Frédéric Merienne

Automatic Stress Classification With Pupil Diameter Analysis

This article proposes a method based on wavelet transform and neural networks for relating pupillary behavior to psychological stress. The proposed method was tested by recording pupil diameter and electrodermal activity during a simulated driving task. Self-report measures were also collected. Participants performed a baseline run with the driving task only, followed by three stress runs where they were required to perform the driving task along with sound alerts, the presence of two human evaluators, and both. Self-reports and pupil diameter successfully indexed stress manipulation, and significant correlations were found between these measures. However, electrodermal activity did not vary accordingly. After training, the four-way parallel neural network classifier could guess whether a given unknown pupil diameter signal came from one of the four experimental trials with 79.2% precision. The present study shows that pupil diameter signal has good discriminating power for stress detection.

Switching disturbance due to source inductance for a power MOSFET: analysis and solutions

In this paper some technological rules are given, in order to help the designer to choose correct parameter values (such as gate resistance), avoiding MOSFET switching disturbance due to common impedance coupling. The switching process is modeled, and the good understanding of switching disturbance leads to the desired technological rules, taking into account the MOSFET implementation (source inductance Ls).

Simulation of specular surface imaging based on computer graphics: application on a vision inspection system

This work aims at detecting surface defects on reflecting industrial parts. A machine vision system, performing the detection of geometric aspect surface defects, is completely described. The revealing of defects is realized by a particular lighting device. It has been carefully designed to ensure the imaging of defects. The lighting system simplifies a lot the image processing for defect segmentation and so a real-time inspection of reflective products is possible. To bring help in the conception of imaging conditions, a complete simulation is proposed. The simulation, based on computer graphics, enables the rendering of realistic images. Simulation provides here a very efficient way to perform tests compared to the numerous attempts of manual experiments.

CAD/CAE visualization in virtual environment for automotive industry

In this paper we propose a method to link CAD models to an immersive environment. Since CAD models can not be directly viewed in a real-time visualization environment, we present here a complete chain of adaptation steps to view adapted CAD models in an immersive environment with high quality rendering. Our method allows high quality visualization of complex scenes in an immersive environment such as design reviewing for example.

How 3D interaction metaphors affect user experience in collaborative virtual environment

In this paper we presents the results of our experimental study which aims to understand the impact of three interaction 3D metaphors (ray casting, GoGo, and virtual hand) on the user experience in a semi-immersive collaborative virtual environment (the Braccetto System). For each session, participants are grouped in twos to reconstruct a puzzle by an assemblage of cubes. The puzzle to reconstruct corresponds to a gradient of colors. We found that there is a significant difference in the user experience by changing the interaction metaphor on the copresence, awareness, involvement, collaborative effort, satisfaction usability, and preference. These findings provide a basis for designing 3D navigation techniques in a CVE.

Influence of Inertial Stimulus on Visuo-Vestibular Cues Conflict for Lateral Dynamics at Driving Simulators

This paper explains the effect of having an inertial stimulus (motion platform) for driving simulators on proximity to the reality for the sensed lateral dynamics with respect to the measurements and the perceptual fidelity using a questionnaire technique. To assess this objectively, the vestibular and vehicle level lateral accelerations (ay,sensed=ay_vest, ayv=ay_veh ) were saved by using a motion tracking sensor and SCANeR studio software respectively. A confidence interval of 95% was chosen to test the correlations (Pearson’s correlation) and to fit models for the distributions of the visual-vestibular lateral accelerations with the multiple linear regression between the conditions of static (N=16) and dynamic (N=21) platform cases in terms of visuo-vestibular level lateral accelerations for the group of subjects (N=37). The results showed that the dynamic platform provides a higher lateral dynamics reality (positive correlation with an incidence of 90.48% for N=21) compared to the static configuration (negative correlation with an incidence of 50% for N=16) from Pearson’s correlation and a better fitted model and a lower visuo-vestibular cues’ conflict for the dynamic (R2=0.429, the model is positive sloped, N=21) condition comparing to the static one (R2=0.072, the model is negative sloped, N=16) from the multiple linear regression models. A two-tailed Mann Whitney U test yielded that the Ucomputed (2139)>Uexpected (1300.5) as p<0.0001, there was a significant difference between the sensed lateral acclerations for the static and dynamic platform cases. Disorientation related perception had positive correlations with the vestibular sensed lateral accelerations for the static condition whereas they were negatively correlated in the dynamic case. As conclusion, the dynamic platform presented a reduced level of motion sickness depending on the sensory conflict theory and the perception fidelity studies approved that dizziness was found to have a significant positive correlation with the vestibular level measured lateral acceleration in the static platform (r=0.293, p=0.037<0.05).

