• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 241
  • 69
  • 66
  • 45
  • 14
  • 10
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 528
  • 138
  • 71
  • 56
  • 50
  • 47
  • 46
  • 45
  • 40
  • 38
  • 38
  • 35
  • 33
  • 33
  • 32
  • 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.
341

Analýza a vyhodnocení rizik dopravně spediční firmy / Risk Analysis and Evaluation in a Transporting and Haulage Firm

Čegan, Tomáš January 2016 (has links)
This diploma thesis deals with an analysis and evaluation of risk in the freight transport company – Doprava Vícha s. r. o. The thesis describes the current situation in a freight transport industry, an applicable legislation, and risk analysis methods FMEA and WHAT-IF. Further the thesis analyses risks of a freight transportation and describes the company Doprava Vícha s. r. o. in detail. The thesis proposes a set of actions in order to minimize identified risks. The handbook with most important actions and advices for drivers is attached.
342

Legal aspects in road transport optimization in Europe

Goel, Asvin 24 September 2020 (has links)
Road freight transportation is subject to several legal requirements having direct impact on the practical applicability of routes and schedules. The vast majority of vehicle routing literature, so far, has largely focused on physical constraints such as capacity limits, or customer requirements such as time windows for pickups and deliveries. This paper studies legal requirements for long-distance haulage in the European Union, identifies some major gaps in the current state-of-the-art in vehicle routing, presents approaches for overcoming this gap, and analyzes the impact of the legal requirements studied.
343

Electric Road Systems for Trucks

Edfeldt, Erica, Andersson, Sanna January 2013 (has links)
An increased use of electricity in vehicles is considered an alternative to decrease the usage of fossil fuels. For private cars, plug-in electric vehicles using batteries are continuously being improved. However, the battery technology of today is not sufficient for trucks if they are to use only electricity. The battery technology is not sufficient to be able to supply the truck with enough propulsion energy to perform an entire drive. However, the hybrid drive technology enables a power recovery and charges the battery when the vehicle applies its brakes. The fuel usage can thereby be decreased through the energy recovery. This master thesis examines the potential of electric road systems, ERSs, which enables a continuous electricity supply to the vehicle when in motion. Similar technologies as an ERS has been used for a long time for trams, trolleybuses and trains, and historically there have also existed cases of electric truck systems. In this thesis the potential for ERSs is examined from the haulage contractor companies’ perspective, which would be users of this system. The potential is in regard to the energy usage per km, the CO2 emissions per km and the cost per km for an ERS vehicle (a hybrid vehicle using an ERS) compared to a hybrid vehicle and to a conventional vehicle. The cost per km includes energy cost, cost for using the ERS infrastructure and the additional vehicle cost. The method used in this study was first to create a broad picture of the concept of ERSs through reading articles, reports, web pages and through conducting interviews with stakeholders within the ERS market. The second part of the method was to create a technology model and an economic model. The models investigate the potential for ERSs through three different cases: a Distribution Case, a Long-Haulage Case and a Mining Case. For all three cases, the energy usage, the cost and the CO2 emissions per km for using a conventional vehicle, a hybrid vehicle and ERS vehicle were generated. Four alternative future scenarios were also tested, in which factors such as energy costs and infrastructure costs were varied. The results show the energy usage, the CO2 emissions and the profitability from the haulage contractor companies’ perspective. The results show that ERSs are not profitable for the Distribution Case in any of the tested scenarios. For the Long-Haulage Case, however, it is profitable in four out of the five tested scenarios. The Mining Case shows mixed profitability results, many times being just above or just below profitable. The energy usage decreased for all the cases and scenarios. Because of this, in combination with the relatively clean electricity production in Sweden, the decrease in CO2 emissions is very large. The 3 conclusions from this thesis are therefore that long-haulage routes show great potential for using ERSs, mining cases have some potential for using ERSs and if distribution routes are to use ERSs this would be only for lowered fossil fuel usage and environmental purposes. / För att minska användandet av fossila bränslen anses ökad användning av elektricitet i fordon vara ett potentiellt alternativ. För laddelbilar inom personbilssektorn förbättras batteritekniken ständigt. Dock ser inte batteriteknikens utveckling ut att vara tillräcklig för lastbilar om de ska kunna köra på enbart el. Även om batteritekniken inte är tillräcklig för att lastbilen ska kunna köra på enbart el så kan batterier användas i lastbilshybrider. Hybridsystemet möjliggör en energiåtervinning där batteriet kan laddas när fordonet bromsar. Bränsleanvändningen kan därmed minskas genom energiåtervinningen. Detta examensarbete utreder potentialen för elektriska vägsystem. Elektriska vägsystem möjliggör kontinuerlig överföring av elektricitet till lastbilar medan de kör. Liknande tekniker har länge använts för spårvagnar, trådbussar, tåg och även i viss utsträckning för trådlastbilar. I detta examensarbete utreds potentialen för elektriska vägsystem utifrån åkeriers perspektiv, eftersom dessa i så fall kommer att vara de som använder systemet. Potentialen bedöms genom att jämföra energianvändning per kilometer, CO2-utsläpp per kilometer och kilometerkostnad för en elvägslastbil jämfört med en konventionell lastbil och jämfört med en hybridlastbil. Kilometerkostnaden innefattar energikostnad, kostnad för att använda elvägsinfrastrukturen och den ytterligare fordonskostnaden. Metoden som användes i denna studie var först att skapa en bred bild av konceptet elektriska vägsystem genom att läsa artiklar, rapporter, hemsidor och att utföra intervjuer med aktörer inom elektriska vägsystem. Den andra delen av metoden var att skapa en ekonomisk och teknisk modell. Tre olika fall modellerades: ett distributionsfall, ett fjärrtrafikfall och ett gruvtransportfall. För dessa tre fall så genererades energianvändningen, CO2-utsläppen och kostnaden per km vid användning av en konventionell lastbil, en hybridlastbil och en hybrid som använder elektriska vägsystem. Fyra alternativa framtidsscenarion testades också, för vilka parametrar såsom energikostnader och infrastrukturkostnader varierades. Alla resultat visar energianvändningen, CO2-utsläppen och lönsamheten utifrån ett åkeriperspektiv. Resultaten visar att elektriska vägsystem inte är lönsamma för distributionsfallet i något av de testade scenarierna. För fjärrtrafik är det lönsamt i fyra av de fem testade scenarierna. Gruvtrafikfallet visar på blandade resultat, där det ofta är precis lönsamt eller nästan lönsamt med elektriska vägsystem. Energianvändningen minskar för alla fall och scenarier. Detta tillsammans med Sveriges relativt rena elektricitetsproduktion innebär att CO2-utsläppen minskar kraftigt. Slutsatserna från detta examensarbete är därför att fjärrtrafik påvisar stor potential för elektriska vägsystem, gruvtrafik har viss potential och distributionstrafik bör endast använda elektriska vägsystem av miljömässiga och fossilbränslereducerande skäl.
344

