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In a context of climate change, energy economy and better resources use, the automotive industry stands inside a major revolution. Car manufacturers strive to innovate to build lighter vehicles, aiming at reductions of carbon dioxide emissions and improved efficiency. Topology optimization, introducing material only where needed, perfectly fits into this perspective. The work described here is related to the mass reduction of a wheel carrier. This component, among the most critical inside the suspension system, is submitted to a high number of requirements and load cases, related to different mechanical fields (frequencies, stresses, etc.). Manufacturing of this part through casting also matters. To maximize the odds of obtaining a design satisfying the constraints, an incremental approach will be adopted to develop a formulation that could hopefully be extended to other components. Dans un contexte de changement climatique, d’économie d’énergie et de meilleure utilisation des ressources, l’industrie automobile se trouve au coeur d’une révolution majeure. Les constructeurs s’efforcent d’innover afin de rendre leurs véhicules plus légers dans un but de réduction des émissions de dioxyde de carbone et d’efficacité accrue. L’optimisation topologique, introduisant le matériau uniquement là où il est nécessaire, s’inscrit parfaitement dans cette perspective. Le travail décrit ici concerne l’allègement d’un porte-roue. Cette pièce, parmi les plus critiques du système de suspension, est soumise à un grand nombre d’exigences et de cas de charge, touchant à différentes disciplines de la mécanique (fréquences, contraintes, etc.). Il importe également de considérer la fabrication par coulage de cet élément. Afin de maximiser les chances d’obtenir un design satisfaisant la demande, une approche incrémentale sera adoptée afin de développer une formulation qui pourra éventuellement être étendue à d’autres composants.
Mechanics --- Topology optimization --- Automotive suspensions --- Manufacturing --- Stresses --- Frequencies --- Mécanique --- Optimisation topologique --- Suspensions automobiles --- Fabrication --- Contraintes --- Fréquences --- Ingénierie, informatique & technologie > Ingénierie mécanique
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Nowadays, increasingly concerning environmental problems, energy economy and raw resource scarcity urge automotive manufacturers to rethink the design of chassis and body components in such a way that the material is used to its full potential. With this mindset, Topology Optimization proved its usefulness as an efficient design tool for sustainable and lightweight designs of chassis components, achieving better fuel economy through mass reduction. However, the initial design provided by the topology optimization algorithm is most frequently relatively complex, requiring additional manual post-processing by manufacturing experts. In the pursuit of ready-to-manufacture, lightweight parts for mass production, this study focuses on the development of a flexible and large-scale Python code for topology optimization with integrated casting constraints. The proposed method uses the open-source FEniCS Project as finite element software, allowing the usage of PETSc as linear algebra back-end for better efficiency. The introduction of casting constraints such as directional molding, splitdrawing, minimum hole and pocket size, minimum member size and draft angle were considered, allowing the generation of ready-to-cast optimized parts. The benefit of such as algorithm is the significant reduction of time spent in post-processing, leading to faster development times of lightweight and innovative designs. De nos jours, les problèmes environnementaux de plus en plus préoccupants, l’économie d’énergie et la rareté des matières premières poussent les constructeurs automobiles à repenser la conception des composants de châssis et de carrosserie de manière à utiliser le matériau à son plein potentiel. Dans cet état d’esprit, l’optimisation topologique a prouvé son utilité en tant qu’outil de conception efficace pour la conception de composants de châssis durables et légèrs, permettant une meilleure économie de carburant grâce à la réduction de la masse. Cependant, la conception initiale fournie par l’algorithme d’optimisation topologique est le plus souvent relativement complexe, ce qui nécessite un post-traitement manuel supplémentaire par les experts en fabrication. Dans la recherche de pièces légères prêtes à être fabriquées pour la production de masse, cette étude se concentre sur le développement d’un code Python flexible pour l’optimisation topologique de grande échelle avec des contraintes de moulage intégrées. La méthode proposée utilise le projet open-source FEniCS comme logiciel d’éléments finis, permettant l’utilisation de PETSc comme back-end d’algèbre linéaire pour une meilleure efficacité. L’introduction de contraintes de coulée telles que le moulage directionnel, l’emboutissage fractionné, la taille minimale des trous et des poches, la taille minimale des éléments et l’angle de dépouille a été prise en compte, permettant la génération de pièces optimisées prêtes à couler. L’avantage d’un tel algorithme est la réduction significative du temps passé en post-traitement, ce qui permet d’accélérer le développement de conceptions légères et innovantes.
