A Plataforma de Stewart é um dos exemplos mais populares dos manipuladores do tipo paralelo, disponibilizando 6 graus de liberdade, apresentando ao mesmo tempo propriedades superiores de precisão e relação peso/carga, quando comparadas com mecanismos do tipo serial, o que a converte em uma opção atrativa para ser aplicada como simulador de movimentos. Neste contexto, o presente trabalho estuda o controle de seguimento de trajetória de um Manipulador Plataforma Stewart (MPS) com atuadores hidráulicos para ser aplicado como simulador de movimentos de navios. O estudo envolve a análise da cinemática, dinâmica, e controle do manipulador, incluindo a modelagem matemática dos cilindros hidráulicos usados como atuadores. Atenção especial é dispendida à formulação da dinâmica do MPS no espaço de juntas, procurando demonstrar a propriedade de antissimmetría das Matrizes de Inércia e Coriolis. O controle proposto foi validado como estável pelo critério de Lyapunov, e, leva em consideração tanto o sistema mecânico da Plataforma de Stewart, quanto o sistema de acionamento hidráulico dos atuadores. Através de simulações de controle usando trajetórias similares às do movimento de um navio, comprovou-se que o sistema proposto consegue disponibilizar fielmente os movimentos de uma embarcação. / The Stewart Platform is one of the most representative examples of parallel manipulators. It has six degrees of freedoms, and superior precision and load/weight ratio when compared to serial manipulators, properties that make them suitable and attractive options for motion simulation applications. In this sense, this work focuses on robust tracking control design for a high load capacity hydraulically driven Stewart Platform manipulator, capable of vessel motion simulations. The kinematic, dynamic and control analysis of the manipulator are presented, as well as a mathematical model of the hydraulic cylinders used as actuators. Especial attention is given to the derivation of the manipulator dynamics formulation, the skew symmetric property of the Inertia and Coriolis matrices is carefully proven in both Cartesian and joint state spaces. The proposed controller takes into consideration the manipulator mechanical dynamics and the actuators hydraulic dynamics. Furthermore, the Lyapunov criteria is used to guarantee control closed loop stability. The control performance is verified by means of computer simulations.

In aviation industry, one of the most important aspects is weight savings. This since with a lowered weight, the performance of the aircraft can be increased together with increased fuel savings and thus lowered running costs. One way of saving weight is to reduce energy consumption, since with lowered energy consumption, lowered mass of fuel is required etc. Most aircraft are today maneuvered with hydraulic systems due to its robustness and power density. It is the primary source of power for primary and secondary flight controls. The control of a conventional system which is using proportional valves is done by altering flow by restricting it to the extent where the desired output is achieved, which implies heat losses since the full performance of its supply is wasted through the valve. In previous research, more energy efficient hydraulic systems called digital hydraulics has been investigated. In difference with conventional hydraulics, digital hydraulics uses low cost, high frequency on/off valves, which either are fully opened, or fully closed, instead of proportional valves to achieve the desired output. With this comes the benefit of no energy losses due to leakage and restriction control. The downsides with digital hydraulics is the controlabillity. One way of controlling it is by using several pressure sources which outputs different pressure levels. By using the on/off valves in different combinations, different outputs can be achieved in a discrete manner. In this thesis, the aim was to remove the impact of the discrete force steps which are present in digital hydraulics by creating concepts with hybrid solutions containing both digital hydraulics and restrictive control. Three concepts were developed and investigated using simulation. The energy consumption and performance was analysed and compared with a reference model, the concepts redundancy compared to conventional systems was discussed and finally the concepts were tested with an aircraft simulation model. The concepts were found to reduce the energy consumption with different magnitude depending on the load cycle. The performance was found to be almost as good as the reference model. The redundancy compared with conventional systems should be possible to maintain with slight modifications, but further investigation is needed. It was found that one of the most important aspects regarding energy consumption is which combination of supply pressures is used to supply the system since it influences leakage and flow due to compression.

