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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.
1

Tyre Inflation Pressure control to improve vehicle ride comfort on rough roads

Komana, Tokologo M.G. 26 August 2020 (has links)
Tyres behave similar to a spring and damper systems smoothing out road irregularities as the tyre rolls. Tyre stiffness and damping characteristics are largely influenced by the tyre pressure. As a result, tyre pressure has an influence on tyre enveloping and ride comfort. To take advantage of the influence of tyre pressure on ride comfort, a pressure controlled tyre was developed to vary the tyre pressure, thus varying the tyre characteristics as the road conditions change to improve ride comfort. Literature exists on TIS (Tyre Inflation Systems) and smart suspension control strategies optimised for ride comfort, which indicate that a pressure controlled tyre can be developed by managing a TIS with a ride comfort controller. A VDG (Vehicle Dynamics Group) test trailer was used to complete this study. The trailer was modelled on three platforms; MATLAB, Cosin and ADAMS View; with the co-simulation managed through Simulink. Three tests were conducted to parametrise and validate the model, namely; pneumatic system parametrisation tests, APG (Aberdeen Proving Ground) bump tests and Belgian paving tests. The pneumatic system parametrisation tests show that the discharge coefficient is approximately 0.07 for choked flow and tappers off to zero for unchoked flow. Also, tests show that the tyre can be inflated from 1.0 bar to 3.0 bar in 8 s and deflated from 3.0 barto 1.0 bar in 13 s. The APG bump tests and Belgian paving tests were conducted to validate the model over discrete obstacles and rough roads, respectively. These tests indicate that the model correlates with the actual trailer. The validated model was used to develop the TIPc (Tyre Inflation Pressure controller), which uses a running RMS control strategy to manage the TIS. The objective of the TIPc is to maintain a NOT uncomfortable ride comfort level. The TIPc achieves this by deflating the tyre to a suitable tyre pressure when the ride comfort level is above NOT uncomfortable. The TIPc is robust to evaluate ride comfort on smooth roads and rough roads, as well as, detecting discrete obstacles. The TIPc ignores discrete obstacles when evaluating ride comfort to determine a suitable tyre pressure to improve ride comfort. The TIPc was able to achieve a 4−7% RCI (Ride Comfort Improvement). / Dissertation (MEng)--University of Pretoria, 2020. / Mechanical and Aeronautical Engineering / MEng / Unrestricted
2

Future certification of autonomous vehicles and the use of virtual testing methods / Framtida certifiering av autonoma fordon och användning av virtuella testmetoder

Nordenström, Martin January 2020 (has links)
One of the biggest obstacles to launching autonomous vehicles is the current legislation, which currently does not cover automation level higher than level 2. Work on developing the legal requirements takes place at UN level within WP29 (The UNECE World Forum for Harmonization of Vehicle Regulations). As a world-leading vehicle manufacturer, Scania is aspiring to pave the way for sustainable transport solutions. At Scania, well-established methodologies on certification of different systems exist, although the process of certification of autonomous driving systems needs to be developed.This master thesis investigates the current situation regarding the elaboration of regulations to cover autonomous vehicles, future certification methods related to these systems, and how this applies to Scania. Particular focus is being on the investigation of virtual certification methods. This can form the basis for various departments at Scania in their work with future autonomous systems and how to get these certified.The future certification work for autonomous vehicles will be based on a validation process based on a process called the ‘Multi-pillars approach’ / ‘Three-pillars approach’. The idea is that the autonomous vehicle should be certified based on a process where the basis for certification is made by validating and justifying its systems. This will be done through simulations and other methods to ensure that the systems are satisfactory. A less extensive work should then be done in the testing of the autonomous vehicle on the test track and in traffic, where only less demanding situations must be validated.The functional requirements of the autonomous vehicle will largely control the validation process that is carried out for the ‘Multi-pillars approach’ / ‘Three-pillars approach’. For example, the definition of ODD (Operational Design Domain) is crucial for the validation that the vehicle will undergo at a later stage. / Ett av de största hindren för att lansera självkörande fordon är den nuvarande lagstiftningen som i dagsläget inte täcker automationsnivå högre än nivå 2. Arbetet med att ta fram lagkraven sker på FN nivå inom WP29 (The UNECE World Forum for Harmonization of Vehicle Regulations). Som en världsledande fordonstillverkare strävar Scania efter att bana väg för hållbara transportlösningar. På Scania finns väletablerade metoder för certifiering av olika system, men processen för certifiering av autonoma fordon måste dock utvecklas.Detta examensarbete undersöker den aktuella situationen när det gäller utformandet av regelverk för att täcka autonoma fordon, framtida certifieringsmetoder relaterade till dessa system och hur detta påverkar Scania. Särskilt fokus ligger på utredning av virtuella certifieringsmetoder. Detta kan ligga till grund för olika avdelningar på Scania i deras arbete med framtida autonoma system och hur man får dessa certifierade.Det framtida certifieringsarbetet för autonoma fordon kommer att bygga på en valideringsprocess som bygger på en process som kallas för ”Multi-pillars approach”/”Three- pillars approach”. Tanken är att fordonet ska certifieras utifrån en process där grunden till certifiering görs genom att validera och rättfärdiga sina system. Detta ska ske genom simulering och andra metoder för att säkerhetsställa att systemen är tillfredställande. Ett mindre omfattande arbete ska sedan göras i testningen av fordonen på testbana och ute i trafik, där endast mindre krävande situationer ska valideras.De funktionella kraven på fordonen kommer till stor del att styra den valideringsprocessen som görs med för ”Multi-pillars approach”/”Three-pillars approach”. Exempelvis är definierandet av ODD (Operational Design Domain) avgörande för den validering som fordonet i ett senare skede ska genomgå.
3

