor real-time operation within the previously determined size constraints. Numerical results have been carried out referring to a Ro-Pax ferry powered by an electrical motor. • Onboard electrical energy storage is used for load levelling. • The use of the storage refers to a ship sailing in irregular sea states. • A threshold frequency is identified for the choice of storage technology. • A proper decomposition of the load request signal is performed. • An optimal control strategy based on an autoregressive model is used. [ABSTRACT FROM AUTHOR]

The ship's dynamic performance (acceleration, turning ability, crash stop) strongly depends on both the propulsion system and its control. The steady-state performance analysis of propulsion systems has shown that onboard energy usage benefits from the employment of simulation techniques. Besides, these techniques provide significant advantages in designing the control logic of sophisticated and complex systems. The present work summarizes the research activities conducted to develop suitable simulation framework for the propulsion systems of naval vessels. Theoretical and mathematical models have thus been developed in this paper to simulate the propulsion of ships. Model-scale experiments and full-scale trials have been used to increase the fidelity of the models. The research outcome is a conceptual framework and a fully validated parametric software representing the vessel's dynamic behaviour and propulsion system in steady-state and abrupt manoeuvres. Thanks to this simulation framework, the propulsion control system could be designed, validated, and calibrated before its installation on board, reducing the commissioning time and minimising the propulsion control system's onboard calibration during the acceptance sea trials. • A new holistic approach for designing complex propulsion plant is shown. • Mathematical models to simulate the dynamics of several ship' subsystems have been conceptualised. • Real-time ship simulation platform has been developed. • Validation by sea trials demonstrates the methodology validity. [ABSTRACT FROM AUTHOR]