topology optimization --- manufacturing --- casting --- molding --- automotive --- lightweight --- mass reduction --- sustainability --- chassis components --- optimisation topologique --- fabrication --- coulée --- moulage --- automobile --- légèreté --- réduction de la masse --- durabilité --- composants de châssis --- Ingénierie, informatique & technologie > Ingénierie civile
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Autonomous vehicles require improved comfort without loss in handling. To accomplish this, a controller for active suspension is necessary. This thesis focuses on controller design and answers the following question: which controllers perform best for comfort and handling in the context of road preview and active suspension? Active suspension requires three components: force elements, sensors, and controllers. Controllers exploit road preview data from sensors then command force elements like actuators to counter disturbances. Four controller groups are defined: feedforward, feedback, robust and objective function control. A quarter-car model and Gaussian-curve road obstacle are established, along with a single, hard constraint on tire load to ensure road contact. Controller performance is measured in terms of comfort, handling, suspension deflection, and actuation. A global index considers all in one term. Pertinent controllers for the formulated problem are feedforward, skyhook, PID, fuzzy logic, H2/H∞, LQR and MPC. A pre-selection process yields feedforward, MPC and skyhook for implementation. Certain and uncertain simulations are carried out on the selected controllers, plus a combined feedforward-skyhook. MPC performs the best globally but has robustness issues. Despite worse comfort and handling than feedforward, it wins by greatly conserving on actuation. Feedforward performs globally better than skyhook but adding skyhook to feedforward does not improve performance. Indeed, MPC performs best, but this conclusion should not be overvalued, as it is subjective. The proposed framework on comparing and testing controllers is more important since it can be used by anyone with their own performance priorities.
active suspension --- road preview --- controllers --- feedforward --- skyhook --- MPC --- Ingénierie, informatique & technologie > Ingénierie mécanique
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Cost-effective lightweight design emerges as a pivotal focus for the automotive industry's future. Global competitiveness, stringent regulatory standards, and the integration of weight-intensive electronic elements in modern propulsion systems require the development of lighter, more efficient chassis components. With this perspective, topology optimization is extensively applied for the design of lightweight components. The casting process stands as a time and cost-efficient method for automotive mass production, widely adapted within the industry. Typically, weight optimization process does not consider castability, leading to later-stage modifications . These modifications incur additional time spent for manufacturability and often result in a heavier design than the initially optimized one. This thesis introduces an optimization process that optimizes weight and castability concurrently during the early design phase, offering a solution to this challenge. The study focuses on incorporating casting simulations into previously developed topology optimization framework, which involves accommodating geometric casting constraints, including directional molding, split-drawing, minimum member size, and draft angle considerations. A previously established Python code, designed for topology optimization incorporating casting constraints, offers flexibility and scalability. This code utilizes the open-source FEniCS Project as its finite element software, enabling the utilization of PETSc as a backend for linear algebra operations to enhance efficiency. A casting simulation is performed using OpenFOAM, focusing on flows involving heat transfer. A dedicated solver, employing the continuous adjoint approach, is implemented within OpenFOAM to calculate sensitivities. These outcomes are then merged with the topology optimization optimizer in FEniCS, leading to the establishment of an integrated optimization approach. The established solver undergoes validation by comparing the sensitivities computed with the finite difference method. Subsequently, the integrated approach's validation is carried out through a 2-dimensional cantilever beam problem.
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