Dissertations / Theses on the topic 'Thrust vector'

A parametric study on Secondary Injection Thrust Vector Control (SITVC) has been accomplished numerically with the help of a commercial Computational Fluid Dynamics (CFD) code called FLUENT®
. This study consists of two parts
the first part includes the simulation of three dimensional flowfield inside a test case nozzle for the selection of parameters associated with both computational grid and the CFD solver such as mesh size, turbulence model accompanied with two different wall treatment approaches, and solver type. This part revealed that simulation of internal flowfield by a segregated solver with Realizable k-&
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(Rke) turbulence model accompanied by enhanced wall treatment approach is accurate enough to resolve this kind of complex three dimensional fluid flow problems. In the second part a typical rocket nozzle with conical diverging section is picked for the parametric study on injection mass flow rate, injection location and injection angle. A test matrix is constructed
several numerical simulations are run to yield the assessment of performance of SITVC system. The results stated that for a nozzle with a small divergence angle, downstream injections with distances of 2.5-3.5 throat diameters from the nozzle throat lead to higher efficiencies over a certain range of total pressure ratios, i.e., mass flow rate ratios, upstream injections should be aligned more to the nozzle axis, i.e., higher injection angles, to prevent reflection of shock waves from the opposite wall and thus low efficiencies. Injection locations that are too much downstream may result reversed flows on nozzle exit.

The design of control mixing algorithms for launch vehicles with multiple vectoring engines yields competing objectives for which no straightforward solution approach exists. The designer seeks to optimally allocate the effector degrees of freedom such that maneuvering capability is maximized subject to constraints on available control authority. In the present application, such algorithms are generally restricted to linear transformations so as to minimize adverse control-structure interaction and maintain compatibility with industry-standard methods for control gain design and stability analysis. Based on the application of the theory of ellipsoids, a complete, scalable, and extensible framework is developed to effect rapid analysis of launch vehicle capability. Furthermore, a control allocation scheme is proposed that simultaneously balances attainment of the maximum maneuvering capability with rejection of internal loads and performance losses resulting from thrust vectoring in the null region of the admissible controls. This novel approach leverages an optimal parametrization of the weighted least squares generalized inverse and exploits the analytic properties of the constraint geometry so as to enable recovery of more than ninety percent of the theoretical capability while maintaining linearity over the majority of the attainable set.

This dissertation focuses on the constrained control of multi-body systems which are actuated by vectorized thrusters. A general control framework is proposed to stabilize the task configuration while ensuring constraints satisfaction at all times. For this purpose, the equations of motion of the system are derived using the Euler-Lagrange method. It is seen that under some reasonable conditions, the system dynamics are decoupled. This property is exploited in a cascade control scheme to stabilize the points of equilibrium of the system. The control scheme is composed of an inner loop, tasked to control the attitude of the vectorized thrusters, and an outer loop which is tasked to stabilize the task configuration of the system to a desired configuration. To prove stability, input-to-state stability and small gain arguments are used. All stability properties are derived in the absence of constraints, and are shown to be local. The main result of this analysis is that the proposed control scheme can be directly applied under the assumption that a suitable mapping between the generalized force and the real inputs of the system is designed. This thesis proposes to enforce constraints by augmenting the control scheme with two types of Reference Governor units: the Scalar Reference Governor, and the Explicit Reference Governor. This dissertation presents two case studies which inspired the main generalization of this thesis: (i) the control of an unmanned aerial and ground vehicle manipulating an object, and (ii) the control of a tethered quadrotor. Two further case studies are discussed afterwards to show that the generalized control framework can be directly applied when a suitable mapping is designed.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.
Includes bibliographical references (leaves 119-124).
by Jackson H. Jung.
M.S.