Adaptiv varvtalsstyrning vid användning av en lastbils kraftuttag / Adaptive speed control for truck PTO usage

Claesson, Adam January 2010 (has links)
Med ett växande fokus på ett långsiktigt hållbart samhälle som tar ansvar för miljön strävar fordonstillverkare efter att sänka energiförbrukningen på sina fordon. Detta arbete behandlar hur man kan sänka bränsleförbrukningen för lastbilar med påbyggnader. En påbyggnad kan t.ex. vara en kran, en lastväxlare eller en betongpump. En metod för att sänka energiförbrukningen är att sänka det varvtal som lastbilens dieselmotor arbetar vid. Vid lägre varvtal jobbar motorn oftast mer effektivt och en mindre del av motorarbetet försvinner då i förluster, dock kan inte motorn belastas lika hårt. Varvtalet kan i vissa situationer sänkas under drift av påbyggnaden. Mellan drift då applikationen väntar på användarens kommando kan varvtalet alltid sänkas så att energiförbrukningen sjunker.För att veta när varvtalet ska sänkas används en signal från motorn som anger vilket lastmoment som motorn jobbar mot. Vid låg last sänks varvtalet och bränsle kan sparas, vid hög last höjs varvtalet för att kunna möta det pålagda momentet.Fältstudier har genomförts för att kunna undersöka vilka typer av lastbilspåbyggnader som skulle kunna ha nytta av en funktion som sänker varvtalet när lasten är låg. Under arbetet har även uppskattningar över hur mycket bränsle som skulle kunna sparas om varvtalet sänks mellan operationerna med påbyggnaden gjorts. Resultatet pekar på att det i många fall går att spara bränsle genom att sänka motorns varvtal då lastbilens påbyggnad inte används. De visar också på att det inte går att spara bränsle med denna metod i de fall där föraren sitter kvar i hytten under påbyggnadsanvändningen.
345

A comparative Life Cycle Analysis of new and old designs of crane truck frames : Case study at Vemservice

