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See detailA bi-value coding parameterization scheme for the discrete optimal orientation design of the composite laminate
Gao, Tong ULg; ZHANG, Weihong; Duysinx, Pierre ULg

in International Journal for Numerical Methods in Engineering (2012), 91(1), 98-114

The discrete optimal orientation design of the composite laminate can be treated as a material selection problem dealt with by continuous topology optimization method. In this work, a new bi-value coding ... [more ▼]

The discrete optimal orientation design of the composite laminate can be treated as a material selection problem dealt with by continuous topology optimization method. In this work, a new bi-value coding parameterization (BCP) scheme is proposed to this aim. The idea of the BCP scheme is to “code” each material phase using integer values of +1 and -1. Each available material phase has one unique “code” consisting of +1 and/or -1 assigned to design variables. Theoretical and numerical comparisons between the proposed BCP scheme and existing schemes show that the BCP has the advantage of an evident reduction of the number of design variables in logarithmic form. This is very beneficial when the number of candidate materials becomes important. Numerical tests with up to 36 candidate material orientations are illustrated for the first time to indicate the reliability and efficiency of the proposed scheme in solving this kind of problem. It proves that the BCP is an interesting and potential scheme to achieve the optimal orientations for large-scale design problems. [less ▲]

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See detailAdvanced Engine Dynamics Using MBS and a Mixed Nonlinear FEM and Super Element Approach
Louvigny, Yannick ULg; Duysinx, Pierre ULg

in Eberhard; Ziegler (Eds.) Proceedings of the IMSD2012 - The 2nd Joint International Conference on Multibody System Dynamics (2012, May 31)

Dynamic simulations of a twin-cylinder boxer engine are carried out with rigid and flexible multibody models. Pistons and connecting rods are considered as rigid bodies while the crankshaft is modeled as ... [more ▼]

Dynamic simulations of a twin-cylinder boxer engine are carried out with rigid and flexible multibody models. Pistons and connecting rods are considered as rigid bodies while the crankshaft is modeled as a flexible part and meshed with brick elements. With this model, calculation of crankshaft stresses and displacements is possible. For constant speed studies, flexible simulations are carried out on one or two engine cycles but simulations with a variable rotation speed has to be performed on a larger number of engine revolutions. Due to the complex shape of the crankshaft, the simulation times become important and it is difficult to keep on working with the complete crankshaft model. Thus several simplified models, including super element models, are developed. In this paper, a particular method, using also the super element technique, is proposed. A large part of the crankshaft is substructured and modeled with super elements. While a critical area, identified by a simulation performed with a coarse crankshaft mesh, is not modified and modeled by nonlinear finite element. Several methods of linking the super elements and the finite element mesh are experimented. Once the best connection method determined, results and computation time of the simulation using this model will be compared to those obtained with the complete crankshaft model and the other simplified models. [less ▲]

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See detailTraffic Situation Assessment and Intervention Strategy of a Collision Avoidance System based on Galileo Satellite Positioning
Christen, Fréderic ULg; Ewald, Christian; Eckstein, Lutz et al

Conference (2012, April 25)

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behavior of ... [more ▼]

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behavior of the driver. Up to date prototypic CAS are based on on-board environmental sensors, such as camera or radar systems, that scan the vehicle's surrounding environment in order to assess the situation's hazardousness. The functionality of the used sensors under varying environmental conditions and the limited sensor covering area require an enormous effort to ensure a reliable detection of obstacles, and thus limit the application of the systems. In order to expand the operating field of such systems, a Galileo-based CAS will be developed within the project ‘Galileo above’ (application centre for ground based traffic). This advanced driver assistance system (ADAS) detects surrounding vehicles that are on collision course and reacts autonomously, if the driver does not intervene to avoid the crash. For this purpose the system initiates an emergency stop and/or an emergency steering maneuver. For the development of the CAS the Galileo test centre automotiveGATE in Aldenhoven, Germany will be used. On this test area pseudolites will be installed which provide Galileo-like navigation signals. Thus, the development respectively tuning of Galileo-based vehicle systems will be enabled, so as to have them available on the market when the Galileo satellite system reaches its full operational capability (FOC). The focus of this paper is on the traffic situation assessment and intervention strategy of the CAS. This includes the perception and analysis of the driving situation, the detection of potential collision situation, the definition of an adequate system reaction and the planning of an evasion trajectory. Furthermore, an outlook on the model predictive control for longitudinal and/or lateral control (braking and/or steering maneuver) will be presented. [less ▲]

