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Dissertations / Theses on the topic 'Aircraft applications'
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1
Chopra, Shubh. "Development of mobile applications for crop scouting with small unmanned aircraft systems." Kansas State University, 2017. http://hdl.handle.net/2097/35507.
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Master of ScienceDepartment of Computer Science
Antonio R. Asebedo
Mitchell L. Neilsen
Small unmanned aircraft systems (sUAS) have been in commercial use since the1980’s and over 8-12% of its current uses are in the agricultural sector, but only involving limited uses like surveying, mapping and imaging, which is expected to increase to 47% according to AUVSI with the association of Artificial Intelligence over the next decade. Our research is one such effort to help farmers utilize advanced sUAS technology coupled with Artificial Intelligence and give them meaningful results in a widely used and user friendly interface, like a mobile application. The vision for this application is to provide a completely automated experience to the farmer for a repetitive and periodic analysis of his/her crops where all the instruction needed from the farmer is a push of a button on a one time configured application and ultimately providing results in seconds. This would help the farmer scout their crops, assess yield potential, and determine if additional inputs are needed for increasing grain yield and profit per acre. For making this application we focused on user-friendliness by abstracting crop algorithms, minimized necessary user inputs, and automate the construction of flight paths. Due to internet connection not always being available at farm fields, processing was kept to on-board compute systems and the mobile device to give live results to farmers without reliance on cloud-based analytics. The application is configured to work with DJI Aircraft using OpenCv for video processing and mobile vision, GIS and GPS data for accurate mapping, locating device, sUAS on the mobile application, and FFMPEG for encoding and decoding compressed video data. An algorithm developed by Precision-Ag Lab at the K-State Agronomy Department was implemented into the sUAS application for providing real time yield estimations and nitrogen recommendation algorithm for winter wheat.
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Austrin, Lars. "On magnetic amplifiers in aircraft applications." Licentiate thesis, Stockholm : Elektrotekniska system, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4439.
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Avery, Christopher Richard. "Current source converters for aircraft applications." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546197.
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Andersson, Victor. "Thermal Contact Conductance in Aircraft Applications." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72512.
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Ramamoorthy, Siddhartan Weheba Gamal. "Lean Six-Sigma applications in aircraft assembly." Diss., A link to full text of this thesis in SOAR, 2007. http://soar.wichita.edu/dspace/handle/10057/1167.
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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering."May 2007." Title from PDF title page (viewed on Dec. 28, 2007). Thesis adviser: Gamal Weheba. Includes bibliographic references (leaves 49-52).
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Alrashed, Maher M. "Polyurethane/Polysiloxane Ceramer Coating for Aircraft Applications." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386679739.
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Jawed, S. M. A. H. "Sensitivity applications in structural design synthesis." Thesis, Cranfield University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356199.
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Shao, Liang. "GNSS performance modelling for high interrity aircraft applications." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7442.
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Till recently, no significant attempts have been made of developing Aircraft
Based Augmentation System (ABAS) architectures capable of generating
integrity signals suitable for safety-critical GNSS applications and no
commercial ABAS products are available at present.
The aim of this research is to support the design a system that generates
integrity signals suitable for GNSS application. The conceptual design and key
mathematical models were recently developed by the Italian Air Force
Experimental Flight Test Centre (CSV-RSV) [1, 2]. Such a system, would be
able to provide steering information to the pilot, allowing for real-time and
continuous integrity monitoring, avoidance of safety/mission-critical flight
conditions and fast recovery of the required navigation performance in case of
GNSS data losses.
The key elements addressed in this thesis are the development of a CATIA
model for military and civil aircraft, supporting antenna obscuration and
multipath analysis. This is to allow the ABAS system to generate suitable
integrity flags when satellites signals are lost. In order to analyse the GNSS
signal loss causes, the GNSS constellation models, the flight dynamics models,
fading models, multipath models, Doppler shift models, and GNSS receiver
tracking technology previously developed by CSV-RSV, are considered in this
research.
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Roth, Richard. "Materials substitution in aircraft gas turbine engine applications." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13112.
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Powell, Stephen. "Applications and enhancements of aircraft design optimization techniques." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348869/.
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The aircraft industry has been at the forefront in developing design optimization strategies ever since the advent of high performance computing. Thanks to the large computational resources now available, many new as well as more mature optimization methods have become well established. However, the same cannot be said for other stages along the optimization process - chiefly, and this is where the present thesis seeks to make its first main contribution, at the geometry parameterization stage. The first major part of the thesis is dedicated to the goal of reducing the size of the search space by reducing the dimensionality of existing parameterization schemes, thus improving the effectiveness of search strategies based upon them. Specifically, a refinement to the Kulfan parameterization method is presented, based on using Genetic Programming and a local search within a Baldwinian learning strategy to evolve a set of analytical expressions to replace the standard 'class function' at the basis of the Kulfan method. The method is shown to significantly reduce the number of parameters and improves optimization performance - this is demonstrated using a simple aerodynamic design case study. The second part describes an industrial level case study, combining sophisticated, high fidelity, as well as fast, low fidelity numerical analysis with a complex physical experiment. The objective is the analysis of a topical design question relating to reducing the environmental impact of aviation: what is the optimum layout of an over-the-wing turbofan engine installation designed to enable the airframe to shield near-airport communities on the ground from fan noise. An experiment in an anechoic chamber reveals that a simple half-barrier noise model can be used as a first order approximation to the change of inlet broadband noise shielding by the airframe with engine position, which can be used within design activities. Moreover, the experimental results are condensed into an acoustic shielding performance metric to be used in a Multidisciplinary Design Optimization study, together with drag and engine performance values acquired through CFD. By using surrogate models of these three performance metrics we are able to find a set of non-dominated engine positions comprising a Pareto Front of these objectives. This may give designers of future aircraft an insight into an appropriate engine position above a wing, as well as a template for blending multiple levels of computational analysis with physical experiments into a multidisciplinary design optimization framework.
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Brown, Mark Anthony. "An investigation of three-dimensional displays for real-time, safety-critical command/control applications : with application to air traffic control." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336445.
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Perez, Ruben E. "Soft Computing techniques and applications in aircraft design optimization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63122.pdf.
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Mattioni, Filippo. "Thermally induced multi-stable composites for morphing aircraft applications." Thesis, University of Bristol, 2009. http://hdl.handle.net/1983/1a808d25-f44d-42b9-8c43-d5664f1d2417.
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This research focuses on the realisation of 'shape-adaptable' systems through unsymmetrical laminates. The residual stress field which is built-into this type of laminates, is used to obtain panels with two or more equilibrium states. Such systems provide a possible solution for the realisation of morphing structures because they allow to simultaneously fulfil the contradictory requirements of flexibility and stiffness.
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Sobron, Alejandro. "On Subscale Flight Testing : Applications in Aircraft Conceptual Design." Licentiate thesis, Linköpings universitet, Fluida och mekatroniska system, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-152488.
