La synthèse dimensionnelle se focalise sur la détermination des dimensions des piècesconstituant le mécanisme et de leur placement. Cependant, malgré les nombreux travaux dansce domaine, les techniques actuelles de dimensionnement n’offrent des solutions satisfaisantesque pour des classes de mécanismes particulières.Dans nos travaux, nous décrivons une approche de résolution générique de problèmes desynthèse dimensionnelle de mécanismes. Une spécification déclarative par contraintes facilitela prise en compte de tout type de mécanismes (plans ou spatiaux, à topologie ouverteou fermée et comportant un nombre quelconque de pièces et de liaisons cinématiques). Lamodélisation des problèmes proposée rend possible la génération automatique d’équationstraduisant simultanément l’objectif à atteindre et les contraintes à respecter ainsi que laconstruction des différents mécanismes solution.Les équations résultantes étant non linéaires, fortement couplées et n’admettant pas nécessairementde solution exacte, nous proposons de les traiter par des méthodes d’optimisation.De plus, la stratégie développée se concentre sur la recherche de plusieurs minima locauxdu problème de synthèse et non sur la recherche d’un minimum global. En premier lieu, uneméthode d’optimisation globale par essaims particulaires explore le domaine de recherche etfournit plusieurs points approchant des minima. Plusieurs processus d’optimisation locale,basés sur la méthode de Nelder-Mead, exploitent ensuite de manière concurrente ces points.Cette stratégie permet d’améliorer considérablement la robustesse de chacune des méthodesprises indépendamment et surtout de proposer plusieurs configurations à l’utilisateur quipourra finalement sélectionner la meilleure solution d’après ses critères.Nous avons développé une maquette d’application de synthèse dimensionnelle de mécanismes,complètement intégrée dans un environnement de conception assistée par ordinateurindustriel qui nous permet de valider la démarche de conception que nous proposons sur unensemble de problèmes classiques. / Mechanism synthesis deals with design of mechanical devices capable of performing adesired task. Dimensional synthesis focuses on the determination of the parts’ dimensionsand locations in order to fulfill the requirements. Despite many works in this research field,current design techniques are lacking in generality and are only suitable for specific classesof mechanisms.This work proposes a generic approach to solve mechanism dimensional synthesis. Adeclarative specification based on constraints facilitates the design of almost any systemtopology such as planar and three-dimensional mechanisms with open and closed loop kinematicchains containing any number and type of joints. The modeling approach presentedallows automatic generation of systems of equations representing both the constraints tosatisfy and the target objectives to minimize, while enabling geometric construction of theobtained solutions.The resulting polynomial equations are nonlinear, highly coupled and do not necessarilyadmit an exact solution. Therefore, we propose to solve them by optimization methods. Thedeveloped strategy focuses on finding several local minima of synthesis problems instead offinding a global minimum. First, a particle swarm global optimization explores the searchdomain and provides points approximating these minima. Then, various Nelder-Mead basedlocal optimization processes handle these points concurrently. This strategy significantlyimproves the robustness of each optimization method taken independently. It also makes itpossible for the designer to choose the best solution among several configurations accordingto his criteria.A dimensional mechanism synthesis prototype, fully integrated with a commercial computeraided design software, has also been developed. It allows validating our design approachon a set of classical problems.

Skid-steer loaders are also called mini loaders. Skid-steer loaders are capable of zero turning radiuses, which make them extremely maneuverable and suitable for confined spaces. The aim of this thesis study is to design the loader mechanism for skid-steer loaders. Primarily, the loader mechanism synthesis will be performed to determine the basic link dimensions for the mechanism of the loader. Genetic algorithm will be used in the design process. Besides, the hydraulic cylinders dimensions and working pressure of the loader mechanism will be chosen according to the forces that will be applied. After the link dimensions of the loader are determined, 3D modeling of the loader mechanism will be performed. Afterwards, the finite element analysis of the system will be carried out. Finally, improvements will be made on the model according to the results of the analysis.

In this thesis, design of a car door window regulator is presented. This design comprises a mechanism in order that the car door window makes a specified translational motion. First, conceptual design is carried out to obtain the best suitable concept for the design and best suitable concept comes out to be a scissor mechanism. Afterwards, detailed design of the chosen concept is given. In the detail design stage, kinematic synthesis of the mechanism is performed basically using the Cardan motion. Lastly, implementation of the design on a car door is described.

