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Stochastic Modal Analysis of Structures with Random Shape Using X-FEM ; Van Miegroet, Laurent ; Duysinx, Pierre Conference (2008, July) Detailed reference viewed: 44 (2 ULg)Analysis of hybrid hydraulic vehicles and comparison with hybrid electric vehicles using batteries or super capacitors Louvigny, Yannick ; ; Duysinx, Pierre Conference (2008, March 12) Hybrid Hydraulic Vehicle (HHV) technology is an alternative solution to classical Hybrid Electric Vehicles (HEV). The authors’s previous studies of hybrid hydraulic systems clearly demonstrated that HHV ... [more ▼] Hybrid Hydraulic Vehicle (HHV) technology is an alternative solution to classical Hybrid Electric Vehicles (HEV). The authors’s previous studies of hybrid hydraulic systems clearly demonstrated that HHV can lead to fuel savings even though smaller than HEV. Hydraulic energy recovery systems are well adapted for heavy urban vehicles with frequent starts and stops because the weight penalty of the hydraulic system can be mitigated while taking benefit of their high specific power property for power assist. This recent work investigates and compares, from an economical and technical point of view, both HHV and HEV buses using batteries or super capacitors as energy storage systems. The fuel consumption of different hybrid busses is simulated using ADVISOR on the basis of three European SORT driving cycles. The results show that HHV and HEV with super capacitors can not rival from the consumption point of view with the HEV using batteries as energy storage system. But they can be economically interesting because of their lower cost and the longer service life of their energy storage system. [less ▲] Detailed reference viewed: 165 (9 ULg)Eco-efficiency optimization of Hybrid Electric Vehicle based on response surface method and genetic algorithm ; Louvigny, Yannick ; Duysinx, Pierre in Proceedings of EET-2008 European Ele-Drive Conference and International Advanced Mobility Forum (2008, March) The electric vehicles (EV) and sometimes the hybrid electric vehicle (HEV) technologies are environmentally very efficient but can not succeed on the market because of a smaller ability to satisfy ... [more ▼] The electric vehicles (EV) and sometimes the hybrid electric vehicle (HEV) technologies are environmentally very efficient but can not succeed on the market because of a smaller ability to satisfy customer’s requirements. Comparison of clean technologies in automotive and transportation systems has been measured using different analysis tools such as LCA (life cycle analysis). However, these instruments never account for the user’s satisfaction which partly explains the market acceptance problems. The Eco efficiency is a global index which accounts for both environment impacts and user satisfaction. The main objective of vehicle powertrain hybridization is to improve the fuel consumption and environment pollutants impact (Eco-score) without decreasing the vehicle performances and other user satisfaction criteria. The objective of this study is to minimize the Eco-score indicator of HEV with respect to the user satisfaction criteria. The approach is formulated as a multidisciplinary optimization problem. At first the EV or HEV are modeled and simulated using ADVISOR (advanced vehicle simulator) with respect to several driving situations. Then emissions can be determined and the Ecoscore indicator can be calculated. User Satisfaction can be evaluated based on performance criteria extracted from ADVISOR simulation and on simple evaluation tools relying on the state-of-the art of technological information for safety, reliability and daily cost. In this study the design problem is stated as follows: select mechanical and electric components (like engine, motor and battery sizes) to minimize the Ecoscore indicator and to maximize user satisfaction criteria subject to catalogue constraints on the choice of the components. The approach is illustrated on applications dealing with parallel hybrid electric vehicles. [less ▲] Detailed reference viewed: 131 (6 ULg)Stress constrained topology and shape optimization : Specific character and large scale optimization algorithms Duysinx, Pierre ; ; Van Miegroet, Laurent et al in Proceedings of the 8th World Congress on Computational Mechanics (WCCM) (2008) Detailed reference viewed: 24 (6 ULg)Electromechanical microdevice pull-in voltage maximization using topology optimization Lemaire, Etienne ; Rochus, Véronique ; Golinval, Jean-Claude et al Conference (2008) Detailed reference viewed: 47 (9 ULg)Microbeam pull-in voltage topology optimization including material deposition constraint Lemaire, Etienne ; Rochus, Véronique ; Golinval, Jean-Claude et al in Computer Methods in Applied Mechanics & Engineering (2008), 197 Because of the strong coupling between mechanical and electrical phenomena existing in electromechanical microdevices, some of them experience, above a given driving voltage, an unstable behavior called ... [more ▼] Because of the strong coupling between mechanical and electrical phenomena existing in electromechanical microdevices, some