References of "Bruls, Olivier"
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See detailUnilateral contact condition enhanced with squeeze film modelling in automotive differentials
Virlez, Geoffrey; Bruls, Olivier ULg; Duysinx, Pierre ULg et al

in Proceedings of the Institution of Mechanical Engineers - Part C - Journal of Mechanical Engineering Science (in press)

The dynamic behaviour of automotive drivetrains is significantly influenced by contacts occurring between the various parts. In this paper, a three-dimensional formulation is proposed to model unilateral ... [more ▼]

The dynamic behaviour of automotive drivetrains is significantly influenced by contacts occurring between the various parts. In this paper, a three-dimensional formulation is proposed to model unilateral and frictional contact conditions between two rigid planar rings. The magnitude of the contact force is determined by a penalty method. In a second step, a simple squeeze film model is developed to account for the damping effect produced by the lubricating oil filling the gap between the two contacting bodies. The relevance and the accuracy of these models are illustrated through the global multibody modelling of a TORSEN differential. [less ▲]

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See detailGait pattern of healthy old people for fast walking condition
GILLAIN, Sophie ULg; Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg et al

in Gerontechnology (2016, September)

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See detailGait pattern of healthy old people for dual task walking condition
GILLAIN, Sophie ULg; Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg et al

in Gerontechnology (2016, September)

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See detailModelling of multibody systems in the local frame
Bruls, Olivier ULg; Sonneville, Valentin

in Proceedings of the 24th International Congress of Theoretical and Applied Mechanics (ICTAM) (2016, August)

A local frame finite element approach is proposed to describe the kinematics of a flexible multibody system, derive the equations of motion and solve them numerically. It is argued that this approach ... [more ▼]

A local frame finite element approach is proposed to describe the kinematics of a flexible multibody system, derive the equations of motion and solve them numerically. It is argued that this approach leads to reduced geometric nonlinearities and improved computational efficiency. [less ▲]

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See detailOptimal design of flexible mechanisms using a generalized equivalent static load method
Tromme, Emmanuel; Sonneville, Valentin; Guest, James K. et al

in Proceedings of the 24th International Congress of Theoretical and Applied Mechanics (2016, August)

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response ... [more ▼]

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response optimization under multiple load cases. The ESLs are defined based on the transient analysis response whereupon all the standard techniques of static response optimization can be used. In the last decade, the ESL method has been applied to perform structural optimization of flexible components of mechanical systems modeled as multibody systems. This method considers the optimization of isolated component during the static response optimization. The present research proposes a generalized ESL method accounting for the entire system during the static response optimization, which enables to formulate the constraints with respect to the mechanism and not restricted to the individual components. The proposed method relies on a Lie group formalism which has appealing properties to derive efficiently the ESL. Examples validate the method. [less ▲]

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See detailOn the compatibility equations in geometrically exact beam finite element
Sonneville; Bruls, Olivier ULg; Bauchau, Olivier A.

in Proceedings of the 12th International Conference on Multibody Systems, Nonlinear Dynamics and Control (MSNDC) within the ASME/IDETC/CIE Conference (2016, August)

This paper discusses the compatibility equations which relate the velocity field and the strain field in geometrically exact beam theory. The analysis is carried out in the context of intrinsic equations ... [more ▼]

This paper discusses the compatibility equations which relate the velocity field and the strain field in geometrically exact beam theory. The analysis is carried out in the context of intrinsic equations, namely the dynamic equilibrium equations are formulated in terms of velocity and strain only. In addition to the well established objectivity and path-independence requirements of the spatial discretization, these compatibility equations show that a consistent spatial interpolation of the velocity field should depend on the curvature of the beam, including initial curvature and curvature from the deformation, and it is shown that this consistency is connected to the ability of the element to represent rigid body motion velocity. A two node interpolation scheme is studied and it appears that, as the element gets smaller under mesh refinement, the effect of this dependency reduces, leading eventually to the classical linear shape functions. [less ▲]

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See detailReproducibility of a tennis serve protocol
Tubez, François ULg; FORTHOMME, Bénédicte ULg; Croisier, Jean-Louis ULg et al

Conference (2016, July 08)

INTRODUCTION Serve in modern tennis game is a real offensive weapon for players. In kinematic analysis, it is the most studied stroke of this game because it is the only stroke played in a closed skill ... [more ▼]

