Les bateaux sport sont conçus pour performer à haute vitesse, mais au détriment de la maniabilité à basse vitesse. Un système de propulsion omnidirectionnel et contrôlé par un joystick trois axes est présenté pour améliorer la maniabilité du bateau à basse vitesse. Le bateau est équipé de deux pompes à jet. La propulsion s'effectue en redirigeant l'écoulement des pompes dans un ensemble de jets d'eau autour de la coque. Chaque jet est équipé d'une valve et est fixé selon une position et un angle qui optimise la maniabilité, tel qu'évalué par un index basé sur l'omnidirectionnalité. Afin d'exécuter une commande de force en provenance du joystick, on contrôle les valves et le régime des pompes à jet pour moduler le débit et donc, la poussée à chaque jet. L'optimisation du système de propulsion et la conception de la loi de contrôle s'appuient sur un modèle de propulsion qui calcule la force des jets au centre de masse pour une configuration de valves et de régimes moteurs. L'inversion du modèle de propulsion est l'étape principale pour la conception de la loi de contrôle. Un outil de simulation en 3D permet de valider différents paramètres de conception. Le simulateur sert aussi de plateforme pour le développement d'algorithmes de contrôle plus sophistiqués.Les résultats expérimentaux démontrent l'atteinte des critères de conception pour la propulsion omnidirectionnelle.

Unlike conventional propellers, flapping wings may generate large amplitude oscillating forces, which can make them difficult to incorporate into a craft design. This is particularly true for a single, vertically oscillating hydrofoil, as part of a surface water craft where the cyclic lift of the hydrofoil disrupts the craft stability. This thesis begins by reviewing the history of human-powered watercraft with a focus on those having flapping foil propellers. This review combined with a review of the literature provides a balanced overview on how flapping wing propellers are currently designed. Current literature shows that although the mean performance of an oscillating foil has been determined in terms of the Strouhal number and the angle of attack, relatively little describes performance directly in terms of the foil motion. Hence, predicting temporal hydrodynamic forces acting on an oscillating foil is difficult. This provides motivation for research investigating the temporal performance of an oscillating foil directly in terms of its motion. In this thesis, experimental equipment designed to measure the hydrodynamic forces on a heaving object is presented. Key features of the equipment are analysed to show how measurement accuracy is maintained. Experimental measurements of unsteady hydrodynamic forces acting on a heaving cylinder, flat plate, symmetrical foil, and an asymmetrical foil are analysed with respect to the heaving motion. Firstly, the object motion is limited to one degree of freedom; pure heaving with zero forward velocity, to investigate the start-up conditions of the oscillating hydrofoil propeller. Secondly, these results are expanded on by adding a steady forward velocity component to the object motion to investigate how the hydrodynamic forces on the object are affected by the cross-flow. Experimental temporal hydrodynamic force measurements presented in this thesis show how the relative composition of hydrodynamic drag and inertia forces change with oscillating frequency, and forward velocity, affecting the phase, magnitude, and profile of the force cycles. This composition is also influenced by the cross-section of the oscillating object and the presence of a free surface. Current marine engineering equations for unsteady hydrodynamic forces on an object in an oscillating flow are validated for a cylinder. However, they are found to contain significant error when predicting the unsteady hydrodynamic forces on an oscillating hydrofoil. Contributions of this thesis link oscillating foil propulsion research to common marine engineering equations with the intent of making flapping wing propeller design more accessible to the general engineering community.

No description available.

There has been recent interest by the military to have platforms capable of operating close to a point of interest without being detected while providing critical surveillance. By providing information that is not readily available, these platforms could provide a useful tool for small unit commanders in potentially life-threatening situations. Highly maneuverable, slow-flying micro air vehicles could fly under canopies, through alleys, or indoors to provide such intelligence. This study consists of a survey of current micro-sized technologies and commercially available components. The findings are presented and used in the design process of a larger payload-carrying variant of the NPS flapping wing micro air vehicle. The intent is to develop a readily deployable, backpackable, slow-flying micro air vehicle that can be used by smaller-size ground units in theatre for urban reconnaissance.

The United States Navy is currently in a state of transition from mechanical to electric propulsion. Future warships, such as the new destroyer class, will contain an Integrated Power System (IPS) that provides power to all propulsion and ship service loads. These warships will likely have a dramatic increase in the number of power electronic loads, both AC and DC. For ship service loads, a DC Zonal Electric Distribution System (DCZEDS) will likely be used. DCZEDS requires a device that provides galvanic isolation between the feeder buses and the zones to prevent fault propagation between zones. For DCZEDS to be practical, DC-DC converters that provide galvanic isolation with an efficiency and reliability approaching that of existing low frequency AC isolation transformers must be placed between the feeder buses and the zones. This thesis examines the construction and operation of a prototype galvanically isolated DC-DC converter using commercial-off-the-shelf parts. The converter uses a single-phase high-frequency transformer link to provide galvanic isolation. This work shows that this converter topology is reliable enough to be used in an IPS. A three-phase solution using this topology can provide sufficient power density at the megawatt level, necessary for an interface converter in DCZEDS.