<p dir="ltr">In recent years increasingly stringent regulations regarding the pollution emissions and greenhouse gasses (GHG) of off-highway vehicles have emerged. However, recent studies underscores that off-highway vehicles have an average efficiency of 30%. In response, researchers are exploring the possibility of electrifying these vehicles with electric machines (EMs) potentially undertaking one, multiple, or all the vehicular functions previously reliant on internal combustion engines (ICEs).</p><p dir="ltr">Contemporary off-highway vehicle technology revolves around hydraulic systems tailored for diesel engines, tuned to specific torque characteristics and operating at a single speed. While replacing the prime mover with electric machines, the proper hydraulic supply capable of matching the same torque speed characteristics must be found. Furthermore, it must be determined whether an integration capable of reducing the mass, cost, and volume can be implemented, and if energy recuperation is possible. </p><p dir="ltr">In essence, achieving the desired transformation in off-highway vehicle technology necessitates a comprehensive reevaluation of both hydraulic systems and power sources, with electrification emerging as a promising strategy for harmonizing efficiency, emission standards, and performance expectations. </p><p><br></p><p dir="ltr">This work proposes guidelines to systematically design EMs and positive displacement hydraulic gear machines (HMs), along with their integration in an electro-hydraulic unit (EHU). To do so, three different variants of EHU are produced. The first variant features an external gear machine (EGM) integrated in a permanent magnet synchronous electric machine (PMSEM). The second and third variants integrate an internal gear machine (IGM) and a PMSEM, wherein the final variant introduces features endowing its operation at high rotational velocities.</p><p dir="ltr">The EM and HM constituting all variants of EHU are designed using a genetic algorithm-based optimization framework. This optimization framework encapsulates dedicated models for the EM and the HM that allow the calculation of the EHU performance. The first optimization objectives are the minimization of power consumption over the duty cycle of the selected reference machine, the minimization of the pressure and flow ripple, and maximization of the power density of the EHU. The optimization of the second and third variants instead only aims to maximize the total efficiency and power density of the EHU. </p><p dir="ltr">After having determined the parameters of the EHU through the optimization procedure the designs are refined with thorough simulations focusing on the fluid-dynamic features and the design of the axial balance system of the HMs. </p><p dir="ltr">The three variants present an increasing level of HM and EM integration and component reduction. While in the first variant HM and EM have a dedicated housing, and the HM is only positioned in the inert region of the EM, in the latest variants the HM and the EM also share the same casing. The first variant of EHU is air cooled by a radial fan system attached to the EM rotor and openings machined in the casing. The second variant takes advantage of the extreme integration and the differential pressure generated across the HM to liquid cooling the EM. The third variant necessitates the use of an external system to cool the EM. </p><p dir="ltr">To prove the effectiveness of the design process the first two EHU variants are prototyped and tested. The first EHU variant is tested both in a standalone configuration and on the reference machine showing total efficiency values up to 69%, proving its functionality and proving the capability of recuperating energy. The tests conducted on the second variant EHU show a volumetric efficiency that ranges between 81% and above 96% for a pinion rotation velocity of 6000 rpm proving the value of the presented design process. Despite the good quality of the volumetric efficiency values, this EHU variant present morphological limitations that negatively impact its mechanical efficiency. Finally, the third EHU concept is presented not only to remedy the morphological limitations of the second variant but also to address the challenges raised by high rotational velocity operation. </p>

In this paper, we present a new compact hydraulic linear actuator. The concept is developed to change the rolling piston diameter of an active air spring during usage. By doing so, the air spring can actively apply pressure and tension forces. The actuator is designed for small movements at high forces. It is insensitive to side forces, which are introduced by the bellows rolling on the rolling piston of the air spring. A diaphragm sealing is used to minimize friction. Hence a precise adjustment of small displacements at high dynamics is possible and the system is completely leakage-free. We describe the design and development of this actuator and show first measurement results from preliminary tests to show its functionality.

