Ship Applications Research Articles

COLREGs-Compliant Unmanned Surface Vehicles Collision Avoidance Based on Multi-Objective Genetic Algorithm

Autonomous ships or Unmanned Surface Vehicles (USV) collision avoidance and path planning problems among multi-vessels are investigated in this paper. Firstly, a modified fuzzy dynamic risk of collision model based on time and space collision risk index is proposed, which is much closer to real ship applications. Then, the fitness functions based on the risk of collision, navigational economy, International Regulations for Preventing Collisions at Sea 1972 (COLREGs) and collision avoidance timing are established respectively to ensure the rationality of ship collision avoidance decisions. Moreover, path planning with global search capability is realized by the multi-objective decision theory combined with a genetic algorithm. The practicability and rationality of the recommended trajectory are guaranteed. Meanwhile, the problem of the non-inferior solution can be addressed by adapting the weight method and the constraint method and the optimized solution of the decision-making system can be achieved finally. Simulation results are further presented to validate the effectiveness of the proposed path planning and collision avoidance methods.

A Ship Is a Microgrid and a Microgrid Is a Ship: Commonalities and Synergies [About This Issue

This issue combines these two applications, marine systems and microgrids, and looks at possible synergies and commonalities. First, the Technology Leaders column, Shipboard Electric Power Conversion: System Architecture, Applications, Control, and Challenges by Pramod Ghimire, Daeseong Park, Mehdi Karbalaye Zadeh, Jade Thorstensen, and Eilif Pedersen, describes the impact of power electronics on the evolution of ship applications. Power electronics is the main driver enabling the decarbonization of both the whole energy system and maritime applications. The process started about 30 years ago, with solutions such as the retrofit of the Queen Elizabeth II in 1988, which introduced electric propulsion.

Smart Resistor: Stabilization of DC Microgrids Containing Constant Power Loads Using High-Bandwidth Power Converters and Energy Storage

Power electronic converters and electric motor drives have found increased application in dc microgrids, electric automobiles, and ships. Such converters when driving loads in a regulated fashion act as constant power loads (CPLs). These CPLs can cause destabilizing effects on the grid because of their negative incremental impedance. This paper proposes a method to dynamically stabilize CPLs at the point of load by making them behave as adaptive Smart Resistors by using high-bandwidth power converters and energy storage units. These Smart Resistors can work with smart sources to realize ultimate intelligent power networks. The control strategies needed to achieve the concept, including voltage and current trajectory control principles, are analyzed and validated with a hardware test setup.

Study of constrained nonlinear thrust allocation in ship application based on optimization and SOM

The constrained nonlinear thrust allocation problem in ship application is studied in this work, based on optimization and multivariate analysis. The optimization models in the previous works have been reviewed and a new model is proposed. In order to reduce the complexity of searching space, slack variables are discarded based on optimization equivalence. Only two components of fuel consumption generated from real thrusts and rotations of azimuth thrusters are considered. The singularity avoiding is achieved by adding the rank constraint of the configure matrix, rather than just adding into objective function through weight. Additional computation mechanism, Multi-Start is added to the traditional sequential quadratic programming (SQP) to enhance the global searching ability. A newly developed metaheuristic algorithm, mine blast algorithm (MBA) is used for finding the solution of new model. Its improved version, IMBA, which aims to strengthen the searching ability in exploitation phase, is also investigated. Moreover, the multiobjective optimization concept is introduced for thrust allocation. The Pareto set of fuel consumption from thrust and rotation is studied then. Finally, the hidden information in the optimization model is mined through a widely used data mining technique, self-organizing map (SOM). A remote operated vessel (ROV) example is employed in this work to illustrate the above analysis procedure. The results show that the discard of slack can be reasonable without degrading the accuracy of the model. The objective function of new model has clear physical meaning. SQP combined with Multi-Start mechanism is an effective way to find close to global solution. Metaheuristic algorithms can treat any fitness functions and should be given further considerations. Some new insight can be obtained from multiobjective optimization problem analysis and data mining.