of them experience, above a given driving voltage, an unstable behavior called pull-in effect. The present paper investigates the application of topology optimization to electromechanical microdevices for the purpose of delaying this unstable behavior by maximizing their pull-in voltage. Within the framework of this preliminary study, the pull-in voltage maximization procedure is developed on the basis of electromechanical microbeams reinforcement topology design problem. The proposed sensitivity analysis requires only the knowledge of the microdevice pull-in state and of the first eigenmode of the tangent stiffness matrix. As the pull-in point research is a highly non-linear problem, the analysis is based on a monolithic finite element formulation combined with a normal flow algorithm (homotopy method). An application of the developed method is proposed and the result is compared to the one obtained using a linear compliance optimization. Moreover, as the results provided by the developed method do not comply with manufacturing constraints, a deposition process constraint is added to the optimization problem and its effect on the final design is also tested. [less ▲] Detailed reference viewed: 109 (31 ULg)Modelling the electromechanical coupling of RF switch using Extended Finite Element Rochus, Véronique ; Van Miegroet, Laurent ; Duysinx, Pierre et al (2008) Detailed reference viewed: 57 (13 ULg)Analysis of hydraulic hybrid vehciles and economical comparison with hybrid electric vehicles Louvigny, Yannick ; ; Duysinx, Pierre Conference (2007, June 01) Hybrid Hydraulic Vehicle (HHV) technology is an alternative to HEV. This technology deserves new attention because of recent development in reversible hydraulic motor pumps with high efficiency. The HHV ... [more ▼] Hybrid Hydraulic Vehicle (HHV) technology is an alternative to HEV. This technology deserves new attention because of recent development in reversible hydraulic motor pumps with high efficiency. The HHV technology is based on parallel architecture of motor assist systems. A first preliminary study investigated the fuel consumption of a passenger car, a SUV and an urban bus. It clearly demonstrated that the fuel efficiency benefits are the better for heavy vehicles with frequent stops and starts. The second part of the work then compared both HEV and HHV buses. The fuel consumption is simulated using ADVISOR on the basis of 3 SORT driving cycles. The results showed that the HHV are penalized by his weight but they can be economically interesting because of the lower cost and longer life time of the hydraulic system. [less ▲] Detailed reference viewed: 117 (18 ULg)Topology optimization of microbeams including layer deposition manufacturing constraints Lemaire, Etienne ; ; et al Conference (2007, May) As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use ... [more ▼] As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use of automatic design tools like topology optimization is not possible. For instance, optimal topologies generally contain closed cavities that cannot be produced using the usual microfabrication techniques like layer deposition. The present paper intends to add a layer deposition constraint to the optimization problem using recent developments of CONLIN software. However, with this new optimization procedure we could observe that classical sensitivities filtering makes optimization problem rather unstable while filtering the density field itself keeps good convergence properties. [less ▲] Detailed reference viewed: 61 (6 ULg)Topology Optimization of Structural Components Included in Flexible Multibody Systems Bruls, Olivier ; Lemaire, Etienne ; et al in Proceedings of the 7th World Congress on Structural and Multidisciplinary Optimization (2007, May) This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural ... [more ▼] This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-sta tic load cases to mimic the complex loadings in service. In contrast, this paper proposes an optimization procedure based on the dynamic simulation of the full multibody system with large amplitude motions and elastic deflections. We show that the simulation model, which involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis, can be efficiently exploited in an optimization loop. The method is applied to truss structural components. Each truss is represented by a structural universe of beams with a topology design variable attached to each one. A SIMP model (or a variant of the power law) is used to penalize intermediate densities. The optimization formulation is stated as the minimization of the mean compliance over a time period or as the minimization of the mean tip deflection during a given trajectory, subject to a volume constraint. In order to illustrate the benefits of the integrated design approach, the case of a two degrees-of-freedom robot arm is developed. [less ▲] Detailed reference viewed: 64 (12 ULg)Recent developments in fixed mesh optimization with X-FEM and Level Set description Van Miegroet, Laurent ; ; Duysinx, Pierre (2007, May) Detailed reference viewed: 98 (4 ULg)The global modal parameterization