Search

Utility mining (UM) is an efficient technique for data mining which aim to discover critical patternsfrom various types of database. However, mining data can reveal sensitive information of individuals. Privacy preserving utility mining (PPUM) emerges as an important research topic in recent years. In the past, integer programming approach was developed to hide sensitive knowledge in a database. This approach required a significant amount of time for preprocessing and formulating a constraint satisfaction problem (CSP). To address this problem, we proposed a new algorithm based on a hash data structure which performs more quickly in itemsets filtering and problem modeling. Experiment evaluations are conducted on real world and synthetic datasets.

This article introduces a sensorless model predictive control (MPC) scheme for a grid-connected inverter with an inductive–capacitive–inductive ( LCL ) filter using only the grid-side current measurement. A state estimator and a disturbance observer are designed based on the Lyapunov stability theory to reduce the number of sensors and to eliminate the steady-state error. A cost function penalizing the state tracking error is used for the MPC design, and the optimal weights of the cost function are systematically obtained by solving a linear matrix inequality (LMI)-based optimization problem. The variation in grid impedance is taken into account in the LMI optimization. The stability analysis of the overall system is presented, and the frequency responses of the closed-loop and open-loop systems are presented to verify suppression of the filter resonance frequency component. The effectiveness and feasibility of the proposed controller are validated through frequency response analysis and comparative simulation results. Experimental results are also presented to demonstrate the efficacy of the proposed control scheme compared to the linear quadratic regulator method.

In addition to the mature renewable electricity production, solar fuels production possibly combined with fuel cells devices promises a sustainable and environmentally friendly solution to answer both the global ever-increasing energy demand and the damages to the biosphere brought by the abuse of fossil fuels. Countless efforts have been made in improving the individual materials and components required to drive the overall water splitting for solar H2 fuel production. However, the ultimate goal of this research field is the fabrication of operational devices and prototypes. Through the collaboration between the two laboratories in France and Vietnam, we successfully construct two types of unassisted solar fuels generators. The first device is a monolithic integrated PV-electrolyzer in artificial leaf configuration, which was made famous by D. Nocera (Harvard University), that is capable of producing hydrogen fuel through direct solar water splitting. The leaf features a pair of water electrolysis catalysts deposited on a commercial triple junction silicon solar cell through a novel self-assembly approach from a single deposition solution. The second device is a tandem hybrid photoelectrochemical cell based on a dye-sensitized photocathode and a BiVO4¬-based photoanode that can produce syngas without any external bias. Performance study of the devices was done employing an operando setup comprises of multiple potentiostats coupled with gas chromatography. It was shown that the artificial leaf exhibits comparable performance to the similar but more complex to fabricate one featured by D. Nocera. However, the degradation of the light harvesting unit in the electrolyte is a big problem and suitable protection is required to increase the overall stability of the device. For the tandem device, the photocathode is currently the limiting component due to desorption of the dye from the corresponding electrode. Nevertheless, the successful fabrication of the devices and the implementation of an experimental setup to monitor their important parameters during operation is a prominent milestone for future improvements., En parallèle de la production d’électricité renouvelable, la production de carburants solaires, éventuellement combinée à leur conversion ultérieure via des piles à combustible, est une solution durable et respectueuse de l'environnement à la fois pour répondre à la demande énergétique mondiale toujours croissante et éviter les dommages causés à la biosphère par l'utilisation de combustibles fossiles. De nombreux efforts ont été accomplis pour améliorer les composants individuels et matériaux capable d’effectuer les réactions conduisant à la production de tels carburants solaires. Cependant, l’objectif de ce champ de recherche reste la fabrication de dispositifs et prototypes opérationnels. Grâce à la collaboration entre deux laboratoires en France et au Vietnam, nous avons construit avec succès deux types de générateurs autonomes de carburants solaires. Le premier dispositif monolithique est un photo-électrolyseur intégré selon une configuration de feuille artificielle telle que popularisée par D. Nocera (Université d’Harvard) capable de produire de l'hydrogène par décomposition solaire directe de l'eau. La feuille renferme des catalyseurs bimétalliques d’anode et de cathode différents mais déposés en une seule étape grâce à la mise au point d’une solution de dépôt unique sur une cellule solaire commerciale à triple jonction en silicium. Le deuxième dispositif est une cellule photoélectrochimique tandem hybride qui renferme une photocathode à colorant et une photoanode à base de vanadate de bismuth qui, combinées, produisent sous irradiation du gaz de synthèse sans autre biais externe. L'étude des performances des dispositifs a été réalisée via leur instrumentation utilisant plusieurs potentiostats couplés à la chromatographie en phase gazeuse. Il a été montré la feuille artificielle atteint des performances comparables à d’autres dispositifs similaires décrit par D. Nocera mais plus compliqués à fabriquer. Cependant, la dégradation du composant photovoltaïque au contact de l'électrolyte est un gros problème et une protection appropriée sera nécessaire pour augmenter la stabilité globale du dispositif. Pour la cellule photoélectrochimique tandem, la photocathode limite actuellement les performances du dispositif en raison de la désorption du colorant de l'électrode. Néanmoins, la fabrication des dispositifs opérationnels et la mise au point d'une configuration expérimentale pour mesurer leurs paramètres de fonctionnement est une étape importante en vue d’améliorations futures de tels prototypes.