Khan, Mahmudur Aryan January 2018 (has links)
The main objective of this Bachelor’s thesis is to investigate and deliver the results of environmental impacts of two different designs of crane truck frames. The aim is to investigate if additional new design of crane truck frames, with less energy and transportation during manufacturing of the crane truck, can improve energy efficiency of crane trucks throughout their lifecycle. Case study object for this report is Vemservice in Vemdalen, Sweden. As basis for the report the The Life Cycle Analysis ISO 14040 and ISO 14044 are used in this report in order to evaluate and compare the environmental impacts related to the lifecycle of new and old designs of 92 tonmeter crane truck frames from cradle to grave. The data was mainly collected and calculated by using the SimaPro software 8.0.5 which is based on the Ecoinvent 3 database. This study mainly analyzes environmental impacts such as GWP (Global Warming Potential), CED (Cumulative Energy Demand) and ReCiPe environmental impacts. The results showed that although new design frame has less transportation and energy demand during the manufacturing phase of the crane truck, the overall life cycle of the new design crane truck frame has higher environmental impacts than the existing old design of the crane truck frame. This is due to that the new design frame is 213kg heavier than the old design frame, which the crane truck is carrying during its using period. This study also investigated whether the new design frame, with stronger steel (Ecoupgraded steel) and a reduction of 15% of the total weight of frame, has a lower environmental impact in the life cycle of the EcoUpgraded steel frame compared to the current new design and old design frames life cycle. / <p>2018-06-29</p>
346

Prototype for automotive roll over safety system

Tevetzidis, Ilias January 2020 (has links)
This thesis presents the theory, methodology and results of building, tuning and testing a prototype for controlling body roll movement. Body roll is a result of lateral acceleration that acts on a vehicle when turning and result in torque on the roll center of the vehicle. The objective of this thesis is, in collaboration with Freno Air AB [7], to build a prototype and, with the help of sensors and micro controllers, restrict the body roll to avoid roll over on a semi-trailer that the company builds. The control unit in this thesis includes two PID controllers that is vastly used today in many different applications. The control unit is fed with signals from two pressure sensors on each side of the prototype frame. The pressures are given by four syringes, two on each side that are connected to the pressure sensors. One PID has small gains of KP = 0.2, KD = 0.005 and KI = 0 to take care of smaller and slower variations of pressure difference and one PID with higher gains of KP = 1, KD = 1 and KI = 0 to take care of faster and bigger variations in pressure difference which in both of the cases the pressure difference translates to body roll. The pressures give is enough of information of the prototypes state to be able to control it with the help of a motion platform that is able to roll in opposite direction to equalize the pressures. The results for the two cases of slow roll and fast roll are promising with a fast response, few oscillations and overshoots, which makes the system fast and stable, two things that are opposites in the world of closed loop control. The experiment was performed in a stationary form with applied disturbances and actuated with a motion platform capable of roll rotation.
347

Bumps along the long and winding road: Factors related to truck driver turnover and job-induced tension

Mansfield, Layla Rhiannon 10 July 2014 (has links)
Voluntary turnover rates among truckload carriers are extremely high, ranging from 50% to more than 100% annually (Griffin & Kalnbach, 2002), furthermore, long-haul truck drivers operate in a stressor-filled environment, which exerts enormous adverse influence not only their well-being but also on their intent to quit. This study explores the relational aspects of the driver's work environment to highlight how the relationships that a driver has with their organization, supervisor, and dispatcher can explain turnover and job-induced tension. Drawing on Social Exchange Theory, Conservation of Resources Theory, and concepts from Hirschman's (1970) theoretical framework of Exit, Voice, and Loyalty, this study hypothesized that Perceived Organizational Support (POS) and Leader-Member Exchange (LMX) have a negative relationship with turnover and job-induced tension and that this relationship is moderated by the dispatchers' sensitivity to voice. Further, this moderation was argued to be mediated by the dispatchers' responsiveness. A modified model, that retains the original theoretical framework, was tested after a number of measurement issues were uncovered. The modified model collapses dispatcher sensitivity to voice and dispatcher responsiveness into one composite variable, dispatcher communication effectiveness. Dispatcher communication effectiveness was hypothesized to moderate the relationships between POS, LMX, turnover, and job-induced tension. The hypotheses were tested in a sample of 166 truck drivers and findings indicate the POS and LMX were directly related to job-induced tension but these same predictor variables were unrelated to turnover. There was marginal support for the buffering effects of dispatcher communication effectiveness on the relationship between LMX and job-induced tension. These findings contribute to the knowledge about the role of POS and LMX on job-induced tension while uncovering the important dynamics in play between a driver and their dispatcher. The theoretical and practical implications of the study are discussed.
348

Real-time Model Predictive Control with Complexity Guarantees Applied on a Truck and Trailer System