for non-linear model-order reduction in flexible multibody dynamics Bruls, Olivier ; Duysinx, Pierre ; Golinval, Jean-Claude in International Journal for Numerical Methods in Engineering (2007), 69(5), 948-977 In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control ... [more ▼] In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control design problems, for which compact ordinary differential equations (ODEs) in closed-form are desirable. In a linear framework, reduction techniques classically rely on a projection of the dynamics onto a linear subspace. In flexible multibody dynamics, we propose to project the dynamics onto a submanifold of the configuration space, which allows to eliminate the non-linear holonomic constraints and to preserve the Lagrangian structure. The construction of this submanifold follows from the definition of a global modal parameterization (GMP): the motion of the assembled mechanism is described in terms of rigid and flexible modes, which are configuration-dependent. The numerical reduction procedure is presented, and an approximation strategy is also implemented in order to build a closed-form expression of the reduced model in the configuration space. Numerical and experimental results illustrate the relevance of this approach. Copyright (c) 2006 John Wiley [less ▲] Detailed reference viewed: 119 (48 ULg)Stress concentration minimization of 2D filets using X-FEM and level set description Van Miegroet, Laurent ; Duysinx, Pierre in Structural and Multidisciplinary Optimization (2007), 33(4-5), 425-438 This paper presents and applies a novel shape optimization approach based on the level set description of the geometry and the extended finite element method (X-FEM). The method benefits from the fixed ... [more ▼] This paper presents and applies a novel shape optimization approach based on the level set description of the geometry and the extended finite element method (X-FEM). The method benefits from the fixed mesh work using X-FEM and from the curves smoothness of the level set description. Design variables are shape parameters of basic geometric features that are described with a level set representation. The number of design variables of this formulation remains small, whereas global (i.e. compliance) and local constraints (i.e. stresses) can be considered. To illustrate the capability of the method to handle stress constraints, numerical applications revisit the minimization of stress concentration in a 2D filet in tension, which has been previously studied in Pedersen (2003). Our results illustrate the great interest of using X-FEM and level set description together. A special attention is also paid to stress computation and accuracy with the X-FEM. [less ▲] Detailed reference viewed: 94 (17 ULg)An introduction to robotics - mechanical aspects Duysinx, Pierre ; Bruls, Olivier ; Géradin, Michel Learning material (2006) Detailed reference viewed: 34 (3 ULg)Generalized Shape And Topology Optimization: Recent Developments And Application Perspectives To Automotive Structures Duysinx, Pierre ; Van Miegroet, Laurent ; et al in New Advances in Body Engineering - Lightweight design, passive safety, pedestrian protection, and numerical optimization (2006, December) More than 15 years after the seminal work by Bendsøe and Kikuchi, topology optimization of structures has taken advantage of my research efforts and has now become a commercial available tool (e.g ... [more ▼] More than 15 years after the seminal work by Bendsøe and Kikuchi, topology optimization of structures has taken advantage of my research efforts and has now become a commercial available tool (e.g. OptiStruct by Altair, Topol by Samtech, etc.). These software tools are daily used in automotive industry and provide engineers with a rational tool for preliminary design of efficient structural components. This paper presents the status of available topology optimization tools and introduces the recent developments that extend their capabilities in order to handle stress constraints, manufacturing constraints, etc. The communication also presents a novel approach of generalized shape optimization that has been introduced to circumvent the difficulties of parametric shape optimization and to complement topology optimization. The approach is based on the eXtended Finite Element Method (XFEM) and the Level Set Description of the geometry. The Level Set description introduces smooth curve descriptions and allows modifying the connectivity of the wholes. The XFEM works with a fixed mesh as in topology optimization, which makes the method very convenient for engineers. Thus the novel approach is likely to bring the next future evolution of structural optimization. Impressive capabilities of this new generation approach will be demonstrated. Application examples from automotive and aerospace engineering will illustrate the different possibilities offered by two approaches. [less ▲] Detailed reference viewed: 111 (5 ULg)Generalized shape optimization using XFEM and Level Set method Duysinx, Pierre ; Van Miegroet, Laurent ; Conference (2006, November) This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended ... [more ▼] This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended Finite Element Method (XFEM). The method takes benefit of the fixed mesh work using XFEM and of the smooth curves description of the Level Set method. Design variables are shape parameters of basic geometric features like circles, triangles etc. The number of design variables of this formulation is small whereas various global and local constraints can be considered. The Level Set description allows to modify the connectivity of the structure as geometric features can merge or separate from each other. However no new entity can be introduced by the programme. A central problem that is investigated here is the sensitivity analysis and the way it can be carried out efficiently. Numerical applications revisit some classical (academic) benchmarks from shape and topology optimization. [less ▲] Detailed reference viewed: 144 (7 ULg)Simulation and optimization of controlled multibody systems: Application to vehicle dynamics Bruls, Olivier ; Duysinx, Pierre ; Golinval, Jean-Claude Conference (2006, November) Detailed reference viewed: 11 (1 ULg)An extended flexible multibody dynamics software for mechatronic applications Bruls, Olivier ; Duysinx, Pierre ; Golinval, Jean-Claude in Proceedings of ISMA 2006 (2006, September) This paper presents some extensions of flexible multibody formalisms for mechatronic applications. The software implementation is realized in a general purpose finite element code, and three specific ... [more ▼] This paper presents some extensions of flexible multibody formalisms for mechatronic applications. The software implementation is realized in a general purpose finite element code, and three specific subjects are discussed: (i) nonlinear model reduction techniques for flexible multibody systems, (ii) integrated modelling of mechatronic systems, (iii) time-integration algorithms for coupled problems. The relevance of those developments are demonstrated for the dynamic analysis and the control design of an experimental lightweight manipulator. [less ▲] Detailed reference viewed: 30 (1 ULg)Optimal synthesis of planar mechanisms via an extensible-link approach ; Duysinx, Pierre ; (2006, September) Detailed reference viewed: 25 (6 ULg)On the implementation of a sensitivity analysis in a flexible multibody dynamics environment Bruls, Olivier ; Duysinx, Pierre ; Conference (2006, June) The dynamic performance of complex mechanisms, such as machine tools, manipulators, vehicles, engines or foldable structures, can be strongly affected by flexible phenomena. Therefore, the deformation ... [more ▼] The dynamic performance of complex mechanisms, such as machine tools, manipulators, vehicles, engines or foldable structures, can be strongly affected by flexible phenomena. Therefore, the deformation effects should be considered as soon as possible in the design procedure, which motivates the development of automatic optimization techniques for flexible multibody systems. Advanced software tools are able to simulate the dynamic behaviour of such systems, but they typically involve extensive numerical treatments. Hence, gradient-based optimization methods are of special interest since they require a quite low number of simulations, but an important problem is to obtain the sensitivities of the objective function with respect to the design parameters. Since finite difference approaches lack robustness and computational efficiency, we propose to investigate analytical or semi-analytical sensitivity analysis. Several difficulties are inherent to the simulation of flexible mechanisms. A consistent geometric formulation is necessary to describe large amplitude motion as well as possible large deformations. Here, according to the nonlinear finite element formulation, the motion is parameterized using absolute nodal coordinates, and an updated Lagrangian point of view is adopted for the rotation parameters. The joints and the rigid-body conditions are represented by algebraic constraints between the nodal coordinates, leading to differential algebraic equations of motion (DAEs). Finally, the computation of the trajectories requires a reliable simulation algorithm for nonlinear DAEs. A strong advantage of the finite element method comes from its very systematic implementation, which facilitates the development of a semi-analytical sensitivity analysis. In this work, sensitivity analysis is performed for beam elements, rigid bodies and ideal joints. The global sensitivity is then obtained by numerical assembly of the elementary contributions and by integration in the time domain. Thus, a single but extended simulation is sufficient to compute the sensitivities with respect to all parameters. In order to illustrate the method and to demonstrate its efficiency, we consider the optimal design of a car engine, where the flexibility of the connecting rods between the crankshaft and the pistons is taken into account. The objective is to find a feasible mechanical design which minimizes the level of vibrations. [less ▲] Detailed reference viewed: 36 (1 ULg) |
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