This paper focuses on thermal analysis of a direct driven hydraulic setup (DDH). DDH combines the benefits of electric with hydraulic technology in compact package with high power density, high performance and good controllability. DDH enables for reduction of parasitic losses for better fuel efficiency and lower operating costs. This one-piece housing design delivers system simplicity and lowers both installation and maintenance costs. Advantages of the presented architecture are the reduced hydraulic tubing and the amount of potential leakage points. The prediction of the thermal behavior and its management represents an open challenge for the system as temperature is a determinant parameter in terms of performance, lifespan and safety. Therefore, the electro-hydraulic model of a DDH involving a variable motor speed, fixed-displacement internal gear pump/motors was developed at system level for thermal analysis. In addition, a generic model was proposed for the electric machine, energy losses dependent on velocity, torque and temperature was validated by measurements under various operative conditions. Results of model investigation predict ricing of temperature during lifting cycle, and flattened during lowering in pimp/motor. Conclusions are drawn concerning the DDH thermal behavior.

Le chrome dur, utilisé comme revêtement de tige d’actionneurs hydrauliques linéaires, a été interdit pour risque sanitaire (directive européenne REACH). A cet effet, un revêtement de WS2 a été sélectionné par Safran Landing Systems pour substituer le chrome dur comme revêtement de tige de piston de frein hydraulique. La démarche de sélection utilisée, est limitée par son incapacité à expliquer les performances observées et démontre le besoin d’une démarche de sélection d’autant plus appropriée que la notion d’étanchéité des actionneurs hydrauliques linéaires est « floue ». Comme, la tribologie n’a pas vocation à caractériser les revêtements de surface, parce que son plus petit objet d’étude est un triplet tribologique, cette étude propose l’évaluation de la compatibilité tribologique du revêtement de WS2, avec la fonction d’étanchéité. La démarche utilisée montre que l’étanchéité est régie, par un critère en pression, et par une vérification des caractéristiques tribologiques du système tige/joints requises pour la réalisation de l’étanchéité ; ce qui nécessite un piston hydraulique instrumenté. L’absence de ce piston est compensée par une « caractérisation tribologique approchée » du contact tige/joints, qui associe les expertises tribologiques de pistons hydrauliques d’essais de qualification, appuyées par un modèle éléments finis (EF) du piston hydraulique d’une part, et les résultats d’un essai de frottement piste/joints, conçus à cet effet à l’aide d’un modèle EF d’autre part. Les résultats montrent que le système tige/joints présente de bonnes caractéristiques tribologiques pour le facteur de frottement et l’usure, alors que la localisation de l’accommodation de vitesses dans le cas du contact tige/joint d’étanchéité, accélère le débit source du revêtement et limite sa durée de vie. Enfin, cette thèse comble un vide méthodologique en proposant, une démarche de sélection d’un revêtement pour une application tribologique, et une démarche de triboconception d’un actionneur hydraulique linéaire dans le cas d’un fonctionnement quasi-statique. / Hard chromium used as rod coating in linear hydraulic actuators has been forbidden by the European Directive REACH. In this situation, a WS2 coating has been selected by Safran Landing Systems to replace the hard chromium coating on rod pistons actuators of landing gear braking systems. The selection method was unable to explain the observed performance, and shows the lack of an appropriate methodology for the rod coating selection, mainly because the sealing concept is rather vague. Since tribology is not intended to characterize surface coatings, because its smallest object of study is a tribological triplet, this study proposes the evaluation of the tribological compatibility of the WS2 coating with the sealing function of the hydraulic piston. The adopted approach shows that the sealing performance is governed by a rod/seal contact pressure criterion and by the verification of the tribological characteristics of the rod/seal contact required to achieve a sealing performance. This tribological characterization requires an instrumented hydraulic piston. The absence of this piston is compensated by an "approximate tribological characterization" of the rod/seal contact, which combines the tribological expert analysis of hydraulic pistons of qualification tests, supported by a finite elements model (FE) of the hydraulic piston, and the results of a plate rod/seal friction test, designed for this purpose using another FE model. The results show that the rod/seal contact exhibits good tribological characteristics for the friction factor and wear, whereas the location of the velocity accommodation in the case of the rod/anti-extrusion seal contact accelerates the 3rd body generation of the coating and limits its life expectancy. Finally, this thesis fills a methodological lack by proposing a method of selecting a coating for a tribological application and a triboconception method of a linear hydraulic actuator in the case of quasi-static operating conditions.