The Multiple Use Plug Hybrid for Nanosats (MUPHyN) prototype thruster incorporates solutions to several major challenges that have traditionally limited the deployment of chemical propulsion systems on small spacecraft. The MUPHyN thruster offers several features that are uniquely suited for small satellite applications. These features include 1) a non-explosive ignition system, 2) non-mechanical thrust vectoring using secondary fluid injection on an aerospike nozzle cooled with the oxidizer flow, 3) a non-toxic, chemically-stable combination of liquid and inert solid propellants, 4) a compact form factor enabled by the direct digital manufacture of the inert solid fuel grain. Hybrid rocket motors provide significant safety and reliability advantages over both solid composite and liquid propulsion systems; however, hybrid motors have found only limited use on operational vehicles due to 1) difficulty in modeling the fuel flow rate 2) poor volumetric efficiency and/or form factor 3) significantly lower fuel flow rates than solid rocket motors 4) difficulty in obtaining high combustion efficiencies. The features of the MUPHyN thruster are designed to offset and/or overcome these shortcomings. The MUPHyN motor design represents a convergence of technologies, including hybrid rocket regression rate modeling, aerospike secondary injection thrust vectoring, multiphase injector modeling, non-pyrotechnic ignition, and nitrous oxide regenerative cooling that address the traditional challenges that limit the use of hybrid rocket motors and aerospike nozzles. This synthesis of technologies is unique to the MUPHyN thruster design and no comparable work has been published in the open literature.

The recent interests in the necessity of high maneuverability and vertical launching triggered namely the unconventional control design techniques that are effective at high angle of attack flight regimes. For most of missile configurations, this interest required thrust vector control together with conventional aerodynamic control. In this study, nonlinear modeling and dynamical analysis of a surface to air missile with both aerodynamic and thrust vector control is investigated. Aerodynamic force and moment modeling of the presented missile includes the challenging high angle of attack aerodynamics behavior and the so called hybrid control, which utilizes both tail fins and jet vanes as control surfaces. Thrust vector and aerodynamic control effectiveness is examined during flight envelope. Different autopilot designs are accomplished with hybrid control. Midcourse and terminal guidance algorithms are implemented and performed on target sets including maneuverable targets. A different initial turnover strategy is suggested and compared with standard skid-to-turn maneuver. Comparisons of initial roll with aerodynamic and thrust vector control are examined. Afterwards, some critical maneuvers and hybrid control ratio is studied with a real coded genetic algorithm. Rapid turnover for low altitude targets, intercept maneuver analysis with hybrid control ratio and lastly, engagement initiation maneuver optimization is fulfilled.

La commande des actionneurs électropneumatiques a été un sujet largement traité au cours des dernières décennies. Le caractère fortement non-linéaire de son comportement en a fait un cas d'étude particulièrement pertinent dans le cadre d'une démarche d'application de la théorie de la commande des systèmes non-linéaires. L'utilisation de ces techniques a été comparée aux approches linéaires traditionnelles et généralement jugée largement supérieure notamment en termes de précision ou de temps de réponse. Dans ce manuscrit nous abordons très spécifiquement l'aspect multivariable du système et introduisons la transformée A-T, similaire à la transformée de Park appliquée classiquement aux systèmes électriques, afin de donner une forme strict feedback à son modèle d'état, de clarifier les phénomènes physiques mis en jeu lors de sa commande et de distinguer les deux degrés de liberté du système. Cette transformée permet en outre une comparaison directe avec les moteurs électriques décrits dans le repère de Park. Ce parallèle rend notamment possible la solution du problème délicat de l'observation de la position à vitesse nulle en transférant des méthodologies déjà validées sur des systèmes électriques. L'exploitation des deux degrés de liberté est illustrée par la synthèse de lois de commande combinant le suivi d'une trajectoire de position du piston au respect d'un second critère variable (réglage de la pressurisation moyenne, optimisation de la consommation instantanée). L'utilisation d'un actionneur électropneumatique asservi comme actionneur à compliance variable est étudiée. Une loi de commande basée sur la transformée A-T est proposée pour contrôler simultanément la position et la raideur pneumatique de l'actionneur. Une méthodologie de réglage des gains de commande est proposée pour définir l'impédance en boucle fermée du système. L'influence de la raideur pneumatique sur la raideur en boucle fermée est étudiée. L'utilisation d'une source d'énergie alternative (de l'hélium sous pression) est également pour la première fois mise en œuvre. L'influence du changement de gaz sur le dimensionnement de l'actionneur électropneumatique est étudiée et une méthodologie permettant d'utiliser les lois de commande prévues pour de l'air est proposée. L'ensemble des propositions faites dans ce manuscrit est testée et validée sur un banc d'essais à la structure inédite. Ce dernier allie deux actionneurs, l'un électropneumatique (l'actionneur étudié) et l'autre, un moteur plat électrique (l'actionneur de charge). L'utilisation de celui-ci permet la génération d'efforts perturbateurs dans une large bande passante ainsi que la modification en temps réel des paramètres mécaniques dynamiques de la charge.