A comparison of a high speed container ship using a rudder versus a podded propulsor is made to study replacing a rudder with a pod. A mathematical model is altered to simulate a ship operating with a rudder and with a pod to maneuver. The model incorporates the nonlinear maneuvering equations and couples the surge and sway forces, yaw and roll moment, and the roll angle induced during a steady turn with varying rudder and pod angles. The model uses the hydrodynamic derivatives and coefficients for a high speed container ship. The equations are numerically integrated in order to predict the roll angle, sway and surge velocities, and the ship's position in the xy-plane. Both transient and steady state results are utilized to quantify the relative efficiency of each system. The results are used as a preliminary study into replacing a rudder on a ship with a podded propulsor. The results indicate that the ship responds faster and has a shorter turning radius with the pod at lower initial speeds and pod angles, while the rudder responds better at high speeds regardless of angle. Further research is necessary to study the effects of changing the pod's position and increasing the number of pods used. / US Navy (USN) author.

Approved for public release; distribution is unlimited / An evaluation was conducted of the various propulsion motors being considered for electric ship propulsion. The benefit of such an evaluation is that all of the propulsion options being considered by the U.S. Navy have been described in one document. The AC induction motor, AC synchronous motor, High Temperature Superconducting (HTS) motor and Superconducting DC Homopolar Motor (SDCHM) are examined. The properties, advantages, and disadvantages of each motor are discussed and compared. The power converters used to control large propulsion motors are also discussed. The Navy’s IPS program is discussed and the results of concept testing are presented. Podded propulsion is introduced and the benefits are discussed. The final chapter presents the simulation results of a volts/Hertz controlled 30 MW induction motor. The evaluation revealed that the permanent magnet motor is the best propulsion motor when considering mature technology, power density, and acoustic performance. HTS motors offer significant volume reductions and improved acoustic performance as compared to conventional motors. This includes both AC and DC HTS motors. The main obstacle for the SDCHM remains the unavailability of high current capacity brushes. / Ensign, United States Navy

Approved for public release; distribution is unlimited / Next-generation U.S. Navy destroyers, known as DD(X), will use electric drive motors to meet their propulsion needs instead of the traditional mechanical drives. The use of electric drive motors in naval vessels has spurred the development of high power converters. This thesis examines the feasibility of using an advanced control algorithm known as Sine-triangle Pulse Width Modulation (SPWM) in combination with a Cascaded Multi-Level Converter (CMLC) in order to meet the U.S. Navy's strict requirements. The SPWM control algorithm was designed in Simulink and experimentally tested on a CMLC previously constructed at the Naval Postgraduate School. The controller and converter successfully powered a quarter horsepower three-phase induction motor. / Ensign, United States Navy

Les propulseurs de Hall sont l’une des techniques de propulsion fusée par plasma les plus utilisés. Ils possèdent une impulsion spécifique moyenne et un haut rapport poussé sur puissance qui les rend idéal pour une grande partie des applications commerciales et scientifiques. Une de leurs limitations principales est l’érosion des parois du propulseur par le plasma qui réduit leur durée de vie. La topologie dite “d’écrantage magnétique” est une solution proposée pour prolonger cette durée de vie. Elle est ici appliquée à un petit propulseur de Hall de 200W. Dans cette thèse les règles de mise à l’échelle pour les propulseurs de Hall de la gamme de 100 à 200W sont testées expérimentalement. Un propulseur écranté de 200W est comparé avec un propulseur standard similaire. Le comportement des ions dans ces deux moteurs est extrêmement différent. Des mesures de performance ont été réalisées avec des parois en BN-SiO2 et graphite. Le courant de décharge augmente de 25% avec le graphite dans le propulseur non-écranté. Le résultat et un rendement maximum de 38% avec le nitrure de bore mais de seulement 31% pour le graphite. Le propulseur écranté quant à lui n’atteint que 25% de rendement quel que soit le matériau.Cette baisse de performance dans les petits moteurs écrantés peut être attribuée à un mauvais rendement d’utilisation de l’ergol. Analyses des résultats expérimentaux ainsi que la conduite de simulations suggèrent que cela est dû au fait que la zone d’ionisation ne couvre pas l’ensemble du canal de décharge. Un nouveau design pour un petit propulseur de Hall écranté est proposé. / Hall thrusters are one of the most used rocket electric propulsion technology. They combine moderate specific impulse with high thrust to power ratio which makes them ideal for a wide range of practical commercial and scientific applications. One of their limitations is the erosion of the thruster walls which reduces their lifespan.The magnetic shielding topology is a proposed solution to prolong the lifespan. It is implemented on a small200W Hall thruster.In this thesis the scaling of classical unshielded Hall thrusters down to 200 and 100W is discussed. A 200W low power magnetically shielded Hall thruster is compared with an identically sized unshielded one. The ion behavior inside the thruster is measured and significant differences are found across the discharge channel.Both thrusters are tested with classical BN-SiO2 and graphite walls. The magnetically shielded thruster is not sensitive to the material change while the discharge current increase by 25% in the unshielded one. The result is a maximum efficiency of 38% for boron nitride in the unshielded thruster but only 31% with graphite.The shielded thruster achieves a significantly lower efficiency with only 25% efficiency with both materials.Analysis of the experimental results as well as simulations of the thrusters reveal that the performance difference is mostly caused by low propellant utilization. This low propellant utilization comes from the fact that the ionization region doesn’t cover all of the discharge channel. A new magnetically shielded thruster is designed to solve this issue.

No description available.