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See detailTraffic Situation Assessment and Intervention Strategy of a Collision Avoidance System based on Galileo Satellite Positioning
Christen, Fréderic ULg; Ewald, Christian; Eckstein, Lutz et al

E-print/Working paper (2012)

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behavior of ... [more ▼]

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behavior of the driver. Up to date prototypic CAS are based on on-board environmental sensors, such as camera or radar systems, that scan the vehicle's surrounding environment in order to assess the situation's hazardousness. The functionality of the used sensors under varying environmental conditions and the limited sensor covering area require an enormous effort to ensure a reliable detection of obstacles, and thus limit the application of the systems. In order to expand the operating field of such systems, a Galileo-based CAS will be developed within the project ‘Galileo above’ (application centre for ground based traffic). This advanced driver assistance system (ADAS) detects surrounding vehicles that are on collision course and reacts autonomously, if the driver does not intervene to avoid the crash. For this purpose the system initiates an emergency stop and/or an emergency steering maneuver. For the development of the CAS the Galileo test centre automotiveGATE in Aldenhoven, Germany will be used. On this test area pseudolites will be installed which provide Galileo-like navigation signals. Thus, the development respectively tuning of Galileo-based vehicle systems will be enabled, so as to have them available on the market when the Galileo satellite system reaches its full operational capability (FOC). The focus of this paper is on the traffic situation assessment and intervention strategy of the CAS. This includes the perception and analysis of the driving situation, the detection of potential collision situation, the definition of an adequate system reaction and the planning of an evasion trajectory. Furthermore, an outlook on the model predictive control for longitudinal and/or lateral control (braking and/or steering maneuver) will be presented. [less ▲]

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See detailTopology optimization of electrostatic micro-actuators including electromechanical stability constraint
Lemaire, Etienne ULg; Van Miegroet, Laurent ULg; Rochus, Véronique et al

Conference (2011, November 16)

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See detailModelling of frictional unilateral contact in automotive differentials
Virlez, Geoffrey ULg; Cardona, Alberto; Bruls, Olivier ULg et al

Conference (2011, November 14)

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See detailTopology optimization of compliant mechanisms: Application to vehicle suspensions.
Tromme, Emmanuel ULg; Lemaire, Etienne ULg; Duysinx, Pierre ULg

Conference (2011, November 14)

An efficient method to design a compliant vehicle suspension with only topology optimization.

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See detailExtensions of the Shape Functions with Penalization Parameterization for Composite-Ply Optimization
Bruyneel, Michaël ULg; Duysinx, Pierre ULg; Fleury, Claude ULg et al

in AIAA Journal (2011), 49(10), 2325-2329

The SFP method proposed is an alternative to the discrete material optimization (DMO) approach developed. Both approaches are an extension of the multiphase topology optimization. Here, SFP is used to ... [more ▼]

The SFP method proposed is an alternative to the discrete material optimization (DMO) approach developed. Both approaches are an extension of the multiphase topology optimization. Here, SFP is used to select composite plies in a set of candidate orientations, in a formulation including ontinuous design variables. [less ▲]

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See detailNew developments for an efficient solution of the discrete material topology optimization of composite structures
Duysinx, Pierre ULg; Gao, Tong; Zhang, Weihong et al

in Faester, S.; Juul Jensen, D.; Ralph, B. (Eds.) et al Composite materials for structural performance: towards the higher limits (2011, September 05)

Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund (2005), the optimal problem ... [more ▼]

Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund (2005), the optimal problem can be stated as a topology optimization problem with multiple materials. The research work carries out a large investigation of different interpolation and penalization schemes for the optimal material selection problem. Besides the classical Design Material Optimization (DMO) scheme and the recent Shape Function with Penalization (SFP) scheme by Bruyneel (2011), the research introduces a generalization of the SFP approach using a bi-value coding parameterization (BCP) (Gao, Zhang, and Duysinx, 2011) The paper provides a comparison of the different parameterization approaches. It also proposes alternative penalization schemes and it investigates the effect of the power penalization. Finally, we discuss the solution aspects in the perspective of solving large-scale industrial applications. The conclusions are illustrated by a numerical application for the compliance maximization of an in-plane composite ply. [less ▲]

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See detailSimulation of differentials in four-wheel drive vehicles using multibody dynamics
Virlez, Geoffrey ULg; Bruls, Olivier ULg; Poulet, Nicolas et al

in Proceedings of the ASME 2011 International Design Engineering Technical Conference & Computers and Information in Engineering Conference IDETC/CIE 2011 (2011, August 31)

The dynamic performance of vehicle drivetrains is significantly influenced by differentials which are subjected to complex phenomena. In this paper, detailed models of TORSEN differentials are presented ... [more ▼]

The dynamic performance of vehicle drivetrains is significantly influenced by differentials which are subjected to complex phenomena. In this paper, detailed models of TORSEN differentials are presented using a flexible multibody simulation approach, based on the nonlinear finite element method. A central and a front TORSEN differential have been studied and the numerical results have been compared with experimental data obtained on test bench. The models are composed of several rigid and flexible bodies mainly constrainted by flexible gear pair joints and contact conditions. The three differentials of a four wheel drive vehicle have been assembled in a full drivetrain in a simplified vehicle model with modeling of driveshafts and tires. These simulations enable to observe the four working modes of the differentials with a good accuracy. [less ▲]

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See detailAdvanced engine dynamics using mbs and super element approach: application to twin-cylinder boxer engines
Louvigny, Yannick ULg; Duysinx, Pierre ULg

in Procedings of Eccomas Multibody dynamics 2011 (2011, July 07)

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See detailModeling of contact between stiff bodies in automotive transmission systems
Virlez, Geoffrey ULg; Bruls, Olivier ULg; Duysinx, Pierre ULg

in Samin, Jean-Claude; Fisette, Paul (Eds.) Proceedings of MULTIBODY DYNAMICS 2011, ECCOMAS Thematic Conference (2011, July 05)

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these ... [more ▼]

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these two kind of parts is essential in the working principle of such differentials. In this paper, two different contact model are presented. The former uses an augmented Lagrangian technique and is defined between a rigid body and a flexible structure. The second contact formulation is a continuous impact modeling based on a restitution coefficient. [less ▲]

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See detailOptimization of flexible components in reciprocating engines with cyclic dynamic loading
Tromme, Emmanuel ULg; Bruls, Olivier ULg; Duysinx, Pierre ULg

in Samin, Jean-Claude; Fisette, Paul (Eds.) Proceedings of Multibody Dynamics 2011, Eccomas Thematic Conference: Brussels (Belgium), 4-7 juillet 2011 (2011, July 05)

This work considers the optimization of flexible components of mechanical systems modeled as multibody systems. This approach permits to better capture the effects of dynamic loading under service ... [more ▼]

This work considers the optimization of flexible components of mechanical systems modeled as multibody systems. This approach permits to better capture the effects of dynamic loading under service conditions. This process is challenging because most state-of-the-art studies in structural optimization have been conducted under static or quasi-static conditions. The formulation of the optimization problem for dynamic systems is fundamental; it is not a simple extension of static optimization. Naive implementation leads to fragile and unstable results. The present paper addresses the optimization of a connecting rod of a reciprocating engine with cyclic dynamic loading. Gradient-based methods are adopted for their convergence speed. Different formulations are investigated and compared. A first numerical application considers the optimization of the connecting rod regarding its mass and its elongation. After, another numerical application is carried on considering the stresses in the connecting rod. A conclusion on the influence of the optimization problem formulation is realized. [less ▲]

