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In this paper, wave-induced motions and loads of a bow flare ship advancing in harsh irregular waves are investigated both numerically and experimentally. A 3D time-domain hydroelasticity theory that includes memory-effect function considering Froude–Krylov nonlinearity is developed to predict ship motions, wave loads and slamming loads in long-crested irregular waves. In the hydroelasticity algorithm, the wave memory effects and forward speed effects are addressed by retardation function method to improve the computing efficiency and provide opportunity for short-term statistical analysis of ship responses in irregular waves. In addition, segmented model tank tests are conducted to experimentally investigate the motions and loads of ship sailing in long-crested irregular waves and also validate the numerical results. To further understand the nonlinear wave loads behavior of ship in short-crested waves, large-scale segmented model sea trials are performed in realistic sea waves. The numerical results and experimental results are systemically analyzed and compared using time series, spectral and probability statistical analysis methods.

We develop the approach to simulate the experiments with surface and underwater vehicles in towing tanks for Reynolds numbers Re, corresponding to sea trials, using discrete injection of polymer additives. The complete dynamic similarity between full-scale and tank tests is possible if both Froude number and Re are equal for a ship and its model. In traditional experiments, the first condition is only satisfied and the viscous and wave resistances are independently studied. The Toms effect is widely used in marine engineering, e.g., to reduce energy cost. In this work, it is applied quite differently. Re is higher and the skin friction coefficient c f is hence less for sea trials than for towing tanks. Injection of polymer additives allows decreasing c f on ship model to full-scale values, providing the complete similarity and reproducing sea trials in that way. We report the selected results of such novel approach that, in particular, include velocity profiles and c f for sea trial, towing tank and pipe experiments, plane boundary layer and 3D flow around propeller, rough and smooth surfaces. The data for full-scale and tank experiments agree well with each other.

Full scale measurement, model testing and a hybrid CFD method were used to characterize the Underwater Radiated Noise (URN) of a ship at design speed. The CFD method consists of a multiphase Delayed Detached Eddy Simulation and the Ffowcs-Williams Hawkings acoustic analogy. The paper discusses the correlation of the noise spectra with the observed cavitation behavior and compares the measured full scale data with those predicted by the model testing and the CFD method. The comparison shows that the sheet cavity and Tip Vortex Cavitation (TVC) predicted by the model testing are in reasonably good agreement with the full scale observations. The pressure pulses are somewhat higher than the full-scale data. Overall, the predicted URN has a good correlation with the noise spectra obtained from the sea trial. The CFD method shows the potential to resolve turbulence eddy structures in the wake. It captures the dynamic development of sheet cavitation and the collapse and rebound of TVC as observed in the model test and the sea trial, but under-predicts the extent of TVC. The pressure pulses and tonal noise are in close agreement with the respective measured data for the first five orders of blade passing frequency. The method underestimates the broadband noise level in the frequency range 50–112 Hz where the TVC is expected to have an important contribution. The maximum under-prediction in this range is about 28 dB at 72 Hz. At frequencies above 200 Hz, the broadband noise becomes more and more under-predicted with increasing frequency.

Autonomous underwater vehicles (AUVs) are advanced near-bottom platforms that can be used for magnetometric analysis of the seafloor. However, the vehicle itself can cause interference with the magnetic measurements, which need to be corrected. Here, we derive a functional relation between the magnetic measurements and AUV's heading that is based on the composition and causes of an AUV's near-bottom magnetic anomaly. We set up a method to correct tri-axial magnetometer interference caused by the AUV. Magnetic induction intensity is removed using magnetic data collected during the spinning of the AUV. Connatural magnetic field of the AUV is collected and subtracted by using portable magnetometer. The method performs very well during QianlongII AUV experimental tests performed on land and in lake. The method also corrects magnetic data by an autonomous benthic explorer (ABE) AUV and yields good results. The effects of main components of QianlongII AUV on the magnetic measurement results are analyzed and make sure dominating interference produced by the batteries. That is mitigated using a probe extension pole. Furthermore, excellent survey data and satisfactory correction results are obtained during the AUV sea trials. This verifies the efficacy of the proposed method for correcting tri-axial magnetometer interference caused by AUV.