Machine vision system for surface inspection on brushed industrial parts

This work aims at detecting defects on metallic industrial parts with streaked surface. The orientation of those parallel streaks is totally random. The searched defects are scratch and lack of machining. A specific machine vision system has been designed to deal with the particular inspected surface features. One image is acquired with an annular lighting in bright field and six images are acquired with a rotating lighting in dark field. A particular image processing is applied on the six images in order to get one image that represents all the revealed imperfections. A thresholding processing is then applied on this image in order to segment the imperfections. A trained classification, created with well known typical objects of each class, is performed. The classification has to recognize the different defects and the small imperfections that are not defects. The decision phase is used to know if the defects are acceptable, and therefore if the inspected part is acceptable. Some acceptability rules are defined for every defect class. The developed machine vision system has been implemented on an experimental industrial production line and it gives 2% of sub-detection and 16% of over-detection.

Study of the imaging conditions and processing for the aspect control of specular surfaces

A vision system capable of imaging and detecting defects on reflective nonplanar surfaces in the production line at a high cadence is presented in this paper. Defects are typically dust located under the metallic layer of packaging products used in cosmetic industries. To realize this processing, structured lighting which reveals the defects in the image is proposed. Defects appear clearly in the images like a set of brilliant pixels in dark zones. The signature of the defect is then obtained. The size of this signature does not depend linearly on the size of the defect. It is a function of the observation angle. In order to realize a precise and robust process, the necessity of acquiring several images of the same defect is demonstrated. Because of the acquisition rate, it has been necessary to optimize image processing time by the means of an original laplacian filter and of high level techniques of programming. Results obtained using this detection system are finally presented.

Virtual Distance Estimation in a CAVE

Past studies have shown consistent underestimation of distances in virtual reality, though the exact causes remain unclear. Many virtual distance cues have been investigated, but past work has failed to account for the possible addition of cues from the physical environment. We describe two studies that assess users’ performance and strategies when judging horizontal and vertical distances in a CAVE. Results indicate that users attempt to leverage cues from the physical environment when available and, if allowed, use a locomotion interface to move the virtual viewpoint to facilitate this.

Visual Scale Factor for Speed Perception

Speed perception is an important task depending mainly on optic flow that the driver must perform continuously to control his/her vehicle. Unfortunately it appears that in some driving simulators speed perception is under estimated, leading into speed production higher than in real conditions. Perceptual validity is then not good enough to study driver’s behavior. To solve this problem, a technique has recently seen the light, which consists of modifying the geometric field of view (GFOV) while keeping the real field of view (FOV) constant. We define our visual scale factor as the ratio between the GFOV and the FOV. The present study has been carried out on the SAAM dynamic driving simulator and aims at determining the precise effect of this visual scale factor on the speed perception. 20 subjects have reproduced 2 speeds (50 km/h and 90 km/h) without knowing the numerical values of these consigns, with 5 different visual scale factors: 0.70, 0.85, 1.00, 1.15 and 1.30. We show that speed perception significantly increases when the visual factor increases. A 0.15 modification of this factor is enough to obtain a significant effect. Furthermore, the relative variation of the speed perception is proportional to the visual scale factor. Besides, the modification of the geometric field of view remained unnoticed by all the subjects, which implies that this technique can be easily used to make drivers reduce their speed in driving simulation conditions. However, this technique may also modify perception of distances.