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Downscaled physical models, also referred to as subscale models, have played an essential role in the investigation of the complex physics of flight until the recent disruption of numerical simulation. Despite the fact that improvements in computational methods are slowly pushing experimental techniques towards a secondary role as verification or calibration tools, real-world testing of physical prototypes still provides an unmatched confidence. Physical models are very effective at revealing issues that are sometimes not correctly identified in the virtual domain, and hence can be a valuable complement to other design tools. But traditional wind-tunnel testing cannot always meet all of the requirements of modern aeronautical research and development. It is nowadays too expensive to use these scarce facilities to explore different design iterations during the initial stages of aircraft development, or to experiment with new and immature technologies. Testing of free-flight subscale models, referred to as Subscale Flight Testing (SFT), could offer an affordable and low-risk alternative for complementing conventional techniques with both qualitative and quantitative information. The miniaturisation of mechatronic systems, the advances in rapid-prototyping techniques and power storage, as well as new manufacturing methods, currently enable the development of sophisticated test objects at scales that were impractical some decades ago. Moreover, the recent boom in the commercial drone industry has driven a quick development of specialised electronics and sensors, which offer nowadays surprising capabilities at competitive prices. These recent technological disruptions have significantly altered the cost-benefit function of SFT and it is necessary to re-evaluate its potential in the contemporary aircraft development context. This thesis aims to increase the comprehension and knowledge of the SFT method in order to define a practical framework for its use in aircraft design; focusing on low-cost, short-time solutions that don’t require more than a small organization and few resources. This objective is approached from a theoretical point of view by means of an analysis of the physical and practical limitations of the scaling laws; and from an empirical point of view by means of field experiments aimed at identifying practical needs for equipment, methods, and tools. A low-cost data acquisition system is developed and tested; a novel method for semi-automated flight testing in small airspaces is proposed; a set of tools for analysis and visualisation of flight data is presented; and it is also demonstrated that it is possible to explore and demonstrate new technology using SFT with a very limited amount of economic and human resources. All these, together with a theoretical review and contextualisation, contribute to increasing the comprehension and knowledge of the SFT method in general, and its potential applications in aircraft conceptual design in particular.
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Demus, Justin Cole. "Prognostic Health Management Systems for More Electric Aircraft Applications." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1631047006902809.
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Becerra, Pozo Natalia I. "Analysis and optimisation of composite truss structures for aircraft applications." Thesis, Oxford Brookes University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444336.
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Khatre, Manas. "Reduced DC-link capacitor drives for more-electric aircraft applications." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531753.
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Siyabi, Mohammed Al. "Aircraft datalink approach for DTN applications and fair resource allocation." Thesis, University of Surrey, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543920.
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Vetter, Theodore Arnold. "Considerations for space and Naval aircraft applications of ferroelectric memory." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23845.
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Approved for public release; distribution is unlimitedThe purpose of this thesis is to introduce the reader to Ferroelectric memory and discuss considerations for possible space and Naval aviation applications. Ferroelectric memory's characteristics and basic mechanism are discussed. A broad spectrum of existing computer memory types are presented for comparison. The memory requirements of Space Shuttle, Landsat, Intelsat V and Hubble Space telescope as well as the Navy E-2 Hawkeye and EA-6B Prowler aircraft are given as examples of possible space and Naval aviation applications of ferroelectric memory.
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Qu, Zheng Ph D. Massachusetts Institute of Technology. "Adaptive output-feedback control and applications to Very Flexible Aircraft." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104223.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-141).
Very Flexible Aircraft (VFA) corresponds to an aerial platform whose flight dynamics critically depends on its flexible wing shape, and has been investigated as a potential solution to generate high-altitude low-endurance flights. The dominant presence of model uncertainties and potential actuator anomalies motivate an adaptive approach for control of VFA. Another particular control challenge for VFA is that its flexible modes cannot be measured accurately, which necessitates an output-feedback multi-input multi-output (MIMO) control approach. The focus of this thesis is on an adaptive output-feedback controller for a generic class of MIMO plant models with an emphasis on the control of a VFA so as to execute desired flight maneuvers. The proposed adaptive controller includes a baseline design based on observers and parameter adaptation based on a closed-loop reference model (CRM), and is applicable for a generic class of MIMO plants of arbitrary relative degree, and therefore the overall design is suitable for control in the presence of uncertainties in flexible effects, sensor dynamics, and actuator dynamics. In addition, the proposed controller can accommodate plant models whose number of outputs exceeds number of inputs. One major advantage of the proposed design is that the number of integrators required for implementation is significantly less than that of previous methods and therefore the controller can be implemented even for large-dimensional VFA models. Conditions are delineated under which asymptotic stability and command tracking can be guaranteed, and the overall design is verified using realistic simulations on a high-fidelity VFA model with unknown varying wing shape and actuator anomalies.
by Zheng Qu.
Ph. D.
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Franzén, Kenzo, and Fredrik Jangelind. "States and Prospects of Hydrogen Storage Technologies in Aircraft Applications." Thesis, KTH, Energiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298996.
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In recent years, more than 100 000 commercial flights have departed daily, and the number of passengers worldwide are expected to double within the next two decades, assuming there are no long-term impacts of the Covid-19 pandemic. Meanwhile, the aviation industry will need to undergo a shift to more sustainable fuels, due to the growing issue of climate change and implementation of policies that regulate the use of fossil-based fuels such as kerosene. Hydrogen has been established as one proposed fuel for aviation, due to its properties of high energy contents and the main emissions being water vapor. For hydrogen to be used as an aviation fuel, there is a need for efficient, safe and low-cost storage systems. Based on a set of quantifiable parameters the report aims to, based on technical, economical and safety perspectives as well as conclusions from previous studies, identify and quantify the current states and prospects of some of the most promising methods and technologies for hydrogen storage in commercial aircrafts. Furthermore, other important parameters are being identified and discussed after analyzing the viability of several physical and material storage technologies. The results show that although none of the technologies are sufficiently developed and ready for aircraft applications, cryogenic liquid hydrogen storage offers the best opportunities for the near future. Other forms of physical storage show some promise, whereas some material storage methods have large theoretical potential but require rapid development. While the other studied systems can’t be dismissed, a lot of research and development would have to be successful in order to reach technological and commercial viability. Further research is necessary for quantifying storage costs as well as prospects and targets for costs and gravimetric energy densities. All things considered, it is concluded that for hydrogen to be viable as an aviation fuel, hydrogen storage systems need to perform on a level much higher than today.Under de senaste åren har över 100 000 kommersiella flygningar avgått dagligen, och antalet passagerare världen över förväntas fördubblas inom de närmaste två decennierna, förutsatt att Covid-19-pandemin inte har några långvariga effekter på flygindustrin. Samtidigt behöver branschen genomföra en omställning till mer hållbara bränslen, till följd av det växande problemet med klimatförändringar och implementering av policy som reglerar användningen av fossilbaserade bränslen som Jet A1 (flygfotogen). Vätgas har etablerats som ett föreslaget flygbränsle tack vare sitt höga energiinnehåll och att dess utsläpp mestadels består av vattenånga. För att vätgas ska kunna användas som flygbränsle finns ett behov av effektiva, säkra och billiga lagringssystem. Baserat på en uppsättning av kvantifierbara parametrar syftar rapporten till, baserat på tekniska, ekonomiska och säkerhetsmässiga perspektiv, att identifiera och kvantifiera nuvarande tillstånd och framtidsutsikter hos flera av de mest lovande metoderna och teknologierna för vätgaslagring i kommersiella flygplan. Vidare identifieras och diskuteras andra viktiga parametrar efter att förutsättningarna för teknologier för fysisk lagring och materiallagring har analyserats. Resultaten visar att även om ingen av teknologierna är tillräckligt utvecklade eller redo att appliceras på flygplan, så erbjuder kryogen, flytande vätgaslagring de bästa möjligheterna för en nära framtid. Även andra former av fysisk lagring visar sig vara ganska lovande, medan vissa metoder för materiallagring har hög teoretisk potential men kräver en snabb utveckling i mognadsgrad. Även om de andra studerade systemen inte helt kan avfärdas så behöver mycket forskning och utveckling lyckas för att nå en teknologisk och kommersiell gångbarhet. Ytterligare forskning är nödvändig för att kvantifiera flyganpassade lagringskostnader samt utsikter och mål för kostnader och gravimetrisk lagringstäthet. Sammantaget dras slutsatsen att vätgaslagringssystem behöver prestera på en nivå långt över idag för att vätgas ska kunna bli lämpligt som flygbränsle.