In this paper, seakeeping performance of vessels is comparatively investigated by means of improved 2.5D theoretical calculation, small-scale model towing tank test and large-scale free running model sea trial. This study also provides a scheme of ship vertical motion stabilization technique by using Semi-Submerged Bow (SSB) appendages. Firstly, an improved strip theory based 2.5D theoretical seakeeping algorithm, which considers the viscous flow effects attributed to bow appendages, is developed to estimate ship vertical motion responses in regular waves. Short-term predictions are also made on the basis of spectral analysis theory to predict ship motion responses in irregular waves. Then corresponding small-scale models are made and tested in a laboratory towing tank for both regular and irregular wave conditions to confirm the numerical results. The tank testing results between different ship schemes are also compared to experimentally investigate the effects of SSB and fin on hull vertical motion stabilization. Furthermore, large-scale model sea trials are conducted in coastal waves for a final validation of the ship seakeeping performance in short-crested sea waves. Finally, comparisons of the results by different testing approaches are systematically made and analyzed.

Measurement, data transfer, modelling, controller systems are the main subjects of interdisciplinary area during prototyping of marine automatic control systems. Experimental parameter identification is an essential step for modelling and control system design are in question for various marine applications. The selection of variables to be measured, type of measurement sensors, type of control algorithms and controller systems, communication, signal conditioning are all important topics for parameter identification and real-time control applications in maritime engineering. The objective of this paper is to present a brief review of these important topics based on our case studies, such as ship roll motion reduction control, optimal trim control of a high speed craft, and dynamic position control of underwater vehicles. These projects involved extensive dynamic modelling, simulation, control algorithm design, real-time implementation and full-scale sea trials. In this paper, the presented methods, and the required characteristics of the marine control systems are demonstrated with the results obtained by the simulation studies and full-scale sea trials. Also, insight into the selection of hardware and software components for mechatronic applications in marine engineering is provided.

Ship owners and classification societies have recently begun to require assessments of the maneuverability of twin-screw ships under machinery failure. Since such an assessment has not yet been previously conducted, its concept and process have not been clearly established. In this paper, we construct a simulation that predicts the maneuverability of a ship under machinery failure and propose a process to conduct IMO maneuvering tests under machinery failure, and this is referred to as single propeller failure, single rudder failure, aligned combination failure, and cross combination failure. A mathematical model for the simulation under normal operating condition is verified, and assumptions are applied to the existing mathematical model to introduce machinery failure. The suggested procedure is followed to verify a mathematical model with these assumptions under machinery failure by conducting sea trials. Finally, numerical simulations for mandatory tests are conducted for the defined failures, and the physical characteristics of each failure are investigated compared to those under normal operating conditions.

To achieve a continuous and accurate navigation solution that avoids interruption, GPS is integrated with dead reckoning techniques such as inertial navigation and speed log. A common approach to obtain a low-cost navigation solution is to utilize a multisensor system consisting of MEMS-based inertial measurement unit (IMU), and the whole system is integrated with GPS. However, these sensors provide significant inherent errors because of their complex error characteristics. Particle filter (PF) is considered as a nonlinear filtering technique to accommodate for arbitrary inertial sensor characteristics and motion dynamics. An adaptive fission PF (AFPF) method is proposed to overcome the shortcoming of sample impoverishment problem and improve particle quality. Moreover, further improvement of the MEMS-based IMU/GPS integration navigation system performance during GPS unavailability is achieved by integrating measurement updates from speed log data. The performance of the proposed GPS/IMU/LOG integration using AFPF is evaluated by sea trial, and results indicate that the AFPF solution outperform three different solutions.

This paper described a procedure for predicting the ice loads acting on a hull of an icebreaker that employs a six degrees-of-freedom (6-DOF) inertial measurement system method. Ice loads were calculated using the data measured in full-scale ice sea trials of the Korean ice breaking research vessel (IBRV) ARAON during her Arctic Ocean voyage in 2015. In the measured data, it was found that the sway, roll, and yaw motions were larger than other motions because the ship usually met with pack ice during her voyage. To calculate the maximum ice loads, the center of gravity (COG) approach and the point of impact (POI) approach were used. Ice loads ranged from 1.41 to 4.87 MN when estimated using the COG approach, and from 0.11 to 1.06 MN when estimated using the POI approach. The measured ice loads through the COG and POI approaches were compared with the resultant forces measured using strain gauges.

The cavitation inception speed (CIS) is very important capability for a navy vessel because the underwater radiated noise dramatically increases when cavitation occurs. Therefore, the CIS has been severely restricted and evaluated at sea trial test steps in the shipbuilding process. After a naval vessel is delivered to the navy, CIS can vary according to the propeller and sea state conditions. However, inspection of CIS cannot be performed frequently due to time and expense limitation. Therefore, real time monitoring of CIS is urgently required by navy personnel. In order to inspect CIS with real time monitoring technique, the measuring method detecting fluctuation pressure of the propeller in a ship at sailing state should be developed. In this research, CIS monitoring techniques using acceleration on the hull above the propeller that can measure the fluctuation pressure of the propeller indirectly are suggested and verified experimentally. In addition, the evaluation algorithm of CIS using the kurtosis of the Detection of Envelope Modulation on Noise (DEMON) spectrum is used to determine the CIS quantitatively.

