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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.
61

Design sensitivity analysis of multibody systems with special reference to four-wheel steering.

Lee, Jong-Nyun. January 1992 (has links)
Sensitivity analysis methods are investigated for the optimal design of multibody systems. In order to overcome the shortcomings inherent in existing methods, a "mixed" method is developed. The beneficial features of the finite difference and the direct differentiation methods, and equations of motion in the joint coordinates are employed in this method. As a realistic application of the sensitivity analysis, a Four-Wheel-Steering vehicle with complete suspension systems and comprehensive analytical tire model is implemented. This model keeps full nonlinearity in the governing equations of motion for accuracy, and it is simulated using an existing general-purpose multibody dynamics simulation package. However, by using the transient dynamic analysis of the nonlinear model, optimal design parameters are dependent on driving scenarios. Therefore, the transient behavior of the system is represented by a series of steady state configurations. Hence, a steady state analysis procedure which finds a steady state configuration from an arbitrary initial condition is developed. By using the steady state analysis and the sensitivity analysis, the optimal steering ratios between the angles of the front and the rear wheels are obtained over various driving conditions. A steering control strategy is developed for the vehicle simulation to follow a prescribed path. Finally, the simulation results using the optimal steering ratio are compared against the results of the conventional two-wheel steering and the steering ratio based on the linear bicycle model.
62

LOOPHOLE : How sports cars will find a way to survive the autonomous future.

Striedieck, Robert January 2017 (has links)
What will happen to sport cars once our society and infrastructure allow for a fully autonomous transport systems? My concern for the ”survival of the sports car” clearly originates from an emotional viewpoint rather than a reasonable argument. We know about the benefits that come along with autonomy but that doesn’t make the fear of loosing the emotional side of driving unfounded. My aim was to create a scenario that allows both reason and emotion to coexist and furthermore to benefit from each other rather than to create a conflict. The result is a PORSCHE for 2040 that shows an exciting concept for steering fully autonomous cars of the future. It combines the benefits of autonomy with the emotions of sports cars.
63

Multi-Reference Pseudo-Random Phase-Encoded Joint Transfrom Correlation

Mwatibo, Edward 20 January 2006 (has links)
We propose and demonstrate the superiority of using a phase SLM only in a multi-reference phase encoded joint transform correlator(JTC) compared to an ordinary JTC. Maximal length sequences are shifted to form two dimensional orthogonal arrays referred as m-arrays. The phase mask is used in one step to encode multiple reference images and at the same time eliminate false correlation peaks through power spectrum dispersion. A theoretical model of the implemented JTC is mathematically expressed and explained in this thesis. Basic performance criteria, PSR (peak to side lobe ratio) and PCE (peak to correlation energy), are used for comparative analysis, and their relationship to joint input image size and SLM size are investigated and the results simulated.
64

Reconfigurable Fiducial-Integrated Modular Needle Driver For MRI-Guided Percutaneous Interventions

Ji, Wenzhi 25 April 2013 (has links)
Needle-based interventions are pervasive in Minimally Invasive Surgery (MIS), and are often used in a number of diagnostic and therapeutic procedures, including biopsy and brachytherapy seed placement. Magnetic Resonance Imaging (MRI) which can provide high quality, real time and high soft tissue contrast imaging, is an ideal guidance tool for image-guided therapy (IGT). Therefore, a MRI-guided needle-based surgical robot proves to have great potential in the application of percutaneous interventions. Presented here is the design of reconfigurable fiducial-integrated modular needle driver for MRI-guided percutaneous interventions. Further, an MRI-compatible hardware control system has been developed and enhanced to drive piezoelectric ultrasonic motors for a previously developed base robot designed to support the modular needle driver. A further contribution is the development of a fiber optic sensing system to detect robot position and joint limits. A transformer printed circuit board (PCB) and an interface board with integrated fiber optic limit sensing have been developed and tested to integrate the robot with the piezoelectric actuator control system designed by AIM Lab for closed loop control of ultrasonic Shinsei motors. A series of experiments were performed to evaluate the feasibility and accuracy of the modular needle driver. Bench top tests were conducted to validate the transformer board, fiber optic limit sensing and interface board in a lab environment. Finally, the whole robot control system was tested inside the MRI room to evaluate its MRI compatibility and stability.
65

Proposta e validação de uma nova metodologia para medição automatizada de folgas de trabalho em sistemas de direção automotiva

