L’amélioration des performances des robots est un enjeu important dans le domaine industriel. Les objectifs visés sont l’augmentation de l’espace de travail, de la capacité de charge transportable, de la vitesse de travail et de la précision du robot. Pour atteindre ces objectifs, il faut en général augmenter la rigidité, diminuer la masse et augmenter la capacité d’amortissement du robot. Les robots actuels sont généralement fabriqués en métaux : aluminium ou acier, ce qui limite leurs performances en raison des faibles capacités d’amortissement des vibrations de ces matériaux. Les matériaux composites présentent l’avantage de combiner des matériaux différents, ce qui conduit à une variété de leurs performances. Parmi les types de renforts, les fibres de carbone présentent un module d’élasticité élevé permettant la conception de pièces de grandes rigidités statiques mais elles possèdent une faible capacité d’amortissement. Les fibres végétales, par contre, possèdent une faible densité, de bonnes propriétés spécifiques et des capacités d’amortissement élevées. Cette thèse porte sur l’amélioration des performances d’un robot parallèle 3CRS en utilisant des matériaux composites pour reconcevoir des pièces initialement fabriquées en aluminium. La thèse commence d’abord par une caractérisation des comportements statiques et dynamiques du robot initial constitué de bras en aluminium. Ensuite, la forme des segments des bras robotiques est optimisée par rapport aux sollicitations mécaniques sur le robot. Un nouveau composite stratifié hybride renforcé par des fibres de carbone et des fibres de lin est alors proposé. Cette combinaison permet d’allier les avantages des deux types de fibres dans un composite pour le dimensionnement des composants sous sollicitation élevée. La structure de ce nouveau composite a été optimisée puis un segment est fabriqué pour valider la conception. Finalement, l’étude du nouveau robot avec des bras en matériaux composites a été réalisée, les résultats montrent que la rigidité du robot augmente, sa masse diminue légèrement et sa capacité d’amortissement augmente considérablement par rapport au robot initial. Donc, l’application du composite stratifié hybride peut améliorer les performances statiques et dynamiques et augmenter significativement la précision en fonctionnement du robot 3CRS. / Improvement of the robot’s performances is a major challenge in the industrial field. In general, improvement objectives are increasing workspace, transportable capacity, speed and precision of the robot. To achieve these objectives, it must increase rigidity, reduce weight and increase damping capacity of the robot. Currently, the robots are generally made of metals: aluminum or steel, which limits their performances due to low damping capacity of these materials.Composite materials present an advantage to combine different materials, which leads to a variety of composite material properties. Among the types of reinforcements, carbon fibers show high modulus that enables robotic parts with high static rigidities to be designed. However, carbon fibers have generally a low damping capacity. Natural fibers have low density, good specific properties and high damping capacity.This thesis focuses on the improvement of the performances of the 3CRS parallel robot by using the composite material to redesign robot parts initially made of aluminum. The thesis begins with static and dynamic characterizations of the original robot. Then, the shape of segments of the robotic arms is optimized with respect to applying force on the robot. A hybrid laminated composite reinforced with carbon fibers and flax fibers is proposed for the use. This combination enables to combine the advantages of two fiber types in a composite for using in high loaded components. The structure of the new hybrid laminated composite is optimized and a composite segment is then fabricated in order to validate the design. Finally, the analysis of the new robot with composite arms is executed. The result shows that the new robot has a slightly higher rigidity, lighter mass and considerably greater damping capacity in comparison with the original robot. Therefore, the application of the hybrid composite could improve the static and dynamic performances and increases considerably the accuracy in operation of the robot 3CRS.

