Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 118 for “"hover"”.
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Propeller-Driven Rotor Twirl Phenomenon: Hover Performance, Dynamics, and Controls
… and model developments in three major areas: hover performance, dynamics, and controls. The idea of a propeller-driven rotor has become attractive over the last several years due to the advances in electrification of aircraft, for several reasons. First, large mechanical transmissions and …
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Transitions Between Hover and Level Flight for a Tailsitter UAV
… desirable characteristics, such as being able to hover and take-off or land in confined areas. One type of VTOL airframe, the tailsitter, has all of these advantages, as well as being able to fly in the more energy-efficient level flight mode. The tailsitter can track trajectories that …
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Performance Analysis of a Coaxial Helicopter in Hover and Forward Flight
… while the coaxial rotor performs better in hover. The inter-rotor spacing profoundly affected the performance of the coaxial rotor system, giving higher power requirements at lower inter-rotor spacing. Finally, it was shown that the upper rotor becomes affected by the lower rotor in hover, …
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Optimization of the Aerodynamics of Small-scale Flapping Aircraft in Hover
… for flapping flight with an emphasis on hovering with each their advantages and drawbacks. The first method was developed by Hall et al. It is an extremely fast and powerful three-dimensional approach. However, the assumptions made to develop this theory limit its use to lightly loaded …
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Perception-based synthetic cueing for night-vision device rotorcraft hover operations
… states being spatial in nature and in the hover regime. While hardware changes such as increasing the field of view or image resolution may alleviate some of the problems, it is unlikely that they will address all of the perceptual issues. The approach proposed in this thesis is to augment …
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Design and characterization of Hover Nano Aerial Vehicle (HNAV) propulsion system
On October 4th 2005, DARPA released a request for proposals for a Nano-Air Vehicle (NAV) program. The program sought to develop an advanced urban reconnaissance vehicle. According the requirement imposed by DARPA, the NAV was to have dimensions smaller than 7.5 cm in diameter, and a weight of …
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Hover : A wearable object identification system for audio augmented reality interactions
… identification system which allows users to "hover" their hands over objects of interest and get access to contextual information that may be tied to them, through an intelligent personal assistant. The system uses a fusion of sensors to be able to perform the identification of an object under …
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Adaptive Control Techniques for Transition-to-Hover Flight of Fixed-Wing UAVs
… aerial vehicles (UAVs) with the ability to hover combine the speed and endurance of traditional fixed-wing fight with the stable hovering and vertical takeoff and landing (VTOL) capabilities of helicopters and quadrotors. This combination of abilities can provide strategic advantages for UAV …
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An output-based adaptive and high-order method for a rotor in hover
… presented and applied to an isolated rotor in hover. A simplex cut-cell mesh generation technique is used to support robust and autonomous creation of higher-order meshes. The calculations are performed using a parallel implementation of the DG discretization and the results are compared to …
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Instrumentation and Control of a Ducted Fan Unmanned Aerial Vehicle in Hover Mode
… with vertical take-off and landing (VTOL) and hovering capabilities are of interest for functions such as surveillance and inspection where the ability to hold the position of the vehicle is desired. Ducted fan vehicles are of particular interest because of their high efficiency per unit …
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The use of foil generated vorticity as a hover actuator system for undersea vehicles
The hover actuator system is a proof of concept platform. The design models the ability of a flapping foil to assist an undersea vehicle's shallow water sea-keeping performance. Goals of this study are to demonstrate an effective regime of foil motion amplitude, frequency, pitch angle offset, pitch …
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DESIGN OF AVIONICS AND CONTROLLERS FOR AUTONOMOUS TAKEOFF, HOVER AND LANDING OF A MINI-TANDEM HELICOPTER
… are responsible for autonomous take-off, hover and landing of this unmanned aerial vehicle (UAV). Both time and frequency domain system identification approaches were evaluated and a selection was made based on hardware limitations. A systematic approach is developed to demonstrate that a …
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Guidance, Navigation and Control of a Fly-By-Wire Transport Category Airship Designed for Hover Cargo Delivery
… maintain position, heading, and attitude during hover and cargo operations. Owing to the large body area, most airships require that they be pointed into the wind to maintain their position. This research aims at controlling an airship attitude and position during hover cargo delivery, …
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An Experimental Investigation of Ground Effect on a Quad Tilt Rotor in Hover and Low Speed Forward Flight
… fuselage/wing model of the QTR was tested in hover and very low speed forward flight. Fixed-pitch propellers were used to model the rotors. In order to avoid the boundary layer problems associated with wind tunnel testing of rotorcraft IGE, a unique moving setup was developed for testing in …
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Study of Contra-Rotating Coaxial Rotors in Hover: A Performance Model Based on Blade Element Theory Including Swirl Velocity
… and are assessed based on the power required to hover at the same weight. Also, the impact of the swirl velocity induced by the upper rotor is included and discussed. In order to verify the credibility of the model, results are compared to what was obtained from other researches. The main result …
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Effects of Duct Lip Shaping and Various Control Devices on the Hover and Forward Flight Performance of Ducted Fan UAVs
… capacity for their size, and their ability to hover for surveillance missions. However, undesirable aerodynamic characteristics are associated with these vehicles in crosswinds, namely momentum drag and asymmetric duct lift. Because the duct itself, and not the fan, is the root cause of these …
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Assessing adaptive winter behaviors of beneficial arthropods, with a focus on the long-distance migratory ecology of Nearctic hover flies (Diptera: Syrphidae)
… the long-distance migratory ecology of Nearctic hover flies (Diptera: Syrphinae), while Chapter 3 examines the effects of field borders on arthropod natural enemy communities. Syrphid hover flies of the subfamily Syrphinae are an important group of arthropods. Adults are pollinators for a variety …
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Design and Implementation of a Control System for a Quadrotor MAV
… quadratic regulator to augment its dynamics for hover. The quadrotor's nonlinear dynamics are linearized about hover in order to be used in controller formulation. Feedback comes both directly from sensors and a Luenberger observer that computes the rotor velocities. A Simulink simulation uses …
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Use and sizing of rocket hoppers for planetary surface exploration
… of planetary environments. Furthermore, using a hover hop rather than a ballistic hop can provide many operational advantages. As the distance between target sites increases, the advantages of a single hopper compared to multiple landers decreases. However, in certain cases, in-situ resource …
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Gesture sensing with flexural ultrasonic transducers
… that are capable of sensing touch and hover gestures through a metal substrate. Electromagnetic, optical, and acoustic technologies are explored. Capacitive and pinhole camera approaches for sensing through a mostly metal substrate are presented briefly. The bulk of the thesis focuses …
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