Mosquito-borne viruses, such as dengue virus (DENV), Zika virus (ZIKV), chikungunya virus (CHIKV), yellow fever virus (YFV), Japanese encephalitis virus (JEV), and West Nile virus (WNV) are major threats to global public health resulting in millions of infections and hundreds of thousands of deaths annually. The presence of these viruses and their increasing emergence/spread continues to escalate. Notably, Usutu virus (USUV; Genus: Flavivirus; Family: Flaviviridae) is one such pathogen currently causing mass die-offs of avian hosts throughout Europe. USUV is categorized in the Japanese Encephalitis virus (JEV) antigenic complex and thus shares many antigenic and pathologic characteristics with fellow members, such as JEV and WNV. Respective to human infections, USUV cases are generally asymptomatic; nonetheless, acute cases have been reported. These acute cases typically cause mild symptoms, such as fevers and rashes; however, more severe cases can result in neurologic diseases, such as encephalitis and/or meningoencephalitis. In addition to these pathologic similarities, USUV shares several ecological and geographical traits with WNV, a pathogen responsible for several outbreaks during its spread from Africa, to Europe, and eventually the United States. Currently, WNV is considered endemic in areas across the United States due to its transmission via Culex spp.; mosquitoes that are ubiquitous in the United States. These parallels suggest the possible emergence of USUV into the United States and therefore, it is imperative to broaden our knowledge of USUV and assess its potential to become a major global health concern. The overall goal of this thesis was to characterize USUV and evaluate its emergence potential in the United States by: (1) developing infectious clones of recent European and African USUV isolates as tools for characterization and analysis of USUV and (2) assessing the transmission potential of several species of North American mosquitoes. In Aim 1, we show that the aforementioned infectious clones infect and replicate similarly to their parental strains in vitro in both vertebrate and invertebrate models, as well as in transiently immunocompromised CD-1 and IFNAR-/- murine models, and thus serve as useful tools for future molecular studies focusing on USUV. Furthermore, in Aim 2, we describe the ability of field-caught (Southwest Virginia, USA) Culex spp. and Aedes spp. mosquitoes to become infected with a recent European isolate of USUV; although, we report an overall limited potential for these species to transmit this virus. Altogether, these studies form a foundation for understanding the potential emergence of USUV in the United States as well as provide necessary tools needed to aid future research on USUV emergence, transmission, and pathogenesis.
Master of Science
Usutu virus (USUV) is an emerging mosquito-borne virus that was first isolated from a mosquito in 1959 in South Africa, and since then, has become a major problem throughout Africa and Europe causing acute to severe infection in dozens of patients. Additionally, this virus is causing massive die-offs in Eurasian blackbird populations. This is particularly problematic because birds play a critical role in ecosystems as they act as forms of pest control, pollinators, and seed dispersers. Depletion of these species could lead to an imbalance and, eventually, collapse of our natural ecosystem. Additionally, there is a growing concern of USUV making its way into the United States, following a similar track of emergence to WNV's introduction in New York in 1999 and its subsequent spread throughout the states. WNV's introduction to the United States was detrimental to native bird populations and humans, and has caused tens of thousands of infections and thousands of deaths since this introduction. Research has shown USUV causes similar disease symptoms to WNV. The self-limiting illness from these viruses typically includes fever and rashes but some infections can result in more severe cases causing inflammation of the brain and surrounding areas. Like many other prominent mosquito-borne viruses, there is no specific treatment or vaccine for WNV or USUV. Because USUV is so closely related to WNV, and their similar characteristics may point towards similar emergence in the United States, it is essential to garner more information on USUV. The overall goal of this thesis was to establish a reliable tool(s) for further characterization of USUV and demonstrate the potential for USUV emergence in the United States. We first developed molecular tools, known as viral clones, that are valuable to the scientific community which allows the manipulation of USUV genetic material to perform further downstream studies. Our objective for this initial study was to create a molecular tool that would behave similarly to their natural, or "parental", virus. The results from this study suggest we have successfully produced these tools. Furthermore, we sought to determine the potential for field-caught mosquitoes from Southwest Virginia, USA to transmit a recently isolated strain of USUV. These data suggest that while these mosquitoes do have the ability to become infected with USUV, they have a limited potential to transmit this virus to animal hosts. Altogether, these studies have allowed us to expand our knowledge on USUV's potential emergence in the United States and develop powerful tools to continue this essential research.