An efficient neural-network based approach to automatic ship docking

Automatic ship docking is one of the applications of autonomous ships. How to realize autonomous low-speed maneuver under environmental disturbances for docking is the fundamental problem at present. This paper presents an efficient approach based on artificial neural network (ANN) for automatic ship docking. The problem is formulated and well-modeled for simulating ship docking operation. A joystick implementation in simulation provides manual maneuvering and thus enables collection of sufficient and reliable data from successful maneuvers. To keep consistent with the manual control, an ANN with two parallel structure is proposed to control the ship’s thrust and rudder, respectively. Feature selection technique and genetic algorithm (GA) are utilized to optimize the structure and reduce the training cost. Numerical simulations under different environmental disturbances, including no wind, constant wind and dynamic wind are carried out. The results show the ship is able to reach the dock smoothly, which confirms the effectiveness of the proposed approach.

A New Submersion Detection Sensor Using Two Resistance Temperature Detectors Operating on the Thermal Equilibrium Principle.

In this study, a new submersion detection sensor with improved reliability and stability is proposed. The new sensor uses two Resistance Temperature Detectors (RTDs) and operates on the thermal equilibrium principle. The submersion detection sensor controls two RTDs that maintain a constant temperature difference between them in the surrounding environment. The first RTD is used as a reference sensor to measure ambient temperature and the second RTD is supplied with higher current than the reference sensor for self-heating. When submerged, because the thermal conductivity and convective heat transfer coefficient of water are higher than that of air, the temperature difference between the two RTDs is lower in water than in air based on the thermal equilibrium principle. Under these conditions, a submersion detector with a signal conditioning circuit detects these temperature differences. The static performance of the proposed sensor was evaluated by checking whether malfunctions occurred at varying ambient temperatures, differing humidities, and when there was rainfall. In addition, the dynamic performance was evaluated using the response time at varying ambient air temperatures before submersion and with changing water temperatures after submersion, as a metric. The proposed submersion detection sensor is expected to find useful application in aircrafts, ships, and various other industrial fields.

Ro-Ro Kargo Gemisi İçin Tanımlanan Kurutuculu Buharlaşmalı Soğutma Sistemlerinin Termodinamik Analizi

This study presents the results of thermodynamic feasibility of the new desiccant- evaporative- cooling system for an air conditioning application in ships. The desiccant- evaporative- cooling system is characterized by energy efficiency and low environmental impact. In this work, thermodynamic possibility to install desiccant cooling system (DCS) has been studied for a M/V ASSTAR Trabzon Ro-Ro cargo vessel, by using fraction of the heat rejected by existing on-board engine. The baseline system is incorporated a desiccant dehumidifier, a heat exchanger, an indirect evaporative cooler, and a direct evaporative cooler. The system offered sufficient sensible and latent cooling capacities for a wide range of climatic, while allowing in flux of outside air in excess of what is typically required for Ro-Ro cargo vessel. The present work aims at identifying the parameters of the system cycle and investigates their effect on the performance of the waste-heat driven cooling systems. And, the effect of different return air flow rates usage on the system performance is another aspect of the study. Two approaches for mixing of the return air and outside air are introduced; one is consists of two recirculation cycles, other one is a ventilation cycle, all of them have been examined and demonstrated. The maximum coefficient of performance (COP) of a waste-heat driven cooling cycles were determined by assuming that the cycles are totally reversible.

A Study of Fiberglass Material with Different Compositions

Fiberglass composites are widely used in different applications of aerospace, automotive, sports, ships and constructional work due to having higher demands. These are having many advantages due to their low cost of production, easy to fabricate, light weight, higher strength to weight ratio. The objective of the work is to study the The Mechanical properties of fiberglass without filler at different fiberglass loading, and the effect of different fiber loading and filler content on the mechanical properties like hardness, Flexural property, tensile strength and impact property etc and the mechanical and abrasive behaviour of coated and uncoated E-glass fiber reinforced epoxy based composites. A study is also performed to study the effect of various factors on the sliding wear behaviour of the composites and the Surface morphology of composites before and after the tensile test was studied by optical microscope.