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See detailElectrostatic Simulation using XFEM for Conductor and Dielectric Interfaces
Rochus, Véronique ULg; Rixen, Daniel; Van Miegroet, Laurent ULg et al

in International Journal for Numerical Methods in Engineering (2011), 85(10), 12071226

ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to ... [more ▼]

ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to evaluate accurately the electrostatic forces acting on the devices. Extended Finite Element (X-FEM) approaches can easily handle moving boundaries and interfaces in the electrostatic domain and seem therefore very suitable to model Micro-Electro-Mechanical Systems. In this study we investigate different X-FEM techniques to solve the electrostatic problem when the electrostatic domain is bounded by a conducting material. Preliminary studies in one-dimension have shown that one can obtain good results in the computation of electrostatic potential using X-FEM. In this paper the extension of these preliminary studies to 2D problem is presented. In particular a new type of enrichment functions is proposed in order to treat accurately Dirichlet boundary conditions on the interface. [less ▲]

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See detailOptimization of multibody systems and their structural components
Bruls, Olivier ULg; Lemaire, Etienne ULg; Duysinx, Pierre ULg et al

in Blajer, W.; Arczewski, K.; Fraczek, J. (Eds.) et al Multibody Dynamics: Computational Methods and Applications (2011)

This work addresses the optimization of flexible multibody systems based on the dynamic response of the full system with large amplitude motions and elastic deflections. The simulation model involves a ... [more ▼]

This work addresses the optimization of flexible multibody systems based on the dynamic response of the full system with large amplitude motions and elastic deflections. The simulation model involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis and it can be efficiently exploited in an optimization loop. In particular, the paper focuses on the topology optimization of structural components embedded in multibody systems. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. In contrast, we show that an optimization directly based on the dynamic response of the flexible multibody system leads to a more integrated approach. The method is applied to truss structural components. Each truss is represented by a separate 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 ▲]

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See detailAdvances in optimization of flexible components in mutlibody systems: Application to robot-arms design
Duysinx, Pierre ULg; Emonts-Alt, Jonhatan; Virlez, Geoffrey ULg et al

in Proceedings of the 5th Asian Conference on Multibody Dynamics (2010, August)

The paper considers the optimization of the flexible components of mechanical systems modeled as multibody systems. This approach aims at considering as precisely as possible the dynamic loading of the ... [more ▼]

The paper considers the optimization of the flexible components of mechanical systems modeled as multibody systems. This approach aims at considering as precisely as possible the dynamic loading of the structural components under service conditions in their mechanical systems. While most of the structural optimization developments have been conducted under static or quasi static conditions, the approach is clearly a challenge. Naïve applications of this approach generally lead to fragile and unstable results. To elaborate a robust and reliable approach, we investigate and compare several formulations of the optimization problem. Different optimization algorithms are also tested. To explain the efficiency of the various solution approaches, the complex nature of the design space is investigated. The developments are illustrated using the test-case of the structural design of the links of a two-arm robot subject to a trajectory tracking constraint. [less ▲]

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See detailAdvanced engine dynamics using MBS: Application to twin-cylinder boxer engines
Louvigny, Yannick ULg; Duysinx, Pierre ULg

Conference (2010, May 27)

Engine simulation is an important issue to design mechanical components and to reduce the development cost of new vehicles. Dynamic simulations of a twin-cylinder boxer engine are carried out with rigid ... [more ▼]

Engine simulation is an important issue to design mechanical components and to reduce the development cost of new vehicles. Dynamic simulations of a twin-cylinder boxer engine are carried out with rigid and flexible multibody models using the finite element approach. In a first step, simulations of the engine running at constant revolution speed (4000 rpm) are done taking advantages of the actual geometry of engine parts coming from CAD models. Forces due to the gas pressure are added in the simulation to calculate more precisely the load applied on each engine part. A mixed model is developed; pistons and connecting rods are considered as rigid bodies while the crankshaft is meshed with flexible brick elements. With this model, calculation of crankshaft stresses and displacements is possible. Then, simulations are made with engine speed variations to evaluate the effect of inertia. Due to the complex shape of the crankshaft, the CPU time and computer resources can be important. As simulations with a variable rotation speed have to be carried out on a larger number of engine revolutions, it becomes difficult to work with the fully detailed crankshaft geometry. So, simplified models (a tridimensional model with simplified geometry and a beam model) of the crankshaft are developed and compared. These models are first validated with different tests including results of constant speed flexible simulations. [less ▲]