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Bell, John J. (Jack), James Mileshko, Edward L. Payne, and Paul Wagler. "A MULTIFUNCTION SATELLITE BACKHAUL SYSTEM FOR AIRCRAFT FLIGHT TEST APPLICATIONS." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605336.
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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaThis paper will present the design of a network used to receive and record sensor data and provide voice communications between a flight controller and the pilot of an aircraft undergoing flight testing in remote areas. The network utilizes a completely self-contained mobile tracking subsystem to receive and relay the sensor data and cockpit voice in real-time over a geostationary satellite. In addition to the aircraft tracking and data/voice relay functions, the system also provides local data recording at the mobile station, telephone and intercom connectivity between the mobile station and the control center, and remote equipment setup via the satellite link.
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Kozak, Tugrul Mustafa. "Investigation Of Model Updating Techniques And Their Applications To Aircraft Structures." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607558/index.pdf.
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Mathematical models that are built in order to simulate the behavior of structures, most often, tend to respond differently than the actual structures in their initial state. In order to use the mathematical models and their computational outputs instead of testing the real structure under every possible case, it is mandatory to have a mathematical model that reflects the characteristics of the actual structure in the best possible way. In this thesis, the so called model updating techniques used for updating the mathematical models in order to make them respond in the way the actual structures do are investigated.
Case studies using computationally generated test data are performed using the direct and indirect modal updating techniques with the software developed for each method investigated. After investigating the direct and indirect modal updating techniques, two of them, one using frequency response functions and the other using modal sensitivities, are determined to be the most suitable ones for aircraft structures. A generic software is developed for the technique using modal sensitivities. A modal test is carried out on a scaled aircraft model. The test data is used for updating of the finite element model of the scaled aircraft using the modal sensitivities and the usability of the method is thus evaluated. The finite element
model of a real aircraft using the modal test data is also updated using the modal sensitivities.
A new error localization technique and a model updating routine are also proposed in this thesis. This modal updating routine is used with several case studies using computationally generated test data and it is concluded that it is capable of updating the mathematical models even with incomplete measured data.
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Torabzadeh-Tari, Mohsen. "Analysis of Electro-Meachanical Actuator Systems in More Electric Aircraft Applications." Licentiate thesis, KTH, School of Electrical Engineering (EES), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255.
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Conventional hydraulic actuators in aircraft are demanding regarding maintenance which implies high operation costs. In recent years the focus therefore has been set on electro-hydrostatic and electro-mechanical actuators.
The aim of this work is to analyze and evaluate the possibility of introducing electro-mechanical actuators (EMAs) in more electric aircraft applications. The major goal is to optimize the weight of such actuator systems including the electro-machine (electric motor) gear mechanism and power converter, without loss of reliability. Other optimisation criteria on such solutions are low losses and good thermal properties.
A quasi-static model approach of EMAs is used here in order to decrease the simulation time. It is possible because the low (mechanical) and high (electrical) frequency components are separated in the model, see [1]. The inverters and converters are described as fictive DC-DC transformers with corresponding efficiencies, see [2]. By introducing an object oriented approach the model is flexible and re-usable and can be used as a framework in the future build-up of models of entire MEA aircrafts, see [3].
Power density, cost and weight of the actuator systems are some of the important key factors for comparing purpose and as a platform for the dimensioning of the aircraft. The next issue becomes the scalability of the model and the key factors, because of the diversity of the actuators used in different parts of the MEA aircraft. Therefore the ambition is set to build up a database of different scalable actuator solutions which among others returns these key factors as output.
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Torabzadeh-Tari, Mohsen. "Analysis of Electro-mechanical actuator systems in more electric aircraft applications /." Stockholm : Department of electrical engineering, Royal Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255.
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Rogers, Walter L. "Applications of modern control theory synthesis to a super-augmented aircraft." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26890.
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Littleboy, Darren M. "Numerical techniques for eigenstructure assignment by output feedback in aircraft applications." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259495.
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Nusawardhana, 1969. "Evaluation of deterministic and statistical failure detection algorithms for aircraft applications." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/49976.
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Crispin, Christopher. "Path planning algorithms for atmospheric science applications of autonomous aircraft systems." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/397081/.
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Among current techniques, used to assist the modelling of atmospheric processes, is an approach involving the balloon or aircraft launching of radiosondes, which travel along uncontrolled trajectories dependent on wind speed. Radiosondes are launched daily from numerous worldwide locations and the data collected is integral to numerical weather prediction. This thesis proposes an unmanned air system for atmospheric research, consisting of multiple, balloon-launched, autonomous gliders. The trajectories of the gliders are optimised for the uniform sampling of a volume of airspace and the efficient mapping of a particular physical or chemical measure. To accomplish this we have developed a series of algorithms for path planning, driven by the dual objectives of uncertainty and information gain. Algorithms for centralised, discrete path planning, a centralised, continuous planner and finally a decentralised, real-time, asynchronous planner are presented. The continuous heuristics search a look-up table of plausible manoeuvres generated by way of an offline flight dynamics model, ensuring that the optimised trajectories are flyable. Further to this, a greedy heuristic for path growth is introduced alongside a control for search coarseness, establishing a sliding control for the level of allowed global exploration, local exploitation and computational complexity. The algorithm is also integrated with a flight dynamics model, and communications and flight systems hardware, enabling software and hardware-in-the-loop simulations. The algorithm outperforms random search in two and three dimensions. We also assess the applicability of the unmanned air system in ‘real’ environments, accounting for the presence of complicated flow fields and boundaries. A case study based on the island South Georgia is presented and indicates good algorithm performance in strong, variable winds. We also examine the impact of co-operation within this multi-agent system of decentralised, unmanned gliders, investigating the threshold for communication range, which allows for optimal search whilst reducing both the cost of individual communication devices and the computational resources associated with the processing of data received by each aircraft. Reductions in communication radius are found to have a significant, negative impact upon the resulting efficiency of the system. To somewhat recover these losses, we utilise a sorting algorithm, determining information priority between any two aircraft in range. Furthermore, negotiation between aircraft is introduced, allowing aircraft to resolve any possible conflicts between selected paths, which helps to counteractany latency in the search heuristic.
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Mackay, Justin Keith. "Automated Landing Site Determination for Unmanned Rotocraft Surveillance Applications." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5531.
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Unmanned air vehicles have been increasing in their autonomous capabilities. This research furthers these capabilities by focusing on the automation of landing site determination for rotorcraft in urban environments. Automated landing saves energy and allows the aircraft to choose areas that are safe for people and the aircraft. Two methods are used to gather information about the terrain of potential landing sites. One method is 3D reconstruction from multiple camera images. The other method uses a range sensor to reconstruct the terrain. Both of these methods create an inertial terrain map of the environment in the form of a point cloud that can be investigated for possible landing sites. Two strategies were developed to search the terrain map for possible landing sites: grid-based RANSAC and Recursive-RANSAC (R-RANSAC). Both strategies search for flat stable areas for landing. Grid-based RANSAC separates the terrain map into discrete portions for plane fitting analysis. These fitted planes are used to determine whether portions of the terrain map are suitable for landing. Two additional variations of grid-based RANSAC were explored that resulted in improvements to the approach. This strategy can quickly find landing sites from large terrain maps. The other strategy, R-RANSAC, is a recursive approach that analyzes each point in the terrain map for plane fitting. New planes are created as needed to fit points in the terrain map. Planes that fit a large number of points are analyzed for possible landing locations. This strategy is more complex to implement, but results in a simpler model of the environment: a small set of 3D planes. The results are displayed with the possible landing locations. Both landing-site strategies were implemented onboard a hexrotor aircraft and successfully demonstrated in flight.