In this paper, the movements of the analytical models of complete underwater tracked vehicle (UTV) and cutter bar (CB) tool systems on a surface as well as their movements up and down a slope in the up-cutting mode operation are fully studied and analyzed. First, the mathematical expression of the mechanics, for which the forces, moments, and energy from the CB to the UTV are analyzed, is related. Next, analyses on the systemic parameters and their sensitivity are conducted to observe the variations of the operational and geometric parameters, as well as the cutter-tool and material-condition effects on the force, moment, and power components. Also, a design process composed of seven typical steps is proposed as the reference of a trencher-machine design. The important design parameters of the trenching machine such as the length of the CB, the nose radius of the CB, and the height of the pivot point are designed according to the proposed design process; furthermore, these parameters are used for the estimation of the slope-angle range when the trencher system is working on the slope. To demonstrate the application of derived equations to practical problems of the machine design, a number of numerical simulations are performed. Through the numerical simulations, the important parameters of the system such as the tangential force, Ft, the tractive thrust, H, the normal reaction, V, the cutting moment, Mc, the maximum carrier weight, W, and the available power are analyzed. From these, as a reference data for the designing of a trencher machine, the previous design of the system can be improved.

Hybrid underwater glider (HUG) is an advanced autonomous underwater vehicle with propellers capable of sustainable operations for many months. Under the underwater disturbances and parameter uncertainties, it is difficult that the HUG coordinates with the desired depth in a robust manner. In this study, a robust adaptive control algorithm for the HUG is proposed. In the descend and ascend periods, the pitch control is designed using backstepping technique and direct adaptive control. When the vehicle approaches the target depth, the surge speed control using adaptive control combined with the pitch control is used to keep the vehicle at the desired depth with a constant cruising speed in the presence of the disturbances. The stability of the proposed controller is verified by using the Lyapunov theorem. Finally, the computer simulation using the numerical method is conducted to show the effectiveness of the proposed controller for a hybrid underwater glider system.

This work was supported by the Geoscience Australia internship program, the Australian Department of Foreign Affairs and Trade, and the Australian Research Council through linkage Grant ARCLP110100525.

This paper presents an algorithm for docking a torpedo-shaped autonomous underwater vehicle (AUV). We propose a new docking assessment algorithm comprising three phases: depth tracking, docking-feasibility region analysis, and docking-success probability evaluation. For depth-tracking analysis, a neural network-generated path is used to satisfy constrained docking conditions of depth and distance. With regard to docking feasibility region analysis, the working space of the AUV can provide a possibility region of successful docking. In the analysis, working space is expressed by a turning ellipsoid, which is the numerical solution of the maximum yawing motion. An algorithm is presented to evaluate the probability of docking success, based on the probability of sensor data. A good contribution of this approach is that a criterion for assessing the feasibility of the desired path for docking is given through the proposed docking assessment algorithm.

Unmanned underwater vehicle (UUV) is a type of robot that operates underwater for multi purposes such as underwater exploration purpose, hydro-meteorological exploration, and military purposes…. One of the most important part in the UUV is its thruster. This paper presents the design, analysis and control results of an underwater thruster of 300 W, which can be used for a small-sized UUV. The underwater thruster is designed by integrating different modules and built according to each system from mechanical design, hardware design, and control algorithm to ensure the thruster can operate underwater continuously in the depth of 100 m lifespan (equal to 145 psi) for long time. The thruster use magnetic coupling for waterproof and also can perform the overload protection for thruster. The housing and magnetic coupling were analyzed by using finite element analysis to optimize the thickness of the housing in deep water level. The mathematical model and simulation result of the speed control using PID and Fuzzy controllers are also presented.