<p align="justify">Many different active control techniques can be used to control the vibrations of a mechanical structure: they however require at least a sensitive signal amplifier (for the sensor), a power amplifier (for the actuator) and an analog or digital filter (for the controller). The use of all these electronic devices may be impractical in many applications and has motivated the use of the so-called shunt circuits, in which an electrical circuit is directly connected to a transducer embedded in the structure. The transducer acts as an energy converter: it transforms mechanical (vibrational) energy into electrical energy, which is in turn dissipated in the shunt circuit. No separate sensor is required, and only one, generally simple electronic circuit is used. The stability of the shunted structure is guaranteed if the electric circuit is passive, i.e. if it is made of passive components such as resistors and inductors.</p><p><p><p align="justify">This thesis compares the performances of the electric shunt circuits with those of classical active control systems. It successively considers the use of piezoelectric transducers and that of electromagnetic (moving-coil) transducers.</p><p><p><p align="justify">In a first part, the different damping techniques are applied on a benchmark truss structure equipped with a piezoelectric stack transducer. A unified formulation is found and experimentally verified for an active control law, the Integral Force Feedback (IFF), and for various passive shunt circuits (resistive and resistive-inductive). The use of an active shunt, namely the negative capacitance, is also investigated in detail. Two different implementations are discussed: they are shown to have very different stability limits and performances.</p><p><p><p align="justify">In a second part, vibration isolation with electromagnetic (moving-coil) transducers is introduced. The effects of an inductive-resistive shunt circuit are studied in detail; an equivalent mechanical representation is found. The performances are compared with that of resonant shunts and with that of active isolation with IFF. Next, the construction of a six-axis isolator based on a Stewart Platform is presented: the key parameters and the main limitations of the system are highlighted.</p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Forests represent one of the biggest terrestrial ecosystems of Earth, that can produce important raw renewable materials such as wood with the help of sun, air and water. To efficiently extract these raw materials, the tree harvesting process is highly mechanized in developed countries, meaning that advanced forestry machines are continuously used to fell, to process and to transport the logs and biomass obtained from the forests. However, working with these machines is demanding both mentally and physically, which are known factors to negatively affect operator productivity. Mental fatigue is mostly due to the manual operation of the on-board knuckleboom crane, which requires advanced cognitive work with two joystick levers, while the most serious physical strains arise from cabin vibrations. These vibrations are generated from knuckleboom crane vibrations as a result of aggressive manual operation. To enhance operator workload, well-being, and to increase productivity of the logging process, semi-automation functions are suggested, which are supervised automatic executions of specific work elements. Some of the related issues are addressed in the current thesis. Therefore, the content is divided into: (1) the design and development of a semi-automation function focused only on the base joint actuator (slewing actuator) of a knuckleboom crane, and (2) active vibration damping solutions to treat crane structure vibrations induced by the main lift cylinder (inner boom actuator). The considered reference machine is a downsized knuckleboom crane of a forwarder machine, which is used to pick up log assortments from a harvesting site. The proposed semi-automation function presented in the first part could be beneficial for operators to use during log loading/unloading scenarios. It consists from a closed-loop position control architecture, to which smooth reference slewing trajectories are provided by a trajectory planner that is automated via operator commands. The used trajectory generation algorithms are taken from conventional robotics and adapted to semi-automation context with proposed modifications that can be customizable by operators. Further, the proposed active vibration damping solutions are aimed to reduce vibrations of the knuckleboom crane excited by the inner boom actuator due to aggressive manual commands. First, a popular input shaping control technique combined with a practical switching logic was investigated to deal with the excited payload oscillations. This technique proved to be useful with a fixed crane pose, however it did not provide much robustness in terms of different link configurations. To tackle this problem an H2-optimal controller is developed, which is active in the pressure feedback-loop and its solely purpose is to damp the same payload oscillations. During the design process, operator commands are treated and explained from input disturbance viewpoint. All of the hypothesis throughout this thesis were verified with extensive experimental studies using the reference machine.

This master´s thesis is focused on obtaining electrical energy from vibration control car using electromagnetic dampers. The primary use of the electromagnetic damper is the production of electrical energy, which can then be used to power electrical appliances in your car or battery charging. The thesis is divided into six main parts: a literature review of possible ways of getting electricity from the car damping, theoretical and mathematical analysis of problems, the choice of design with computational analysis of dampers and power calculation.