Background. Smart home assistants are becoming more common in our homes. Often taking the form of a speaker, these devices enable communication via voice commands. Through this communication channel, users can for example order a pizza, check the weather, or call a taxi. When a voice command is given to the assistant, the command is sent to cloud services over the Internet, enabling a multitude of functions associated with risks regarding security and privacy. Furthermore, with an always active Internet connection, smart home assistants are a part of the Internet of Things, a type of historically not secure devices. Therefore, it is crucial to understand the security situation and the risks that a smart home assistant brings with it. Objectives. This thesis aims to investigate and compile threats towards smart home assistants in a home environment. Such a compilation could be used as a foundation during the creation of a formal model for securing smart home assistants and other devices with similar properties. Methods. Through literature studies and threat modelling, current vulnerabilities towards smart home assistants and systems with similar properties were found and compiled. A few  vulnerabilities were tested against two smart home assistants through experiments to verify which vulnerabilities are present in a home environment. Finally, methods for the prevention and protection of the vulnerabilities were found and compiled. Results. Overall, 27 vulnerabilities towards smart home assistants and 12 towards similar systems were found and identified. The majority of the found vulnerabilities focus on exploiting the voice interface. In total, 27 methods to prevent vulnerabilities in smart home assistants or similar systems were found and compiled. Eleven of the found vulnerabilities did not have any reported protection methods. Finally, we performed one experiment consisting of four attacks against two smart home assistants with mixed results; one attack was not successful, while the others were either completely or partially successful in exploiting the target vulnerabilities. Conclusions. We conclude that vulnerabilities exist for smart home assistants and similar systems. The vulnerabilities differ in execution difficulty and impact. However, we consider smart home assistants safe enough to usage with the accompanying protection methods activated.
Bakgrund. Smarta hemassistenter blir allt vanligare i våra hem. De tar ofta formen av en högtalare och möjliggör kommunikation via röstkommandon. Genom denna kommunikationskanal kan användare bland annat beställa pizza, kolla väderleken eller beställa en taxi. Röstkommandon som ges åt enheten skickas till molntjänster över internet och möjliggör då flertalet funktioner med associerade risker kring säkerhet och integritet. Vidare, med en konstant uppkoppling mot internet är de smarta hemassistenterna en del av sakernas internet; en typ av enhet som historiskt sett är osäker. Således är det viktigt att förstå säkerhetssituationen och riskerna som medföljer användningen av smarta hemassistenter i en hemmiljö. Syfte. Syftet med rapporten är att göra en bred kartläggning av hotbilden mot smarta hemassistenter i en hemmiljö. Dessutom kan kartläggningen fungera som en grund i skapandet av en modell för att säkra både smarta hemassistenter och andra enheter med liknande egenskaper. Metod. Genom literaturstudier och hotmodellering hittades och sammanställdes nuvarande hot mot smarta hemassistenter och system med liknande egenskaper. Några av hoten testades mot två olika smarta hemassistenter genom experiment för att säkerställa vilka hot som är aktuella i en hemmiljö. Slutligen hittades och sammanställdes även metoder för att förhindra och skydda sig mot sårbarheterna. Resultat. Totalt hittades och sammanställdes 27 stycken hot mot smarta hemassistenter och 12 mot liknande system. Av de funna sårbarheterna fokuserar majoriteten på manipulation av röstgränssnittet genom olika metoder. Totalt hittades och sammanställdes även 27 stycken metoder för att förhindra sårbarheter i smarta hemassistenter eller liknande system, varav elva sårbarheter inte förhindras av någon av dessa metoder. Slutligen utfördes ett experiment där fyra olika attacker testades mot två smarta hemassistenter med varierande resultat. En attack lyckades inte, medan resterande antingen helt eller delvis lyckades utnyttja sårbarheterna. Slutsatser. Vi konstaterar att sårbarheter finns för smarta hemassistenter och för liknande system. Sårbarheterna varierar i svårighet att uföra samt konsekvens. Dock anser vi att smarta hemassistenter är säkra nog att använda med medföljande skyddsmetoder aktiverade.