Ship acceleration manoeuvre is important in terms of safety and engine performance. Head seaways are one of the most challenging conditions for the ship propulsion. A detailed simulation of the propulsion system's transient response during dynamic acceleration in harsh conditions can result in a thorough investigation of the engine performance, a better management of control system and the monitoring of engine limiters application in real conditions. For the overall propulsion system performance assessment during ship acceleration, a computational tool has been developed that consists of a number of sub-systems for the simulation of engine, turbocharger, propeller components and their interaction. The developed tool has been first validated against available shop and sea trials data and subsequently it has been tested for the simulation of propulsion system performance during acceleration in dynamic conditions. Based on the simulation results, a sensitivity analysis has been performed for the investigation of the governor control unit limiters that apply on the engine during acceleration. As a result, the effect of engine governor limiters on the overall engine and hydrodynamic performance of the ship during acceleration is quantified and discussed.

Wave driven robots (WDRs) are a new type of autonomous ocean observation platform driven by wave energy. This paper is concerned with the multi-body yawing filter problem of the WDR. The adaptive multi-body yawing filter (AMF) of WDR was presented by considering the driven principle of the yawing motions of the submerged glider (glider) and the float body (float). The linearized yawing response models of the glider and the float were derived. The adaptive amending method of the dynamic response coefficients (DRCs) of the glider and the float were proposed. On this basis, the AMF of WDR was developed within the extended Kalman filter (EKF) framework. The AMF method utilized input and output (I/O) data to extract model information and is independent of the accurate mechanism model of the system. Numerical simulations of step steering and continuous steering under nominal model and the model with parameter perturbation were performed. The sea trial was conducted and the filtering results of the actual sensor data by AMF, EKF and tracking differentiator (TD) were presented. The proposed AMF method was found to be with good performance in suppressing noise and tracking speed.

This paper describes an open and extensive validation study carried out by the Specialist Committee on Ships in Operation at Sea (SOS) of the International Towing Tank Conference (ITTC) on the newly developed SHOPERA-NTUA-NTU-MARIC (SNNM) wave-added resistance prediction method. The SNNM method aims at a simple, fast and transparent determination of the added resistance in regular waves of arbitrary encounter directions, even when the hull geometry is not available. Prior to the validation study, a series of acceptance criteria for the new method were specified by the committee. Contributions of 1,477 added resistance experimental data samples from 8 institutions were collected, analyzed and cross-checked with satisfactory outcome, which finally led to the inclusion of the new method into the ITTC recommended sea trial procedure as an important progress. Some aspects of concerns are discussed in detail and further work in the future is recommended.

With the outstanding performance of unmanned surface vehicles (USVs) in maritime missions with scientific and commercial applications, increasing numbers of ships have begun to carry USVs to perform tasks. For the autonomous recovery of a USV along a preset trajectory to the docking station under various sea conditions, we propose a new navigation strategy with dual-attention-based optical terminal guidance. Monocular vision systems with creatively designed identification light sources are mounted on the docking station and USV, respectively. Thus, the azimuth angle, heading angle and relative distance between the docking station and the USV can be accurately measured. This method achieves centimeter-level homing accuracy and a 0.1-degree angle measurement error. A tracking control algorithm based on a line-of-sight method is suggested , and the control quantity of the USV is directly generated. Sea trials were conducted under various weather conditions to validate the proposed algorithm. This method provides reliable USV guidance to the docking station with a stern ramp from the maximum capture distance of approximately 100 meters. The proposed dual-attention method provides convenient implementation and transplantation to various unmanned platforms.

In this study, we investigated the hydrodynamic characteristics of marine aquaculture net cages used for farming silver salmon (Oncorhynchus kisutch). Two sets of experiments were conducted: model-scale testing, which was used to measure the drag force and deformation of a model net cage at different current velocities, and full-scale testing, which involved a sea trial at a silver salmon farm site. In the sea trial, an acoustic wave and current meter was deployed to record the current velocities around the net cage, and the cage deformation was estimated from the several vertical positions of net using 13 depth sensors. The precision of estimating the cage deformation using only the depth information was evaluated by comparing the estimated cage deformation with that determined from the images in model-scale testing. Comparing the model-scale and full-scale testing results showed that only the bottom netting was found to be deformed under lower water currents. The trends observed for the drag force, cage deformation, and cross-section area estimated from the depth data in full-scale testing were generally consistent with those converted from the model-scale testing using Tauti's similarity law. However, the drag force values of a full-scale net cage converted from the model-scale testing were higher than those estimated from the depth data in the full-scale testing. In contrast, the converted cross-sectional areas from model-scale testing were smaller than the estimated values in full-scale testing. In future, the cage deformation should be examined under higher current velocities, and the drag force should be measured in the full-scale testing to validate the results of the model-scale testing and the hydrodynamic model.