Aimi, Vinícius January 2010 (has links)
Todos os anos, milhões de reais são gastos para cobrir os custos de garantia de caixas de direção que apresentam problemas de ruído e inconvenientes são causados nas linhas de montagem das grandes montadoras devido a este mesmo problema. Parte destas ocorrências se devem a um ruído específico chamado de Rattle Noise originado por uma operação de regulagem incorreta do bujão de ajuste. Em caixas de direção cujo “design” não permite uma medição direta da regulagem do sistema de ajuste, não existe um meio de avaliar a qualidade da operação e garantir que todas as peças estejam dentro das especificações. Baseado neste problema, este trabalho visa propor uma metodologia de avaliação da qualidade da operação de ajuste da caixa de direção de uma maneira indireta, porém com uma representação muito próxima do resultado que seria apresentado por uma medição direta, se o “design” do produto permitisse. Para tornar isso possível, foram realizados ensaios com caixas de direção em uma bancada experimental de testes aplicando-se a cremalheira cargas perpendiculares a seu eixo e momentos torsores. Foram avaliadas as respostas da amplitude do movimento angular descrito e também do deslocamento da cremalheira no sentido do seu raio observando-se a correlação que as respostas tinham com a real folga do mancal no interior do sistema de ajuste. Estes ensaios mostram que existe uma correlação muito forte entre as variáveis medidas externamente e a real flutuação do mancal no interior do sistema de ajuste e, através da regressão linear, uma equação foi definida para expressar este correlacionamento. Uma máquina foi construída para que a verificação fosse feita em 100% dos mecanismos produzidos na linha de montagem de um modelo de caixa de direção. Depois de construída a máquina, validou-se o seu funcionamento através dos estudos de R&R (Repetitividade e Reprodutibilidade), que ficaram abaixo de 20%, e da calibração da mesma comparando-se os resultados fornecidos pela máquina com as leituras realizadas de forma direta através de peças com o “design” alterado de forma a tornar isto possível, mostrando uma correlação de 99%. Hoje, o sistema está rodando perfeitamente em uma linha de montagem de um grande fabricante de sistemas de direção nacional. / Every year, millions of dollars are spent to cover the insurance costs of steering systems that have noise problems and inconveniences are caused in assembly lines of major car industry because of this same problem. Most of these occurrences are due to a specific noise called Rattle Noise caused by an incorrect operation of the adjustment screw to adjust the steering box. In cases where the direction of "design" does not allow a direct measurement of the values of the adjustment system, there is no way to assess the quality of operation and thus ensure that all parts are within specifications. Based on this problem, this work proposes a methodology to assess the quality of the adjust operation of the steering system in an indirect way, but with a very close representation of the results to be presented by a direct measurement if the "product design" had allowed. To make this possible, tests on steering systems were conducted in a test bench each exciting to rack with loads perpendicular to its axis and torsion loads. We studied responses of the magnitude of angular momentum described by the system and also the displacement of the rack along its radius by observing the correlation within the measured values to the actual bearing clearance into the system. These tests showed that there was a very strong correlation between the measured variables and externally real bearing fluctuation within the system of adjustment and using a linear regression, an equation was defined to express this correlation. A machine was built in order to verify 100% of the products in the assembly line of a vehicle steering system. Once built the machine and validated its operation through R & R studies, which has shown results below of 20%, the system was calibrated comparing the output of the machine with the readings taken directly in parts with the altered "design" to make this possible, showing a correlation of 99%. Today, the system is running perfectly on an assembly line of a major national manufacturer of steering systems.
66

Redesign of the interior of the JU solar car

Bielsa, Germán January 2017 (has links)
This thesis analyzes the interior of the solar car, used by the JU Solar Team, to improve the user experience in terms of user interaction and ergonomics. Following the Design Thinking methodology, it starts with a research phase to understand how the user interacts with the car and the elements required for this interaction during the race. It also studies the dimension of the actual interior and the anthropometric factors, some changes are proposed for a more efficient use of the space. The next phase explores new buttons and configurations for the steering wheel. The use of prototypes and sketches leads the development of the ideas, which are further developed and defined, including the graphical design and the dimensions of the interior. In the findings, the redesign of the steering wheel and interior is shown in several renders with an explanation of the final design decisions, which can be summarized in: A new shape for the steering wheel where most of the buttons have been added with new shapes and colors. The emergency buttons and light indicators have been allocated on a central control panel. The user has access to the buttons without releasing the steering wheel and the dimension of the canapé has been reduced thanks to a more efficient use of the space. As a part of the thesis a full scale model of the steering wheels and a 1:10 scale model of the interior is provided. This thesis solves some of the problems in the actual design of the solar car and explore some of the important factors in user interaction. A human-centered design approach to a project usually driven by the performance of the car and not the user experience. / Denna avhandling omfattar utveckling av interiör för solbilar med inriktning mot att förbättra för användaren. Arbetet avser att appliceras på Ju Solar teams solbil som ska delta för Högskolan i Jönköping i World Solar Challenge 2017. Forskningen i projektet fokuserar på att förstå hur användaren interagerar och samspelar med bilen och de faktiska problem som föraren har att hantera under tävlingen. Studien omfattar också antropometriska mått där förslag på ändringar gjorts för att optimera utrymmet. Utvärdering av idéer har gjorts med hjälp av skisser och prototyper, som inkluderar den grafiska designen Designbesluten kan sammanfattas med följande: • De viktiga knapparna är alla samlade i ratten. • Användning av form och färg samt position för att enkelt kunna skilja mellan knappar och dess funktioner. • Ny form för ratten med en extra grepp-zon i den övre delen. Ny utformning av knappar, former och konfiguration för ratten. • En central manöverpanel med ljusindikatorer för föraren. • Nya dimensioner av interiören för att minska förarhuvens storlek och därmed minska luftmotståndet. Som en del av avhandlingen finns en fullskalemodell av ratten och en modell i skala 1:10 av interiören tillhandahålls. Solbilar utvecklas vanligen med prestanda som prioritet men denna avhandling utforskar de problemområden som finns i anslutning till solbilens förarmiljö med människan i centrum.
67

