References of "Bruls, Olivier"
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See detailModelling of joints with clearance and friction in multibody dynamic simulation of automotive differentials
Virlez, Geoffrey ULg; Bruls, Olivier ULg; Tromme, Emmanuel ULg et al

in Proceedings of the 6th Asian Conference on Multibody Dynamics (2012, August 27)

Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the ... [more ▼]

Defects in kinematic joints can sometimes highly influence the simulation response of the whole multibody system within which these joints are included. For instance, the clearance, the friction, the lubrication and the flexibility affect the transient behaviour, reduce the component life and produce noise and vibration for classical joints such as prismatic, cylindric or universal joint. In this work, a new 3D cylindrical joint model which accounts for the clearance, the misalignment and the friction is presented. This formulation has been used to represent the link between the planet gears and the planet carrier in an automotive differential model. [less ▲]

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See detailInvestigations on a Level Set based approach for the optimization of flexible components in multibody systems with a fixed mesh grid
Tromme, Emmanuel ULg; Bruls, Olivier ULg; Van Miegroet, Laurent ULg et al

in Proceedings of The 6th Asian Conference on Multibody Dynamics: Shanghai (China), 26-30 aout 2012 (2012, August)

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on ... [more ▼]

This paper considers the optimization of flexible components in mechanical systems thanks to a "fully integrated" optimization method which includes a flexible multibody system simulation based on nonlinear finite elements. 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 (quasi-)static loading conditions or vibration design criteria and also because this ``fully integrated" optimization method is not a simple extension of static optimization techniques. The present paper proposes an approach based on a Level Set description of the geometry. This method leads to an intermediate level between shape and topology optimizations. Gradient-based optimization methods are adopted for their convergence speed. Numerical applications are conducted on the optimization of a connecting rod of a reciprocating engine with cyclic dynamic loading to show the feasibility and the promising results of this approach. [less ▲]

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See detailA Newmark-type integrator for flexible systems considering nonsmooth unilateral constraints
Chen, Qiongzhong ULg; Acary, Vincent; Virlez, Geoffrey ULg et al

in Proceedings of the First Joint International Conference on Multibody System Dynamics (2012, June)

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this ... [more ▼]

Mechanical systems are usually subjected not only to bilateral constraints but also to unilateral constraints. Inspired by the HHT time integration method for smooth flexible multibody dynamics, this paper presents a Newmark-type integrator, denoted by nonsmooth HHT method, to include the nonsmooth property of unilateral constraints. Through numerical examples accounting for both rigid and flexible body models, a bunch of methods are compared with the unilateral constraints on both velocity level and position level. Results show that the presented nonsmooth HHT method benefits from the accuracy and stability property of the classical HHT method with controllable numerical damping. In particular, when it comes to the analysis of flexible systems, the nonsmooth HHT method shows much better accuracy property than that of the other methods, including the Moreau–Jean time-stepping method and the fully implicit Newmark methods. [less ▲]

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See detailModelling the Position Control of a Segment of the E-ELT using OOFELIE::Multiphysics Integrated FEM-based Approach
Nachtergaele, Philippe; Gamonal Rozas, Leonardo Alfredo ULg; Bruls, Olivier ULg

in Proceedings of the 13th International Conference on New Actuators (2012, June)

This paper presents the extension of a multiphysics software solution allowing to perform integrated simulation of multiphysics controlled systems. This enhancement relies on an innovative formulation of ... [more ▼]

This paper presents the extension of a multiphysics software solution allowing to perform integrated simulation of multiphysics controlled systems. This enhancement relies on an innovative formulation of time integration schemes allowing to take into account simultaneously, in an integrated FEM-based approach, the non linear structural response of a system and the controller dynamics. Interest and feasibility of this unified approach is illustrated through the Modelling of the position control of a segment of the primary mirror of the E-ELT (European Extremely Large Telescope), a highly representative application of complex multiphysics controlled systems. [less ▲]

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See detailFormulation of Kinematic Joints and Rigidity Constraints in Multibody Dynamics using a Lie Group Approach
Sonneville, Valentin ULg; Bruls, Olivier ULg

in Proceedings of the 2nd Joint International Conference on Multibody System Dynamics (IMSD) (2012, May)

The matrix Lie group approach allows to formulate and solve the equations of motion of a multibody system in a parametrization-free framework. The kinematic joints and the rigidity constraints should also ... [more ▼]

The matrix Lie group approach allows to formulate and solve the equations of motion of a multibody system in a parametrization-free framework. The kinematic joints and the rigidity constraints should also be formulated as constraint equations on the Lie group. Working on the Special Euclidean group SE(3), we introduce a method to obtain appropriate vectorial constraint equations in terms of mixed coordinates. Moreover, we present an absolute coordinates formulation, based on an relative coordinates elimination method, so that the minimum number of constraint equations necessary to describe the joints is used. [less ▲]

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See detailInverse dynamics of parallel kinematic manipulators with flexible links
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

Conference (2012, May)

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See detailIntegrated control and structural analysis of DFIG wind turbines using a monolithic approach
Chen, Qiongzhong ULg; D'Ambrosio, Flavio; Defourny, Michel et al

in Proceedings of the European Wind Energy Conference and Exhibition 2012 (EWEA 2012) (2012, April)

Design of wind turbines requires the coupled analysis among the mechanical, control and aerodynamic subsystems. Different from previous research, which either uses a complicated mechanical model with a ... [more ▼]

Design of wind turbines requires the coupled analysis among the mechanical, control and aerodynamic subsystems. Different from previous research, which either uses a complicated mechanical model with a simple control system model, or vice versa, this paper studies the coupling of subsystems’ dynamics using a high-fidelity aeroelastic model of wind turbine and a detailed analytical model of control generating systems. A monolithic time integration approach is applied so that better numerical accuracy and stability are achieved. Control strategies on power optimization are discussed taking into account the influence of structural flexibility. Simulation examples are given on both stable and turbulent wind situation. [less ▲]