This paper proposes a control architecture of autonomous underwater vehicle (AUV) for coverage mission in irregular region (CMIR) with an improved task planner. The CMIR control architecture is structured in four layers: perception layer, reactive layer, decision making layer and execution layer. To improve the task planner in decision making layer of control architecture, we adopted convex partitioning method and Success-History Based Adaptive Differential Evolution Algorithm (SHADE) including linear population size reduction (L-SHADE) as the computing engine, which make CMIR control architecture more suitable to coverage problems. Through statistical analysis, we obtained a set of optimized control parameters. Simulation experiments were carried out, three task planners were compared in terms of convergence speed, optimized path length and computing time consumption. The results show that the coverage efficiency of the task planner based on L-SHADE is higher than that of task planner based on particle swarm optimization (PSO) and differential evolution (DE). Sea trial was performed with Sailfish-AUV, which proved that the CMIR control architecture is feasible in actual marine environment.

The form-changeable boats have received much attention due to its far-ranging applicability, strong combat capability and the low operating cost. This paper constructs a variable-structure boat whose mainhull is planing hull form and twin retractable deep-V side-hulls are placed on both sides of the mainhull, aims at assessing its seakeeping performance in the monomer-form state (MFS) and the trimaran-form state (TFS) by model tests, numerical simulation and sea trials. Regular head wave tests were conducted at volume Froude numbers (Fr∇) ranging from 0.44 to 2.67 for the MFS and TFS models. Verification and validation of the CFD method were performed, the influences of side-hull draft on the seakeeping of TFS model under different wave configurations were analysed. Sea trials of the full-scale vessel (USV) in irregular sea were also carried out at the design velocities. The results show that the TFS has different effects on motion responses and vertical accelerations of the model at different speeds and wavelengths, the applicable range of side-hulls with gain effect is in the diaplacement and semi-planing stage, and the maximum velocity is suggested not to exceed Fr∇ = 2.22. For the USV at Fr∇ = 1.33, the TFS mainly cut down its roll in irregular head sea, followed by following and beam sea; when the Fr∇ increases to 1.78, the roll gain declines, but the pitch gains more, the better side-hull draft ratios are 1.0 and 0.67, corresponding to the above two design speeds, respectively.

Most sea trials of large merchant ships are carried out with the filling ballast water in cargo, and the trial environment may involve mild waves as well. It causes the ship to undergo a coupling effect between external wave excitation and internal sloshing motion, and an understanding of such coupling is important to analyze the components of the total resistance measured in sea trials. In this study, a blunt modified Wigley equipped with two inner tanks is selected to observe its hydrodynamic responses under head waves, using both experimental measurement and numerical computations. Ship is considered to have a forward motion at the Froude number of 0.2, and three filling conditions varying from low filling to high filling have been arranged for two inner tanks. For validation, numerical computation is performed based on the three-dimensional Rankine panel method with the linearized boundary value problems. Both seakeeping and internal sloshing flow are analyzed using the linear potential theory. The validation presents a sufficient agreement between experimental measurement and numerical results with or without the sloshing effect, and both two methods have shown that the sloshing coupling effect is generally insignificant for present ship model. However, when the wave encounter frequency becomes very close to the tank natural frequency, the medium filling tanks generate a strong coupling effect which can restrain ship motion responses as well as added resistance.

This study proposes a path planning method based on behavioral decision-making (PPM-BBD). An optimized path is planned for autonomous underwater vehicle (AUV) to save energy during the diving process. The key idea is to apply success-history based adaptive differential evolution algorithm including linear population size reduction (L-SHADE) to the optimization of energy. In addition, motion constraints are considered during the diving process to ensure that the path points are reachable. We take the sequence of motion angles as the population, and propose an angle modification strategy to apply to the population evolution process, so that the angle sequence remains in the space of feasible solutions. The modification strategy lays a theoretical foundation for the application of L-SHADE in this path planning problem. The performance of PPM-BBD is evaluated on data from simulation test. The most suitable control parameters are determined through simulation experiments. The effects of PPM-BBD with L-SHADE and five types of DE are compared. The experimental evaluation was performed through sea trials in Tuandao Bay, Qingdao, China. Results show that PPM-BBD saves at least 9% energy compared to the other algorithms. It is concluded that it is workable to obtain a reachable path with optimized energy consumption during diving process.