Techno-economic analysis of PV systems integrated into ship power grid: A case study

The integration of a photovoltaic (PV) system into a ship power grid has recently become an important strategy of saving energy and reducing emissions from ships. Since the close relationship between the energy derived from the PV system and the navigation plans of ships including location, navigation routes and times, the techno-economic evaluation of the PV systems integrated into ship power grid is very important to ensure their proper application in ships. In this study, a ship-PV grid-connected power system incorporating in the COSCO TENGFEI pure car and truck carrier is selected as a case to conduct a comprehensive techno-economic analysis and an environmental performance assessment based on single and multi-criteria evaluation methods. Taking into account the uncertainty of navigation plan, the techno-economic efficiency of the power system along six main navigation routes are evaluated separately. The evaluation results show that the hybrid power system has high financial feasibility and environmental performance. Furthermore, the Asia-Malacca-Gibraltar-Europe navigation route has the best feasibility while the Asia-Bering-Europe navigation route has the worst feasible among the six main navigation routes. This case study provides a reliable reference for investment of hybrid power system.

Multi-attribute decision-making method for prioritizing maritime traffic safety influencing factors of autonomous ships’ maneuvering decisions using grey and fuzzy theories

Ship maneuvering decisions are influenced by several factors, and it is essential to prioritize the main influencing factors for efficient selection of the corresponding maneuvering decisions. Meanwhile, the autonomous ship maneuvering decision-making influencing factors constitute a typical grey system, which is suitable for research by grey relational analysis. Furthermore, in the fuzzy approach, linguistic assessment of factors is evaluated to obtain priorities numbers. Therefore, this study mainly focuses on the concept of human-like maneuvering for autonomous ships. Based on experimental data of experienced seafarers and using a simulation platform under the scenario of the Shanghai Waigaoqiao wharf, an inference model utilizing grey and fuzzy theories is proposed. The proposed model combined with expert linguistic terms in order to select the ship maneuvering decision-making main influencing factors from multi-source influencing factors (in overall and separated categories of natural environment, ship motion, force parameters, draft, and position), and to study the decision-making prioritization for maritime traffic safety for specific ship maneuvering scenarios. This method can prioritize the main factors which affect maneuvering decisions as well as guide an autonomous ship-assisted or automatic maneuvering evaluation system for the research of human-like maneuvering behavior. This study provides a new perspective on the identification of main ship maneuvering decision-making influencing factors in theory and in practice. It can be utilized for better decision-making concerning maritime traffic safety of autonomous ship maneuvering, which in turn makes shipping safer and promote the application and spreading of autonomous ships.

Multi-objective design optimization of combined cooling, heating and power system for cruise ship application

In recent years, the size (weight and volume) of cruise ships are experiencing spectacular increase, coherently with the increase in energy consumption and carbon emissions. However, the regulations about pollutant emissions imposed by the International Maritime Organization are becoming more and more strict. In order to face up to this issue, the energy system of cruise ships is constantly being modified. In this paper, the structure of the cruise ship's energy system with multiple facilities such as an internal combustion engine, gas turbine, dual fuel engine, PV panels, and the wind turbine is pre-established. Then, a multi-objective mathematical programming model is formulated to determine the selection and capacity of facilities with minimal total annual cost and size, while the emissions, energy balance and technical constraints are taken into account. By adopting the augmented ε-constraint method, the design and operation strategies could be obtained. As an illustrated example, the model is applied to a real cruise ship, and the Pareto frontier could provide ship designers with well-balanced solutions based on economic and size priorities, and with the increase in the proportion of size objective, the total annual cost increases and size decreases gradually. Compared with the reference energy system, the optimal energy system could reduce the total annual cost by 12.6% if only the economic objective is considered and reduce the size by 21.1% if only the size objective is considered. In multi-objective condition, the CO, NOx, and SOx emissions could be reduced by 29.1%–61.3%, 42.8%–61.3%, and 42.8%–61.3% per year, respectively. Moreover, a sensitivity analysis is conducted, and the result shows that the size and consumption cost of Marine Gas Oil (MGO) and Liquefied Natural Gas (LNG) are more sensitive to the change of the proportion of size objective compared to Heavy fuel oil (HFO) and Marine diesel oil (MDO).