An experimental study on the stability and control of a tailless aircraft

Stenfelt, Gloria January 2009 (has links)
No description available.
4

Lateral Stability of High-Speed Trains at Unsteady Crosswind

Thomas, Dirk January 2009 (has links)
<p>Crosswind stability of rail vehicles has been a research area for several decades,mainly motivated by vehicle overturning accidents and higher speeds, but in recenttimes also by issues of lower energy consumption and track maintenance costsdemanding lower vehicle weights. During everyday operation, rail vehicles are subjectedto large lateral influences from track irregularities, track curves and crosswind,leading to large suspension deflections and increased crosswind sensitivity.Also unsteady crosswind like gusts calls for attention. Simulations of possible vehicleoverturning are necessary, but need to take large deflections and high shear inthe suspension into account. If delivering reasonable results, simulations representan important tool for overturning prediction of the vehicle.</p><p>In the present work, multibody simulations of a high-speed vehicle at large lateralinfluences from track curves and track irregularities have been carried out, using ahalf-vehicle model in 2D and a model of a whole vehicle in 3D. The vehicle modelsalso include different suspension models. Corresponding field measurements ofthe relative lateral and vertical deflections in the secondary suspension have beenperformed on a fast train and used for validation of the multibody simulations,resulting in good agreement between measurements and simulations.</p><p>The 3D vehicle model was further used to study the vehicle response to unsteadycrosswind during curve negotiation where aerodynamic loads obtained by unsteadyComputational Fluid Dynamics, namely Detached Eddy Simulations, representingthree types of gusts were used. In addition, the method of Quasi Transient GustModelling was evaluated in terms of overturning risk. Strong lateral and roll responsesof the vehicle and influences of the gust duration and the relative differencebetween mean and maximum wind speed were observed. Further, variations of suspensionand mass properties of the vehicle were performed to study the influenceon crosswind sensitivity. The position of the centre of mass of the carbody and thelateral bumpstop clearance showed significant influence on the crosswind stability.</p>
5

Heat Transfer Prediction of In Service Welding in a Forced Flow of Fluid

Lindström, Per January 2005 (has links)
An algorithm for heat transfer prediction of in-service welding operations in a forcedflow of fluid is presented. The algorithm presented is derived from Rosenthal’s 3D heatflow equation and boundary layer approximations. This was possible by the introductionof an apparent thermal conductivity kPL, which is a function of the boundary layer’s heattransfer coefficient f and the base material’s thickness . This implies that a weldcooling time ΔtT1 /T2 in a forced flow of fluid can now be calculated by an ordinaryengineering calculator and thus enabling suitable welding parameters to be determined.The magnitude of kPLf , was established by regression analysis of results from aparametric finite element analysis series of a total number of 112 numerical simulations.Furthermore, the result of the regression analysis was validated and verified by a weldingexperiment series accomplished on an in-house designed and constructed in-servicewelding rig. The principle design of the welding rig as well as its instrumentation, a PCbased Data Acquisition system, is described. In addition, a method to measure the weldmetals cooling time ΔtT1 /T2 by means of thermocouple elements is described. Finally,the algorithm presented in this study proved feasible for industrial in-service weldingoperations of fine-grained Carbon and Carbon–Manganese steels with a maximum Carbon Equivalent (IIW) (CE) of 0.32. / Funktionsstabilitet
6

Finite Element Modeling of Contact Problems

Rashid, Asim January 2016 (has links)
Contact is the principal way load is transferred to a body. The study of stresses and deformations arising due to contact interaction of solid bodies is thus of paramount importance in many engineering applications. In this work, problems involving contact interactions are investigated using finite element modeling. In the first part, a new augmented Lagrangian multiplier method is implemented for the finite element solution of contact problems. In this method, a stabilizing term is added to avoid the instability associated with overconstraining the non-penetration condition. Numerical examples are presented to show the influence of stabilization term. Furthermore, dependence of error on different parameters is investigated. In the second part, a disc brake is investigated by modeling the disc in an Eulerian framework which requires significantly lower computational time than the more common Lagrangian framework. Thermal stresses in the brake disc are simulated for a single braking operation as well as for repeated braking. The results predict the presence of residual tensile stresses in the circumferential direction which may cause initiation of radial cracks on the disc surface after a few braking cycles. It is also shown that convex bending of the pad is the major cause of the contact pressure concentration in middle of the pad which results in the appearance of a hot band on the disc surface. A multi-objective optimization study is also performed, where the mass of the back plate, the brake energy and the maximum temperature generated on the disc surface during hard braking are optimized. The results indicate that a brake pad with lowest possible stiffness will result in an optimized solution with regards to all three objectives. Finally, an overview of disc brakes and related phenomena is presented in a literature review. In the third part, a lower limb donned in a prosthetic socket is investigated. The contact problem is solved between the socket and the limb while taking friction into consideration to determine the contact pressure and resultant internal stress-strain in the soft tissues. Internal mechanical conditions and interface stresses for three different socket designs are compared. Skin, fat, fascia, muscles, large blood vessels and bones are represented separately, which is novel in this work.
7