The oscillating buoy wave energy converter (OBWEC) is a popular and widely used wave energy converter (WEC) due to the simplicity of its structure and its strong adaptability. In this paper, the “Haiyuan No. 1″ OBWEC is taken as the research object, in which the buoys adopt heave mode of motion. In order to further enhance the hydrodynamic performance of the buoys, an improved scheme with longitudinal swing motion is proposed through theoretical analysis for the buoy. A 2D numerical wave tank (NWT) model based on the RANS equation is established by using CFD software. The numerical model is applied to compare and analyze the hydrodynamic performance differences of the buoy under two different motion forms: heaving and longitudinal swing, and the consistency of the numerical results is validated by the experimental data under regular waves. Finally, the irregular wave data obtained during the sea trial of the “Haiyuan No. 1″ OBWEC is used to numerically simulate the two buoys. The results show that the buoy with longitudinal swing motion is more effective in improving the hydrodynamic performance compared to the buoy with heave motion, in both regular and irregular waves. The conclusions of this paper can serve as a guide to improve the design of the hydrodynamic performance of the buoy.

Deep-water or open sea area developments bring technology challenges to offshore pipeline installation safeties. With low oil price, offshore contractors endure considerable pressure and struggle to provide cost-effective services. To achieve safe operations with higher efficiencies, it is essential to acquire better understanding of pipeline conditions in-process, which benefits operation planning and decision making. Offshore operational window and pipeline fatigue damage significantly depends on vessel motions. Current engineering practices generally predict motions through metocean and hydrodynamics based numerical simulations. This approach is useful but naturally leads itself to prediction uncertainties, which are most likely conservatism. With deep-water and open sea application, the uncertainties may become underestimations of key parameters due to possibly insufficient metocean data and inapplicable hydrodynamic methods. Subsequently, a real-time offshore pipeline installation monitoring system has been developed to predict realistic pipeline behavior by adoption of real-time operation parameters including vessel motions. A sea-trial for the system has been conducted on a pipelay project in 2016. As an alternative treatment to pipeline installation planning and decision making, the system has been proven capable of accurate simulations and additional functions such as touch point monitoring and fatigue tracking.

Operating in the depth-varying oceanic environment, the buoyancy of deep-sea underwater gliders (UGs) will change with depth due to pressure hull deformation and seawater density variation. As the buoyancy variation caused by these two factors is of the same order of magnitude as the nominal net buoyancy, hull deformation and seawater density variation will accordingly affect the dynamic behaviors of deep-sea UGs. In this paper, a full dynamic model was established using Newton-Euler method for a deep-sea UG, PETREL-II. The hull deformation and seawater density variation, fitted as the functions of depth, are considered in the model. Comparisons of results obtained by sea trials, the full dynamic model and the simpler dynamic model without considering hull deformation and seawater density variation showed that the proposed full dynamic model can more truly reflect dynamic behaviors of the glider. Comparisons of simulation results for the full and simpler dynamic models showed hull deformation and seawater density variation have great effect on pitch angle and velocity of the gliders. Through analysis of motion control strategy, a buoyancy compensation scheme was proposed to reduce the negative effect of hull deformation and seawater density variation, and was validated to be effective by sea trials.

In order to optimize the utilization of the kinetic energy derived from the hydrostatic energy to collect more sediment core, the paper focus on the analysis and the modeling of the percussion coring of a hydrostatic seafloor sediment corer, including the modeling of the stress wave traveling along the tube and the construction of the dynamic model of the tube-sediment system. The hydrostatic corer is feature by using both the hydrostatic energy of the seawater and gravity potential energy to collect the sediment in a percussive way. The analysis results reveal the under-sampling phenomenon of the corer which was observed and confirmed by the sea trial. To weaken the under-sampling and improve the utilization of the hydrostatic energy, several effective factors have been studied through the dynamic model and the results shows that the large inner diameter of the tube and the high mechanical impedance of the cushion and the increase of the single percussion energy and the adequate area ratio of the tube can considerably weaken the under-sampling and improve the recovery ratio. The modeling method and analysis results can provide some instructive information for the design and improvement of the percussive seafloor sediment corer.