This study evaluates the roles of temperature variability and disease awareness in the emergence of Chagas disease (American trypanosomiasis). Chagas disease is endemic in Latin America and primarily spreads to humans directly via the triatomine vector. Hosts for most triatomine species are mainly rodents and occasionally dogs. The disease itself is caused by a parasitic protozoan, Trypanosoma cruzi (T. cruzi) which is found in the triatomineâ s feces and is often spread while the triatomine is consuming a blood meal. T. cruzi from feces enters the body via an abrasion on the skin, the mucous membranes, conjunctivae, or through consumption. To determine the risk of Chagas disease transmission one must define qualities that make the triatomine an effective disease vector as well as investigate the level of disease awareness among physicians and the population within the vectorâ s range. This thesis maps triatomine species within the U.S. that harbor T. cruzi naturally and that exhibit qualities of domesticity. These qualities are defined by whether the species bites humans and dogs as well as reports that the species has been found in the domestic setting. Ranges illustrating temperature thresholds for increased triatomine activity for 2000 and 2030 are also depicted. Additionally, outcomes of a physician survey are presented to gauge the status of Chagas disease awareness in areas at higher risk for disease transmission. Results reveal limited consideration of Chagas disease in physician diagnosis despite the higher risk range which extends through the southern U.S. and is predicted to expand significantly by 2030.
Master of Science

碩士
國立臺灣大學
電機工程學研究所
88
A nonlinear missile guidance controller with Thrust Vector Control(TVC) inputs for the interception of a theater ballistic missile is presented. In this thesis, the midcourse phase of the missile is discussed, during which many non-ideal conditions must be considered, such as variation of the inertia of the missile and the aerodynamic force, and the controller is designed according to the properties of TVC. A 3D optimal midcourse guidance law is designed to minimize the control effort and the distance between the missile and the target without the estimation of intercept time. And the quaternion-based sliding mode attitude controller is designed to execute the attitude command and eliminate the influence of the variation of the missile’s inertia and the aerodynamic force simultaneously. The stability of the overall system is proved by Lyapunov theory. Extensive simulations are performed to verify the validity of the overall system.

碩士
中原大學
機械工程研究所
105
Infrastructure deterioration is one of the biggest problem in engineering, thus, regular inspection of the bridge is a must. Traditional inspection method involving human inspector using aerial ladder, which is dangerous and most importantly, the inspection visual only. For these reason, many enterprise and university are using unmanned aerial vehicle to capture aerial image/video to perform building inspection. However, all vehicle suffer attitude change when performing translation x and y direction, which effect the qualities of photos. This thesis aims at tackle the problem to increase the photo qualities by removing attitude change. The method that will be applied is vector thrust propulsion system, which instead of attitude change in vehicle, the motor will change its attitude to allow the vehicle to maneuver to perform building inspection and collect image data. By constructing conventional multi-rotor vehicle mathematical model as starting point, this thesis will focus on the modeling of vector thrust and actual mechanism for the multi-rotor vehicle. Hardware realization will be based on the modification of “motor arm” in the existing frame, and lastly, the inspection experiment will be carry out to compare image qualities between conventional design and vector thrust design.

Thesis (M.S.)--State University of New York at Buffalo, 2008.
Title from PDF title page (viewed on Nov. 14, 2008) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Forliti, David J. Includes bibliographical references.