In this paper, we present a new compact hydraulic linear actuator. The concept is developed to change the rolling piston diameter of an active air spring during usage. By doing so, the air spring can actively apply pressure and tension forces. The actuator is designed for small movements at high forces. It is insensitive to side forces, which are introduced by the bellows rolling on the rolling piston of the air spring. A diaphragm sealing is used to minimize friction. Hence a precise adjustment of small displacements at high dynamics is possible and the system is completely leakage-free. We describe the design and development of this actuator and show first measurement results from preliminary tests to show its functionality.

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Made available in DSpace on 2014-12-17T14:58:24Z (GMT). No. of bitstreams: 1 JoaoDBS_DISSERT.pdf: 2950294 bytes, checksum: b123f316a60d2e367696c4d97c359a71 (MD5) Previous issue date: 2013-11-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The development of non-linear controllers gained space in the theoretical ambit and of practical applications on the moment that the arising of digital computers enabled the implementation of these methodologies. In comparison with the linear controllers more utilized, the non -linear controllers present the advantage of not requiring the linearity of the system to determine the parameters of control, which permits a more efficient control especially when the system presents a high level of non-linearity. Another additional advantage is the reduction of costs, since to obtain the efficient control through linear controllers it is necessary the utilization of sensors and more refined actuators than when it is utilized a non-linear controller. Among the non-linear theories of control, the method of control by gliding ways is detached for being a method that presents more robustness, before uncertainties. It is already confirmed that the adoption of compensation on the region of residual error permits to improve better the performance of these controllers. So, in this work it is described the development of a non-linear controller that looks for an association of strategy of control by gliding ways, with the fuzzy compensation technique. Through the implementation of some strategies of fuzzy compensation, it was searched the one which provided the biggest efficiency before a system with high level of nonlinearities and uncertainties. The electrohydraulic actuator was utilized as an example of research, and the results appoint to two configurations of compensation that permit a bigger reduction of the residual error / O desenvolvimento de controladores n?o lineares ganharam espa?o nos ?mbitos te?rico e de aplica??es pr?ticas no momento que o surgimento de computadores digitais possibilitou a implementa??o destas metodologias. Em compara??o aos controladores lineares mais utilizados, os controladores n?o lineares apresentam a vantagem de n?o necessitarem da lineariza??o do sistema para determinar os par?metros de controle, o que permite um controle mais eficiente principalmente quando o sistema apresenta elevado grau de n?o linearidade. Outra vantagem adicional ? a redu??o dos custos, uma vez que para obter o controle eficiente atrav?s dos controladores lineares ? necess?ria a utiliza??o de sensores e atuadores mais refinados do que quando se utiliza um controlador n?o linear. Dentre as teorias de controle n?o linear, o m?todo de controle por modos deslizantes se destaca por ser um m?todo que apresenta maior robustez frente ?s incertezas. J? ? comprovado que a ado??o de t?cnicas de compensa??o na regi?o do erro residual permite melhorar ainda mais o desempenho desses controladores. Assim, neste trabalho ? descrito o desenvolvimento de um controlador n?o linear que busca a associa??o da estrat?gia de controle por modos deslizantes com a t?cnica de compensa??o fuzzy. Mediante a implementa??o de algumas estrat?gias de compensa??o fuzzy, buscou-se aquela que proporcionasse maior efici?ncia frente a um sistema com elevado grau de n?o linearidades e incertezas. O atuador eletrohidr?ulico foi utilizado como exemplo de estudo, e os resultados apontam para duas configura??es de compensa??o que permitem uma maior redu??o do erro residual

This diploma thesis deals with the design of several variants of test rig for tests of axial ball joints of passenger cars. The individual design variants are evaluated based on the evaluation matrix and then the best option is selected. Selected proposal includes a complete design including 3D models and strength analyses that focus on the most stressed construction nodes. These design nodes are solved using the finite element method. Hydraulics and hydraulic elements are equipped by the existing equipment from a test lab. At the end of this thesis is solved risk analysis of the new construction and its economic evaluation.