This paper compares the skill of two algorithms that enable real-time estimation of the directional wave spectra exciting a ship from its measured motions. One algorithm consists of a nonlinear optimization of a parametric or non-parametric spectral model and the other is a Kalman filter based observer. Sea trials have been conducted on an oceanographic vessel that was instrumented with a six degree of freedom fiber optic gyro, complemented with a rate gyro, several accelerometers, a dedicated GPS receiver and a bow mounted down-looking wave radar with motion compensation. The two algorithms are applied to the measured data and a discussion is provided on their skill to recover the properties of existing sea states.

Shanghai University has developed an unmanned survey vehicle (USV) named JingHai-I. The mission of JingHai-I is to work as a test bed USV for the development and validation of various algorithms. One main innovation of the USV is the capability to achieve hydrographic surveying and charting in nearshore shallow waters. The highly resistant overturning ability and low draft (0.43 m) enables the USV to move safely in shallow waters. Moreover, the USV can sail on a setting track and automatically avoid obstacles. This paper presents a review of our research work on the development of the USV, with a performance evaluation by a series of tests. In addition, the system design and implementation of the USV is detailed in the introduction. In order to get better control effects, a numerical model for the USV was built and a GPC-PID cascade controller was proposed, which combines generalized predictive control and PID control. A series of test results and discussions of the results are presented. Compared with the actual sea trial test data, the results show that the USV offers good maneuverability.

Cavitating ship propellers are known to be the dominant noise source contributing significantly to the underwater radiated noise (URN) level. Innovative measurement methods using on-board devices need to be further investigated as they offer a serious alternative to traditional methods in terms of cost-efficiency and practicality. This exploratory study combined simultaneous on- and off-board noise and vibration measurements with cavitation views captured by digital photography and high speed cameras.Comprehensive full-scale trials were conducted on Newcastle University’s research vessel, The Princess Royal, in the framework of the FP7-EU project SONIC. On-board data were captured from multiple measurement systems (including. hull pressure sensors, accelerometers, optical devices, shaft strain gauges) provided by SONIC project partners CETENA, Wärtsilä , University of Southampton and Newcastle University. A new semi-empirical correlation method based on cavitating propeller pressure fluctuation and the URN level was established. Results offer clear evidence of successfully estimating URN with on-board measurements up to the middle frequency region where the blade passing fundamental and low harmonic frequencies occur. These illuminating insights reported in this paper provide valuable benchmark sea trial data in full scale.

The wave driven glider is a kind of unmanned ocean surface vehicle solely powered by waves and solar energy, which allows marine monitoring in large temporal and spatial scales. Therefore, it has a broad application prospect in ocean survey and observation. This paper focuses on the development of the control system for the wave driven glider. The hardware distribution and the robot operating system based software framework are developed. The sailing control strategies corresponding to position keeping, path following and heading control are presented and validated by numerical experiments. Moreover, the wave driven glider named “SJTU Mouse” were developed, including the first generation based on side propeller control and the second generation based on rudder control. Besides, the Wave Glider Remote Control & Management Platform (WGRCMP) was developed. Sea trials were also conducted in the South China Sea. Results show that, with the proposed control system, the wave driven glider can adapt to different mission and ensure successful vehicle operations, demonstrating the feasibility and applicability of the control system.

Currently, most autonomous underwater gliders (AUGs) operate on primary lithium batteries. As the state of charge of a primary lithium battery and the influence of marine environment on the glider are difficult to measure, it is hard to forecast the energy consumption of a glider accurately, which has caused the failure of many glider missions. For the purpose of safely deploying the AUG mission and effectively optimizing the motion parameters to increase the endurance, it is very important to make an accurate energy consumption prediction model of the AUG. In this paper, a novel model based on the least squares support vector machine (LSSVM) and particle swarm optimization (PSO) algorithm, namely the LSSVM-PSO model, is proposed to forecast the energy consumption of the AUG. Considering that the kernel function and the LSSVM related parameters have a great influence on the performance of the prediction model, several LSSVM models based on different kernel functions for energy consumption prediction are established, and the parameters are optimized by the PSO algorithm. The performance of LSSVM-PSO models with different kernel functions are compared based on the sea trial data. The results indicate that the LSSVM-PSO model with a radial basis kernel function has a higher accuracy than other models for energy consumption prediction. Moreover, the performance of the LSSVM-PSO model trained by different sample sizes and that of the conventional mathematical energy consumption prediction model are compared. The results demonstrate that the LSSVM-PSO model is superior with a large enough training sample size.