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Ali, Shaaban Aerospace Civil & Mechanical Engineering Australian Defence Force Academy UNSW. "Intelligent adaptive control for nonlinear applications." Awarded by:University of New South Wales - Australian Defence Force Academy, 2008. http://handle.unsw.edu.au/1959.4/39185.
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The thesis deals with the design and implementation of an Adaptive Flight Control technique for Unmanned Aerial Vehicles (UAVs). The application of UAVs has been increasing exponentially in the last decade both in Military and Civilian fronts. These UAVs fly at very low speeds and Reynolds numbers, have nonlinear coupling, and tend to exhibit time varying characteristics. In addition, due to the variety of missions, they fly in uncertain environments exposing themselves to unpredictable external disturbances. The successful completion of the UAV missions is largely dependent on the accuracy of the control provided by the flight controllers. Thus there is a necessity for accurate and robust flight controllers. These controllers should be able to adapt to the changes in the dynamics due to internal and external changes. From the available literature, it is known that, one of the better suited adaptive controllers is the model based controller. The design and implementation of model based adaptive controller is discussed in the thesis. A critical issue in the design and application of model based control is the online identification of the UAV dynamics from the available sensors using the onboard processing capability. For this, proper instrumentation in terms of sensors and avionics for two platforms developed at UNSW@ADFA is discussed. Using the flight data from the remotely flown platforms, state space identification and fuzzy identification are developed to mimic the UAV dynamics. Real time validations using Hardware in Loop (HIL) simulations show that both the methods are feasible for control. A finer comparison showed that the accuracy of identification using fuzzy systems is better than the state space technique. The flight tests with real time online identification confirmed the feasibility of fuzzy identification for intelligent control. Hence two adaptive controllers based on the fuzzy identification are developed. The first adaptive controller is a hybrid indirect adaptive controller that utilises the model sensitivity in addition to output error for adaptation. The feedback of the model sensitivity function to adapt the parameters of the controller is shown to have beneficial effects, both in terms of convergence and accuracy. HIL simulations applied to the control of roll stabilised pitch autopilot for a typical UAV demonstrate the improvements compared to the direct adaptive controller. Next a novel fuzzy model based inversion controller is presented. The analytical approximate inversion proposed in this thesis does not increase the computational effort. The comparisons of this controller with other controller for a benchmark problem are presented using numerical simulations. The results bring out the superiority of this technique over other techniques. The extension of the analytical inversion based controller for multiple input multiple output problem is presented for the design of roll stabilised pitch autopilot for a UAV. The results of the HIL simulations are discussed for a typical UAV. Finally, flight test results for angle of attack control of one of the UAV platforms at UNSW@ADFA are presented. The flight test results show that the adaptive controller is capable of controlling the UAV suitably in a real environment, demonstrating its robustness characteristics.
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Tarimci, Onur. "Adaptive Controller Applications For Rotary Wing Aircraft Models Of Varying Simulation Fidelity." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611168/index.pdf.
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This thesis concerns the design, analysis and testing of adaptive controllers for rotary wing
aircraft, in particular helicopters. A non-linear helicopter model is developed and validated by
trim and dynamic response analyses. A inner-outer loop cascade controller is designed with
a trajectory generator in the most outer layer and an adaptive neural network controller is
implemented to the inner loop. Controller is then challenged to carry out complex maneuvers
autonomously under turbulence. Finally, the center of gravity location is varied to severe
values to observe adaptation characteristics to investigate the requirement on the knowledge
of the center of gravity location during such adaptive controller design.
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Lavopa, Elisabetta. "A novel control technique for active shunt power filters for aircraft applications." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12049/.
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The More Electric Aircraft is a technological trend in modern aerospace industry to increasingly use electrical power on board the aircraft in place of mechanical, hydraulic and pneumatic power to drive aircraft subsystems. This brings major changes to the aircraft electrical system, increasing the complexity of the network topology together with stability and power quality issues. Shunt active power filters are a viable solution for power quality enhancement, in order to comply with the standard recommendations. The aircraft electrical system is characterized by variable supply frequency in the range 360-900Hz, hence the harmonic components occur at high and variable frequencies, compared to the terrestrial 50/60Hz systems. In this kind of system, fast and accurate algorithms for the detection of the reference signal for the active filter control and robust high-bandwidth control techniques are needed, in order for the active filter to perform the harmonic elimination successfully. In this thesis, two novel algorithms are proposed. The first algorithm is a frequency and harmonic detection technique, particularly suitable for tracking the variable supply frequency and the harmonic components of voltages and currents in the aircraft electrical system. Complete identication of the reference signal for the active filter control is possible when applying this technique. The second algorithm is a control technique based on the use of multiple rotating reference frames. Only the measurement of the voltage at the Point of Common Coupling and the active filter output current are needed, hence no current sensors are required on the distorting loads. Both the techniques have been validated by means of simulation and experimental analysis. The results show that the proposed methods are effective for a successful harmonic compensation by means of active shunt filters, in the More Electric Aircraft environment.
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Lopez, Leones Javier. "Definition of an aircraft intent description language for air traffic management applications." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/270/.