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.

Flap, aileron, rudder, elevator, speed brake, stick, landing gear and similar movable systems used in aerospace industry have to operate according to the defined requirements and mechanisms used in those systems have to be synthesized in order to fulfill those requirements. Generally, without the use of synthesis tools, synthesis of mechanisms are done in CAD environment by trial-error and geometrical methods due to the complexity of analytical procedures. However, this approach is time consuming since it has to be repeated until the synthesized mechanism has suitable mechanism properties like transmission angle and connection points. Due to above reasons, a software developed for synthesis of mechanisms within the CAD environment can utilize all the graphical interfaces and provides convenience in mechanism design. In this work, it is aimed to develop a four-bar mechanism synthesis tool which is compatible with CATIA V5 by considering the requirements of aerospace industry. This tool performs function, path and motion synthesis and shows suitable mechanisms in CATIA according to input obtained from CATIA and mechanism properties.

CADSYN (Computer Aided Design SYNthesis) is a visual, interactive computer program working under Computer Aided Design (CAD) enviroment, which accomplishes the synthesis and analysis of planar four-bar mechanisms. The synthesis tasks are motion generation, path generation and function generation. During synthesis, the dyadic approach is utilized which introduces vector pairs and complex number algebra to model the motion. The possible solutions can be limited for link dimensions, the center circle point curves within a certain region, transmission angle characteristics, branch and order defects. The designed mechanism can be analyzed for velocity, acceleration and transmission angle and any of the data can be exported to Excel&reg / for further analysis. The software is designed to provide the user maximum feasible number of solutions. In four multiply separated position synthesis, if there is flexibility in the value(s) of one or any number of input parameter(s), designer can obtain different Burmester curves by changing those parameter(s). Designer can also simulate the kinematics of the mechanism by using drawing functions that are available from the CAD iv enviroment at any time. Drawing parts in the design plane can be attached to any link of the mechanism and can be simulated throughout the motion as part of the link it is attached. As a whole, this computer program is designed to satisfy the needs of mechanism designers while working in CAD enviroment.

Please read the abstract in the section 00front of this document / Thesis (PhD(Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

Este trabalho apresenta um mecanismo alternativo para suspensões veiculares traseiras, com mobilidade igual a três, de arquitetura paralela e assimétrico, com três cadeias cinemáticas ativas distintas. O mecanismo é capaz de variar simultaneamente os ângulos de cambagem e de esterçamento das rodas traseiras do veículo, além de atuar sobre a rolagem da massa suspensa. Aplicando-se métodos de síntese de mecanismos paralelos, obtiveram-se topologias de mecanismos de suspensão com estrutura cinemática paralela e, por meio de um critério sistemático, selecionou-se uma estrutura cinemática que atendeu aos três movimentos independentes no espaço tridimensional, desejados para o mecanismo. Um modelo cinemático e outro cinetoestático foram desenvolvidos para verificar a adequação do mecanismo à aplicação veicular. Três análises são apresentadas para avaliar o potencial do mecanismo paralelo sintetizado em aplicações veiculares: análise de desempenho, análise de viabilidade e análise cinemática. Na análise de desempenho, constatou-se que, a atuação do mecanismo sobre os ângulos de cambagem e de esterçamento das rodas traseiras, bem como a atuação sobre a rolagem da massa suspensa trazem benefícios sobre o comportamento dinâmico do veículo, quando comparado com o desempenho dinâmico de um veículo com suspensão convencional. Por meio da análise de viabilidade, determinou-se o curso, a velocidade, a força e a potência demandada pelo sistema de atuação, onde se observou que a atuação do mecanismo pode ser obtida a partir de atuadores comerciais. Nas análises de desempenho e viabilidade o comportamento dinâmico do veículo foi simulado em três manobras distintas: curva de raio constante em regime permanente, dupla mudança de faixa e manobra do anzol (fishhook), empregando uma cosimulação entre os programas CarSim e MATLAB/SIMULINK. Pela análise cinemática, percebeu-se que não há configurações singulares dentro do espaço de trabalho especificado para o mecanismo. O espaço de trabalho disponível atende ao especificado para a aplicação proposta do mecanismo e os erros que os ângulos de cambagem e de esterçamento possam apresentar, devido à imprecisão no posicionamento dos atuadores ou às tolerâncias inerentes ao processo de fabricação das peças do mecanismo, não comprometem os ganhos no comportamento dinâmico que o veículo com o mecanismo proposto apresentou nas simulações da análise de desempenho. / This work introduces an alternative three-degree-of-freedom mechanism for automotive rear suspensions, capable to adjust simultaneously the camber, toe and roll angles. Topologically, the mechanism is parallel and asymmetric with three distinct active kinematic chains. The mechanism is able to adjust the camber, toe and roll angles simultaneously. After applying the methods to perform synthesis of mechanisms, the architecture candidates were ranked in accordance with some proposed indices. Two mathematical models are developed: the kinematic and kinetostatic ones. In order to evaluate how promising this mechanism is, three analyses are conducted: a performance analysis, a feasibility analysis and a kinematic analysis. The obtained results have shown the capability of the mechanism actuation to improve vehicle handling performance, when compared to a car equipped with a conventional suspension system. Moreover, the mechanism feasibility analysis has shown that the actuators stroke, velocity and force can be obtained by using standard hydraulic or eletromechanical actuators. The evaluation was based on three maneuvers: a steady-state cornering, a fishhook and a double lane change. Regarding to the kinematic analysis, three considerations were made. First, there is not singular configuration inside the workspace. Second, the available workspace can attend the camber and rear steer angles stroke. Third, the vehicle dynamic behavior is not affected by the errors due to the manufacturing tolerance and actuators position inaccuracy.