In worldwide, to overcome a future shortage of resource, deep-sea mining (DSM) system and technology have been developed for great commercial values. As a core component, deep-sea mining vehicle (DSMV) plays an important role in deep-sea operation. Based on the development in last decades, this paper presents the significance and challenge of DSMV and reviews the existing deep-sea mining system in sea trial. Firstly, the dynamic analysis of DSMV is reviewed, including dynamic modeling method, track characteristics and mining collection systems. The interaction considering deep-sea sediment to the tracked DSMV performance is discussed, which is well to understand the work mechanisms of DSMV. Then, for engineering application in deep-sea environment, key control strategies of DSMV are reviewed in the field of dynamic motion control, path control, navigation, and positioning control, which aims to adapt to deep-sea operation. In the end, some existing issues and future study priorities are proposed. This paper may provide a comprehension of the current research status of deep-sea mining system, which enlightens the future development for balancing technology and deep-sea ecological environment.

A full-coupled three-dimensional dynamic model of a towed cable body system is developed. The towed cable with the axial elasticity, bending stiffness, and torsional stiffness is approximated by the finite difference method. The towed body is model as a rigid body with six degrees of freedom that seamlessly incorporated into the cable dynamics. The generalized alpha algorithm is applied as the time integration method. First, the sensitivity analysis of the different time integration methods and the number of elements impacting the dynamic response is conducted. Then, numerical simulations are conducted for different maneuvers, the straight tow and the U-turn tow, and the results are compared to the experimental sea trial data. The comparison results show the proposed approach matches the sea trial data well, and the prediction response based on the proposed method is reliable.

As being increasingly used for underwater explorations, Autonomous Underwater Vehicles (AUVs) are diversified in their structures and outlines to match up with various mission requirements, which brings challenges to the design of customized submerged docking stations. Aiming at providing a generalized solution, this paper proposes an omnidirectional and positioning-tolerant planar type AUV docking and charging platform, which has no constraints on AUV structures. In order to solve the planar-type docking issues, an integrated visual navigation and docking algorithm is developed for the miniaturized prototype AUV. The adopted monocular Simultaneous Localization and Mapping (SLAM) program takes charge of the wide-range underwater locationing, and handles practical problems such as scale drift and tracking failure. A combined control strategy of horizontal dynamic positioning and vertical visual servo docking is developed for the terminal docking process. The strategy is robust against constant water flow disturbance and performs stable docking using a roll motion adjustment. The visual navigation and docking performances and other system functions are successfully validated in simulation, water pool experiment, and sea trial.

The development of large scale model measurements for ship hydrodynamic tests in natural environment in China is presented in this paper. Previous works of testing large scale monoblock models for seakeeping performance performed by Harbin Engineering University (HEU) are reviewed at first. To verify whether it is acceptable to perform tests near the shore instead of in deep-ocean, coastal waves were measured at different locations in the Bohai Sea and the Yellow Sea of China, and were compared with theoretical spectra. Then, a description of large scale model set-up, testing equipments, and experimental procedure regarding the segmented self-propelled model project is introduced and some typical results obtained from a recent sea trial are presented. Moreover, testing results by a corresponding small scale model in a laboratory basin as well as numerical results are compared with the large scale model experimental results to validate that the proposed testing method is reliable. Finally an overview of the ongoing large scale model laboratory plan and its future development directions is prospected.

Path following control plays an essential role in improving accuracy of navigation and achieving a smooth motion control. However, the performance will exhibit large lateral errors caused by weak maneuverability, large time-lag, and large ocean current disturbance when the wave glider is gliding with a low and time-varying speed. An adaptive path following control integrated an adaptive line-of-sight (ALOS) algorithm and an improved artificial potential field (IAPF) algorithm was put forward in this paper, which could extremely guarantee path following accuracy. The adaptive control based a LOS was introduced to dynamically adjust a parameter of the LOS so that the output desired heading of the wave glider was on-time updated based on the velocity of the wave glider and path following error. The IAPF was applied to analyze and modify the output of the ALOS guiding the vehicle always convergent to the desired path, which could make a real time self-diagnosing, monitoring and correction in path following control. Following this, a closed-loop control was put forward with a dynamic model of the “Black Pearl” wave glider and the given path following control. The proposed control was verified by simulations and sea trials compared with conventional LOS, which demonstrated its effectiveness and long-term reliability.