Bourelius, Edvin January 2022 (has links)
In model predictive control an optimization problem is solved in every time step, which in real-time applications has to be solved within a limited time frame. When applied on embedded hardware in fast changing systems it is important to use efficient solvers and crucial to guarantee that the optimization problem can be solved within the time frame. In this thesis a path following controller which follows a motion plan given by a motion planner is implemented to steer a truck and trailer system. To solve the optimization problems which in this thesis are quadratic programs the three different solvers DAQP, qpOASES and OSQP are employed. The computational time of the active-set solvers DAQP, qpOASES and the operator splitting solver OSQP are compared, where the controller using DAQP was found the fastest and therefore most suited to use in this application of real-time model predictive control.  A certification framework for the active-set method is used to give complexity guarantees on the controller using DAQP. The exact worst-case number of iterations when the truck and trailer system is following a straight path is presented. Furthermore, initial experiments show that given enough computational time/power the exact iteration complexity can be determined for every possible quadratic program that can appear in the controller.
349

Optimalizace parkovacích stání pro autobusy a nákladní vozidla / Optimization of parking spaces for buses and trucks

Bedřich, Marek Unknown Date (has links)
Main focus of diploma thesis is optimalization of dimensions stated in parking norm ČSN 73 6056 Parking areas for road vehicles. Goal of the thesis was to optimalize dimensions stated in norm from 2011, eventually come up with a new type of parking space. Thesis is based on recherche, which was done on both previous and actual Czech norms as well as on foreign norms. Change in dimension was possible due to evaluation of swept paths of the individual parking slots. New suggested dimensions are stated in the conclusion.
350

Evaluation of real drive data of a refuse fuel cell truck / Utvärdering av verkliga kördata för en sopbil med bränslecell

Eurén, Hampus January 2023 (has links)
Ett konsortium bestående av Scania, JOAB, Powercell, KTH och Renova samarbetade för att designa och konstruera en bränslecellsdriven sopbil inom ett FFI-finansierade projekt. Sopbilen har sedan dess varit i drift i Göteborg från 2020 till 2023, med en vätgasinfrastruktur bestående av en tankstation vid tidpunkten för detta arbete. Under den tiden har bränslecellen genomgått kör- och stillastående tester. Verkliga kördata på sopbilens system och bränslecell registrerades. Databaserna var osynkroniserade i tid och därför krävdes datasynkronisering. Detta examensarbete inleddes med huvudsyftet att utveckla ett accelererat åldringstest för bränslecellen baserat på denna applikation. Ett ytterligare syfte var att utvärdera bränslecellens åldrande. På grund av de tillgängliga variablerna baserades bränslecellens åldrande på försämring av elektrisk effekt vid konstanta temperaturer och strömmar. En testcykel (eller effekt-cykel) baserad på testkörningen av sopbilen utvecklades istället. Genom att använda den etablerade metoden "k-means clustering" på bränslecellens effekt-cykler skapades en testcykel som var representativ för sopbils-körning från 2020 till 2023. Testcykeln validerades baserat på ett statistiskt kriterium, verifiering och ytterligare arbete krävs dock. Efter 141,80 timmars bränslecellsdrift kunde ingen åldring identifieras. Mer data från sopbilen behövs och faktumet att ytterligare en vätgastankstation kommer att installeras under 2023 i Göteborg innebär att sopbilens körmönster kan förändras. Resultaten från denna avhandling lägger dock grunden för framtida forskning och erbjuder ett tillvägagångssätt för att studera den bränslecellsdrivna sopbilen. / A consortium consisting of Scania, JOAB, Powercell Sweden AB, KTH, and Renova collaborated to design and engineer a fuel cell-powered refuse truck within a FFI-funded project. The refuse truck has been operational in Gothenburg since 2020, with a hydrogen gas infrastructure of one refuelling station at the time of this work. From 2020 to 2023, the fuel cell has gone through driving and standing still tests. Real drive data on the truck's system and fuel cell was recorded. The databases were unsynchronised in time, hence data synchronisation was required.  This thesis began with the main aim of developing an accelerated stress test for the fuel cell based on this application. Additionally, the aim was to evaluate the ageing of the fuel cell. Due to the available variables, fuel cell ageing was based on deterioration of fuel cell powers at constant temperatures and currents.  A test cycle (or power cycle) based on refuse truck test driving was developed instead. By utilising the established “k-means clustering” method on fuel cell power cycles, a test cycle representative of the truck operation from 2020 to 2023 was made. The test cycle was validated based on a statistical criterion, although verification and further work are required. After 141.80 hours of fuel cell power requests no ageing could be identified. More data from refuse truck operation is needed, also considering that an additional hydrogen refuelling station will be put in place in 2023 in Gothenburg, hence the drive pattern might vary. In this context, however, the results from this thesis lay the foundation for future research and offer an approach to study the fuel cell truck.

Page generated in 0.2506 seconds