This paper presents an active component damage reducing control approach for driving manoeuvres of a wheel loader. For this purpose, the front and rear axle loads will be manipulated by force pulses induced into the machine chassis via the lifting cylinders of the function drive. The associated control approach is based on the principles of Reinforcement Learning. The essential advantage of such methods against linear control approaches is that no descriptive system properties are required, but the algorithm automatically determines the system behaviour. Due to the high number of necessary training runs, the algorithm is designed and taught using a validated wheel loader simulation model. After over 850 training runs, an optimal strategy for damping the axle loads could not yet be determined. In spite of the unprecedented convergence, initial improvements of the damage values have already been achieved on tracks that deviate from the training track. Some of these results show a 4.9 % lower component damage compared to a machine setting with no damping system. The results and limits of this strategy are discussed due to a comparison with other scientific active vibration damping approaches. Currently, a linear control method (P-PI-controller) has a higher damage reduction potential, but it is expected that further training runs and another learning algorithm could make the reinforcement learning approach even more effective. Coupling the linear control method with the selflearning approach shows the highest potential for the axle damage reduction.

Le projet CLIC (City Lightweight Innovative Cab) dans lequel s’inscrit cette thèse de doctorat vise à développer une cabine de camion allégée sans dégrader les performances vibratoires et acoustiques. Pour cela il est nécessaire d’établir dans un premier temps un modèle de prédiction vibroacoustique du système couplé structure/espace intérieur incluant l’influence des matériaux dissipatifs (amortissement ou absorption) dans le domaine des moyennes fréquences. Les méthodes basées sur les éléments finis et les approches statistiques les plus couramment utilisées étant peu adaptées pour ce domaine de fréquence (coût de calcul important, méthodes peu flexibles), nous utiliserons le formalisme de la méthode SmEdA (Statistical modal Energy distribution Analysis). L’objectif principal de cette thèse de doctorat est dès lors, d’étendre cette méthode à la prise en compte de l’effet d’amortissement induit par des matériaux dissipatifs. La méthodologie se divise en trois étapes: 1. Les modèles équivalents des matériaux dissipatifs sont établis: (1) un modèle de plaque équivalent pour décrire la plaque amortie par un ou plusieurs patch(s) viscoélastique(s) et (2) un modèle de fluide équivalent pour décrire un matériau poreux agissant dans la cavité. 2. Chaque sous-système amorti est modélisé par éléments finis. Les méthodes MSE (Modal Strain Energy) et MSKE (Modal Strain Kinetic Energy) sont ensuite utilisées pour estimer les facteurs de perte modaux de chaque sous-système. 3. Le calcul SmEdA est effectué sur le système couplé en prenant en compte les facteurs de pertes modaux de chaque sous-système estimés dans la deuxième étape. Le point d’excitation est appliquée à la plaque, en supposant la force stationnaire et large bande. Afin de valider la méthodologie proposée un cas semi-complexe composé d’une plaque rectangulaire couplée à une cavité parallélépipédique est considéré. Ce système peut être utilisé pour étudier l’interaction vibroacoustique entre la structure de la cabine et l’intérieur de l’habitacle. Deux cas d’amortissement sont étudiés pour le système semi-complexe plaque-cavité: (1) un cas où la plaque est amortie avec un (ou plusieurs) patch(s) viscoélastique(s) et (2) un cas où un matériau poreux est placé dans la cavité. Le problème vibroacoustique est pour chaque cas modélisé suivant les trois étapes proposées et analyses dans le formalisme de la méthode SmEdA. Les résultats sont ensuite comparés au cas de référence (sans matériau dissipatif). La dernière partie de la thèse porte sur la validation expérimentale pour chaque cas test de la méthodologie numérique proposée. a mobilité d’éntrée, la puissance injectée et les énergies des sous-systèmes sont comparées aux prédictions numériques. Enfin les facteurs de pertes modaux des sous-systèmes estimés par les méthodes MSE et MSKE sont comparés aux résultats expérimentaux obtenus par la méthode d’analyse modale à haute résolution (méthode ESPRIT). / The project CLIC (City Lightweight Innovative Cab) aims to develop a lighter-weighted truck that maintains NVH performances of the initial design. This PhD research is then to establish a vibroacoustic prediction model of a complex structure-bounded fluid system (cabin structure coupled to cabin space) including dissipative treatments (damping or absorbing materials) for the mid-frequency domain. Since most commonly used element based and statistical methods are not suitable for this frequency domain, a proper prediction tool, which should be flexible in modeling capabilities and feasible in computational cost, must be implemented. The SmEdA (Statistical modal Energy distribution Analysis) method is considered in this thesis to comply with these requirements. The main objective of this research is to extend this method for taking account of the damping effect induced by dissipative materials. Development and validation of the methodology are carried out. 1. Dissipative materials are represented by simplified equivalent models: (1) the equivalent single layer model for describing the plate covered with a viscoelastic layer and (2) the equivalent fluid model for describing a porous material into the cavity. 