Gate Rudder® system is a new type of energy-saving and manoeuvring device to provide additional thrust, similar to an accelerating ducted propulsor. Individual control of the twin rudder blades aside the propeller also provides enhanced manoeuvrability. Based on the first full-scale application on a domestic container vessel in Japan, the Gate Rudder® system improved the propulsive efficiency (by ~14% fuel saving in sea trials) as well as manoeuvring, noise and vibrations characteristics of this vessel. More power saving in-service condition was also reported as high as 20–30%. In summary, the power-saving measured with the ship system was more than the predictions based on the CFD analyses and model tests. This has prompted the authors with further investigations on the Gate Rudder® system by detailed CFD analyses and new model tests with a larger size model of this container ship conducted at the Ata Nutku Ship Model Testing Laboratory of Istanbul Technical University (ITU). This paper investigates the influence of the Gate Rudder® on the ship performance by using two different scales of models for the same container ship and the full-scale data which are complemented by the RANS based CFD analyses. The results from the study are discussed to shed light on the scale effect as well as providing further information on the powering performance prediction of vessels with the Gate Rudder® system.

Wind measurements made on ships are used for general navigation, maritime operations, and in some cases logged to support oceanographic research. They are particularly important for aircraft-carrying ships as operations can be restricted in certain wind conditions. Shipboard wind measurements are subject to biases and inaccuracies as a result of air flow changing as it passes over and around the ship, its structures, and features. Ship-induced wind distortion and the resulting bias on anemometer readings can range from insignificant to severe. Anemometer bias cannot be completely eliminated for all conditions, but it can be managed so that reliable and accurate assessments of wind at sea can be identified. This paper describes the basic concepts related to ship wind distortion along with procedures and considerations on how bias can be quantified using simulations or model tests and validated using sea trials. An example case of a helicopter-carrying frigate is used to demonstrate the process of quantifying bias, calculating metrics, determining useful ranges, and developing and applying correction-functions. Wind tunnel measurements and a sea trial successfully demonstrated and validated the proposed ship anemometer bias management methodology.

With the large progress in tidal current energy, the size of tidal current turbine (TCT) rotors has increased, leading to more substantial asymmetrical loads. In this study, severe asymmetrical loads were investigated by a sea trial experiment with a 600-kW two-bladed horizontal-axis TCT. Individual pitch control (IPC) has been recommended and validated to be effective for load reductions. Each blade is individually and actively controlled during IPC to compensate for asymmetrical loads within the rotational cycle. IPC has significant engineering implications but may cause partial energy loss under below-rated conditions. However, the conventional IPC method has limitations for two-bladed turbines. Thus, to alleviate the fatigue loads of two-bladed TCTs, a new IPC method based on vector analysis is presented in this paper. An integral sliding mode controller is designed for the proposed IPC to eliminate the phase lag resulting from the signal filter and actuator. To validate the feasibility and investigate the performance of the proposed sliding mode control (SMC) strategy, a collaborative simulation using GH-Bladed and Simulink was carried out. The comparative simulation results demonstrated the feasibility of the proposed IPC method and the better performance of the proposed SMC controller compared with a conventional PI controller.

Short-term deterministic sea wave prediction (DSWP) can facilitate the safe implementation of a number of maritime operations. Wave profile radars, based on the conventional X-band radars, have recently been proven to provide a low-cost convenient source of two-dimensional wave measurement for DSWP. The Golden Arrow sea trial in the North Atlantic was dedicated to collecting wave and vessel motion data for DSWP purposes, particularly under the large sea conditions that are of practical interest in marine operations. The field data were collected using a wave profiling radar and other measurement technologies for validation. This paper reports on the successful application of a recently developed technique by Al-Ani et al. in DSWP to the dedicated sea trial.

This paper addresses a state-of-the-art navigation system aided by an intelligent velocity model for autonomous underwater vehicle (AUV). It's critical to obtain a precise navigation for the safety and effectiveness of AUV missions. The reliability of AUV navigation-related sensors becomes particularly important, while the accuracy of sensors, especially the Doppler velocity log (DVL), which is easy to be interfered, affects navigation accuracy directly. However, standard AUV does not have redundant velocity sensors. Once DVL is invalid caused by fish movement, sound scattering, or DVL overrange, it will have a catastrophic effect on AUV missions. To improve navigation robustness and avoid the effects of DVL dropouts, an intelligent velocity model is proposed to assist navigation by using optimally pruned extreme learning machine. The performance of model-aided navigation system is evaluated on data from our research platform Sailfish 210 AUV during sea trials on the high seas of yellow sea, which achieve 0.5% navigation accuracy. In addition, the intelligent velocity model without modifying the model parameters is more flexible in model acquisition than the traditional vehicle dynamic model when AUV sensor distribution and AUV mass change. Results show that it is possible to improve accuracy and robustness of navigation as a redundant velocity information for standard AUV.