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See detailFrom direct to inverse analysis in flexible multibody dynamics
Bruls, Olivier ULg

Conference (2012, March)

Today, state-of-the-art simulation packages in flexible multibody dynamics allow the high-fidelity analysis of industrial mechanisms and machines in many application fields including robotics, automotive ... [more ▼]

Today, state-of-the-art simulation packages in flexible multibody dynamics allow the high-fidelity analysis of industrial mechanisms and machines in many application fields including robotics, automotive systems, aeronautics, deployable structures or wind turbines. The dynamic response of a given system can thus be evaluated in the time-domain for given load cases and given initial values. However, in many practical cases, the engineer does not have a precise knowledge of the mechanical design, the loading conditions and the initial state. This situation occurs for example in structural optimization, optimal control, experimental identification and health monitoring problems. The complexity of simulation codes and the computational cost of high-fidelity models are still important obstacles for the development of efficient resolution methods for these inverse problems. A current challenge is thus to elaborate simplified and more efficient modelling strategies in flexible multibody dynamics in order to enable the development of inverse analysis methods. The talk is divided into three parts. The first part provides an overview of available simulation techniques for flexible mechanisms with a particular emphasis on finite element-based approaches and time integration methods. Some illustrations are presented in the fields of deployable structures, vehicle dynamics and wind turbines. In the second part, optimization problems in flexible multibody dynamics are addressed and solved using gradient-based methods. Efficient methods for sensitivity analysis are discussed and special problems are treated such as the structural optimization of mechanical components or the numerical solution of inverse dynamics problems. The third part discusses a recently-developed Lie group approach which allows the formulation of the equations of motion of a multibody system in a parameterization-free setting. Based on this general formalism, which is characterized by an increased modularity and a reduced complexity, a large variety of Lie group solvers are foreseen not only for time integration but also for model reduction, sensitivity analysis and optimization. [less ▲]

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See detailSpurious oscillations in generalized-alpha time integration methods
Arnold, Martin; Bruls, Olivier ULg; Cardona, Alberto

Conference (2012, March)

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See detail3D Analysis of Normal and Pathological Gait Based on Low-Cost Wireless Accelerometers
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Bruls, Olivier ULg et al

in URSI Benelux Forum 2012 “Antennas: multiple designs, multiple applications” (2012)

We describe the principle and use of a new low-cost, wireless, 3-axis accelerometer-based device that records acceleration signals and automatically analyses them to characterize normal and pathological ... [more ▼]

We describe the principle and use of a new low-cost, wireless, 3-axis accelerometer-based device that records acceleration signals and automatically analyses them to characterize normal and pathological gait. [less ▲]

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See detailLie group generalized-alpha time integration of constrained flexible multibody systems
Bruls, Olivier ULg; Cardona, Alberto; Arnold, Martin

in Mechanism & Machine Theory (2012), 48

This paper studies a Lie group extension of the generalized-alpha time integration method for the simulation of flexible multibody systems. The equations of motion are formulated as an index-3 ... [more ▼]

This paper studies a Lie group extension of the generalized-alpha time integration method for the simulation of flexible multibody systems. The equations of motion are formulated as an index-3 differential-algebraic equation (DAE) on a Lie group, with the advantage that rotation variables can be taken into account without the need of introducing any parameterization. The proposed integrator is designed to solve this equation directly on the Lie group without index reduction. The convergence of the method for DAEs is studied in detail and global second-order accuracy is proven for all solution components, i.e. for nodal translations, rotations and Lagrange multipliers. The convergence properties are confirmed by three benchmarks of rigid and flexible systems with large rotation amplitudes. The Lie group method is compared with a more classical updated Lagrangian method which is also formulated in a Lie group setting. The remarkable simplicity of the new algorithm opens interesting perspectives for real-time applications, model-based control and optimization of multibody systems. [less ▲]

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See detailQuelques activités de recherche en robotique à l’ULg
Bruls, Olivier ULg

Conference given outside the academic context (2011)

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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 detailImproved stability and transient behaviour of generalized-alpha time integrators for constrained flexible systems
Arnold, Martin; Bruls, Olivier ULg; Cardona, Alberto

Conference (2011, November)

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See detailTwo optimal control methods for the inverse dynamics of underactuated multibody systems
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

Conference (2011, November)

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This work studies the inverse dynamics of non-minimum ... [more ▼]

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This work studies the inverse dynamics of non-minimum phase underactuated multibody systems, e.g. for end-effector control of flexible manipulators or manipulators with passive joints. Unlike for minimum phase systems, the inverse dynamics of non-minimum phase systems cannot be solved by adding trajectory constraints to the equations of motion and by applying a forward time integration. Indeed, the inverse dynamics of a non-minimum phase system is known to be non-causal, which means that the control forces and torques should start before the beginning of the trajectory (pre-actuation phase) and continue after the end-point is reached (post-actuation phase). The existing stable inversion method proposed for general nonlinear non-minimum phase systems requires to derive explicitly the equations of the internal dynamics and to solve a boundary value problem. In this work, an alternative solution strategy is proposed which is based on an optimal control approach. More precisely, the direct collocation method and the multiple shooting are considered to solve the resulting optimization problem. The method is illustrated for the inverse dynamics of rigid and flexible underactuated mechanisms. An important advantage of the proposed approach is that it can be applied directly to the standard equations of motion of multibody systems either in ODE or in DAE form. Therefore, it is easier to implement this method in a general purpose simulation software. [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 ▲]

Detailed reference viewed: 83 (24 ULg)