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To accommodate the expected growth of the air transport industry, the Air Traffic Management (ATM) system is required to increase its performance in terms of capacity, efficiency and security whilst maintaining adequate levels of safety and reducing the environmental impact of aircraft operations. In addition, there is a urgent need to allow the different actors in the ATM system the flexibility to accommodate their preferences,so that they can better pursue their respective business objectives. To deal effectively with all these challenges, the current trend is to increase the levels of automation and integration in the system. Different ATM modernisation initiatives pursuit the shift towards a Trajectory Base Operations (TBO) environment, where different ATM users (e.g., Air Navigation Service Providers (ANSP), Airlines Operations Center (AOC), pi- lots, controllers, airport authorities) will exchange trajectory-related information in order to collaboratively make decisions in an e±ficient and fair way. An increasing number of Decision Support Tools (DSTs) are being developed and implemented to enhance both airborne and ground-based automation systems to support the human in TBO. Since these DSTs have to help humans to make decisions in TBO, they must contain the capability to predict trajectories. However, different DSTs will in principle rely on different trajectory predictors (TP), which may produce different, inconsistent trajectories for the same flight. This lack of consistency among predictions is seen as a key issue for the integration of current and future DSTs. Coordination between TPs is the key to ensure coordination between air-ground, ground -ground and air-air DSTs and hence the successful evolution and application of the TBO concept. This thesis proposes a standard method to describe trajectories that can allow different DSTs to express and exchange their views of the predicted trajectory of an aircraft. This method, called the Aircraft Intent Description Language (AIDL), provides the necessary mechanisms to formulate the aircraft intent. The aircraft intent is defined as the unambiguous description of how the aircraft is to be operated within a certain time frame. Since the mathematical formulation of this concept is needed for the computation of a trajectory, each TP has their own format of aircraft intent. However, the uncoordinated research in trajectory prediction has driven to different models of this aircraft intent,which has precluded its use to coordinate trajectory predictions of different TPs. The use of the AIDL as an standard mean to describe trajectories permits an easy construction and manipulation of trajectories between different TPs. The scope of this thesis is limited to an AIDL that describes airborne operations of civil aircraft, in particular turbofan and turbojet aircraft. However, the methodology exposed in this thesis to obtain the AIDL can be easily applied to ground operations and other type of aircraft and air vehicles (e.g., propellers, helicopters) to extend the scope and applicability of the AIDL. The AIDL is characterised by an alphabet and a grammar. The AIDL grammar contains both lexical and syntactical rules. These rules ensure that the aircraft intent contains the necessary and sufficient information that is needed to compute a trajectory. The development of these rules is based on a rigourous mathematical analysis using Differential Algebraic Equations (DAE) theory. The lexical rules in the AIDL's grammar govern the formulation of the words of the language by combining elements from the AIDL's alphabet. This alphabet contains a set of atomic primitives, equivalent to the letters in the English alphabet, called instructions, which capture basic commands and guidance modes at the disposal of the pilot/FMS to direct the operation of the aircraft in the ATM context. Instructions can be seen as minimal indivisible pieces of information describing distinct ways of closing one of the aircraft motion's degrees of freedom. Mathematically, an instruction is characterised by an equation that is to be satisfied simultaneously with the equations of motion during a certain time interval, denoted as the execution interval of the instructions. The words of the AIDL are called operations. An operation represents an elemental aircraft behaviour that determines its motion unambiguously during a specific time interval denoted as the operation interval. An operation is the result of a set of compatible instructions simultaneously active during the corresponding operation interval. The syntactical rules in the AIDL govern the definition of sentences, which are formed by sequences of operations. These rules allow expressing any possible behaviour that can be elicited from an aircraft in the ATM context. While each DST may have a different input format to describe aircraft intent, the AIDL is designed in such a way that these different inputs can be seen as 'dialects' of the AIDL. Thus, the AIDL can be used as a lingua franca by different the DSTs, which would use it as the common standard to communicate aircraft intent with each other. The possible applications of the AIDL in a TBO environment are manifold. For instance, aircraft intent information expressed using the AIDL could be exchanged as part of a negotiation process between airborne and ground-based automation systems. Air-air synchronisation based on aircraft intent could permit the coordinated operation of Unmanned aerial vehicles (UAVs) by means of exchanging their future behaviour expressed as aircraft intent. Ground-ground aircraft intent sharing would enable a common and efficient treatment of aircraft trajectories in such a way that any amendment could be easily shared between different automation tools.
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Kural, Aleksander. "Ultrasonic lamb wave energy transmission system for aircraft structural health monitoring applications." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/58395/.
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In this project an investigation of a wireless power transmission method utilising ultrasonic Lamb waves travelling along plates was performed. To the author’s knowledge, this is the first time such a system was investigated. The primary application for this method is the supply of power to wireless structural health monitoring (SHM) sensor nodes located in remote areas of the aircraft structure. A vibration generator is placed in a location where electricity supply is readily available. Ultrasonic waves generated by this device travel through the aircraft structure to a receiver in a remote wireless sensor node. The receiver converts the mechanical vibration of the ultrasonic waves back to electricity, which is used to power the sensor node. An experimental setup comprising a 1000 × 821 × 1.5 mm aluminium plate was designed to model an aircraft skin panel. Pairs of piezoelectric transducers were positioned along the longer edges of the plate. The electric impedance characteristics of three transducer types were measured. A circuit simulation MATLAB code was written. An input and output power measurement system was developed. The MFC M8528-P1 transducer type was identified as providing the best performance. The use of inductors to compensate for the capacitive characteristics of transducers was shown to provide up to 170-fold power throughput increase. The propagation of Lamb waves in the experimental plate was mapped using a scanning laser vibrometer and simulated using LISA finite difference method software. An optimised laboratory system transmitted 17 mW of power across a distance of 54 cm while being driven by a 20 V, 224 kHz signal. This figure can be easily increased by using a higher drive voltage. This shows that the system is capable of supplying sufficient power to wireless SHM sensor nodes, which currently have a maximum power requirement of approximately 200 mW.
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Au, Hiu. "Pitting and crack initiation in high strength aluminum alloys for aircraft applications." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/11240.
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Mallik, Wrik. "Aeroelastic Analysis of Truss-Braced Wing Aircraft: Applications for Multidisciplinary Design Optimization." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71650.
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This study highlights the aeroelastic behavior of very flexible truss-braced wing (TBW) aircraft designs obtained through a multidisciplinary design optimization (MDO) framework. Several improvements to previous analysis methods were developed and validated.
Firstly, a flutter constraint was developed and the effects of the constraint on the MDO of TBW transport aircraft for both medium-range and long-range missions were studied while minimizing the take-off gross weight (TOGW) and the fuel burn as the objective functions. Results show that when the flutter constraint is applied at 1.15 times the dive speed, it imposes a 1.5% penalty on the take-off weight and a 5% penalty on the fuel consumption while minimizing these two objective functions for the medium-range mission. For the long-range mission, the penalties imposed by the similar constraint on the minimum TOGW and minimum fuel burn designs are 3.5% and 7.5%, respectively. Importantly, the resulting TBW designs are still superior to equivalent cantilever designs for both of the missions as they have both lower TOGW and fuel burn. However, a relaxed flutter constraint applied at 1.05 times the dive speed can restrict the penalty on the TOGW to only 0.3% and that on the fuel burn to 2% for minimizing both the objectives, for the medium-range mission. For the long-range mission, a similar relaxed constraint can reduce the penalty on fuel burn to 2.9%. These observations suggest further investigation into active flutter suppression mechanisms for the TBW aircraft to further reduce either the TOGW or the fuel burn.
Secondly, the effects of a variable-geometry raked wingtip (VGRWT) on the maneuverability and aeroelastic behavior of passenger aircraft with very flexible truss-braced wings (TBW) were investigated. These TBW designs obtained from the MDO environment while minimizing fuel burn resemble a Boeing 777-200 Long Range (LR) aircraft both in terms of flight mission and aircraft configuration. The VGRWT can sweep forward and aft relative to the wing with the aid of a Novel Control Effector (NCE) mechanism. Results show that the VGRWT can be swept judiciously to alter the bending-torsion coupling and the movement of the center of pressure of wing. Such behavior of the VGRWT is applied to both achieve the required roll control as well as to increase flutter speed, and thus, enable the operation of TBW configurations which have up to 10% lower fuel burn than comparable optimized cantilever wing designs.
Finally, a transonic aeroelastic analysis tool was developed which can be used for conceptual design in an MDO environment. Routine transonic aeroelastic analysis require expensive CFD simulations, hence they cannot be performed in an MDO environment. The present approach utilizes the results of a companion study of CFD simulations performed offline for the steady Reynolds Averaged Navier Stokes equations for a variety of airfoil parameters. The CFD results are used to develop a response surface which can be used in the MDO environment to perform a Leishman-Beddoes (LB) indicial functions based flutter analysis. A reduced-order model (ROM) is also developed for the unsteady aerodynamic system. Validation of the strip theory based aeroelastic analysis with LB unsteady aerodynamics and the computational efficiency and accuracy of the ROM is demonstrated. Finally, transonic aeroelastic analysis of a TBW aircraft designed for the medium-range flight mission similar to a Boeing 737 next generation (NG) with a cruise Mach number of 0.8 is presented. The results show the potential of the present approach to perform a more accurate, yet inexpensive, flutter analysis for MDO studies of transonic transport aircraft which are expected to undergo flutter at transonic conditions.Ph. D.