INTRODUCTION Serve in modern tennis game is a real offensive weapon for players. In kinematic analysis, it is the most studied stroke of this game because it is the only stroke played in a closed skill. Players have a maximum of control on this stroke. It is unclear whether 3D kinematic tests are reproducible for the same player under identical conditions and if a familiarization session is necessary. In practice, with professional players, who have little time available to perform tests, familiarization sessions are difficult. The aim of our study is to measure the reproducibility of a 3D serve protocol test. METHODS Nine tennis players (righties, regional level, 20 ± 2 years) were asked to hit first flat serves in a 1 m² area placed on the "T" zone of deuce diagonal of the tennis court. Two identical tests are performed one week apart. For each test, we selected the three best serves of the 25 trials (with the highest speed and the highest accuracy). Kinetics measurements were performed using a 3D analysis system (Codamotion), a force platform (Kistler) and a radar gun. 28 markers were placed on the players’ bodies to measure kinematics of the movements: ankles, knees, hips, trunk, shoulder, elbow and wrist dominant side. We measured ball speed, leg drive, linear velocity of the racket and joints, joints range of motion and maximum angular velocities at different positions (armed, maximum external rotation and impact) (1). RESULTS All analyzed parameters (linear speeds of racket and joints, leg drive force, joint angles and angular velocities) are reproducible with exception of a small part of them. Our study shows that 5,7% (7 of 122 measurements) joint position parameters and 8,3% (4 of 48 measures) angular velocity parameters are not reproducible from a session to another. DISCUSSION Various errors sources encountered in 3D analysis can justify the presence of non-reproducible parameters (2-3). However, after this work, we can state that the established protocol provides reproducible results when analyzing the tennis serve. [less ▲]

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See detailNonlinear analysis of compliant mechanisms: application to tape springs
Dewalque, Florence ULg; Bruls, Olivier ULg

Poster (2016, July 07)

Brief summary of the mechanical behaviour of tape springs. Main results obtained by the means of finite element models. Description of the experimental set-up and results. See the extended abstract for ... [more ▼]

Brief summary of the mechanical behaviour of tape springs. Main results obtained by the means of finite element models. Description of the experimental set-up and results. See the extended abstract for more details. [less ▲]

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See detailInverse dynamics of a flexible 3D robotic arm for a trajectory tracking task
Lismonde, Arthur ULg; Sonneville, Valentin; Bruls, Olivier ULg

Scientific conference (2016, May 30)

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See detailNonlinear Interpolation on Manifold of Reduced Order Models in Magnetodynamic Problems
Paquay, Yannick ULg; Bruls, Olivier ULg; Geuzaine, Christophe ULg

in IEEE Transactions on Magnetics (2016), 52(3), 1-4

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See detailOn the equivalent static load method for flexible multibody systems described with a nonlinear finite element formalism
Tromme, Emmanuel ULg; Sonneville, Valentin ULg; Bruls, Olivier ULg et al

in International Journal for Numerical Methods in Engineering (2016)

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response ... [more ▼]

The equivalent static load (ESL) method is a powerful approach to solve dynamic response structural optimization problems. The method transforms the dynamic response optimization into a static response optimization under multiple load cases. The ESL cases are defined based on the transient analysis response whereupon all the standard techniques of static response optimization can be used. In the last decade, the ESL method has been applied to perform the structural optimization of flexible components of mechanical systems modeled as multibody systems (MBS). The ESL evaluation strongly depends on the adopted formulation to describe the MBS and has been initially derived based on a floating frame of reference formulation. In this paper, we propose a method to derive the ESL adapted to a nonlinear finite element approach based on a Lie group formalism for two main reasons. Firstly, the finite element approach is completely general to analyze complex MBS and is suitable to perform more advanced optimization problems like topology optimization. Secondly, the selected Lie group formalism leads to a formulation of the equations of motion in the local frame, that turns out to be a strong practical advantage for the ESL evaluation. Examples are provided to validate the proposed method. [less ▲]

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See detailSolving the inverse dynamics of a flexible 3D robot for a trajectory tracking task
Lismonde, Arthur ULg; Sonneville, Valentin; Bruls, Olivier ULg

in Methods and Models in Automation and Robotics (MMAR), 2016 21th International Conference on (2016)

The end-effector trajectory tracking of robotic manipulators with flexible links requires advanced control concepts. In order to compute the feedforward component of the control scheme, the inverse ... [more ▼]

The end-effector trajectory tracking of robotic manipulators with flexible links requires advanced control concepts. In order to compute the feedforward component of the control scheme, the inverse dynamics of such flexible 3D multibody system is solved using an optimal control method. The robot is modeled using nonlinear finite elements formulated on the SE(3) group. Hence singularity and parameterization issues that can arise from 3D rotations are avoided. A numerical example of a 3D flexible arm is analyzed to demonstrate the capabilities of the method. [less ▲]

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See detailA Lie algebra approach to Lie group time integration of constrained systems
Arnold, Martin; Cardona, Alberto; Bruls, Olivier ULg

in Betsch, Peter (Ed.) Structure-preserving integrators in nonlinear structural dynamics and flexible multibody dynamics (2016)

Lie group integrators preserve by construction the Lie group structure of a nonlinear configuration space. In multibody dynamics, they support a representation of (large) rotations in a Lie group setting ... [more ▼]

Lie group integrators preserve by construction the Lie group structure of a nonlinear configuration space. In multibody dynamics, they support a representation of (large) rotations in a Lie group setting that is free of singularities. The resulting equations of motion are differential equations on a manifold with tangent spaces being parametrized by the corresponding Lie algebra. In the present paper, we discuss the time discretization of these equations of motion by a generalized-alpha Lie group integrator for constrained systems and show how to exploit in this context the linear structure of the Lie algebra. This linear structure allows a very natural definition of the generalized-alpha Lie group integrator, an efficient practical implementation and a very detailed error analysis. Furthermore, the Lie algebra approach may be combined with analytical transformations that help to avoid an undesired order reduction phenomenon in generalized-alpha time integration. After a tutorial-like step-by-step introduction to the generalized-alpha Lie group integrator, we investigate its convergence behaviour and develop a novel initialization scheme to achieve second-order accuracy in the application to constrained systems. The theoretical results are illustrated by a comprehensive set of numerical tests for two Lie group formulations of a rotating heavy top. [less ▲]

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See detailExtraction of temporal gait parameters using a reduced number of wearable accelerometers
Boutaayamou, Mohamed ULg; Denoël, Vincent ULg; Bruls, Olivier ULg et al

in Proceedings of the 9th International Conference on Bio-inspired Systems and Signal Processing (2016)

Wearable inertial systems often require many sensing units in order to reach an accurate extraction of temporal gait parameters. Reconciling easy and fast handling in daily clinical use and accurate ... [more ▼]

Wearable inertial systems often require many sensing units in order to reach an accurate extraction of temporal gait parameters. Reconciling easy and fast handling in daily clinical use and accurate extraction of a substantial number of relevant gait parameters is a challenge. This paper describes the implementation of a new accelerometer-based method that accurately and precisely detects gait events/parameters from acceleration signals measured from only two accelerometers attached on the heels of the subject’s usual shoes. The first step of the proposed method uses a gait segmentation based on the continuous wavelet transform (CWT) that provides only a rough estimation of motionless periods defining relevant local acceleration signals. The second step uses the CWT and a novel piecewise-linear fitting technique to accurately extract, from these local acceleration signals, gait events, each labelled as heel strike (HS), toe strike (TS), heel-off (HO), toe-off (TO), or heel clearance (HC). A stride-by-stride validation of these extracted gait events was carried out by comparing the results with reference data provided by a kinematic 3D analysis system (used as gold standard) and a video camera. The temporal accuracy ± precision of the gait events were for HS: 7.2 ms ± 22.1 ms, TS: 0.7 ms ± 19.0 ms, HO: ‒3.4 ms ± 27.4 ms, TO: 2.2 ms ± 15.7 ms, and HC: 3.2 ms ± 17.9 ms. In addition, the occurrence times of right/left stance, swing, and stride phases were estimated with a mean error of ‒6 ms ± 15 ms, ‒5 ms ± 17 ms, and ‒6 ms ± 17 ms, respectively. The accuracy and precision achieved by the extraction algorithm for healthy subjects, the simplification of the hardware (through the reduction of the number of accelerometer units required), and the validation results obtained, convince us that the proposed accelerometer-based system could be extended for assessing pathological gait (e.g., for patients with Parkinson’s disease). [less ▲]

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See detailMechanical behaviour of tape springs used in the deployment of reflectors around a solar panel
Dewalque, Florence ULg; Collette, Jean-Paul; Bruls, Olivier ULg

in Acta Astronautica (2016), 123

In order to increase the production of power on small satellites, solar panels are commonly deployed and, in some cases, reflectors are added to improve the concentration factor on solar cells. In this ... [more ▼]

In order to increase the production of power on small satellites, solar panels are commonly deployed and, in some cases, reflectors are added to improve the concentration factor on solar cells. In this work, reflectors are deployed by the means of compliant mechanisms known as tape springs. Their attractive characteristics are, among others, their passive behaviour, their self-locking capacity, their elastic deformations and their robustness. However, their mechanical behaviour is highly nonlinear and requires thorough analyses in order to develop predictive numerical models. It is shown here through parametric studies that the nonlinear behaviour of a tape spring is mainly governed by its geometry. Thus, for each specific application, its dimensions can be determined in order to minimise two critical features: the maximum stress affecting the structure and the maximum motion amplitude during deployment. In this paper, an optimisation procedure is proposed to meet these requirements. [less ▲]

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See detailGender effect on the scapular 3D posture and kinematic in healthy subjects
Schwartz, Cédric ULg; Croisier, Jean-Louis ULg; Rigaux, Elise et al

in Clinical Physiology and Functional Imaging (2016)

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However ... [more ▼]

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However the literature reports, for the shoulder, differences in the range of motion between genders. The specific influence of gender on the scapula-thoracic kinematics has not been studied yet. The dominant shoulder of two populations of men and women composed of 11 subjects each were evaluated in three dimensions for three distinct motions: flexion in the sagittal plane, abduction in the frontal plane and gleno-humeral internal/external rotation with the arm abducted at 90°. Posture, kinematics and range of motion were studied separately. For flexion and abduction and with regard to the scapular kinematic, external rotation were significantly larger for women than men. The differences were of at least 5° at 120° of humeral elevation. Upward rotations were identical. Women also showed larger average active humero-thoracic range of motion. The mean differences were of 13°, 7°, 12° and 5° for abduction, flexion, internal rotation and external rotation, respectively. No difference was observed between the scapular resting positions of both populations. The observed differences concerning both the scapular and humeral patterns would indicate that the shoulder behavior of men and women should not be expected to be similar. [less ▲]

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