Publications

2018

Speed Profile Optimization for Enhanced Passenger Comfort: An Optimal Control Approach

Authors : WANG, Yuyang CHARDONNET, Jean-Rémy MERIENNE, Frédéric
Publisher : IEEE
Autonomous vehicles are expected to start reaching the market within the next years. However in practical applications, navigation inside dynamic environments has to take many factors such as speed control, safety and comfort into consideration, which is more paramount for both passengers and pedestrians. In this paper, a novel speed profile planner based on an optimal control approach considering passenger comfort is proposed. The approach is accomplished by minimizing jerk under certain comfort constraints, which inherently gives a speed profile for the central nervous system to follow naturally. Imposed with the same conditions, the widely used Jerk Limitation method is interpreted as an equivalent of the minimum time control method, the latter being used to verify that our method can ensure better continuity and smoothness of the speed profiles. A validation test was specifically designed and performed in order to show the feasibility of our method.
+
2019

A model of heterogeneous thermoviscoplastic material preserving uniform normal strains under combined compression, tension (or compression) and shearing. Instability and homogenization results

Authors : CHATZIGEORGIOU, George CHARALAMBAKIS, Nicolas
Publisher : Elsevier BV
In this paper, we present the special solution of the two-dimensional problem of a continuously graded composite made of thermovisco- rigid plastic materials under combined biaxial quasistatic compression and tension (or compression) and shear, that preserves prescribed uniform normal strains. The related reference initial-boundary value problem is fully defined and the corresponding solution is analyzed and computed numerically. In the context of a linearized instability analysis, critical conditions, as the critical shear banding angle, in terms of the loading level and material heterogeneities, are presented. In the context of non-linear instability, these results are examined and explained. Additionally, in the same context of non-linear analysis, the destabilizing mechanism, the onset of instability and the critical time for prescribed lower and upper bounds of equivalent strain-rate and upper bound of equivalent strain are defined and related to the lateral normal stress. The limitations of linearized analysis results are also revealed. Moreover, a semi-analytical homogenization scheme for a periodically-graded plate is presented. The related results are used for the derivation of a homogenized problem of a multilayered composite with continuously graded interlayers.
+
2018

Optimal perturbation for two-dimensional vortex systems: route to non-axisymmetric state

Authors : NAVROSE JOHNSON, Author H. G. BRION, Véronique JACQUIN, Laurent ROBINET, Jean-Christophe
Publisher : Cambridge University Press
We investigate perturbations that maximize the gain of disturbance energy in a two-dimensional isolated vortex and a counter-rotating vortex pair. The optimization is carried out using the method of Lagrange multipliers. For low initial energy of the perturbation ( ), the nonlinear optimal perturbation/gain is found to be the same as the linear optimal perturbation/gain. Beyond a certain threshold , the optimal perturbation/gain obtained from linear and nonlinear computations are different. There exists a range of for which the nonlinear optimal gain is higher than the linear optimal gain. For an isolated vortex, the higher value of nonlinear optimal gain is attributed to interaction among different azimuthal components, which is otherwise absent in a linearized system. Spiral dislocations are found in the nonlinear optimal perturbation at the radial location where the most dominant wavenumber changes. Long-time nonlinear evolution of linear and nonlinear optimal perturbations is studied. The evolution shows that, after the initial increment of perturbation energy, the vortex attains a quasi-steady state where the mean perturbation energy decreases on a slow time scale. The quasi-steady vortex state is non-axisymmetric and its shape depends on the initial perturbation. It is observed that the lifetime of a quasi-steady vortex state obtained using the nonlinear optimal perturbation is longer than that obtained using the linear optimal perturbation. For a counter-rotating vortex pair, the mechanism that maximizes the energy gain is found to be similar to that of the isolated vortex. Within the linear framework, the optimal perturbation for a vortex pair can be either symmetric or antisymmetric, whereas the structure of the nonlinear optimal perturbation, beyond the threshold, is always asymmetric. No quasi-steady state for a counter-rotating vortex pair is observed.
+
2018

Three-dimensional instability of a ow past a sphere: Mach evolution of the regular and Hopf bifurcations

Authors : SANSICA, Andrea ROBINET, Jean-Christophe ALIZARD, Frédéric GONCALVES, Eric
Publisher : Cambridge University Press
A fully three-dimensional linear stability analysis is carried out to investigate the unstable bifurcations of a compressible viscous fluid past a sphere. A time-stepper technique is used to compute both equilibrium states and leading eigenmodes. In agreement with previous studies, the numerical results reveal a regular bifurcation under the action of a steady mode and a supercritical Hopf bifurcation that causes the onset of unsteadiness but also illustrate the limitations of previous linear approaches, based on parallel and axisymmetric base flow assumptions, or weakly nonlinear theories. The evolution of the unstable bifurcations is investigated up to low-supersonic speeds. For increasing Mach numbers, the thresholds move towards higher Reynolds numbers. The unsteady fluctuations are weakened and an axisymmetrization of the base flow occurs. For a sufficiently high Reynolds number, the regular bifurcation disappears and the flow directly passes from an unsteady planar-symmetric solution to a stationary axisymmetric stable one when the Mach number is increased. A stability map is drawn by tracking the bifurcation boundaries for different Reynolds and Mach numbers. When supersonic conditions are reached, the flow becomes globally stable and switches to a noise-amplifier system. A continuous Gaussian white noise forcing is applied in front of the shock to examine the convective nature of the flow. A Fourier analysis and a dynamic mode decomposition show a modal response that recalls that of the incompressible unsteady cases. Although transition in the wake does not occur for the chosen Reynolds number and forcing amplitude, this suggests a link between subsonic and supersonic dynamics.
+
2018