Este trabalho apresenta um mecanismo alternativo para suspensões veiculares traseiras, com mobilidade igual a três, de arquitetura paralela e assimétrico, com três cadeias cinemáticas ativas distintas. O mecanismo é capaz de variar simultaneamente os ângulos de cambagem e de esterçamento das rodas traseiras do veículo, além de atuar sobre a rolagem da massa suspensa. Aplicando-se métodos de síntese de mecanismos paralelos, obtiveram-se topologias de mecanismos de suspensão com estrutura cinemática paralela e, por meio de um critério sistemático, selecionou-se uma estrutura cinemática que atendeu aos três movimentos independentes no espaço tridimensional, desejados para o mecanismo. Um modelo cinemático e outro cinetoestático foram desenvolvidos para verificar a adequação do mecanismo à aplicação veicular. Três análises são apresentadas para avaliar o potencial do mecanismo paralelo sintetizado em aplicações veiculares: análise de desempenho, análise de viabilidade e análise cinemática. Na análise de desempenho, constatou-se que, a atuação do mecanismo sobre os ângulos de cambagem e de esterçamento das rodas traseiras, bem como a atuação sobre a rolagem da massa suspensa trazem benefícios sobre o comportamento dinâmico do veículo, quando comparado com o desempenho dinâmico de um veículo com suspensão convencional. Por meio da análise de viabilidade, determinou-se o curso, a velocidade, a força e a potência demandada pelo sistema de atuação, onde se observou que a atuação do mecanismo pode ser obtida a partir de atuadores comerciais. Nas análises de desempenho e viabilidade o comportamento dinâmico do veículo foi simulado em três manobras distintas: curva de raio constante em regime permanente, dupla mudança de faixa e manobra do anzol (fishhook), empregando uma cosimulação entre os programas CarSim e MATLAB/SIMULINK. Pela análise cinemática, percebeu-se que não há configurações singulares dentro do espaço de trabalho especificado para o mecanismo. O espaço de trabalho disponível atende ao especificado para a aplicação proposta do mecanismo e os erros que os ângulos de cambagem e de esterçamento possam apresentar, devido à imprecisão no posicionamento dos atuadores ou às tolerâncias inerentes ao processo de fabricação das peças do mecanismo, não comprometem os ganhos no comportamento dinâmico que o veículo com o mecanismo proposto apresentou nas simulações da análise de desempenho. / This work introduces an alternative three-degree-of-freedom mechanism for automotive rear suspensions, capable to adjust simultaneously the camber, toe and roll angles. Topologically, the mechanism is parallel and asymmetric with three distinct active kinematic chains. The mechanism is able to adjust the camber, toe and roll angles simultaneously. After applying the methods to perform synthesis of mechanisms, the architecture candidates were ranked in accordance with some proposed indices. Two mathematical models are developed: the kinematic and kinetostatic ones. In order to evaluate how promising this mechanism is, three analyses are conducted: a performance analysis, a feasibility analysis and a kinematic analysis. The obtained results have shown the capability of the mechanism actuation to improve vehicle handling performance, when compared to a car equipped with a conventional suspension system. Moreover, the mechanism feasibility analysis has shown that the actuators stroke, velocity and force can be obtained by using standard hydraulic or eletromechanical actuators. The evaluation was based on three maneuvers: a steady-state cornering, a fishhook and a double lane change. Regarding to the kinematic analysis, three considerations were made. First, there is not singular configuration inside the workspace. Second, the available workspace can attend the camber and rear steer angles stroke. Third, the vehicle dynamic behavior is not affected by the errors due to the manufacturing tolerance and actuators position inaccuracy.

