Publications of Olivier Bruls
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See detailA mortar formulation for frictionless line-to-line beam contact
Bosten, Armin ULiege; Cosimo, Alejandro ULiege; Linn, Joachim et al

in Multibody System Dynamics (2021)

This paper describes the quasi-static formulation of frictionless line contact between flexible beams by employing the mortar finite element approach. Contact constraints are enforced in a weak sense ... [more ▼]

This paper describes the quasi-static formulation of frictionless line contact between flexible beams by employing the mortar finite element approach. Contact constraints are enforced in a weak sense along the contact region using Lagrange multipliers. A simple projection appropriate for thin beams with circular cross-sections is proposed for the computation of contact regions. It is combined with the geometrically exact beam formalism on the Lie group SE(3). Interestingly, this framework leads to a constraint gradient and a tangent stiffness invariant under rigid body transformations. The formulation is tested in some numerical examples. [less ▲]

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See detailA foot/ground contact model for biomechanical inverse dynamics analysis
Van Hulle, Romain ULiege; Schwartz, Cédric ULiege; Denoël, Vincent ULiege et al

in Journal of Biomechanics (2020), 100

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See detailDevelopment of a robot-aided modal analysis measurement method using laser Doppler vibrometry
Devigne, Olivier ULiege; Hoffait, Sébastien ULiege; Bruls, Olivier ULiege

in Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering (2020)

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See detailA robust nonsmooth generalized-alpha scheme for flexible systems with impacts
Cosimo, Alejandro ULiege; Galvez Buezo, Javier ULiege; Cavalieri, Federico J. et al

in Multibody System Dynamics (2020), 48(2), 124-149

The aim of this work is the development of a robust and accurate time integrator for the simulation of the dynamics of multibody systems composed of rigid and/or flexible bodies subject to frictionless ... [more ▼]

The aim of this work is the development of a robust and accurate time integrator for the simulation of the dynamics of multibody systems composed of rigid and/or flexible bodies subject to frictionless contacts and impacts. The integrator is built upon a previously developed nonsmooth generalized-alpha scheme time integrator which was able to deal well with nonsmooth dynamical problems avoiding any constraint drift phenomena and capturing vibration effects without introducing too much numerical dissipation. However, when dealing with problems involving nonlinear bilateral constraints and/or flexible elements, it is necessary to adopt small time-step sizes to ensure the convergence of the numerical scheme. In order to tackle these problems more efficiently, a fully decoupled version of the nonsmooth generalized-alpha method is proposed in this work, avoiding these inconveniences. Several examples are considered to assess its accuracy and robustness. [less ▲]

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See detailAlgorithm for extracting initial and terminal contact timings during treadmill running using inertial sensors
Prijot, Laura ULiege; Schwartz, Cédric ULiege; Watrin, Julien et al

Conference (2020)

Inertial measurement units (IMUs) are now considered as an economical solution for long term assessment in real conditions. However, their use in running gait analysis is relatively new and limited ... [more ▼]

Inertial measurement units (IMUs) are now considered as an economical solution for long term assessment in real conditions. However, their use in running gait analysis is relatively new and limited. Detecting the timing at which the foot strikes the ground (initial contact, IC) and the timing at which the foot leaves the ground (terminal contact, TC) gives access to many relevant temporal parameters such as stance, swing or stride durations. In this paper, we present an original algorithm to extract IC and TC timings and associated parameters from running data. These data have been measured using a newly developed IMU-based hardware system in ten asymptotic participants who ran at three speeds (slow, normal, and fast) with different running patterns (natural, rearfoot strike, mid-foot strike, and forefoot strike). This algorithm has been validated against a 200 Hz video camera based on 7056 IC and TC timings and 6861 temporal parameters. This algorithm extracted ICs and TCs with an accuracy and precision of (median [1st quartile; 3rd quartile]) 5 ms [-5 ms, 15 ms] and 0 ms [-5 ms, 5 ms], respectively. The relative errors in the extraction of stride and stance durations are -1.56 ± 3.00% and 0.00 ± 1.32%, respectively. [less ▲]