TEAM: a Tool for Eco Additive Manufacturing to optimize environmental impact in early design stages

Authors : LAVERNE, Floriane BOTTACINI, Enrico SEGONDS, Frederic PERRY, Nicolas D'ANTONIO, Gianluca CHIABERT, Paolo
Publisher :
Nowadays, the environmental impact of a product is a major factor for the design team and for the end customer. To decrease the environmental impact of a product during its whole lifecycle, many design methods are available focusing on the multitude of data from the product once it is fully designed (Lifecycle Analysis etc ...). However, the design choices made in the early design stages have a crucial importance on the environmental impact of the chosen solution. It is therefore necessary to propose to the multidisciplinary design team a tool to help them choosing the best concept and the best way to produce it as early as possible. The emphasis in this paper is on Additive Manufacturing technologies, which are widely used in concept development. A design tool prototype is presented and evaluated in order to foster early eco-additive manufacturing of concepts.
+
2018

Design in context of use: An experiment with a multi-view and multi-representation system for collaborative design

Authors : LI, Bo SEGONDS, Frédéric MATEEV, Céline LOU, Ruding MERIENNE, Frédéric
Publisher : Elsevier BV
The current trend of product design leads to a change in the collaborative working style. To find the most efficient way to exchange information on the digital mock-up of a product, a synchronous co-located collaborative design environment with recent technologies is in needed. A new groupware of multi-view system allows multiple users to have individual visual information of a domain-specific representation of digital mock-up. In this paper, we propose a case study for the development and testing of a co-located multi-view system in collaborative virtual reality, aiming at enhancing the multidisciplinary early collaborative design. An ergonomic method of Personas is introduced to the evaluation of the tool, considering various user performance. With a multidisciplinary mug design scenario, experiments are presented, validating the benefits of the proposed system.
+
2018

Performance Evaluation of Passive Haptic Feedback for Tactile HMI Design in CAVEs

Authors : LASSAGNE, Antoine KEMENY, Andras POSSELT, Javier MERIENNE, Frédéric
Publisher : Institute of Electrical and Electronics Engineers (IEEE)
This article presents a comparison of different haptic systems, which are designed to simulate flat Human Machine Interfaces (HMIs) like touchscreens in virtual environments (VEs) such as CAVEs, and their respective performance. We compare a tangible passive transparent slate to a classic tablet and a sensory substitution system. These systems were tested during a controlled experiment. The performance and impressions from 20 subjects were collected to understand more about the modalities in the given context. The results show that the preferences of the subjects are strongly related to the use-cases and needs. In terms of performance, passive haptics proved to be significantly useful, acting as a space reference and a real-time continuous calibration system, allowing subjects to have lower execution durations and relative errors. Sensory substitution induced perception drifts during the experiment, causing significant performance disparities, demonstrating the low robustness of perception when spatial cues are insufficiently available. Our findings offer a better understanding on the nature of perception drifts and the need of strong multisensory spatial markers for such use-cases in CAVEs. The importance of a relevant haptic modality specifically designed to match a precise use-case is also emphasized.
+
2018

Vibrotactile and Force Collaboration within 3D Virtual Environments

Authors : TARNG, Stanley ERFANIAN, Aida HU, Yaoping MERIENNE, Frédéric
Publisher : IEEE
In a three-dimensional (3D) virtual environment (VE), proper collaboration between vibrotactile and force cues - two cues of the haptic modality - is important to facilitate task performance of human users. Many studies report that collaborations between multi-sensory cues follow maximum likelihood estimation (MLE). However, an existing work finds that MLE yields a mean and an amplitude mismatches when interpreting the collaboration between the vibrotactile and force cues. We thus proposed mean-shifted MLE and conducted a human study to investigate the mismatches. For the study, we created a VE to replicate the visual scene, the 3D interactive task, and the cues from the existing work. Our participants were biased to rely on the vibrotactile cue for their tasks, departing from unbiased reliance on both cues in the existing work. Assessments of task completion time and task accuracy validated the replication. We found that based on task accuracy MLE explained the cue collaboration to certain degrees, agreed with the existing work. Mean-shifted MLE remedied the mean mismatch, but maintained the amplitude mismatch. Further examinations revealed that the collaboration between both cues may not be entirely additive. This sheds an insight for proper modeling of the collaboration between the vibrotactile and force cues to aid interactive tasks in VEs.
+
2018

Augmented Reality assistance for R&D assembly in Aeronautics

Authors : PRUVOST, Martin MIALOCQ, Pierre ABABSA, Fakhreddine
Publisher :
This paper presents an AR system architecture for assisting complex assembly work by adding visual information superimposed on the physical assembly parts.
+
2015

Pitch tilt rendering for an 8-DOF driving simulator

Authors : COLOMBET, Florent FANG, Zhou KEMENY, Andras
Publisher : DSC
Tilt coordination technique is used for reproducing a sustained linear acceleration in driving simulation by tilting the simulator cabin. Thus a part of gravity is interpreted as a horizontal acceleration. Between the slow rotational motion limited by the rotational perception threshold of semi-circular canals of vestibular system and the fast change of acceleration to render, the design of coupling motions of rotation and translation plays a critical role in the realism of driving simulator. We present here an experiment focusing on longitudinal accelerations rendering with pitch tilt coordination technique. Eight drivers experienced the same accelerations and decelerations on a straight double-lane motorway. During the driving, we varied the pitch rate (4, 5, 6 and 7 °/s) and the pitch acceleration (8 and 30 °/s²) used to render these accelerations with the tilt coordination technique. We have found an acceptability threshold of about 6°/s, similar to the value found in our previous work on roll tilt rendering. We have also shown a strong role of pitch rotational acceleration on acceptability, involving that it should be taken into account to properly render accelerations with the tilt coordination technique.
+