Orientador: Fábio Roberto Chavarette / Banca: Gustavo Luiz Chagas Manhães de Abreu / Banca: Nelson José Peruzzi / Resumo: Diversos protótipos de sistemas Maglev (transporte de levitação magnética) em todo o mundo, principalmente na Alemanha e Japão, têm demonstrado que este modo de transporte pode lucrativamente competir com o transporte aéreo. No entanto, um sistema Maglev tal como o Transrapid da Alemanha é inerentemente instável. Esta instabilidade deve-se ao sistema de suspensão eletromagnética, a qual usa força atrativa para levitar o trem. Com isto, algum sistema de controle da levitação deve ser implementado para tornar a operação segura. A partir de um modelo simplificado para o sistema experimental Transrapid é possível investigar a instabilidade e consequentemente propor algum projeto de controle. Neste trabalho, é proposto dois projetos de controladores ótimos. As seguintes técnicas são utilizadas para projetar os controladores: Regulador linear Quadrático (LQR) e Equação de Riccati Dependente do Estado (SDRE). O primeiro projeto é um controlador linear, já o outro é não-linear. As simulações computacionais mostram que o controlador SDRE permite o sistema Maglev operar com perturbações muito maiores no entreferro do que o controlador LQR permite / Abstract: Several experimental Maglev (magnetic levitation transport) systems all around the world, mainly in Germany and Japan have demonstrated that this mode of transportation can profitably compete with air travel. However, a system such as the German Maglev train (called Transrapid) is inherently unstable. This instability is because the electromagnetic suspension system uses attractive force to levitate the train. Herewith, some levitation control system must be implemented to make safe operation. From a simplified model for the Transrapid experimental system is possible to investigate the instability and to propose some control design. In this work, we propose two control designs for the system. The following techniques are used to design the controllers: Linear Quadratic Regulator (LQR) and State-Dependent Riccati Equation (SDRE). The first project is a linear controller, while the other is non-linear. Simulations shows that the SDRE controller allows the Maglev system to operate with much larger disturbances in the air gap than the LQR controller does / Mestre

Thesis (MTech. degree in Mechanical Engineering)--Tshwane University of Technology, 2010. / This research aimed to develop a Reconfigurable Parallel Kinematic Machine Tool (RPKMT) to be utilized in the maintenance and reconditioning of moulds and dies. The dissertation presents three conceptual designs of a mechanical manipulator, based on specifications required for refurbishing of moulds and dies. Kinematics and mechanical requirements were derived from manufacturing processes and the recommended repair solutions (i.e. steps/operations) required for the specific defect. These requirements resulted in translating customer requirements into engineering/technical characteristics using Quality Function Deployment (QFD) techniques, specifically House of Quality (HoQ). This was followed by the concept design phase, which consisted of the use of the following techniques: Product Function Decomposition and the Morphological Matrix. A comparison study was performed on the conceptual designs, employing kinematic analysis and workspace analysis. The Pugh's Method was used as the concept-selection techniques to aid in selecting the most suitable RPKMT concept. It was for this concept that a model of the design was developed. This phase included selection of the materials for the links, bearing mounts, the base plate and the statics analysis. This was followed by the selection of the link actuators, the spindle drive and the presentation the assembled drawing of the design concept. Finally, a discussion of how the repair process of typical mould/die would be carried out on the RPKMT is presented.

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (p.144-149).