In order to improve the design of mechanical or mechatronic systems, mathematical optimization techniques have become an efficient and attractive tool with the increasing development of computer resources. However, the application of such optimization methods to multibody systems (MBS) remains a challenge when the MBS analysis requires the solving of assembly constraints. Hence, this PhD research focuses on the optimization of such closed-loop MBS, particularly when the objective function is of geometrical or kinematic nature. For kinematic optimization of MBS, we propose two penalty strategies to deal with assembly constraints during optimization. Both strategies are compared and illustrated via applications such as the isotropy maximization of parallel manipulators: the 3-dof Delta robot and the 6-dof Hunt platform. Following the same strategies, geometrical optimization of MBS is then investigated. However, due to a higher complexity, we propose to relax the problem, combining two modeling approaches: rigid-body and extensible-link formulations. This leads to a two-step strategy which is then successfully applied to synthesize mechanisms for path-following or function-generation problems. Through these applications, the existence of multiple local optima is highlighted. Therefore, instead of focusing on the unique global optimum solution, we have developed original methods to search and propose several local solutions for the design problem. This approach is called morphological optimization. This enables the designer to choose finally the best solution among several local optima using additional design criteria. Such morphological optimization techniques open the doors for the topology optimization of MBS which remains a challenging problem for future research / Afin d'améliorer la conception de systèmes mécaniques ou mécatroniques, les techniques d'optimisation mathématique sont devenues un outil efficace et attrayant étant donné le développement croissant des ressources informatiques. Cependant, l'application de telles méthodes d'optimisation sur les systèmes multicorps demeure un défi quand l'analyse du système nécessite la résolution de contraintes d'assemblage. C'est pourquoi cette recherche doctorale se concentre sur l'optimisation de tels systèmes multicorps, particulièrement lorsque la fonction objectif est de nature géométrique ou cinématique. Pour l'optimisation cinématique des systèmes multicorps, nous proposons deux stratégies de pénalité pour traiter les contraintes d'assemblage en cours d'optimisation. Ces deux stratégies sont comparées et illustrées par des applications telles que la maximisation d'isotropie de manipulateurs parallèles. Suivant les mêmes stratégies, l'optimisation géométrique des systèmes multicorps est alors étudiée. Cependant, vu la plus grande complexité, nous proposons de relaxer le problème en combinant deux approches de modélisation : une formulation en termes de corps rigides et une autre en termes de liens extensibles. Ceci nous mène à une stratégie en deux étapes qui est alors appliquée avec succès pour la synthèse de mécanismes. A travers ces applications, on a mis en évidence l'existence d'optimums locaux multiples. Dès lors, plutôt que de se focaliser sur l'unique optimum global, nous avons développé des méthodes originales afin de rechercher et proposer plusieurs solutions locales pour le problème de conception. Cette approche est baptisée "optimisation morphologique". Elle permet au concepteur de choisir finalement la meilleure solution parmi plusieurs optimums locaux en utilisant des critères supplémentaires de conception. De telles techniques d'optimisation morphologique ouvrent les portes pour l'optimisation topologique des systèmes multicorps qui demeure un challenge motivant pour des recherches futures.