Fartygstrafik genom naturreservat : Salvorev: Östersjöns genväg

Andersson, Johan, Hallgren, Einar January 2017 (has links)
Den här studien undersöker hur utsläppen av CO2 samt NOx skulle påverkas av att man tog en längre rutt runt ett Natura 2000 område mellan Gotska sandön och Fårö norr om Gotland i Östersjön. Detta för att undvika att köra i ett natura 2000 området och på så sett minska sjöfartens påverkan på djurlivet där. Med hjälp av AIS data har information tagits fram om hur många fartyg som använder rutten genom natura 2000 området. En sammanställning av vilka typer av fartyg samt dess maskineri har också tagits fram med hjälp av detta. Som ligger till grund för uträkningarna för CO2 samt NOx utsläppen. Studien visar på att CO2 utsläppen kan öka med upp till 4,72 ton genom att köra en längre rutt runt området, även NOx utsläppen ökar, med upp till 0,13ton.
8

MD-80 Engine Change Kit

Nogueira, Tiago, Twofik, Twana January 2007 (has links)
<p>Den här rapporten ämnar svara på frågan om och med hur mycket tröskelvärdena av alla inkommande komponenter, tillhörande ett MD-80 Engine change kit, kan höjas med och vilka kostnadsbesparingar en sådan höjning kan medföra. Undersökningen har föranletts av företaget SAS Components vilja att få reda på om en optimering av tröskelvärden kan leda till en minskning av kasserade komponenter hos dem.</p> / <p>This report’s aim is to verify if it is possible, and if so, by how much SAS Component could increase the threshold values of all incoming components belonging to an MD-80 Engine Change Kit. How would this raise in the components threshold lower SAS Component’s expenses?</p>
9

Experimentell motståndsanalys av kåpkonfigurationer på Scaniamodells busstak

Karlsson, Robert January 2008 (has links)
<p>Sammanfattning</p><p>Dagens stigande bränslepriser gör det alltmer viktigt för tillverkare samt brukare av fordon, att fokusera på detaljer som kan minimera drivmedelåtgången. Scania linjetrafikbussar är utrustade med ett antal olika konfigurationer av kåpor som figurerar på bussarnas tak.</p><p>Projektet har således innefattat att undersöka dessa ur ett aerodynamisk perspektiv i Mälardalens högskolas låghastighetsvindtunnel, förlagt vid Hässlö i Västerås.</p><p>Resultaten som uppnåddes är att motståndskofficienten kan reduceras från CD=0,46 till CD=0,41 genom att omplacera orginalkåporna på andra positioner över taket. CD =0,39 erhålls genom att bruka de aerodynamiskt modifierade kåporna. Det skapar en vinst på 55-60 000 kr för orginalkåporna och motsvarande en vinst på 75-80 000 kr för de modifierade kåporna, räknat under bussens livslängd och en drivmedelkostnad på 8 kr/l. Beräkningarna är snålt tilltagna för att ej ge ett överskattat värde, utan är mer ett resultat i underkant. I bilagorna figurerar även andra värden som ger än mer större vinst i kronor</p><p>Resultat uppnås då man tenderar minimera det återcirkulerande och energialstrande flöde som skapas inledningsvis på bussens tak under dess färd.</p>
10

Effects of Mach cruise number on conventional civil jet aircraft sizing

Bergman, Niklas January 2009 (has links)
<p>This thesis work was executed at Swift Engineering Incorporated located in San Clemente, California during spring in 2009. Placement supervisor from Swift was Mark Page and advisor and examiner from the Division of future products at Mälardalen University, Sweden was Gustaf Enebog.</p><p>The objective with this thesis work was to examine the effects of fitness ratio, lift over drag, lift coefficient at cruise, winglet span, wing sweep angle, wing aspect ratio, wing area and weights with respect to Mach number for a conventional business jet capable of 18 passengers. The cruise speed study range from Mach 0.88 to 0.99.</p><p>The Excel based conceptual design tool Jetsizer 2008c was used to make four models with similar configuration and mission but with different cruise Mach numbers.</p><p>A new Jetsizer module was then created to handle a modification process where the models are optimized for their speed and configuration. The result in this report gives guidelines for the needed values when creating an initial CFD model for this type of airplane.</p>

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