碩士
元智大學
機械工程學系
93
In the present work, the effects of friction and material properties on the displacement of the nozzle in thrust vector control systems are firstly studied. Finite element analyses are performed to simulate the three-dimensional nozzle mechanisms in a thrust vector control system. The parameters associated with friction and material properties, such as static and dynamic coefficients of friction and yield strength, are varied in a systematic manner to study their effects on nozzle displacement. It is concluded that friction may be the dominant factor causing the actual nozzle displacement to be deviated from the designed one. The second part of the present work is to study the interface effects on the stress transfer in carbon nanotube-(CNT-)reinforced epoxy-matrix composites subjected to uniaxial loading. Three interface conditions are considered: (1) all interfaces are strong, i.e., perfectly bonded; (2) the epoxy/CNT interface is strong, whereas the CNT wall/wall interface is weak, i.e., frictional sliding is allowed to occur; and (3) all interfaces are weak. Our results indicate that strong interfaces ensure the effective stress transfer in CNT-reinforced composites while weak interfaces degrade the load-carrying capabilities of multi-wall carbon nanotubes.

碩士
國立臺北科技大學
電機工程系
107
Nowadays, the speakers’ accent recognition, speech to text conversion and their applications are becoming popular research areas all over the world. Although some countries’ people speak English as native, almost all except USA, Australia, United Kingdom, and some other countries’ people speak the English language as non-native. The accent of speakers has great influence during communication between different countries’ people to each other. This thesis discusses the speakers’ accent recognition, gender accent recognition and isolated keyword recognition using keywords’ voice of non-native English language speakers. Identification of the accent similarity between non-native English speaker countries and native English speakers is also one part of this research. The accent similarity or gap between 3 countries’ people accent, namely, Ethiopian, Indian and Taiwanese also investigated. In this work, a hybrid model of Convolutional Neural Networks (CNN) and Support Vector Machine (SVM) on the voice recognition applications is proposed. The spectrograms of speech signal feature extractor are pre features extractor, CNN model as post features extractor and SVM as the classifier. In this work, after the voice is converted to spectrogram the speech recognition technique followed the working principle of image recognition. The CNN extracts features from a spectrogram image representation of speech and SVM is applied to extracted features. The performance of the hybrid CNN-SVM model is evaluated by comparing it to CNN and SVM models alone. The fusion model of CNN-SVM converges fast and reduce the overfitting problem unlike to CNN model alone. The result shows that the proposed system carried out multiple tasks at the same time and achieved high recognition accuracy.

碩士
中原大學
機械工程研究所
106
Drone industry is getting prosper nowadays, and bringing huge innovation to other industries as well. Aside from normal consumer, there are more application on industrial and agricultural aspect. For instance, electricity patrolling, forest patrolling, water quality testing and building testing. With aging population and outgoing population in countryside, many farmers and proprietors start to use drones to spread pesticide, crop analysis, disease prevention and hazard assessment of animals and planets. Although it solved most of problems, it also caused other problems, including uneven pesticide spreading and harm to human body and environment caused by overheight pesticide spreading…etc. This thesis would mainly discuss the spreading part, finding the most efficient way of spreading and flying according to the analysis and the test of the flying pattern, drone construct and spreading aproach.

碩士
國立臺北科技大學
自動化科技研究所
106
With the rapid development of network technology, traditional network attacks with intrusion patterns have also evolved continuously. APT (Advanced Persistent Threat) is a more complex and targeted attack mode in today’s cyber threats and it is usually organized with purposes. When hacker groups have targeted some specific targets, they will attack the specified target with customized techniques after a long period of layout and information search. In order to find out the APT threat early, we uses the NSL-KDD dataset to test our proposed methods in this study. First, the PCA (principal component analysis) is used to reduce the dimension to improve the efficiency of detection. Second, the SVM (support vector machine), Naïve Bayes, decision trees and ANN (artificial neural network) are used to classify the pattern form the NSL-KDD dataset for APT detection. The results show that the classification rate of SVM is 97.22% (all internal).With using the SVM model with training, we can establish an early warning mechanism to reduce the APT attacks.