Underwater vehicle-manipulator system (UVMS) has been known as the useful underwater vehicle to perform various tasks under the water. When the UVMS performs the manipulative operation, the movement of manipulator causes stability problems of the UVMS system. To solve this problem, an algorithm for stabilizing the UVMS is necessary. In this paper, Zero Moment Point (ZMP) algorithm is used to improve the stability of the UVMS while the manipulator tracks the given trajectory. Since the UVMS system is the redundant system, some constraints for optimal purposes are necessary. For this, the distance between the ZMP and the mass center of the vehicle is adopted as the performance index. Gradient Projection Method (GPM) is used to minimize the performance index through null space solution of the redundancy resolution. Finally, simulation and experiment will be conducted to verify the algorithm.

Underwater Glider is now the powerful tool for ocean sampling using torpedo shape. Inspired by the manta ray with their effective maneuverability, the ray-type underwater glider is developed with a dual buoyancy engine and a movable mass. The shape of this platform allows for larger payload of battery and sensors. The analysis of fluid resistance performance is carried out through Computational Fluid Dynamics (CFD) for the optimum shape. Simulation of gliding dynamics of ray-type glider is studied for understanding the advantage of what nature has already done for the shape of the manta ray.

Underwater Vehicle-Manipulator System (UVMS) is a useful system to perform diverse and sophisticated operations under the water. However it is difficult to control the motion of UVMS due to external disturbances such as payloads holding underwater objects, currents, etc. In this paper, in order to ensure the dynamic stability of the UVMS, redundancy resolution method is proposed using a zero moment point (ZMP) algorithm. In order to evaluate the proposed ZMP algorithm and redundancy resolution method, a testbed composed of redundant manipulator was developed. The results show that ZMP algorithm helps the stability of the UVMS while the end-effector of the manipulator tracks the desired trajectory accurately.

This paper presents the modeling of a new ray-type hybrid underwater glider (RHUG) and an experimental approach used to robustly and adaptively control heading motion. The motions of the proposed RHUG are divided into vertical-plane motions and heading motion. Hydrodynamic coefficients in the vertical-plane dynamics are obtained using a computational fluid dynamics (CFD) method for various pitch angles. Due to the difficulty of obtaining accurate parameter values for the heading dynamics, a robust adaptive control algorithm was designed containing an adaptation law for the unknown parameters and robust action for minimizing environmental disturbances. For robust action against bounded disturbances, such as waves and ocean currents, sliding mode control was applied under the assumption that the bounds of the external disturbances are known. A direct adaptive algorithm for heading motion was applied in an experiment. Computer simulations of the proposed robust adaptive heading control are presented to demonstrate the robustness of the proposed control system in the presence of bounded disturbances. To verify the performance of the proposed controller for heading dynamics, several heading control experiments were conducted in a water tank and in the sea.

The underwater vehicle-manipulator system (UVMS) is basically a redundant system. Hence, this redundant system can have various combinations of joint velocities that do not affect the given velocity profile of an end-effector and this may induce a self-motion of a vehicle. In the current paper, the performance index based on the concept of Zero Moment Point(ZMP) is proposed to enhance the stability of the redundant UVMS while the specified task is performed by using the underwater manipulator. In order to generate the joint angle trajectories of the manipulator, a redundancy resolution is performed to minimize the distance between the position of ZMP and the mass center of the underwater vehicle, which means the propulsion energy for controlling the vehicle's motion can be reduced. To control the motion of the system with uncertainties, a controller based on the sliding mode theory has been designed. Finally, an example simulation of a simple UVMS is conducted to show the performance of the designed robust controller.

This paper presents a steering and diving control of an autonomous underwater vehicle (AUV) platform named KAUV, which is designed as a torpedo with light weight and small size. Through a unique ducted propeller and rudder located at the aft, the KAUV can perform horizontal motion. It also control pitch angle and depth motion with an inside mass shifter mechanism which changes the vehicle center of gravity. Because the system to be controlled is highly nonlinear, a sliding mode control (SMC) is constructed to compensate the effects of modeling nonlinearity, parameter uncertainty, and disturbance. This proposed control algorithm is derived from the linearized vehicle dynamics for steering and diving planes. To check the response of the vehicle system with the developed controllers, a series of simulation results are also simulated and presented.