Made available in DSpace on 2015-07-13T12:10:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-09. Added 1 bitstream(s) on 2015-07-13T12:25:33Z : No. of bitstreams: 1 000836510.pdf: 733047 bytes, checksum: 0974d0626d02737133a5bde72e9af8d1 (MD5) / Diversos protótipos de sistemas Maglev (transporte de levitação magnética) em todo o mundo, principalmente na Alemanha e Japão, têm demonstrado que este modo de transporte pode lucrativamente competir com o transporte aéreo. No entanto, um sistema Maglev tal como o Transrapid da Alemanha é inerentemente instável. Esta instabilidade deve-se ao sistema de suspensão eletromagnética, a qual usa força atrativa para levitar o trem. Com isto, algum sistema de controle da levitação deve ser implementado para tornar a operação segura. A partir de um modelo simplificado para o sistema experimental Transrapid é possível investigar a instabilidade e consequentemente propor algum projeto de controle. Neste trabalho, é proposto dois projetos de controladores ótimos. As seguintes técnicas são utilizadas para projetar os controladores: Regulador linear Quadrático (LQR) e Equação de Riccati Dependente do Estado (SDRE). O primeiro projeto é um controlador linear, já o outro é não-linear. As simulações computacionais mostram que o controlador SDRE permite o sistema Maglev operar com perturbações muito maiores no entreferro do que o controlador LQR permite / Several experimental Maglev (magnetic levitation transport) systems all around the world, mainly in Germany and Japan have demonstrated that this mode of transportation can profitably compete with air travel. However, a system such as the German Maglev train (called Transrapid) is inherently unstable. This instability is because the electromagnetic suspension system uses attractive force to levitate the train. Herewith, some levitation control system must be implemented to make safe operation. From a simplified model for the Transrapid experimental system is possible to investigate the instability and to propose some control design. In this work, we propose two control designs for the system. The following techniques are used to design the controllers: Linear Quadratic Regulator (LQR) and State-Dependent Riccati Equation (SDRE). The first project is a linear controller, while the other is non-linear. Simulations shows that the SDRE controller allows the Maglev system to operate with much larger disturbances in the air gap than the LQR controller does

In this thesis an analysis is developed to predict the leakage and dynamic characteristics for circumferentially grooved turbulent annular seals used in turbopumps. The flow in the groove is modelled using turbulent shear layer theory and an entrance loss model is applied at the inlet and land regions of the seal. The governing equations are derived using Hirs’ turbulent lubrication theory. The equations are expanded to yield zeroth and first order perturbation equations for small rotor displacements about a centered position. The leakage and velocity distribution is obtained from a numerical solution of the zeroth order equations. The first order equations define the dynamic pressure distribution which is integrated to yield the fluid force reactions. The model predictions are compared to test results for smooth walled and grooved seals. The model shows good qualitative agreement with experimental test results for seal leakage and rotordynamic coefficients. Actual quantitative agreement is unresolved given the high level of experimental uncertainty in the test results. / Master of Science

Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2004. / Granular flow occurs in a broad spectrum of industrial applications that range from separation and mixing in the pharmaceutical industry, to grinding and crushing, blasting, stockpile construction, flow in and from hoppers, silos, bins, and conveyer belts, agriculture, mining and earthmoving. Two totally different approaches of modelling granular flow are the Discrete Element Method (DEM) and continuum methods such as Finite Element Methods (FEM). Continuum methods can be divided into nonpolar or classic continuum methods and polar continuum methods. Large displacements are usually present during granular flow which, without remeshing, cannot be solved with standard finite element methods due to severe mesh distortion. The Particle-in-Cell (PIC) method, which is a so-called meshless method, eliminates this problem since all the state variables are traced by material points moving through a fixed mesh. The main goal of this research was to model the flow of noncohesive granular material in front of flat bulldozer blades and into excavator buckets using a continuum method. A PIC code was developed to model these processes under plane strain conditions. A contact model was used to model Coulomb friction between the material and the bucket/blade. Analytical solutions, published numerical and experimental results were used to validate the contact model and to demonstrate the code’s ability to model large displacements and deformations. The ability of both DEM and PIC to predict the forces acting on the blade and bucket and the material flow patterns were demonstrated. Shear bands that develop during the flow of material were investigated. As part of the PIC analyses, a comparison between classic continuum and polar continuum (Cosserat) results were made. This includes mesh size and orientation dependency, flow patterns and the forces acting on the blade and the bucket. It is concluded that the interaction of buckets and blades with granular materials can successfully be modelled with PIC. In the cases conducted here, the nonpolar continuum was more accurate than the polar continuum, but the polar continuum results were less dependent on the mesh size. The next step would be to apply this technology to solve industrial problems.