Research Status and Development Trend of Path Planning Algorithm for Unmanned Vehicles

With the wide application of unmanned ships in the fields of water surface bleaching, sea exploration, water quality monitoring and emergency rescue, unmanned ship technology has attracted more and more people’s attention. Due to the navigation environment of unmanned ship is very complex, diverse and changeable, it has become the primary task of unmanned ship technology research to study how to use path planning algorithm to integrate a large number of multi-sensor data, quickly and accurately make navigation strategies and achieve accurate motion control. This paper mainly summarizes the current research status of unmanned ship path planning algorithms, analyzes the differences and advantages of various path planning algorithms in practical applications, and finally points out the research trend of unmanned ship path planning algorithms.

Novel Lightweight Semi-Finished Products Made of Poplar Veneer Plywood with Basalt Fibre Reinforcement

Veneer plywood is established in building construction, interior finishing and vehicle construction. Particularly in automotive or ship interior applications, the requirements with regard to strength and stiffness properties are increasing. At the same time, the weight of the panel materials used is to be reduced. The development presented here is a new type of lightweight basalt fibre-reinforced poplar veneer plywood and at the same time rigid alternative to the established birch veneer plywood. By adapting the adhesive and the reinforcing semi-finished products, the material and manufacturing costs are comparatively low. The bonding of the fibre reinforcement to the carrier material is achieved by means of adapted wood adhesives (e.g. polyvinyl acetates), which are also used as matrix material for the fibre reinforcement. An application of the reinforcement layer is integrated into the coating process (e.g. with High Pressure Laminate HPL decorative fabrics) of the carrier material. Essential advantages compared to conventional board materials are shown in this paper. The research results were achieved at the Institute for Structural Lightweight Construction of the TU Chemnitz in cooperation with the company Toms Gerber GmbH within the ZiM cooperation project FuBa.

Prediction of Self-Propulsion Performance of Ship Model with Double L-Type Podded Propulsors and Conversion Method for Full-Scale Ship

In this study, the self-propulsion performance of a ship model with double-L-type podded propulsors was predicted. Additionally, a conversion method for the performance of a full-scale ship was established based on the correction method published by the International Towing Tank Conference (ITTC) for the scaling effect of a single podded propeller and research reports on pod tests conducted by different ship research institutes. The thrust deduction and wake fraction of the ship were also analyzed. Furthermore, the self-propulsion performance of a full-scale ship with double L-type pods was determined, the full- and model-scale ships compared in terms of their flow fields and pressure charts, and the influence of the scaling effect analyzed. In addition, the calculation results were compared with the conversion results of a full-scale ship, and the reliability of the method adopted for the performance estimation of a full-scale ship with double podded propulsors was verified. The findings reported herein can provide statistics and technical support for the design of L-type podded propulsors and their application in full-scale ships, which are of theoretical significance and practical value in the engineering domain.

Investigations on in-process control of penetration depth for high-power laser welding of thick steel-aluminum joints

Over the last few decades, the demand for lightweight constructions has been increased continuously for several industrial applications, like automotive and ship building, to reduce the weight of vessels in order to minimize the CO2 emissions as a result of a lower fuel consumption. Lightweight construction is almost applied for ship applications, especially for yachts, which are designed by using aluminum for the deck constructions and steel for the ship hull. For joining these parts, a high-power laser welding process shall be developed. However, the welding of these dissimilar materials is associated with great challenges, due to the different physical properties and the formation of hard and brittle intermetallic phases, which may influence negatively the properties of the weld seam. The quality of dissimilar joints depends strongly on the mixture ratio between the molten amount of steel and aluminum. However, the mixture ratio varies over the weld seam length due to a high dynamic of the keyhole resulted by welding of this material combination. Furthermore, different batches of materials and varied sheet thicknesses t may influence the mixture ratio. In this study, a high-power laser welding process is developed with in-process control of the penetration depth tP by analyzing the spectral process emissions for dissimilar lap joints of aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5–7 mm). In the context of these investigations, an increase of occurring cracks within the weld seam and ejections of molten material with increasing penetration depth tP can be observed. To achieve a relative high joint strength, the penetration depth tP must be kept constant at a value of 1.4 mm. In case of varied batch of material, thickness t of the used sheets, welding speed vS, and leap of the steel sheet thickness t, the penetration depth tP requested cannot be achieved. Using the in-process control of the penetration depth tP, the weld seam quality remains almost constantly over the weld seam length, as shown in visual inspections, metallographic analyses, profiles of the penetration depth tP, and tensile shear testing. Among other things, the appearance of ejections of molten material can be avoided by using the in-process control of the penetration depth tP.

