References of "Bruls, Olivier"
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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 ▲]

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See detailIntegrated power control analysis of DFIG wind turbines considering structural flexibility
Chen, Qiongzhong ULg; Bruls, Olivier ULg

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

Doubly-fed induction generators (DFIGs) are commonly used in variable-speed wind turbines for more power extraction. Unlike previous research on DFIG wind turbines, which typically uses an equivalent ... [more ▼]

Doubly-fed induction generators (DFIGs) are commonly used in variable-speed wind turbines for more power extraction. Unlike previous research on DFIG wind turbines, which typically uses an equivalent lumped mass model of the drive train dynamics, but does not include detailed aerodynamic/mechanical representations, this paper investigates on the modelling and control of DFIG wind turbines by following a systematic approach based on a flexible multibody simulation software. The wind turbine structure, generator and control subsystem models are modularly developed for the S4WT package (Samcef for Wind Turbines), which is a user interface for the analysis of wind turbines. An extension of the finite element method is available in the flexible multibody dynamics solver, for the representation of the non-mechanical components, i.e., the generator and the control system, so that the coupled mechatronic system is simulated in a strongly coupled way. This integrated approach is less intricate and more robust than approaches based on an external DLL or co-simulation methods. The objective of this work is to analyze the control-generator-structure interactions in a wind turbine system. The power optimization control is elaborated in detail. A 2MW DFIG wind turbine prototype model is presented for validation. Dynamic analysis including the control effects and the influence of the structural flexibility is provided in an overall range. [less ▲]

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See detailTwo Lie Group Formulations for Dynamic Multibody Systems with Large Rotations
Bruls, Olivier ULg; Arnold, Martin; Cardona, Alberto

in Proceedings of the ASME 2011 International Design Engineering Technical Conferences (2011, August)

This paper studies the formulation of the dynamics of multibody systems with large rotation variables and kinematic constraints as differential-algebraic equations on a matrix Lie group. Those equations ... [more ▼]

This paper studies the formulation of the dynamics of multibody systems with large rotation variables and kinematic constraints as differential-algebraic equations on a matrix Lie group. Those equations can then be solved using a Lie group time integration method proposed in a previous work. The general structure of the equations of motion are derived from Hamilton principle in a general and unifying framework. Then, in the case of rigid body dynamics, two particular formulations are developed and compared from the viewpoint of the structure of the equations of motion, of the accuracy of the numerical solution obtained by time integration, and of the computational cost of the iteration matrix involved in the Newton iterations at each time step. In the first formulation, the equations of motion are described on a Lie group defined as the Cartesian product of the group of translations R^3 (the Euclidean space) and the group of rotations SO(3) (the special group of 3 by 3 proper orthogonal transformations). In the second formulation, the equations of motion are described on the group of Euclidean transformations SE(3) (the group of 4 by 4 homogeneous transformations). Both formulations lead to a second-order accurate numerical solution. For an academic example, we show that the formulation on SE(3) offers the advantage of an almost constant iteration matrix. [less ▲]

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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 detailAnalysis of Control-Generator-Structure Interactions in Wind Turbines using an Integrated Simulation Approach
Bruls, Olivier ULg; Cugnon, Frédéric; Defourny, Michel et al

in Proceedings of Multibody Dynamics ECCOMAS Conference (2011, July)

This paper addresses the modelling of the interactions between the generator, the controller and the structural components in wind turbines. Those interactions have a direct influence on the mechanical ... [more ▼]

This paper addresses the modelling of the interactions between the generator, the controller and the structural components in wind turbines. Those interactions have a direct influence on the mechanical loads, which need to be evaluated for the design of the machine. Using the sofware Samcef For Wind Turbines, a model is developed which includes a description of the aeroelastic behaviour of the blades, the gearbox dynamics, the tower flexibility, as well as the electrical and control parts. Electrical and control subsystems can be modelled either by linking an external DLL, by a co-simulation approach or by using an integrated and monolithic model. This paper shows that the monolithic approach can be exploited for the reliable analysis of electrical-control-structure interactions in wind turbines. Non-mechanical elements are represented in a modular way using a newly developed library of block diagram elements. The coupled equations of motion are established by numerical assembly and they include a finite element description of the mechanical components and a block diagram description of the generator and its control system. A fully implicit, stable and reliable solver is then exploited to solve the coupled equations of motion. Simulation results are presented for a 2 MW wind turbine with a doubly-fed induction generator and they illustrate the coupling between the power control system and the dynamic structural response. [less ▲]