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See detailHuman arm motion tracking using IMU measurements in a robotic environnement
Pellois, Robin ULiege; Bruls, Olivier ULiege

in Proceedings of the 21st International Symposium on Measurement and Control in Robotics (2019)

Human-robot interactions (HRI) is an emerging paradigm that aims at combining complementary skills of robot and human. The meaningful human arm motion represent an interesting way of communication to ... [more ▼]

Human-robot interactions (HRI) is an emerging paradigm that aims at combining complementary skills of robot and human. The meaningful human arm motion represent an interesting way of communication to explore with robot. IMUs appear as a simple, lightweight, easy-to-use, technology for human motion tracking compared to other systems such as opto-electronic devices. However, IMUs require important data treatement to reconstruct human motion and are usually coupled with a magnetometer or even other sensors. This paper explores a method only based on IMUs (accelerometer and gyroscope) to track human motion in order to keep the simplicity and robustness of IMUs in an industrial environnement with magnetic disturbances. The signal processing method presented here limit the well-known drift of the gyroscope by gravity measurement. © (2018) by the International Measurement Confederation (IMEKO). All rights reserved. [less ▲]

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See detailProgramming by demonstration using fiducial markers
Deom, Nathan Pierre ULiege; Bruls, Olivier ULiege; Jacques, Thierry

in Proceedings of the Robotix Academy Conference for Industrial Robotics (RACIR) 2019 (2019)

The programming by demonstration is a method that allows one to register a trajectory and to reproduce it by a robot. It could be used to speed up the programming of robots using the practical skills of ... [more ▼]

The programming by demonstration is a method that allows one to register a trajectory and to reproduce it by a robot. It could be used to speed up the programming of robots using the practical skills of workers without the time consuming code development part of classical robotic applications. This article exposes a methodology based on fiducial markers and only one classical camera which is an inexpensive solution. The fiducial markers are based on binary symbols generally used for augmented reality applications. It also presents the experimental setup created at the laboratory of human motion analysis and used to analyze the repeatability and the precision of this solution. The primary results show a promising technology and following developments will be done. [less ▲]

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See detailInter-Session Reliability of the Tennis Serve and Influence of the Laboratory Context
Tubez, François ULiege; Forthomme, Bénédicte ULiege; Croisier, Jean-Louis ULiege et al

in Journal of Human Kinetics (2019), 66(1), 57-67

To meet the demand of a player's entourage (e.g., coaches and medical staff), it is important for the biomechanics specialist to perform repeatable measures. To the best of our knowledge, to date, it has ... [more ▼]

To meet the demand of a player's entourage (e.g., coaches and medical staff), it is important for the biomechanics specialist to perform repeatable measures. To the best of our knowledge, to date, it has not been demonstrated whether similar results are obtained between two sessions of testing or between laboratory and field sport kinematic protocols with regard to the tennis serve. This study had two primary aims. First, the inter-session repeatability of biomechanical variables of a tennis serve was evaluated. Second, the differences between laboratory and field evaluations were studied. Thirteen national tennis players (ITN 3) performed the same 28 markers' set laboratory test twice two weeks apart, and other thirteen national players (ITN 3) performed two 4 markers' set tests both in the laboratory and on an official tennis court one week apart. A 3D motion system was used to measure lower-limb, pelvis, trunk, dominant arm and racket kinematics. A force plate was used to evaluate kinetics of legs' drive in the laboratory. A personal method based on a point scoring system was developed to evaluate the ball landing location accuracy. We observed that the majority of the studied variables were acceptable for excellent relative reliability for the inter-session analysis. We also showed that the impact of the laboratory versus field context on the player's serve was limited © 2019 2019 François Tubez, Bénédicte Forthomme, Jean-Louis Croisier, Olivier Brüls, Vincent Denoël, Julien Paulus, Cédric Schwartz, published by Sciendo. [less ▲]