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Malik, Akshat. "Monitoring and Preventing Data Exfiltration in Android-hosted Unmanned Aircraft System Applications." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/92874.
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With the dominance of Android in the smartphone market, malware targeting Android users has increased over time. Android applications are now being used to control unmanned aircraft systems (UAS) making smartphones the storehouse for all the data that is generated by the UAS. This data can be sensitive in nature which puts the user at the risk of data exfiltration. As most Android-hosted UAS applications are proprietary software, their source code cannot be studied or modified. This thesis discusses an external monitoring system which is devised in order to assess the threat of data exfiltration.
The system is further used to analyze the network behavior of the popular Android-hosted UAS application, DJI GO 4. Current methods to limit data exfiltration are discussed along with their limitations and are categorized based on the ease of deployment.
Even though the Android framework provides a permission system which helps to limit the capabilities of an application, this security mechanism is coarse-grain in nature. The user either allows access to the required permissions or the application fails to function. Moreover, there is no system in place to provide finer control over the existing permissions that are granted to an application. This thesis proposes a fine-grain and application-specific access control mechanism based on system call interposition. The solution focuses on limiting the I/O operations of the target application without any framework or application modification.Master of Science
Advances in smartphone technology has led major consumer and commercial unmanned aircraft system (UAS) manufacturers to provide users with the feature to fly the UAS using their smartphones. The UAS generate and store large amounts of data which may be sensitive in nature. This has led the U.S. Department of Defense to ban the use of all commercial off-the-shelf UAS due to the threat of data leakage. This thesis discusses an external monitoring system which maps the network behavior of an Android-hosted UAS application, along with the existing methods to limit data leakage. To overcome the limitations of existing techniques, a fine-grain and application-specific access control mechanism is proposed. The solution provides users with the ability to enforce custom security policies to safeguard their data.
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Assel, Timothy William. "Computational study of flow over elliptic airfoils for rotor/wing unmanned aerial vehicle applications." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Tim_Assel_Thesis_Final_09007dcc804c796b.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 26, 2008) Includes bibliographical references (p. 102-104).
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Devarakonda, Nagini. "Eco-inspired Robust Control Design for Linear Dynamical Systems with Applications." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313519615.
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Beckman, Mathias, and Gerald Volden Alex Christy. "Performance Assessment of Electrical Motor for Electric Aircraft Propulsion Applications : Evaluation of the Permanent Magnet Motor and its Limitations in Aircraft Propulsion." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-45157.
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This thesis project will evaluate which kind of electrical motor is best suited for aircraft propulsion and which parameters effect the efficiency. An economic analysis was conducted, comparing the fuel price (Jet A1) for a gas turbine and the electricity price for an electric motor of 1MW. The study was conducted by using analytical methods in MATLAB. Excel was used to compile and present the data. The data used in this thesis project were assumed with regards to similar studies or pre-determined values. The main losses for the Permanent Magnet Synchronous Motor (PMSM) were calculated to achieve a deeper understanding of the most important parameters and how these parameters need to improve to allow for future electric propulsion systems. The crucial parameters for the losses were concluded to be the temperature, voltage level, electrical frequency, magnetic flux density, size of the rotor and rotational speed. The three main losses of a PMSM was illustrated through the analytical equations used in MATLAB. The calculations present how the ohmic losses depend on the temperature (0-230°C) at different voltages (700V and 1000V), how the core losses depend on frequency (0-1000Hz) at different magnetic flux densities and how the windage losses depend on rotational speed (7000-10000 rpm). It could be concluded that at 8500 rpm an efficiency of 91,26% could be achieved at 700V, 1.5T and 90.4% at 1000V, 1.65T. The decrease in efficiency is a result of the increase in magnetic flux density. When looking at the economic viability of electrical integration the power to weight ratio and energy price was compared for the gas turbine and electrical motor including an inverter and battery. This resulted in a conclusion that a pure electrical system may not compete with a gas turbine in 30 years of time due to the low energy density of the battery. It was also concluded that the emissions during cruise could be lowered significantly. If the batteries were charged in Sweden the emissions would decrease from ~937 kg CO2 to ~31 kg CO2. If the batteries were charged in the Nordic region the emissions would decrease to ~119kg CO2. However, if the batteries were to be charged in the US the carbon dioxide emission would be ~1084 kg CO2, which is an increase in CO2 emission compared to the gas turbine.
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Abramov, Nikolay. "Modelling of unsteady aerodynamic characteristics for aircraft dynamics applications at high incidence flight." Thesis, De Montfort University, 2005. http://hdl.handle.net/2086/4108.
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A traditional representation of aerodynamic characteristics based on the concept of aerodynamic derivatives fails to be accurate at high angles of attack due to significant dynamic effects generated from separated and vortical flow. As the possibility of performing controlled flight at high angles of attack has already become a common requirement for modern combat aircraft, the problem of an adequate model for aerodynamic loads at high incidences is the issue of the day. This thesis presents a phenomenological approach to modelling of unsteady aerodynamic characteristics at high angles of attack. In this approach aerodynamic characteristics are considered as a combination of two components having different characteristic time scales which describe the contribution to the total aerodynamic load from the different flow structures. It is assumed that all dynamic properties of the flow are amassed in the' slow' component. To describe its behaviour specially designed nonlinear differential equations are used. Depending on the parameters, this model can reproduce both 'weak' and 'strong' nonlinear effects including static hysteresis. A special identification technique has been developed for the estimation of the model parameters using dynamic wind tunnel test data.
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Howe, Katie Sarah. "Design improvements of micro-tubular solid oxide fuel cells for unmanned aircraft applications." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4761/.
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This work contributes to the development of a micro-tubular solid oxide fuel cell (mSOFC) stack for use in a small unmanned aerial vehicle. Fuel cells offer cleaner, near-silent operation. Solid oxide fuel cells were chosen due to their higher efficiency and hydrocarbon fuel tolerance. Micro-tubular cells were chosen due to their simpler sealing requirements and stronger cycling properties. 250 W power is required, necessitating the use of many cells. Cathode manufacture was considered and various changes to current techniques suggested. Dip-coating was tested as an alternative to brush-painting. The acetone-based ink was unsuitable for dip-coating so a novel, cheaper, water-based ink was developed and a patent application registered. Cell power, transient and cycling performances were investigated. This transient work is a significant addition to the literature, improving understanding of mSOFC dynamic behaviour. Brush-painted cells take under half a second to adjust to current changes, without voltage overshooting. Dip-coated cells showed weaker performance, potentially due to lower porosity inhibiting mass transport. A six-cell module was built, using modelling to optimise manifold design, and its power and transient performance assessed. Interconnections present significant issues for mSOFCs. Despite power density decreasing with increasing diameter, fewer, larger tubes were used to reduce this problem. A new interconnection approach was developed, combining current techniques.
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Shah, Ankit Jayesh. "Planning for manipulation of interlinked deformable linear objects with applications to aircraft assembly." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105640.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 83-87).
Manipulation of deformable linear objects (DLO) has potential applications in the fields of aerospace and automotive assembly. In this paper, we introduce a problem formulation for attaching a set of interlinked DLOs to a support structure using a set of clamping points. The formulation describes the manipulation planning problem in terms of known clamping locations; pre-determined ideal clamping locations on the cables, called "reference points", and a set of finite gripping points on the DLOs. We also present a prototype algorithm that generates a solution in terms of primitive manipulation actions. The algorithm guarantees that no interlink constraints are violated at any stage of manipulation. We incorporate gravity in the computation of a DLO shape and propose a property linking geometrically similar cable shapes across the space of cable length and stiffness. This property allows for the computation of solutions for unit length and scaling of these solutions to appropriate length, potentially resulting in faster shape computation.
by Ankit Jayesh Shah.