In the development of engineering products, it is necessary to predict dynamic properties of the modified structures. Achieving such predictions by using the structural properties of the original structure and information on the modifications is commonly referred to as structural modification analysis. In this thesis, &Ouml / zg&uuml / ven&rsquo / s Structural Modification Method and Sherman-Morrison Method are selected as exact methods for structural modifications to predict the dynamics of a locally modified structure. Also, a new structural modification method named as &ldquo / Extended Successive Matrix Inversion Method&rdquo / is developed in this study. These three methods are implemented in a software developed herein, called &ldquo / Structural Modification Toolbox&rdquo / . The software uses modal analysis results of MSC Nastran&copy / for the original structure and calculates the modified frequency response functions by any of the methods above. In order to validate the software, direct modal analysis results of MSC Nastran&copy / for the frequency response functions of the modified structure are used. The methods are compared in terms of computational time, and the effectivity of each method is studied as a function of modification size to determine which of these methods is more suitable. In order to investigate the application of the methods and compare their results with experimental ones, modal tests are conducted on a scaled aircraft structure. The solutions are compared with test results obtained from modified test structure. Additionally, the software is used for comparison of real aircraft test results and frequency response functions of the modified structure.

Gait analysis is one of the primary applications of biomechanics and deals with scientific description of human locomotion, which is a qualitative concept as observed through the human eye. METU Gait Analysis Laboratory has been operating in various fields of gait and motion analyses since 1999. Although several studies have previously been undertaken about METU Gait Analysis System, until now, the effects of methodology and protocol related system parameters on kinematic analysis results have not been fully and exhaustively investigated. This thesis presents an assessment on sensitivity and compatibility of METU Gait Analysis Protocol to variations in experimental methodology and implementation of various joint center estimation methods, performed through investigation of the resulting joint kinematics. It is believed that the performance and reliability of METU Gait Analysis System will be improved based on the findings of this study.

The METU Gait Analysis System employs a computer program called Kiss-GAIT for the calculation of joint angles, moments and powers using force plate data and marker trajectories as input. Kiss-GAIT was developed using Delphi and is confined to calculations related to the standard gait protocol. Because the code lacks the flexibility required to carry out various test cases, the inverse dynamics formulation being used could not be verified and the extent of the error propagation problem could not be determined so far. The first aim of this study was to develop a code for the inverse dynamics model of the METU Gait Analysis System making use of the flexible programming environment provided by MATLAB. Verified and more reliable analysis results, obtained by reformulating the inverse dynamics algorithm in a new code, are presented. Secondly, data smoothing and differentiation techniques conventionally used in gait analysis were critically reviewed. A common tool used for filtering marker trajectories is the Butterworth digital filter. This thesis presents a modified, adaptive version of this classical tool that can handle non-stationary signals owing to its coefficients which are functions of local signal structure. The results of this thesis indicate the dominancy of ground reactions as compared to inertial effects in normal human gait. This implies that the accuracy needed in body segment inertial parameter estimation is not a critical factor. On the other hand, marker trajectories must be as accurate as possible for meaningful kinetic patterns. While any smoothing and differentiation routine that produces reasonable estimates is sufficient for joint moment calculation purposes, the estimation performance becomes a key requirement for the calculation of joint powers.

ABSTRACT DESIGN OF A MECHANISM FOR OPENING HACTHBACK CAR BAGGAGE DOOR Duran, Yusuf M.S., Department of Mechanical Engineering Supervisor: Prof. Dr. Eres S&ouml / ylemez September 2009, 65 Pages In this thesis, a new mechanism design for opening hatchback-car baggage door is introduced. Unlike the classical hinged doors used, this new design will include a mechanism so that the door will be opened vertically and thus occupy less space behind the car during the opening. In this fashion even the hatchback doors of closely parked cars may be opened. First, considering type synthesis, different mechanism types are investigated. In dimensional synthesis, with the help of Burmester theory, motion generation is applied. Using the circle and center point curves, considering link dimensions, transmission angle characteristics, branching and some order issues possible solutions that satisfy the position requirements are found. To actuate the mechanism, an appropriate gas-spring is sought. As a case study a prototype is manufactured and mounted on a sample hatchback car to check the mechanism performance.