Coanda-Assisted Spray Manipulation Implementation to Plasma Spray

Mabey, Katie E. 01 May 2011 (has links)
Coanda-assisted Spray Manipulation (CSM) is a means of modifying the direction of a jet. Previous isothermal static vectoring research is expanded to plasma spray. Two- dimensional Particle Image Velocimetry (PIV) was used to determine the vectoring results for small angles between 5-10°. Suitable parameters were determined for use on a plasma spray gun for small angle vectoring. Three-dimensional PIV was used to determine the elect of high speed rotation on a vectored jet. A 2-piece CSM collar was retrotted to a Praxair SG-100 plasma spray gun that replaced the standard faceplate. Two separate collars were tested: one designed for small vector angles and one for larger vector angles. The small-angle device could modify the trajectory of zirconia powder up to several degrees. Doing so could realign the plasma with the powder, resulting in increased powder temperature and velocity. The large-angle device could vector the plasma jet up to 45°; however the powder did not vector as much. Under large-angle vectoring, the powder velocity and temperature decreased steadily with vector angle. Both devices were tested using a supersonic conguration.
68

Design and Implementation of a Direct Digital Frequency Synthesizer using Sum of Weighted Bit Products

Majid, Abdul, Malik, Abdul Waheed January 2009 (has links)
<p>Direct Digital Frequency Synthesi<em>s </em>(DDFS) is a method of producing an analog waveform by</p><p>generating a time-varying signal in digital form, succeeded by digital-to-analog reconstruction.</p><p>At behavioral level the bit products with specified weights are used to generate the sine wave. In representation of a sine wave both positive and negative weights are generated. Since negative weights are not desired in design, the negative weights are transformed to positive weights. To reduce the number of current sources and control signals, bit product signals of those current sources which cannot be switched on simultaneously and have equal weights are shared. After sharing weights, the control signals are reduced to from 59 to 43 and current sources from 207 to 145.</p><p>Different control words are used by the DDFS system in order to generate different frequencies. The control word is successively added to the previous value in a 20-bit accumulator. Nine most significant bits out of these twenty bits are used for the DAC.</p><p>Since the Current Steering DAC architecture is suitable for high speed and high resolution purposes, so a 9-bit nonlinear current steering DAC is used to convert the output of bit products to the analog sine wave. Seven bits are used to generate one quarter of the sine wave. Eighth and ninth bits are used to generate the full sine wave.</p><p>HCMOS 9 (130 nm) ST Microelectronics process is used by employing high speed NMOS and PMOS transistors. The bit products (control signals) are computed by using complementary static CMOS logic which then act as control signals for the current sources after passing through D-flip flops. Practical design issues of current sources and parts of digital logic were studied and implemented using the Cadence full-custom design environment.</p>
69

AFS-Assisted Trailer Reversing / Aktiv styrning vid backning med släp

Enqvist, Olof January 2006 (has links)
<p>Reversing with a trailer is very difficult and many drivers hesitate to even try it. This thesis examines if active steering, particularly AFS (Active Front Steering), can be used to provide assistance.</p><p>For analysis and controller design a simple geometric model of car and trailer is used. The model seems to be accurate enough at the low speeds relevant for trailer reversing. It is shown that the only trailer dependent model parameter can be estimated while driving. This enables use with different trailers.</p><p>Different schemes to control the system are tested. The main approach is to use the steering wheel as reference for some appropriate output signal, for example the angle between car and trailer. This makes reversing with a trailer more like reversing without a trailer. To turn left, the driver simply turns the steering wheel left and drives. Test driving, as well as theoretical analysis, shows that the resulting system is stable. Of the eight drivers that have tested this type of control, five found it to be a great advantage while two considered it more confusing than helpful.</p><p>A major problem with this control approach has to do with the way AFS is constructed. With AFS, the torque required to turn the front wheels results in a reaction torque in the steering wheel. Together with the reference tracking controllers, this makes the steering wheel unstable. Theoretical analysis implies that this problem has to be solved mechanically. One solution would be to combine AFS with electric power steering.</p><p>This thesis also presents a trajectory tracking scheme to autonomously reverse with a trailer. Starting from the current trailer position and the desired trajectory an appropriate turning radius for the trailer is decided. Within certain limits, this will stabilize the car as well. The desired trajectory can be programmed beforehand, but it can also be saved while driving forward. Both variants have been tested with good results.</p>
70

Measuring and steering in school. To use a measuring tool in education. / Mät och styr i skolan. Att använda en mätbox i undervisningen.

Donner, Gustaf af January 2000 (has links)
<p>In this report I have asked myself why and to some extent how teachers can use a measuring tool, that can be connected to a PC, in their everyday education. I have done this by making three short, fictive lesson plans for the measuring tool and compared them with ordinary lessons. In today's society pupils must know about computers and to attain the goals of school they have to make experiments and understand processes. The measuring tool can be a help in this work.</p>

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