Energy efficiency analysis of inland ship photovoltaic system based on PVsyst

With the current energy crisis and environmental pollution increasing, expanding the use of solar energy is an important trend in the field of energy applications, and the development of photovoltaic systems in the ship field is also very rapid. This paper analyzes the photovoltaic power generation application of inland small ships, designs a photovoltaic power generation system suitable for passenger ships, simulates and optimizes the system with PVsyst software, predicts the power generation and loss of the system, and verifies its value.

A Simplified Space Vector Pulse Width Modulation Implementation in Modular Multilevel Converters for Electric Ship Propulsion Systems

The modularity, fault-tolerability, and voltage scalability features allow the modular multilevel converter (MMC) to be a promising topology for modern electric ship applications. Arm voltage and submodule (SM) capacitor voltage balancing controllers with conventional high-frequency modulation schemes are indispensable for reliable and stable operation of an MMC. This requires an additional external arm controller and the control complexity increases for an MMC with a large number of SMs. Alternatively, the space-vector pulse width modulation (SVPWM) schemes provide more freedom in selecting the voltage vectors to achieve multiple objectives, thus eliminating the arm voltage balancing controller. In this paper, a simplified SVPWM implementation for an $n$ -level MMC is proposed. This scheme utilizes all the available switching states and calculates switching timings by mapping to a two-level space-vector structure. The computational burden of the proposed scheme is independent of converter voltage level, therefore it is computationally efficient and well suited to the MMC with any number of SMs. Experimental results are presented to show the performance of an MMC system using the proposed scheme under steady-state, rapid acceleration and speed-reversal conditions.

Smart Ship Application Platform (SSAP) Project to Advance Ship-Shore IoT System

Smart Ship Application Platform (SSAP) Project to Advance Ship-Shore IoT System

Design of green water quality monitoring vessel based on dual operation mode

Aiming at the heavy workload of water quality monitoring on waters like inland rivers and lakes and the shortage of small-scale surface water quality monitoring equipment, a green water quality monitoring vessel was designed and developed based on dual operation mode from the perspective of practicability. The overall design scheme was put forward, the structure design and function development were completed, the dynamic performance analysis was carried out by using the simulation software such as Ansys, and the performance index of the water quality monitoring vessel for normal operation was obtained. Through the prototype production and launching experiments, the control and function realization of the designed water quality monitoring vessel were verified, which provided the basis for real ship application.

Research on the Improvement Effect and Mechanism of Micro-Scale Structures Treated by Laser Micro-Engraving on 7075 Al Alloy Tribological Properties.

During various applications in aerospace, ships, autos, and aircraft, 7075 Al alloy will frequently contact other materials, and therefore suffer from slight abrasion. However, the poor tribological properties of 7075 Al alloy greatly affect its performance and life length, leading to limitations in its application. Preparing roughness structures on the surface is regarded as a promising method to improve the properties of materials. However, the tribological properties of 7075 Al alloy cannot be enhanced significantly by roughness structures in complex dynamic changeable environments, owing to the incomplete understanding of the effect of roughness structures. Given the above issues, in this paper, micro-scale structures (linear grooves, gridding grooves, and arc grooves) were designed and prepared on 7075 Al alloy surfaces by a surface treatment (laser micro-engraving), which provides excellent controllability of the morphology and dimensions of as-prepared roughness structures. The tribological properties of the as-prepared surfaces were investigated systemically. The effect of micro-scale structures on the tribological properties was studied. The wear mechanism and tribological properties improvement mechanism of the surfaces were clarified. Furthermore, the effect degree of the enhancement factors of the micro-scale structures on the tribological properties was explored under different conditions. The results indicate that the micro-scale structures play an important role in improving the tribological properties of Al alloy under different sliding speeds. The improvement mechanism can be summarized by four factors. However, the effect degrees of these factors on the tribological properties exhibit considerable differences. This study not only develops specific micro-scale structures that can dramatically improve the tribological properties of 7075 Al alloy under different conditions, but also offers guidance for the construction of appropriate roughness structures that can dramatically improve the tribological properties of Al alloy according to the friction conditions.