Optimal control of the heave motion of marine cable subsea-unit systems

One of the key problems associated with subsea operations involving tethered subsea units is the motions of support vessels on the ocean surface which can be transmitted to the subsea unit through the cable and increase the tension. In this paper, a theoretical approach for heave compensation is developed. After proper modelling of each element of the system, which includes the cable/subsea-unit, the onboard winch, control theory is applied to design an optimal control law. Numerical simulations are carried out, and it is found that the proposed active control scheme appears to be a promising solution to the problem of heave compensation

Learning-based ship design optimization approach

With the development of computer applications in ship design, optimization, as a powerful approach, has been widely used in the design and analysis process. However, the running time, which often varies from several weeks to months in the current computing environment, has been a bottleneck problem for optimization applications, particularly in the structural design of ships. To speed up the optimization process and adjust the complex design environment, ship designers usually rely on their personal experience to assist the design work. However, traditional experience, which largely depends on the designer’s personal skills, often makes the design quality very sensitive to the experience and decreases the robustness of the final design. This paper proposes a new machine-learning-based ship design optimization approach, which uses machine learning as an effective tool to give direction to optimization and improves the adaptability of optimization to the dynamic design environment. The natural human learning process is introduced into the optimization procedure to improve the efficiency of the algorithm. Q-learning, as an approach of reinforcement learning, is utilized to realize the learning function in the optimization process. The multi-objective particle swarm optimization method, multiagent system, and CAE software are used to build an integrated optimization system. A bulk carrier structural design optimization was performed as a case study to evaluate the suitability of this method for real-world application

A test case generation approach for mobile APPS based on context and GUI events

The increase of mobile devices with rich innovative feature has become an enabler for developing mobile applications (mobile apps) that offer users an advance and extremely-localized context-aware content. Nowadays mobile apps are developed to address more critical areas of people’s daily computing needs, which bring concern on the applications’ quality. In order to build a high quality and more reliable applications, there is a need for effective testing techniques to test the apps. The most recent testing technique focuses on graphical user interface (GUI) events with little attention to context events. This makes it difficult to identify other defects in the changes that can be inclined by context in which an application runs. The major challenge in testing mobile apps that react to context events is how to identify the events from an application during testing. This study proposes an approach (named TEGDroid) for testing mobile apps considering the two sets of events: GUI and context events. This approach comprises five steps which are; extraction of resources from APK file, static analysis of the extracted app’s byte code to identify GUI events, analysis of mobile apps’ permission to identify different scenarios of context events, generation of test case based on the GUI and context events and validation of the test cases using code coverage and mutation testing. Experiment was performed on real world open source mobile apps to evaluate TEGDroid. Results from the experimental evaluation indicates that the approach is effective in identifying context events and had 61%-91% coverage across the seven (7) selected applications. Results from the mutation analysis shows that 100% of the mutants were killed. This indicates that TEGDroid have the capability to detect faults in mobile apps

Sustainable seabed mining: guidelines and a new concept for Atlantis II Deep

The feasibility of exploiting seabed resources is subject to the engineering solutions, and economic prospects. Due to rising metal prices, predicted mineral scarcities and unequal allocations of resources in the world, vast research programmes on the exploration and exploitation of seabed minerals are presented in 1970s. Very few studies have been published after the 1980s, when predictions were not fulfilled. The attention grew back in the last decade with marine mineral mining being in research and commercial focus again and the first seabed mining license for massive sulphides being granted in Papua New Guinea’s Exclusive Economic Zone.Research on seabed exploitation and seabed mining is a complex transdisciplinary field that demands for further attention and development. Since the field links engineering, economics, environmental, legal and supply chain research, it demands for research from a systems point of view. This implies the application of a holistic sustainability framework of to analyse the feasibility of engineering systems. The research at hand aims to close this gap by developing such a framework and providing a review of seabed resources. Based on this review it identifies a significant potential for massive sulphides in inactive hydrothermal vents and sediments to solve global resource scarcities. The research aims to provide background on seabed exploitation and to apply a holistic systems engineering approach to develop general guidelines for sustainable seabed mining of polymetallic sulphides and a new concept and solutions for the Atlantis II Deep deposit in the Red Sea.The research methodology will start with acquiring a broader academic and industrial view on sustainable seabed mining through an online survey and expert interviews on seabed mining. In addition, the Nautilus Minerals case is reviewed for lessons learned and identification of challenges. Thereafter, a new concept for Atlantis II Deep is developed that based on a site specific assessment.The research undertaken in this study provides a new perspective regarding sustainable seabed mining. The main contributions of this research are the development of extensive guidelines for key issues in sustainable seabed mining as well as a new concept for seabed mining involving engineering systems, environmental risk mitigation, economic feasibility, logistics and legal aspects

