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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Steering Control During μ-split Braking for an Autonomous Heavy Road Vehicle

Haglund, Sebastian, Johansson, Henrik January 2020 (has links)
A critical maneuver for a heavy vehicle is braking with different friction on the left and right hand side of the vehicle, called μ-split. This results in an unwanted yaw torque acting on the vehicle. During this situation, the driver maintains the lateral stability and follows the desired path by corrective steering. In anautonomous heavy vehicle the system must handle this situation by itself. The purpose of this thesis is to analyze how an autonomous vehicle can detect a μ-split situation and then use steering control to maintain its path and stability. Two methods for detecting a μ-split situation are presented where one is based on vehicle kinematics, this detector utilizes the difference in wheel speed between the left and right hand side of the vehicle. The other detector is based on lateral vehicle dynamics, this method uses a sliding mode observer to detect unexpected changes in the yaw rate signal. The detectors were tested in a real vehicle and the results showed that the kinematic detector was fast but had a small risk of false detection, while the dynamic detector was slower but more robust. An analysis of the desired steering behavior showed that the steady state during μ-split braking is to drive with a non zero body slip. If a kinematic path follower is used with kinematic error dynamics this will lead to a contradicting behavior since the body slip is equal to the heading error during straight line braking, assuming that the velocity vector of the vehicle is parallel to the path. Simulations showed that during a μ-split situation the Linear Quadratic pathfollower based on kinematic error dynamics manages to follow the path with a non zero body slip while keeping the path errors small. It has also been shown how the detection of a μ-split situation can be used to change control strategy. By introducing active yaw control or change the tuning on the controller after a detection a better result could be achieved.
222

Evolution of the governance of projects within a program

Enjalbert, Tiphaine January 2013 (has links)
In this thesis is discussed the evolution of the governance for the projects constituting a program. The different kinds of programs are first presented. A strong focus is given to the analysis of the actors of the governance and their role. A literature review of these characteristics for project and program governance shows the important role of the sponsor and the manager of the project. A case study of a global program in the luxury group LVMH has been realized for this thesis. This program, called Sapphire consists of the worldwide implementation of a Swiftnet platform in the affiliate of the group. This platform enables to realize secure payments and to receive account statements every day. One characteristics of the program implementation is that the mother houses implementation is handled by a project unit in the holding company. The implementations in the affiliates of the mother houses are then managed by the mother house itself. The main conclusions were: - The perspective of a first implementation is a governance one from the holding company toward the mother house. However, it shifts to a support perspective between the holding company and the mother house for the next implementation. - The project manager moves from the holding company to the mother house. The broker and the steward are thus in the mother house for the affiliate implementation. This practice enables LVMH to keep a small program team whose role becomes like the one of a program management office. - The project unit thus has first a managerial role which is transformed to a support role. However, it remains able to take decisions in case of potential failures The degree of generalizability of this study is finally addressed. This evolution of the governance could also be observed in other temporary programs like ERP implementations.
223

Control Theoretic Approaches to Computational Modeling and Risk Mitigation for Large Crowd Management

Alrashed, Mohammed 11 1900 (has links)
We develop a computational framework for risk mitigation in high population density events. With increased global population, the frequency of high population density events is naturally increased. Therefore, risk-free crowd management plans are critical for efficient mobility, convenient daily life, resource management and most importantly mitigation of any inadvertent incidents and accidents such as stampedes. The status-quo for crowd management plans is the use of human experience/expert advice. However, most often such dependency on human experience is insufficient, flawed and results in inconvenience and tragic events. Motivated by these issues, we propose an agent-based mathematical model describing realistic human motion and simulating large dense crowds in a wide variety of events as a potential simulation testbed to trial crowd management plans. The developed model incorporates stylized mindset characteristics as an internal drive for physical behavior such as walking, running, and pushing. Furthermore, the model is combined with a visualisation of crowd movement. We develop analytic tools to quantify crowd dynamic features. The analytic tools will enable verification and validation to empirical evidence and surveillance video feed in both local and holistic representations of the crowd. This work addresses research problems in computational modeling of crowd dynamics, specifically: understanding and modeling the impact of a collective mindset on crowd dynamics versus mixtures of heterogeneous mindsets, the effect of social contagion of behaviors and decisions within the crowd, the competitive and aggressive pushing behaviors, and torso and steering dynamics.
224

Hand Gesture Controlled Wheelchair / Handrörelsestyrd Elektrisk Rullstol

Nilsson, Rebecca, Winquist de Val, Almida January 2019 (has links)
Haptical technology is a field that is under constant development and that exists in many of today’s products, for example in VR-games and in the controls for vehicles. This kind of technology could in the same way simplify for disabled people by their being able to control a wheelchair using hand gestures. The purpose of this project is to research if a wheelchair can be controlled with hand gestures, and in that case, in which way that would be the most optimal. To answer the research questions in the project, a small scale prototype wheelchair was developed. This prototype is based on a microcontroller, Arduino, that is controlled by a sensor, IMU, that reads the angle of the user’s hand. Together, the components control two motors and steer the wheelchair. The result shows how hand gestures can steer the wheelchair forward, backward, left and right under constant speed, as well as making it stop. The prototype is able to follow the movements of the user’s hand, but reacts more slowly than would be desirable in a real situation. In spite of the fact that there are many different aspects to haptical steering of a wheelchair, this project shows that there is a large potential in implementing this kind of technology in an actual wheelchair. / Haptiskt styrning är en teknologi som utvecklas snabbt och inkorporeras i många av dagens produkter, till exempel i allt från VR-spel till styrning av fordon. På samma sätt skulle denna teknologi kunna underlätta för rörelsehindrade genom att erbjuda styrning av rullstol med hjälp av handrörelser. Syftet med detta projekt var därför att undersöka om en rullstol kan styras med handrörelser och i så fall vilket sätt som är optimalt. För att besvara rapportens frågeställning har framtagningen av en prototyp av en rullstol i liten skala gjorts. Denna är baserad på en mikrodator, Arduino, som styrs av en sensor, IMU, som mäter vinkeln på användarens hand. Med hjälp av dessa kan motorerna styras och rullstolen manövreras. Resultatet av rapporten har lett till ett förslag på hur handrörelser kan styra rullstolen framåt, bakåt, till vänster och till höger under konstant fart samt få den att stanna. Protypen följer gesterna som användarens hand visar, men reagerar långsammare än vad som vore önskvärt i verkligheten. Trots att många utvecklingsmöjligheter kvarstår för haptisk styrning av en rullstol, visar detta arbete att det finns stor potential i att implementera denna teknik med handrörelsestyrning i en verklig rullstol.
225

DYNAMIC PULSED BEAM STEERING USING VIRTUALLY IMAGED PHASED ARRAY

Jie Wang (16642920) 26 July 2023 (has links)
<p>Optical beam steering is of significant importance for various emerging applications such as light detection and ranging (LiDAR), free space optical communication, and holographic display. However, the development of schemes for dynamic spatio-temporal beam steering has been limited in the past. A previous study achieved dynamic and continuous angular beam steering of isolated ultrashort pulses from a mode-locked laser by using a passive metasurface emulating a diffraction grating followed by a lens. In this thesis, we experimentally demonstrate dynamic spatio-temporal steering of high repetition rate pulse trains using a spatial array of frequency combs with a uniform gradient in their carrier-envelope offsets. To accomplish this, we leverage the capabilities of a virtually imaged phased array (VIPA), which is a side-entrance Fabry-Perot etalon, and employ successive spatial Fourier transforms facilitated by a 4f optical lens system. Our experimental results successfully demonstrate the periodic scanning of ultrashort pulse trains generated from an electro-optic comb at a repetition rate of ~10 GHz. The scanning occurs in discrete steps of ~115 μm and ~20 ps in the spatial and temporal domains, respectively.</p>
226

Precision Navigation for Indoor Mobile Robots

Perko, Eric Michael 08 March 2013 (has links)
No description available.
227

A Data Controller in a Language and Platform Independent Steering System and its interaction with Regular and Agent Based Models

Jayakumar, Adithya 06 August 2013 (has links)
No description available.
228

Receiving Frequency Diverse Array Antenna for Tracking Low Earth Orbit Satellites

Elbelazi, Issa January 2020 (has links)
No description available.
229

Parameter Optimisation of EPAS Using CAE

Bhattacharyya, Shounak, Sivaramakrishnan, Suraj January 2019 (has links)
To keep up with technological as well as logistical challenges of the modern automobile market, major car manufacturing firms have resorted to virtual simulation tools. This enables the development as well as validation of vehicular models much before resources are invested into a new physical prototype.This project focuses on the development of a tool that would help in optimising the handling parameters of a vehicle. This is achieved by creating an optimization routine for tuning the various parameters of the Electronic Power Steering (EPAS). This process is usually done manually, by on-track testing, due to the difficulties in correlating Subjective Assessments (SA) with Objective Metrics (OM). Automating this process would help to reduce the overall research and development time, by providing a baseline tune for the EPAS parameters which could then be finely tweaked by manual track testing.The tool is built by interfacing various software in a multi-objective optimisation environment known as ModeFrontier. The modelling and simulations are performed in IPG CarMaker, with the post processing of the results taken care of by Sympathy for Data. Multiple optimization algorithms were tested to achieve the best optimisation routine. The EPAS parameters, namely the Basic Steering Torque, Active Return and Active Damping, act as the input to the optimization routine. The outputs of the model are the Objective Metrics, which provide a clear indication of the dynamic performance of a component. These metrics are optimized to _t the Steering DNA structure, which uniquely describes the attributes of a vehicle. The final optimised vehicle is manually tested at the track, to determine the real driving feel. / För att upprätthålla ett positivt momentum i såväl tekniska som logistiska utmaningar på dagens bilmarknad har stora biltillverkare börjat använda sig av virtuella simuleringsverktyg. Dessa verktyg möjliggör utveckling av diverse fordonsmodeller långt innan resurser investeras i en fysisk prototyp. Detta projekt fokuserar på utvecklingen av ett verktyg som potentiellt kan hjälpa att optimera dynamiska beteendeparametrar för ett fordon. Detta uppnås genom att skapa en optimeringsrutin för att ställa in de olika parametrarna för den elektroniska servostyrningen (EPAS). Denna process görs vanligtvis manuellt, genom test på provbana, på grund avsvårigheterna att korrelera subjektiva bedömningar (SA) med objektiva mätetal (OM). Att automatisera denna process kan bidra till att minska den övergripande forsknings- och utvecklingstiden genom att tillhandahålla en baslinje för EPAS-parametrarna som i efterhand kan finjusteras genom manuell justering på provbana. Verktyget är byggt genom att ansluta olika program i en optimeringsmiljö som kallas ModeFrontier. Modellering och simuleringar utförs i IPG CarMaker, med efterbehandling av resultaten i Sympathy for Data. Flera optimeringsalgoritmer testades för att uppnå bästa optimeringsrutinen. EPAS-parametrarna består av det grundläggande styrmomentet, aktiv retur och aktiv dämpning, och fungerar som invärden till optimeringsrutinen där utvärdera från modellen är objektiva mätetalen, vilket ger en tydlig indikation på den dynamiska prestandan hos en komponent. Dessa mätvärden optimeras för att passa Steering DNA-strukturen, som unikt beskriver egenskaperna hos ett fordon. Det slutliga optimerade fordonet testas manuellt på provbana för att bestämma den verkliga körkänslan.
230

Styrdokument om miljöhistoria

Ahlberg, Victoria January 2009 (has links)
Syftet med uppsatsen var att undersöka huruvida historieundervisningen för grundskolans senare år ska inkludera miljöhistoria. För denna bedömning gjordes en textanalys av vad sex styrdokument på nationell och internationell nivå föreskriver. Skollagen, läroplanen och kursplanen för historia analyserades. Utöver dessa granskades tre internationella dokument som ligger till grund för läroplanen. Undersökningen utgick från ett perspektiv där historiemedvetande, i bemärkelsen handlingsberedskap inför framtiden, stod i centrum. Den genomfördes i form av en idéanalys där förekomsten av två idéer granskades, dels att miljöhistoria/miljöperspektiv ska finnas med i historieundervisningen, och dels att undervisningen ska skapa handlingsberedskap inför framtiden. Vidare gjordes en jämförelse mellan vad styrdokumenten på de olika nivåerna föreskriver. Resultatet visade att styrdokumenten för grundskolans senare år föreskriver att historieundervisningen ska innehålla ett miljöperspektiv. Det skrivs tydligt fram att undervisningen ska skapa handlingsberedskap inför framtiden, och det uttrycks också att miljöperspektiv kan skapa detta. Det föreskrivs inte att miljöhistoria ska finnas med i historieundervisningen. Två av dokumenten skriver inte fram idéerna alls. Jämförelsen av styrdokumenten på de olika nivåerna visade att de nationella styrdokumenten är föreskrivande och att de internationella styrdokumenten är uppmanande och rekommenderande. Läroplanen har dock fångat upp intentionerna i de internationella styrdokumenten. / The purpose of the essay was to investigate whether the teaching of history in compulsory school should include environmental history. For this assessment an analysis was compiled researching six national and international steering documents. The school law, curriculum and course syllabus for history was analyzed. Also three international documents that form the basis for the curriculum were analyzed. The analysis was made from a perspective where history consciousness , in the context of preparedness for the future, was in the centre. The analysis was conducted in a shape of ideas analysis, where the occurrence of two ideas were investigated, partly if environmental history/environmental perspective should be a part of history teaching, and partly if teaching creates preparedness of action for the future. Furthermore, a comparison between the different level steering documents was made. The results showed that two documents don’t accentuate the ideas at all. The collected evaluation is that the steering documents for the later years of compulsory school prescribe that the teaching of history should contain an environmental perspective. It is clearly stated that teaching should create preparedness for the future, and it is expressed that an environmental perspective can create preparedness for the future. It is not prescribed that environmental history should be included in the teaching. The comparison between the steering documents at the different levels showed that the national steering documents are prescriptive and the international steering documents are requesting and recommending. The curriculum has however captured the intentions of the international governing documents.

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