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See detailGait symmetry in the dual task condition as a predictor of future falls among independent older adults: a 2-year longitudinal study
GILLAIN, Sophie ULiege; Boutaayamou, Mohamed ULiege; Schwartz, Cédric ULiege et al

in Aging Clinical and Experimental Research (2019), 31(8), 1057-1067

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See detailHuman arm motion tracking using IMU measurements in a robotic environnement
Pellois, Robin ULiege; Bruls, Olivier ULiege

Scientific conference (2018, September 26)

Human-robot interactions (HRI) is an emerging paradigm that aims at combining complementary skills of robot and human. The meaningful human arm motion represent an interesting way of communication to ... [more ▼]

Human-robot interactions (HRI) is an emerging paradigm that aims at combining complementary skills of robot and human. The meaningful human arm motion represent an interesting way of communication to explore with robot. IMUs appear as a simple, lightweight, easy-to-use, technology for human motion tracking compared to other systems such as opto-electronic devices. However, IMUs require important data treatement to reconstruct human motion and are usually coupled with a magnetometer or even other sensors. This paper explores a method only based on IMUs (accelerometer and gyroscope) to track human motion in order to keep the simplicity and robustness of IMUs in an industrial environnement with magnetic disturbances. The signal processing method presented here limit the well-known drift of the gyroscope by gravity measurement. [less ▲]

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See detailFlexible models of a three degree of freedom serial elastic robot
Lismonde, Arthur ULiege; Gattringer, Hubert; Bruls, Olivier ULiege

in Proceedings of the fifth Joint International Conference on Multibody System Dynamics (2018)

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See detailP054 - Evaluation of ground reaction forces by inverse dynamics analysis
Van Hulle, Romain ULiege; Schwartz, Cédric ULiege; Denoël, Vincent ULiege et al

in Gait and Posture (2018), 65

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See detailValidated assessment of gait sub-phase durations in older adults using an accelerometer-based ambulatory system
Boutaayamou, Mohamed ULiege; GILLAIN, Sophie ULiege; Schwartz, Cédric ULiege et al

in Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2018) (2018)

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we ... [more ▼]

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we describe (1) a signal processing algorithm to automatically extract not only durations of stride, stance, swing, and double support phases, but also durations of sub-phases that refine the stance and swing phases from foot-worn accelerometer signals in comfortable walking of older adults, and (2) the validation of this extraction using reference data provided by a gold standard system. The results show that we achieve a high agreement between our method and the reference method in the extraction of (1) the temporal gait events involved in the estimation of the phase/sub-phase durations, namely heel strike (HS), toe strike (TS), toe-off (TO), maximum of heel clearance (MHC), and maximum of toe clearance (MTC), with an accuracy and precision that range from ‒3.6 ms to 4.0 ms, and 6.5 ms to 12.0 ms, respectively, and (2) the gait phase/sub-phase durations, namely stride, stance, swing, double support phases, and HS to TS, TO to MHC, MHC to MTC, and MTC to HS sub-phases, with an accuracy and precision that range from ‒4 ms to 5 ms, and 9 ms to 15 ms, respectively, in comfortable walking of a thirty-eight older adults ( (mean ± standard deviation) 71.0 ± 4.1 years old). This demonstrates that the developed accelerometer-based algorithm can extract validated temporal gait events and phase/sub-phase durations, in comfortable walking of older adults, with a promising degree of accuracy/precision compared to reference data, warranting further studies. [less ▲]

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See detailEvaluation of ground reaction forces based on kinematic data
Van Hulle, Romain ULiege; Schwartz, Cédric ULiege; Bruls, Olivier ULiege

Poster (2017, December 01)

Detailed reference viewed: 49 (9 ULiège)