S.M.
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Fossi, Athanase Alain. "Numerical simulations of stationary and transient spray combustion for aircraft gas turbine applications." Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27597.
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Le développement des turbines à gaz d’aviation actuelles et futures est principalement axé sur la sécurité, la performance, la minimisation de la consommation de l’énergie, et de plus en plus sur la réduction des émissions d’espèces polluantes. Ainsi, les phases de design de moteurs sont soumises auxaméliorations continues par des études expérimentales et numériques. La présente thèse se consacre à l’étude numérique des phases transitoires et stationnaires de la combustion au sein d’une turbine à gaz d’aviation opérant à divers modes de combustion. Une attention particulière est accordée à la précision des résultats, aux coûts de calcul, et à la facilité de manipulation de l’outil numérique d’un point de vue industriel. Un code de calcul commercial largement utilisé en industrie est donc choisi comme outil numérique. Une méthodologie de Mécanique des Fluides Numériques (MFN) constituée de modèles avancés de turbulence et de combustion jumelés avec un modèle d’allumage sous-maille, est formulé pour prédire les différentes phases de la séquence d’allumage sous différentes conditions d’allumage par temps froid et de rallumage en altitude, ainsi que les propriétés de la flamme en régime stationnaire. Dans un premier temps, l’attention est focalisée sur le régime de combustion stationnaire. Trois méthodologies MFN sont formulées en exploitant trois modèles de turbulence, notamment, le modèle basé sur les équations moyennées de Navier-Stokes instationnaires (URANS), l’adaptation aux échelles de l’écoulement (SAS), et sur la simulation aux grandes échelles (LES). Pour évaluer la pertinence de l’incorporation d’un modèle de chimie détaillée ainsi que celle des effets de chimie hors-équilibre, deux différentes hypothèses sont considérées : l’hypothèse de chimie-infiniment-rapide à travers le modèle d’équilibre-partiel, et l’hypothèse de chimie-finie via le modèle de flammelettes de diffusion. Pour chacune des deux hypothèses, un carburant à une composante, et un autre à deux composantes sont utilisés comme substituts du kérosène (Jet A-1). Les méthodologies MFN résultantes sont appliquées à une chambre de combustion dont l’écoulement est stabilisé par l’effet swirl afin d’évaluer l’aptitude de chacune d’elle à prédire les propriétés de combustion en régime stationnaire. Par la suite, les rapports entre le coût de calcul et la précision des résultats pour les trois méthodologies MFN formulées sont explicitement comparés. La deuxième étude intermédiaire est dédiée au régime de combustion transitoire, notamment à la séquence d’allumage précédant le régime de combustion stationnaire. Un brûleur de combustibles gazeux, muni d’une bougie d’allumage, et dont la flamme est stabilisée par un accroche-flamme, est utilisé pour calibrer le modèle MFN formulé. Ce brûleur, de géométrie relativement simple, peut aider à la compréhension des caractéristiques d’écoulements réactifs complexes, en l’occurrence l’allumabilité et la stabilité. La méthodologie MFN la plus robuste issue de la précédente étude est reconsidérée. Puisque le brûleur fonctionne en mode partiellement pré-mélangé, le modèle de combustion paramétré par la fraction de mélange et la variable de progrès est adopté avec les hypothèses de chimie-infiniment-rapide et de chimie-finie, respectivement à travers le modèle de Bray-Moss-Libby (BML) et un modèle de flammelettes multidimensionnel (FGM). Le modèle d’allumage sous-maille est préalablement ajusté via l’implémentation des propriétés de la flamme considérée. Par la suite, le modèle d’allumage est couplé au solveur LES, puis successivement aux modèles BML et FGM. Pour évaluer les capacités prédictives des méthodologies résultantes, ces dernières sont utilisées pour prédire les évènements d’allumage résultant d’un dépôt d’énergie par étincelles à diverses positions du brûleur, et les résultats sont qualitativement et quantitativement validés en comparant ceux-ci à leurs homologues expérimentaux. Finalement, la méthodologie MFN validée en configuration gazeuse est étendue à la combustion diphasique en la couplant au module de la phase liquide, et en incorporant les propriétés de la flamme de kérosène dans le modèle d’allumage. La méthodologie MFN résultant de cette adaptation, est préalablement appliquée à la chambre de combustion étudiée antérieurement, pour prédire la séquence d’allumage et améliorer les prédictions antérieures des propriétés de la flamme en régime stationnaire. Par la suite, elle est appliquée à une chambre de combustion plus réaliste pour prédire des évènements d’allumage sous différentes conditions d’allumage par temps froid, et de rallumage en altitude. L’aptitude de la nouvelle méthodologie MFN à prédire les deux types d’allumage considérés est mesurée quantitativement et qualitativement en confrontant les résultats des simulations numériques avec les enveloppes d’allumage expérimentales et les images d’une séquence d’allumage enregistrée avec une caméra infrarouge.The development of current and future aero gas turbine engines is mainly focused on the safety, the performance, the energy consumption, and increasingly on the reduction of pollutants and noise level. To this end, the engine’s design phases are subjected to improving processes continuously through experimental and numerical investigations. The present thesis is concerned with the simulation of transient and steady combustion regimes in an aircraft gas turbine operating under various combustion modes. Particular attention is paid to the accuracy of the results, the computational cost, and the ease of handling the numerical tool from an industrial standpoint. Thus, a commercial Computational Fluid Dynamics (CFD) code widely used in industry is selected as the numerical tool. A CFD methodology consisting of its advanced turbulence and combustion models, coupled with a subgrid spark-based ignition model, is formulated with the final goal of predicting the whole ignition sequence under cold start and altitude relight conditions, and the main flame trends in the steady combustion regime. At first, attention is focused on the steady combustion regime. Various CFD methodologies are formulated using three turbulence models, namely, the Unsteady Reynolds-Averaged Navier-Stokes (URANS), the Scale-Adaptive Simulation (SAS), and the Large Eddy Simulation (LES) models. To appraise the relevance of incorporating a realistic chemistry model and chemical non-equilibrium effects, two different assumptions are considered, namely, the infinitely-fast chemistry through the partial equilibrium model, and the finite-rate chemistry through the diffusion flamelet model. For each of the two assumptions, both one-component and two-component fuels are considered as surrogates for kerosene (Jet A-1). The resulting CFD models are applied to a swirl-stabilized combustion chamber to assess their ability to retrieve the spray flow and combustion properties in the steady combustion regime. Subsequently, the ratios between the accuracy of the results and the computational cost of the three CFD methodologies are explicitly compared. The second intermediate study is devoted to the ignition sequence preceding the steady combustion regime. A bluff-body stabilized burner based on gaseous fuel, and employing a spark-based igniter, is considered to calibrate the CFD model formulated. This burner of relatively simple geometry can provide greater understanding of complex reactive flow features, especially with regard to ignitability and stability. The most robust of the CFD methodologies formulated in the previous configuration is reconsidered. As this burner involves a partially-premixed combustion mode, a combustion model based on the mixture fraction-progress variable formulation is adopted with the assumptions of infinitely-fast chemistry and finite-rate chemistry through the Bray-Moss-Libby (BML) and Flamelet Generated Manifold (FGM) models, respectively. The ignition model is first customized by implementing the properties of the flame considered. Thereafter, the customized ignition model is coupled to the LES solver and combustion models based on the two above-listed assumptions. To assess the predictive capabilities of the resulting CFD methodologies, the latter are used to predict ignition events resulting from the spark deposition at various locations of the burner, and the results are quantitatively and qualitatively validated by comparing the latter to their experimental counterparts. Finally, the CFD methodology validated in the gaseous configuration is extended to spray combustion by first coupling the latter to the spray module, and by implementing the flame properties of kerosene in the ignition model. The resulting CFD model is first applied to the swirl-stabilized combustor investigated previously, with the aim of predicting the whole ignition sequence and improving the previous predictions of the combustion properties in the resulting steady regime. Subsequently, the CFD methodology is applied to a scaled can combustor with the aim of predicting ignition events under cold start and altitude relight operating conditions. The ability of the CFD methodology to predict ignition events under the two operating conditions is assessed by contrasting the numerical predictions to the corresponding experimental ignition envelopes. A qualitative validation of the ignition sequence is also done by comparing the numerical ignition sequence to the high-speed camera images of the corresponding ignition event.