The Response of Pile-Guided Floats Subjected to Dynamic Loading

INE/AUTC 14.10 (Volume 1) and INE/AUTC 14.10b (Volume II Annex

Response of pile-guided floats subjected to dynamic loading

Pile-guided floats can be a desirable alternative to stationary berthing structures. Both floats and guide piles are subjected to time varying (dynamic) forces such as wind-generated waves and impacts from vessels. There is little design information available concerning the dynamic load environment to which the floats will be subjected. So far, the most widely acceptable method used in offshore structure design is the Kinetic Energy Method (KEM). It is a simplified method that is based on the conservation of energy. This approach is straightforward and easy to implement. However, in spite of its simplicity and straightforwardness, the method lacks accuracy. The intent of this project is to develop a rational basis for estimating the dynamic response of floating pile-guided structures, providing necessary insight into design requirements of the guide-piles. In this study, the Dynamic Analysis Method (DAM) will be used to model the dynamic responses of the system. MATLAB codes are written to help calculate the analytic and numerical values obtained from the dynamic models. For the purpose of validation, results from the two systems should be compared to a comprehensive dynamic analysis model created with the ANSYS AQWA Software

Key Challenges and Opportunities in Hull Form Design Optimisation for Marine and Offshore Applications

New environmental regulations and volatile fuel prices have resulted in an ever-increasing need for reduction in carbon emission and fuel consumption. Designs of marine and offshore vessels are more demanding with complex operating requirements and oil and gas exploration venturing into deeper waters and hasher environments. Combinations of these factors have led to the need to optimise the design of the hull for the marine and offshore industry. The contribution of this paper is threefold. Firstly, the paper provides a comprehensive review of the state-ofthe- art techniques in hull form design. Specifically, it analyses geometry modelling, shape transformation, optimisation and performance evaluation. Strengths and weaknesses of existing solutions are also discussed. Secondly, key challenges of hull form optimisation specific to the design of marine and offshore vessels are identified and analysed. Thirdly, future trends in performing hull form design optimisation are investigated and possible solutions proposed. A case study on the design optimisation of bulbous bow for passenger ferry vessel to reduce wavemaking resistance is presented using NAPA software. Lastly, main issues and challenges are discussed to stimulate further ideas on future developments in this area, including the use of parallel computing and machine intelligence

Maintenance/repair and production-oriented life cycle cost/earning model for ship structural optimisation during conceptual design stage

The aim of this paper is to investigate the effect of the change in structural weight due to optimisation experiments on life cycle cost and earning elements using the life cycle cost/earning model, which was developed for structure optimisation. The relation between structural variables and relevant cost/earning elements are explored and discussed in detail. The developed model is restricted to the relevant life cycle cost and earning elements, namely production cost, periodic maintenance cost, fuel oil cost, operational earning and dismantling earning. Therefore it is important to emphasise here that the cost/earning figure calculated through the developed methodology will not be a full life cycle cost/earning value for a subject vessel, but will be the relevant life cycle cost/earning value. As one of the main focuses of this paper is the maintenance/repair issue, the data was collected from a number of ship operators and was solely used for the purpose of regression analysis. An illustrative example for a chemical tanker is provided to show the applicability of the proposed approac

Multi-Phase Fault Tolerant PMSM Drive Systems

The drive to develop electric machines with a wide constant power-speed range (CPSR), high torque capabilities, excellent efficiency, superior reliability, and a reduced environmental footprint for EV traction and ship propulsion systems has led to research interest in various Permanent Magnet Synchronous Motors (PMSM). One particular area of interest is multi-phase fault tolerant PMSM drive systems, which are integral to the development of electric traction systems with all-inclusive motors that include sensors, inverter modules, and a cooling system, much like an automobile engine. Furthermore, these designs simplify fault condition maintenance because their independent single-phase structure allows them to be used with replaceable modular inverter units which have one H-bridge for each phase. In order to provide high reliability for the PMSM drive systems, even in a fault condition, simple but effective current control methods are necessary. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters through a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters though a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems