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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.
351

Arbetsformer och metoder på handelsprogrammet / Work Forms and MethodsWithin the Vocational Upper Secondary SchoolProgram for Business and Administration

Patzauer, Klara January 2010 (has links)
By studying the forms of work and methods teachers choose for their teaching on the Business and Administration Programme and by examining the experiences gained by these teachers, I hope to gain a clearer insight into how the demands of national policy/governing documents are met in the actual teaching of the courses within the programme. In my qualitative study,teachers in a team from a Business and Administrative Programme have been my informants. The team combines multiple forms of work and methods in line with the intentions of the national policy/governing documents. Students usually have an unbroken school day with block teaching where they work with case studies and interdisciplinary  work. Morals and ethics are integrated in class. More progressive ways of working  re combined with so-called traditional teaching. An internet based learning platform supports communication between teachers and pupils. Joint setting of goals, planning, and evaluation are done within the team. Teachers' pedagogical views are consistent with those that permeate the national policy/governing documents.Teachers choose the methods they believe lead to better effectiveness. Their choices are based on experience gained from work experience outside school and their teaching experience. I have grouped factors that contribute to teachers' choice of work as, individual, organizational and infrastructural. It is found that the choice of working methods is partly the result of limited resources. The teachers’ chosen approach also means a better working environment for themselves, which is believed to have positive affects on the pupils work situation and results. / Genom att studera vilka arbetsformer och metoder lärarna på handelsprogrammet väljer för sin undervisning och genom att ta del av de erfarenheter lärarna gjort, ville jag bidra med mer kunskap om hur man i undervisningen omsätter de krav som styrdokumenten formulerar. I min kvalitativa studie har lärare i ett arbetslag på Handelsprogrammet varit mina informanter. Arbetslaget kombinerade flera arbetsformer och metoder i linje med styrdokumentens intentioner. Eleverna hade oftast en samlad skoldag med blockundervisning där man jobbade med case och ämnesöverskridande arbeten. Värdegrundsarbete integrerades. Arbetsformerna kombinerades med s.k. traditionell undervisning. En lärplattform stödde kommunikationen mellan lärare och elever. Gemensam målformulering, planering, och utvärdering gjordes i arbetslaget. Lärarnas pedagogiska grundsyn överensstämde med den som genomsyrar styrdokumenten. Lärarna valde de arbetsmetoder de ansåg leder till bättre måluppfyllelse. Valen var grundade på erfarenheter från arbetsliv utanför skolan och erfarenheter av undervisning. Faktorer som bidragit till lärarnas val av arbetsformer har jag grupperat i individuella, organisatoriska och infrastrukturella. Det framkommer att valet av arbetsformer och metoder delvis var en följd av begränsade resurser. För lärarna innebar valda arbetssättet också en bättre arbetsmiljö vilket man ansåg påverkar även elevernas arbetssituation och resultat positivt.
352

Nonlinear Modeling and Control of Automobiles with Dynamic Wheel-Road Friction and Wheel Torque Inputs

Villella, Matthew G. 12 April 2004 (has links)
This thesis presents a new nonlinear automobile dynamical model and investigates the possibility of automobile dynamic control with wheel torque utilizing this model. The model has been developed from first principles by applying classical mechanics. Inputs to the model are the four independent wheel torques, while the steer angles at each wheel are specified as independent time-varying signals. In this way, consideration of a variety of steering system architectures, including rear-wheel steer, is possible, and steering introduces time-varying structure into the vehicle model. The frictional contact at the wheel-road interface is modeled by use of the LuGre dynamic friction model. Extensions to the existing two-dimensional LuGre friction model are derived and the steady-state of the friction model is compared to existing static friction models. Simulation results are presented to validate the model mathematics and to explore automobile behavior in a variety of scenarios. Vehicle control with wheel torque is explored using the theory of input-output linearization for multi-input multi-output systems. System relative degree is analyzed and use of steady-state LuGre friction in a control design model is shown to give rise to relative degree singularities when no wheel slip occurs. Dynamic LuGre friction does not cause such singularities, but instead has an ill-defined nature under the same no-slip condition. A method for treating this ill-defined condition is developed, leading to the potential for the system to have relative degree. Longitudinal velocity control and combined longitudinal and angular vehicle velocity control are demonstrated in simulation using input-output linearization, and are shown to produce improved vehicle response as compared to the open-loop behavior of the automobile. Robustness of the longitudinal velocity control to friction model parameter variation is explored and little impact to the controller's ability to track the desired trajectory is observed.
353

Quasistatisch auslenkbarer Kippspiegel zur Ablenkung von Licht / Quasistatic deflectable torsional micro mirror for light steering application

Kießling, Torsten 21 February 2008 (has links) (PDF)
This dissertation concerns quasistatic torsional mirror's for optical applications. The intended main area of application is the use as switch in optical network's, replacing the conventional optical-electro-optical conversation. With these actuator's a new concept of electrostatic actuation has been realised. While the drive electrodes are integrated into the deflectable mirror, the whole counter electrode below the mirror plate remains at equal ground potential. The device is manufactured out of two parts using method's of silicon bulk mikro machining. A deflectable mirror plate, torsional spring's and the surrounding support structure are fabricated within the thin device layer at the top of BSOI material. The counter electrode is manufactured out of a highly doped silicon wafer. Both part's are assembled together by adhesive bonding at die level at the end. Since the driving potential is supplied to the mirror plate and the counter electrode is at ground level, lateral tolerances because of device assembly mismatches does not appear with the use of the new concept. In detail the mirror plate itself is divided into two seperate electrodes by a parallel arrangement of filled isolating trenches. The highly doped device layer provides electrical connection via the torsional spring's to the mirror electrodes. A quasistatic torsional actuation is performed if a dc-voltage is applied between one mirror side and the counter electrode. Several design's have been fabricated. The lateral dimension of the torsional mirror plate vary from 0,5 mm to 2,0 mm. The designed characteristic frequencies vary from 0,5 to 3 kHz. For quasistatic actuation the pull in angle vary from 1 to 5 degree and the pull in voltage goes up to several hundred volts. Accessorily the mirror plate is enclosed by a comb drive structure. So that the device could be used for low voltage resonant actuation or an capacitive position read out becomes feasible. Within this thesis the new concept has been verified and functionality has been demonstrated. Depending on their characteristic frequency, devices are suitable to perform quasistatic actuation within 10 ms. Experiments indicated that the electrical isolation damages irreversible at drive voltage's above 400 volt. It limits the maximum deflection of nearly all design's. At prototype actuators repeatability has been studied. No drift was observed in the static characteristic within several cycles for certain designs. Closed-loop position control is not mandatory for the actuators fabricated within this thesis. Mechanical stress inside the mirror plate causes deformation of the reflective surface larger than permitted by optical criteria. This paves the way for further device optimization, yield improvement and system integration.
354

Load Calculation and Simulation of an Asphalt Roller / Last beräkningar och simulation av en Asfalt Vältar

Mohamed, Amer January 2005 (has links)
Free body diagrams of an Asphalt Roller were designed for several load cases and used for an optimisation study. Assumptions for the load calculations for each load case were carried out in MATLAB®. The Roller was built in I-DEAS® and the results were compared with the theoretical results / F.B.D av en Asfalt Vältar designerades för olika last fall och användas för en optimisation studier. Antagandena för de olika last beräkningarna utfördas i MATLAB. Vältar byggdes i I-DEAS och resultaten jämfördes med de teoretiska. / Kungsmarks vägen 97 37144 Karlskrona - Sweden Telefon 045510316
355

Steerable antenna design based on liquid metal actuation / Conception d’une antenne orientable doté d’un actionnement par métal liquide

Le Goff, Denis 20 December 2017 (has links)
L’apparition des objets connectés intelligents dont nous sommes les témoins depuis quelques années a généré un besoin croissant d’antennes à bas coût et énergétiquement sobres. La capacité d’effectuer à la volée une mise en forme du faisceau où sa reconfiguration est une propriété particulièrement intéressante, qui pourrait permettre à l’objet intelligent d’effectuer des tâches telles que la surveillance de zone par exemple ou bien d’optimiser son bilan de liaison en ne visant qu’une seule direction de l’espace. Cela pourrait également mener à un accroissement de l’autonomie de l’objet, via une diminution de sa consommation énergétique, voir à le rendre totalement indépendant s’il devient suffisamment économe pour envisager son alimentation via des systèmes de récupération d’énergie. C’est dans ce contexte que nous proposons ici une nouvelle architecture d’antenne reconfigurable, capable d’un balayage de faisceau sur 360° degrés et basée sur l’utilisation de métal liquide au sein d’un système d’actionnement microfluidique. Dans le premier chapitre, nous ferons une rapide présentation des deux principales technologies de balayage de faisceau utilisées aujourd’hui avant d’étudier les diverses techniques de déplacement de métal liquide utilisées et documentées dans la littérature. L’objectif de ce travail est de sélectionner la technique la plus adaptée à nos besoins. Dans le second chapitre, nous proposerons les deux designs d’antennes envisagés pour notre système, basés sur l’architecture Yagi-Uda. Nous discuterons des avantages et inconvénients de chacun afin d’en sélectionner un qui sera examiné plus en avant dans le chapitre suivant. Dans le troisième chapitre, nous étudierons, à l’aide de simulations électromagnétiques, les performances du design d’antenne sélectionné dans le but de justifier notre choix. Cette étude se concentrera sur l’implémentation graduelle de la complexité du design retenu, en partant d’un système très théorique pour aboutir à une émulation très proche de ce que pourrait être un prototype final. Finalement, dans le quatrième et dernier chapitre nous considérerons deux preuves de concept du système complet ainsi que leurs différentes techniques de fabrications. Étant donné le fait que chaque preuve de concept se concentre soit sur l’aspect RF ou fluidique du système, nous étudierons aussi leurs performances respectives. Nous détaillerons également le développement de certains procédés de fabrication spécifiques utilisés pour réaliser les briques de base, en particulier les objets micro-fluidiques. Ce chapitre nous permet de conclure positivement cette étude de la faisabilité du concept proposé et développé dans ce travail. / The advent of autonomous connected smart objects we are witnessing since a few years has generated a growing need for low cost and energetically sober reconfigurable antennas. The ability to perform on the fly beam shaping and re-configuration is a particularly interesting property which would allow the smart object to perform task such as area surveillance for example and to optimize its link budget by targeting a specific direction of space. This could also allow the increase of the object’s autonomy, through a diminution of its power consumption, or even to render it fully autonomous if it becomes sober enough to envision the use of energy harvesting systems. It is in this context that we propose here a new reconfigurable antenna architecture, capable of 360° beam steering, based on the use of liquid metal within a microfluidic actuation system.In the first chapter, we will do a quick presentation of today’s two main beam steering technics used for antennas before studying the various used and documented technics of liquid metal displacement used in the literature for RF applications. The objective is to single out the better suited one to our requirements.In the second chapter, we will propose the two antenna designs envisioned for our system, based on the Yagi-Uda architecture. We will discuss the advantages and drawbacks of each in order to select one design which will be more closely investigated on the following chapter.In the third chapter, we will study, with the help of electromagnetic simulations, the performances of this selected antenna design in order to justify our choice. This study will focus on the gradual complexity implementation of the chosen design, from a very theoretical system to one very close to what a final prototype would be. Finally, in the fourth and last chapter we will consider two proofs of concept of the complete system and their various fabrications technics. Given that each proof of concept focus either on the RF or the fluidic aspect of the system, we will investigate their performances. We will also detail the development of some of the specific fabrication processes used for the basic building blocks, especially for the fluidic objects. This chapter allow us to conclude positively this study on the feasibility of this concept which was proposed and developed in this work.
356

Vision-based trailer pose estimation for articulated vehicles

de Saxe, Christopher Charles January 2017 (has links)
Articulated Heavy Goods Vehicles (HGVs) are more efficient than conventional rigid lorries, but exhibit reduced low-speed manoeuvrability and high-speed stability. Technologies such as autonomous reversing and path-following trailer steering can mitigate this, but practical limitations of the available sensing technologies restrict their commercialisation potential. This dissertation describes the development of practical vision-based articulation angle and trailer off-tracking sensing for HGVs. Chapter 1 provides a background and literature review, covering important vehicle technologies, existing commercial and experimental sensors for articulation angle and off-tracking measurement, and relevant vision-based technologies. This is followed by an introduction to pertinent computer vision theory and terminology in Chapter 2. Chapter 3 describes the development and simulation-based assessment of an articulation angle sensing concept. It utilises a rear-facing camera mounted behind the truck or tractor, and one of two proposed image processing methods: template-matching and Parallel Tracking and Mapping (PTAM). The PTAM-based method was shown to be the more accurate and versatile method in full-scale vehicle tests. RMS measurement errors of 0.4-1.6° were observed in tests on a tractor semi-trailer (Chapter 4), and 0.8-2.4° in tests on a Nordic combination with two articulation points (Chapter 5). The system requires no truck-trailer communication links or artificial markers, and is compatible with multiple trailer shapes, but was found to have increasing errors at higher articulation angles. Chapter 6 describes the development and simulation-based assessment of a trailer off-tracking sensing concept, which utilises a trailer-mounted stereo camera pair and visual odometry. The concept was evaluated in full-scale tests on a tractor semi-trailer combination in which camera location and stereo baseline were varied, presented in Chapter 7. RMS measurement errors of 0.11-0.13 m were obtained in some tests, but a sensitivity to camera alignment was discovered in others which negatively affected results. A very stiff stereo camera mount with a sub-0.5 m baseline is suggested for future experiments. A summary of the main conclusions, a review of the objectives, and recommendations for future work are given in Chapter 8. Recommendations include further refinement of both sensors, an investigation into lighting sensitivity, and alternative applications of the sensors.
357

Control of electromechanical systems, application on electric power steering systems / Contrôle commande des systèmes électromécaniques, application aux systèmes de directions assistées électriques

Yamamoto, Kazusa 08 November 2017 (has links)
De nos jours, la plupart des véhicules sont équipés de Directions Assistées Electriques (DAE). Ce type de systèmes d'aide à la conduite permet de réduire les efforts que le conducteur doit fournir pour tourner les roues. Ainsi, grâce à un moteur électrique, la DAE applique un couple additionnel en accord avec le comportement du conducteur et la dynamique du véhicule. Il est donc nécessaire de développer une commande en couple basée en particulier sur le signal provenant d'un capteur mesurant le couple agissant au niveau de la barre de torsion (correspondant à une image du couple conducteur). Ce composant est donc essentiel au fonctionnement de la DAE. Or, une défaillance de ce capteur entraine le plus souvent une coupure de l'assistance, pouvant mener à un risque d'accidents. Au regard de la sécurité fonctionnelle, un développement d'un mode de sécurité est recommandé, par de plus en plus de constructeurs automobiles. D'autre part, le marché des équipementiers automobiles reste un secteur très concurrentiel où une baisse des coûts de production est un challenge constamment recherché afin de gagner de nouvelles parts de marchés. Cet aspect de réduction du nombre de capteurs et d'analyse de la dynamique du véhicule s'inscrit donc dans le prolongement de la stratégie de sécurité. Cette thèse, menée au sein de JTEKT Europe, aborde ces divers enjeux. Après une présentation des différents systèmes de directions assistés électriques, des modèles sont présentés pour être utilisés lors de la conception de lois de commande et d'estimateurs. Ensuite deux méthodes d'estimation du couple conducteur sujet aux perturbations de la route et aux bruits de mesures sont proposées : la première est un observateur proportionnel intégral (PI) à synthèse mixte $H_infty/H_2$, et la seconde une approche par filtrage $H_infty$. Puis plusieurs stratégies de commande sont proposées suivant deux cas de figures distincts, soit en utilisant un observateur PI qui estime les états du système et le couple conducteur (LQR, commande LPV par retour d'état), soit en faisant abstraction d'estimateur de couple conducteur (commande $H_infty$ par retour de sortie dynamique). Ce dernier aspect présente l'avantage de nécessiter moins de mesures que le précédent. Ces approches ont été validées en simulation et mises en œuvre sur un véhicule prototype où des résultats prometteurs ont été obtenus. / Nowadays, modern vehicles are equipped with more and more driving assistance systems, among them Electric Power Steering (EPS) helps the driver to turn the wheels. Indeed, EPS provides through an electric motor, an additional torque according to the driver's behaviour and the vehicle's dynamics to reduce the amount of effort required to the driver. Therefore, a torque control is developed based on the torque sensor signal which measures in practice the torsion bar torque (corresponding to an image of the driver torque). Consequently, this component is essential to the functioning of EPS systems.Indeed, a torque sensor failure usually leads to shut-off the assistance which may increase the risk of accident. Regarding functional safety, a back-up mode is recommended and required by more and more car manufacturers. On the other hand, a major challenge for automotive suppliers is to reduce cost production in order to meet growing markets demands and manage in the competitive sector. This issue considering a reduction of sensors' numbers and analysis of vehicle's dynamics is therefore an extension of applying the safety strategy. This thesis, carried out within JTEKT Europe, addresses these various issues.After introducing an overview of the different EPS systems, some models used for the design of controllers and estimators are presented. Then, two methods to estimate the driver torque subject to road disturbances and noise measurements are proposed: the first is a proportional integral observer (PI) with mixed synthesis $H_infty / H_2 $, whereas the second is an $ H_infty $ filtering approach. Then, several control strategies are proposed according to two different cases, either by using a PI observer which estimates the system states and the driver torque (LQR, LPV feedback control) or by not taking into account the driver torque estimation ($ H_infty $dynamic output feedback control). This latter approach has the advantage to require less measurements than the previous one. These approaches have been validated in simulation and implemented on a prototype vehicle where promising results have been obtained.
358

Ledarskapets roll vid förändringsarbeten : Centralt styrda förändringar som verkar på flera enheter

Gunnarsson, Sandra, Kröhnke, Anna January 2018 (has links)
Denna studie har syftat till att undersöka ledarskapets roll vid centrala förändringsarbeten som verkar på flera enheter. Mer än två av tre förändringar misslyckas idag på grund av bland annat bristande ledarskap. Tidigare har dock inte ledarskapet vid centralt styrda förändringar som verkar på flera enheter studerats. Syftet med studien har undersökts genom att studera en implementering av Standard Operating Procedure (SOP) på IKEA. Förändringen har styrts från ett nationellt huvudkontor och verkat på flera varuhus. Tidigare forskning visar att implementering av Standard Operating Procedure aldrig tidigare undersökts i globalt privatägda företag som IKEA, utan endast inom vården och medicinsk forskning. Datainsamling har genomförts genom intervjuer med ledare på tre olika IKEA- varuhus. Studien har baserats på teorier kring förändringsprocesser och ledarskap så som Lewins Change model, John Kotters Accelerate’s 8-Step model samt William Bridges Bridges Transition Model. Utifrån en analys av de intervjuer som gjorts och den teori som legat till grund för undersökningen har flera faktorer kopplat till ledarskap identifierats som centrala. Några av de mest väsentliga delarna som identifierats är vikten av att använda personliga mål kopplade till förändringen, tydligt förmedla vision och syfte, inkludera medarbetarna i förändringsarbetet samt att säkra ett starkt stöd från organisationens ledning. Genom att säkra dessa delar så bemöts motstånd och medarbetare motiveras att genomföra förändringen. Slutsatserna i denna studie visar på många likheter med studerad teori. Det är därför lämpligt att använda teorierna i liknande kontexter där centralstyrda förändringar genomförs på flera enheter. / The aim of this study has been to look deeper into leadership within centralized managed changes that take place in multiple units. More than two thirds of changes within companies fail due to bad leadership. Leadership within centralized managed changes that take place in multiple units have never been studied before. The purpose with this study has been fulfilled by studying an implementation of a Standard Operating Procedure (SOP) at IKEA. The implementation has been managed from a national head office and the change has been executed within a number of IKEA-stores. No previous research has been found that studies the implementation of Standard Operating Procedure within global private owned companies. Found studies of SOP has been within health care and medical research. To gather data, interviews have been made with leaders at three different IKEA- stores. Theories that have been used are mainly based around change process and leadership. The included theories are Lewins Change model, John Kotters Accelerate’s 8- Step model Iand William Bridges Bridges Transition. A number of significant factors related to leadership was identified through analysis of the gathered data and theories. Some of the most essential parts that was identified were the importance of using personal goals connected to the goals of the change, to clear communicate the vision and purpose of the change, include the co-worker in the change process and secure a strong support from the management. By assuring these factors the resistance against the change will be handle in a good way and the co-workers will get motivated to carry through the change. The conclusions found in this study shows similarities with the studied theory. It is therefore appropriate to use these theories where centralized managed changes take place at multiple units within a similar context that is investigated in this study.
359

Využití traktorů s pásovým podvozkem v podniku zemědělské prvovýroby

ROUČKA, František January 2018 (has links)
The diploma thesis, which deals with the usage of tractors with tracked chassis in the agricultural primary production, presents in a literature overview the design of the chassis of wheeled tractors, which is supplemented with front axle suspension systems. Main theoretical part of the overview describes the construction of the tracked chassis. There are mentioned and described all units of significant producers of tracked tractors. Further, the work describes the design of suspension of tracked tractors and the possibility of control of the tracked chassis. The theoretical part ends with a chapter focusing on semi-tracked tractors. Practical part shows the methodology and results of the measuring by use of the tracked tractors in the agricultural company annual production, focused on the utilization of each Tractor-set. Thesis is completed by characteristic of the general agriculture company with the analysis of the investments and costs.
360

Design and Implementation of a Strategy for Path Tracking on Autonomous Heavy-Duty Vehicles

Törnroth, Oscar, Nyberg, Truls January 2018 (has links)
In this thesis, a combined feedforward and feedback controller for improved path tracking on autonomous heavy-duty vehicles is designed and implemented. The steering wheel is controlled in order to follow a reference curvature, computed by a higher-level MPC, responsible for minimizing the distance to a planned path. The steering dynamics, from steering wheel via wheel angles, to a measurable vehicle curvature, is modeled, and a conversion from desired curvature gain to input angle to the steering wheel is derived. Tests with an autonomous Scania R580 show that the desired curvature can be followed with satisfactory small error, both in a designed slalom path and on a more generic test track. By utilizing future curvature values computed by the MPC, a non-causal feedforward controller can reduce the delay from input to the steering wheel to a measured response in curvature, by almost two thirds, compared to the currently implemented solution. Compared to an open-loop control design, tests in simulation show that a feedback controller can reduce errors in curvature gain. However, with the identified steering dynamics and the improved conversion from steering wheel angle to curvature, no further improvement in the curvature gain was seen when implementing the feedback controller in the test vehicle. Care must also be taken not to introduce instability in the system when the feedback controller is implemented in series with a high-level MPC. / Den här rapporten beskriver design och implementering av en regulator med kombinerad framkoppling och återkoppling för förbättrad banföljning av autonoma tunga fordon. Fordonets ratt styrs för att följa en kurvaturreferens beräknad av en överordnad MPC, ansvarig för att minimera avståndet till en planerad bana. Dynamiken i styrningen, från ratten via hjulvinklarna till en mätbar kurvatur för fordonet, är modellerad. En översättning från önskad förstärkning av kurvatur till insignal för rattvinkeln är också framtagen. Tester utförda med en autonom Scania R580 visar att den önskade kurvaturen kan följas med tillfredsställande litet fel, både i en egendesignad slalombana och i en mer generisk testbana. Genom att utnyttja framtida referensvärden för kurvatur beräknade av MPC:n, kan en icke-kausal framkopplande regulator minska fördröjningen från insignal till ratten till en mätbar respons i fordonets kurvatur. Jämfört med den nuvarande lösningen minskas fördröjningen med nästan två tredjedelar. Jämfört med en öppen styrning visar tester i simulering att en återkoppling i regulatorn kan minska stationära fel i kurvatur. Med implementeringen av den identifierade styrdynamiken och den förbättrade översättningen från rattvinkel till kurvatur, syntes dock med återkoppling ingen ytterliggare förbättring i testfordonet. Implementering av den återkopplande regulatorn i serie med den överordnade MPC:n behöver också göras med omsorg för att inte introducera instabilitet i systemet.

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