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See detailConvergence analysis of generalized-alpha Lie group integrators for constrained systems
Arnold, Martin; Bruls, Olivier ULg; Cardona, Alberto

in Proceedings of Multibody Dynamics ECCOMAS Conference (2011, July)

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See detailINVERSE DYNAMICS OF UNDERACTUATED MULTIBODY SYSTEMS USING A DAE OPTIMAL CONTROL APPROACH
Guimaraes Bastos Junior, Guaraci ULg; Seifried, Robert; Bruls, Olivier ULg

in Proceedings of the ECCOMAS Thematic Conference (MULTIBODY DYNAMICS) 2011 (2011, July)

The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper 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 paper 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. This paper proposes an alternative solution strategy which is based on an optimal control approach. The method is illustrated for the inverse dynamics of a planar underactuated manipulator with rigid links and four degrees-of-freedom. 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 detailReproducibility and repeatability of upper limb landmarks palpation for junior operators
Schwartz, Cédric ULg; Fedrigo, Tatiana ULg; Bruls, Olivier ULg et al

Poster (2011, July)

In human motion analysis, bone motions are usually expressed relatively to anatomical reference frames. The anatomical reference frames are constructed thanks to the localization of bony landmarks during ... [more ▼]

In human motion analysis, bone motions are usually expressed relatively to anatomical reference frames. The anatomical reference frames are constructed thanks to the localization of bony landmarks during a static phase prior to the acquisitions. These landmarks are identified by means of palpation. Accurate comparison between subjects and studies implies good reproducibility and repeatability of the palpation process. However, all investigators don’t have a long experience in palpation. In this paper, the reproducibility and repeatability of palpation for junior investigators were measured. Results show worse reproducibility and repeatability than what is usually expected. These errors have particularly an influence on the definition of the reference frames of the arm. This study therefore emphasizes on the need of a specific training of operators working in a motion lab. [less ▲]

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See detailImproving 3D measurements accuracy with camera information redundancy
Schwartz, Cédric ULg; Fringuellini, Anthony ULg; Bruls, Olivier ULg et al

Conference (2011, July)

The accuracy of the Codamotion system for 3D measurement depends mainly on the signal level of the sensors and the resolution of the system at the marker localization. When using several units to cover a ... [more ▼]

The accuracy of the Codamotion system for 3D measurement depends mainly on the signal level of the sensors and the resolution of the system at the marker localization. When using several units to cover a large field of view, the estimated position of the different units might differ. We propose a method taking both resolution and signal level in to account, instead of only the signal level as in the built-in weighting process. This new method offers improved accuracy. [less ▲]

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See detailControl and simulation of doubly fed induction generator for variable speed wind turbine systems based on an integrated finite element approach
Chen, Qiongzhong ULg; Defourny, Michel; Bruls, Olivier ULg

in Proceedings of the European Wind Energy Conference and Exhibition 2011 (EWEA 2011) (2011, March)

Regarding renewable energy and environment- friendly issues, wind energy nowadays has become the fastest-growing energy source in the world, and thus attracts a lot of research interest in the wind ... [more ▼]

Regarding renewable energy and environment- friendly issues, wind energy nowadays has become the fastest-growing energy source in the world, and thus attracts a lot of research interest in the wind turbine generation system. A doubly fed induction generator (DFIG) is used for variable speed operation in a wind turbine system to extract more power. Following a systematic approach, this paper investigates on the modelling and simulation of wind turbine generating systems using the flexible multibody simulation software SAMCEF/MECANO [1]. The objective of this work is to analyze the control-generator-structure interactions in a wind turbine system. Firstly, an extension of the finite element method is integrated into the flexible multibody dynamics solver, and thus extends the solver to represent mechatronic systems in a strongly-coupled way. Secondly, DFIG and the control systems are modularly modeled for the wind turbine package. Control of DFIG for grid synchronization and power optimization are elaborated in detail, and the methods are validated through a 2MW DFIG wind turbine prototype model. At the end, a systematic system model of wind turbine structure connected with the DFIG generating system is presented, which provides the dynamic analysis for the whole system in an overall range. [less ▲]

Detailed reference viewed: 115 (13 ULg)