2. Each subsystem including the equivalent models of the dissipative materials is modeled with FEM(Finite Element Model). The FE matrices including the energy dissipation are then computed. The MSE (Modal Strain Energy) and MSKE (Modal Strain Kinetic Energy) methods are used to estimate the modal damping loss factor of each subsystem mode. 3. The SmEdA calculation is performed on a whole system considering the modal damping loss factors estimated in the second step for each subsystem. The power is injected into the plate at a localized point by the stationary white noise force and subsequently, the SmEdA parameters are computed. To validate the proposed methodology, laboratory test cases of the structure-fluid problem composed of a rectangular plate coupled to a parallelepipedic cavity are considered. Such system can be used to study the vibroacoustic interaction between structure and fluid. Two damped test cases of the plate-cavity system are studied: (1) a system with a viscoelastic damping pad on the plate and (2) a system with a composite fibre in the cavity. The damped test cases are modeled following the three steps and are analyzed in the framework of SmEdA. The results are then compared to the original case with no damping treatment. The last part of the thesis presents an experimental validation of the numerical computation results on each test case. Measured quantities such as input mobility, injected power and subsystem energies are compared to the numerical predictions. The modal damping loss factors of the damped subsystems estimated with MSE and MSKE methods are compared to the experimental results estimated by a high-resolution modal analysis method (ESPRIT method).

Les matériaux architecturés attirent de plus en plus d’attentions de par leur capacité à combiner différentes propriétés ciblées. Dans ce contexte, les matériaux enchevêtrés, et plus particulièrement les matériaux monofilamentaires enchevêtrés, présentent des propriétés intéressantes en terme de légèreté, de ductilité, et de facteur de perte. En raison de l’architecture interne complexe de ces matériaux, leur caractérisation et la compréhension des mécanismes de déformation nécessitent une méthodologie adaptée. Dans cette étude, l’enchevêtrement est réalisé manuellement pour différents fils d’acier et soumis à une compression oedométrique. De manière à étudier le comportement sous charge de ce type de matériaux, un dispositif de compression uniaxiale guidée a été mis en place dans le tomographe. Il est ainsi possible de suivre, à l’aide de mesures quantitatives, la déformation de l’échantillon et l’évolution du nombre de contacts pour différentes fraction volumiques. L’utilisation de ces données microstructurales a permis un meilleure compréhension du comportement mécanique de tels enchevêtrements. Une rigidité pouvant varier de 20 à 200 MPa en fonction des paramètres de mise en forme (diamètre et forme du fil, fraction volumique, matériau constitutif) a été déterminé. Un matériau homogène de rigidité plus faible a pu être obtenu en pré-déformant le fil sous forme de ressort avant enchevêtrement. Le facteur de perte du matériau a ensuite été mesuré à la fois sous chargement statique et dynamique. L’analyse mécanique dynamique a mis en évidence la capacité de ce matériau à absorber de l’énergie avec une valeur de facteur de perte d’environ 0.25. Les propriétés mécaniques du matériau ont tout d’abord été modélisées analytiquement par un modèle de poutres et un bon accord avec les résultats expérimentaux a pu être obtenu en définissant un paramètre d’orientation equivalent, spécifique à la compression oedométrique de matériaux enchevêtrés. En parallèle, un modéle éléments discrets a été developé afin de simuler le comportement en compression de matériaux monofilamentaires enchevêtrés. Ce modèle s’appuie sur une discrétisation du fil en éléments sphériques, acquise à partir de données de tomographie. Bien que seul le comportement élastique du fil constitutif ait été pris en compte, une bonne adéquation entre résultats numériques et expérimentaux a été obtenu en ajustant les coefficients de frottement du modèle. / Playing with the architecture of a material is a clever way of tailoring its properties for multi-functional applications. A lot of