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See detailMultibody Dynamics Analysis of Differentials in Vehicle Drivetrains
Virlez, Geoffrey ULg; Bruls, Olivier ULg; Poulet, Nicolas et al

in Proceedings of the First Joint International Conference on Multibody System Dynamics (2010, May 26)

Differentials are critical components whose behaviour influences the dynamics of vehicles. They often include complex phenomena whose modeling is not always easy. In this paper, a model has been developed ... [more ▼]

Differentials are critical components whose behaviour influences the dynamics of vehicles. They often include complex phenomena whose modeling is not always easy. In this paper, a model has been developed for a limited slip differential (type C Torsen) which is mainly composed of an epicyclic gear train. In order to take into account flexibility, the nonlinear finite element method based on the absolute nodal coordinates has been chosen. The differential is modeled as a multibody system with various gear pairs and contact conditions. The model has been validated qualitatively and future work will address the identification of the various parameters and comparisons with experimental data. [less ▲]

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See detailRecent developments in optimization of flexible components of multibody systems
Duysinx, Pierre ULg; Emonds-Alt, Jonathan; Virlez, Geoffrey ULg et al

Conference (2010, May)

Recently mechanical engineering has extended from a component to a system oriented approach. The structural analysis of components is now completed by the whole mechanical system simulation using ... [more ▼]

Recently mechanical engineering has extended from a component to a system oriented approach. The structural analysis of components is now completed by the whole mechanical system simulation using multibody system analysis. This evolution aims at capturing better the real loading conditions accounting for the component interaction and couplings in the system. Structural optimization is continuing along the same tracks. Recent works in structural optimization have tried to optimize components with respect to loadings conditions defined through dynamic loading coming from multibody system dynamic analysis. Generally, optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. In contrast, we have shown in previous works devoted to topology optimization that an optimization directly based on the dynamic response of the flexible multibody system leads to a more integrated approach. In order to overcome the limitations of some previous approaches, a more integrated optimization technique is proposed here, based on the nonlinear finite element approach for flexible multibody systems. The non linear finite element formalism accounts for both large rigid-body motions and elastic deflection of the structural components. In previous work, the optimal design of components was realized as an optimal truss / beam layout. The present communication investigates the optimal design of components considered as a continuum medium. We study first sizing optimal design of structural components and we later extend the method to optimal material distribution approach to address their lay out optimization. The continuum domain is discretized into finite elements. For sizing optimization, the design variables are wall-thickness and lumped element variables. For topology optimization the design variables are classically density-like parameters associated to a power law interpolation of effective material properties for intermediate densities, also known as Simply Isotropic Material with Penalization (SIMP). This study assesses the feasibility of this approach, which extends optimization techniques to continuum flexible bodies included in MBS. The numerical implementation is conducted in SAMCEF MECANO for the flexible MBS analysis and BOSS Quattro for the optimization shell. The nonlinear equations of motion are solved using a generalized-a time integration scheme while the sensitivity analysis of mechanical responses is based on a direct differentiation method or finite differences. For sizing and parametric optimization the paper investigates and compares several optimization approaches methods such as classical gradient-based methods (SQP, Augmented lagrangian), sequential convex programming methods (CONLIN, MMA), but also surrogate-based optimization method (with Neural Networks) combined with genetic algorithms. The formulation of the problem is also discussed, and its influence on the convergence history is illustrated. Optimal sizing, shape and topology optimization of a simple model of a robot are addressed. The optimization approach is illustrated on numerical applications of sizing optimization of robot arms during trajectory tracking and lightweight layout optimal design of automotive components. [less ▲]

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