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Forsberg, Oscar. "Evaluation of Hall-sensors for motor control in high precision applications for aircraft." Thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296966.
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A functioning prototype test motor with Hall-sensor feedback has been built, and the test results show that the motor performance in terms of speed ripple is well within the specified demands. The temperature demands however, have not been fully met. The minimum operating temperature of the sensor was specified to -55◦C by Saab, and the sensors found on the market has a minimum operating temperature of -40◦C. There was also an operation error, the reason of which could either be failure of the drive unit to deliver enough current, or the stator magnetic field strength being too strong for the sensors to reliably detect the rotor magnets when a sufficiently strong current is run through the stator windings. For the purpose of investigating this error it is proposed to conduct tests with a drive unit that can deliver currents over 5 A.SWE Demo
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El-Okda, Yasser Mohamed. "Jet/Wall Interaction: An Experimental Study with Applications to VSTOL Aircraft Ground Effects." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32207.
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The flow field of a twin jet impinging on ground plane with and without free-stream and at low jet-height-to-diameter ratios was investigated using the Particle Image Velocimetry (PIV) technique. Detailed, time-averaged flow field data are obtained via the high-resolution and the high-sampling rate instantaneous velocity field that is made available via the PIV technique.
A model of twin jet issuing from 0.245m circular plate, with 0.019m jet exit diameter, and with jet span to diameter ratio of 3.0 is placed in a water tunnel with the jets in tandem arrangement with respect to the free-stream. The recently upgraded PIV system, in the ESM department fluid mechanics laboratory at VA-Tech, allowed us to capture instantaneous velocity field images of about 0.076m x 0.076m, at 512(H)x512(V) frame resolution. Sampling rates of 1000 and 1200 fps were employed.
Understanding the flow field at lower heights is of crucial significance to the VSTOL aircraft application. Huge jet thrust is required to initiate the take-off operation due to the high lift loss encountered while the airframe is in proximity to the ground. Therefore, jet-height-to-diameter ratios of 2 and 4 were employed in this study. Jetto-free-stream velocity ratios of 0.12, 0.18 and 0.22 were employed in addition to the no-free-stream case.
In the current study, only time-averaged flow field properties were considered. These properties were extracted from the available instantaneous velocity field data. In order to provide some details in the time-averaged velocity field, the data were obtained along several planes of interrogation underneath the test model in the vicinity of the twin jet impinging flow. Images were captured in a single plane normal to the free-stream and five planes parallel to the free-stream.
A vortex-like flow appears between the main jet and the fountain upwash. This flow is found to experience spiral motion. The direction of such flow spirals is found to be dependent on the jet exit height above the ground, and on the jet-to-free stream, velocity ratios. The flow spirals out towards the vortex flow periphery and upon increasing the free-stream it reverses its direction to be inward spiraling towards the core of the vortex. The flow reversal at certain height of the jet above the ground depends on the free-stream velocity.
In our discussion, more emphasis is given to the case of jet-height-to-diameter ratio of two. We also found that the largest turbulent kinetic energy production rate is found to be at the fountain upwash formation zone.Master of Science
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Backhouse, R. "Multiaxial non-crimp fabrics : characterisation of manufacturing capability for composite aircraft primary structure applications." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/1929.
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Carbon composite reinforcement fabrics aimed at flight critical aircraft structure application were designed and the capability of the process used to manufacture them examined. Studies of the LIBA multiaxial non-crimp fabric manufacturing process focused on the effect of changes to four manufacturing parameters using an experimental design process to design the fabrics and analyse the results. The composite properties measured included microstructural features of the fibre tows and resin distribution, and mechanical performance both in-plane and their damage resistance and tolerance characteristics. Nine pairs of Toray T300 carbon based LIBA multiaxial non-crimp fabrics were manufactured and converted to composite laminates. Processing was accomplished using the interleaved Resin Film Infusion processing route with commercial Fiberdux 914 matrix resin. All the fabrics were of the same reinforcement type, consisting of 816 g/m2 of fibre; 376 g/m2 oriented along the fabric length (0°) and 220 g/m2 oriented in each of the ±45° directions. Differences between the nine pairs of fabrics were restricted to the settings of four manufacturing parameters; stitch course (needle penetrations/cm); stitch tension, 00 tension and 0° coverage (amount of constraint on the 0° material provided by the stitch). Three settings were used for each of the parameters; each representing the upper and lower limits, and standard setting. Microstructural characterisation of the laminates indicated large differences in both resin distribution and levels of 0° fibre crimp caused by the changes in manufacturing parameter settings. In-plane and damage resistance and tolerance tests on their composites allowed relationships between manufacturing settings, microstructure and engineering properties to be deduced. It was found that selected in-plane properties could be increased by as much as 17% relative to standard production materials, although a wide range of influence was observed. For damage resistance and tolerance characteristics, reductions in impact damage area (C-scan) of between 13-50% are expected across a range of energies. Manufacturing settings to maximise the impact force for delamination initiation were found to minimise the impact damage areas. Similarly the same settings maximised both the Mode I propagation strain energy release rate and the Compression After Impact strength of the materials. It was found that polyester knitting yarn was largely responsible for the control of the damage resistance and tolerance characteristics together with the mean size of the resin areas and layers within the composite. The manufacturing/microstructure/property relationships identified provide those wishing to exploit these materials with design guidelines to tailor fabric structure and performance characteristics for the intended application. Above all else the results highlight the need for precision in specifying and controlling the manufacturing process in order to repeatably produce the desired performance. Further work on the same materials could be used to provide a link to processing characteristics such as permeability for liquid resin moulding processes and ability to conform to complex curved surfaces.
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Rini, Giancarlo <1983>. "Analysis and design of high performance multiphase electric drives for vehicle and aircraft applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7141/.
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The first part of this thesis has focused on the construction of a twelve-phase asynchronous machine for More Electric Aircraft (MEA) applications. In fact, the aerospace world has found in electrification the way to improve the efficiency, reliability and maintainability of an aircraft. This idea leads to the aircraft a new management and distribution of electrical services. In this way is possible to remove or to reduce the hydraulic, mechanical and pneumatic systems inside the aircraft.
The second part of this dissertation is dedicated on the enhancement of the control range of matrix converters (MCs) operating with non-unity input power factor and, at the same time, on the reduction of the switching power losses. The analysis leads to the determination in closed form of a modulation strategy that features a control range, in terms of output voltage and input power factor, that is greater than that of the traditional strategies under the same operating conditions, and a reduction in the switching power losses.
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Rowe, Larry W. "Machine vision applications in UAVs for autonomous aerial refueling and runway detection." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4705.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 182 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 151-156).