research have been made, in the past few years, on what is now referred to as “architectured materials” (metal foams, entangled materials, steel wool, etc), mostly for their capacity to be engineered in order to present specific properties, inherent to their architecture. In this context, some studies have been carried out concerning entangled materials but only a few on monofilament entangled materials. Such a material, with no filament ends, could exhibit interesting properties for shock absorption, vibration damping and ductility. In this study, entanglements were manually produced, using different types of wire, and submitted to constrained (inside a PTFE die) in-situ compressive tests within the laboratory tomograph. This technique enabled a 3D, non destructive, microstructural characterization of the complex architecture of these materials, along with the analysis of their macroscopic mechanical properties. The stiffness of this material was found to be in a 20-200 MPa range and homogeneous samples could be obtained, while lowering their stiffness, by pre-deforming the initial wire as a spring. Damping measurements were performed using different types of entanglements (constitutive materials, volume fraction, wire diameter, wire shape) under both monotonic and dynamic loadings and directly linked to the measurements of the number of contacts. The Dynamic Mechanical Analysis underlined the great capacity of this material to absorb energy with a loss factor of about 0.25 and damping was found to decrease with the stiffness of the entanglement. The mechanical properties of this material were first modeled using an analytical “beam” model based on the experimental evolution of the mean distance between contacts and a good agreement was found with the experimental results. In parallel, a Discrete Element Method was used in order to model the compressive behaviour of Monofilament Entangled Materials. Although purely elastic properties were taken into account in the model, a very good agreement with the experimental results was obtained by adjusting the friction coefficients of the model. This tends to prove that the plasticity of these entangled materials is rather due to the structure (friction) than to the constitutive material itself.

Im Forschungsprojekt wurde eine Bauweise für ein modular aufgebautes und flexibel einsetzbares Gestellsystem entwickelt, welches durch integrativen Leichtbau den vorteilhaften Einsatz von Holzfurnierlagenverbund-werkstoffen (WVC) für Verarbeitungs- und Fördermaschinen ermöglicht. Die ingenieurtechnisch relevanten Eigen-schaften des Holzbasiswerkstoffs (u.a. strukturelle Dämpfungseigenschaft) wurden ermittelt und darauf aufbauend ein Profil als Strukturelement des Gestellsystems entwickelt. Hier lag besonderes Augenmerk auf der Gestaltung des Profilquerschnitts. Es wurden verschiedene Querschnittsgeometrien vergleichend untersucht, wobei sich ein ge-schlossenes Kastenprofil als günstig erwies. Ausgehend vom entwickelten Profil wurde die für ein modulares Sys-tem notwendige Verbindungstechnik konzipiert. Folgend wurde schrittweise die modulare Bauweise in Strukturein-heiten umgesetzt sowie parallel Untersuchungen zu Steifigkeit und Festigkeit der Profile fortgeführt. Während der Erprobung von Struktureinheiten unter praxisnahen Bedingungen wurden gewisse konstruktive Verbesserungspo-tentiale deutlich. Diese Änderungen sowie die gewonnenen Erkenntnisse aus der Material- und Strukturprüfung kamen im Prototyp zur Umsetzung. Schallpegelprofile verschiedener fördertechnischer Anlagen und des entwickel-ten Prototypen wurden abschließend aufgenommen und verglichen. / Aim of the present study was to develop a modular designed and widely employable rack system. Positive properties of wood based materials (WVC) in lightweight structures were identified and integrated for the application in fabri-cation and conveyer technologies. For this purpose relevant properties of wood materials had been investigated (e.g. damping properties). The results of these analyses were the basis for the development of a beam profile, the basic structural design element for the future rack system. The most effort was put into finding the optimal beam cross section. Several different cross sections had been compared, a square sectional beam profile showed the best per-formance. Based on the square sectional beam profile proper connection methods for the modular rack were devel-oped. Structural units were subsequently realized step by step, while the investigation of stiffness and strength of the profiles was continued. The testing of the structural units under simulated field conditions revealed some minor constructional improvement capabilities. The constructional improvements and the knowledge from the material and profile testing were put into practice in the prototype. Finally sound measurements were carried out to compare several conveyors made of different materials (including the prototype) in respect to the emitted sound level.