Simulation study of driver stress and performance to an unexpected event

Abstract In this paper, we study the effect of unexpected behaviour of a Driving Assistance System (DAS) on the driver, during a common task of driving in a virtual environment. The considered system is an electrical steering, which allows drivers to reduce efforts needed to handle the steering wheel during cornering manoeuvres. A failure of such system could produce a sudden and permanent loss of steering assistance and make the steering wheel more difficult to turn. The objective of this study is to determine how this event will affect the driver's performance, particularly in terms of stress and visual performance. At last, drivers are able to adapt to this kind of event if it occurs before entering a curve. Moreover, an increase of muscle stiffness has been observed during lane change manoeuvres, which provide a more robust control of the steering wheel to external perturbations. At last drivers are able to manage a sudden increase of stress. The experiment was conducted on the ULTIMATE dynamic driving simulator developed by the Technical Centre for Simulation of RENAULT. The simulator has been fitted with a new steering force feedback system improving dynamical performance. This simulator upgrade and assessment methodology will be presented in more details in this paper. The driver behaviour was studied through questionnaires to assess the stress produced by the different situations. Detection and/or recognition of objects in the virtual scene give cues on the DAS failure effects on the driver's visual attention. In order to quantify the drivers' performance, objective indicators such as steering reversal rate, steering entropy and time-to-lane-crossing were also used. In spite of the unexpected steering event, all drivers have achieved their driving task, without leaving the road. Results show an increase of stress for drivers when the unexpected event occurs. We also notice an alteration of the visual performance revealed by drivers' difficulties to recognize critical objects in the environment. This study suggests that high-performance driving simulators may be valuable to assess the effects of safety-critical events on driving performance. Résumé Dans cet article, nous étudions l'effet sur le conducteur d'un comportement inattendu d'un système d'aide à la conduite (DAS) et ceci lors d'une tâche de conduite ordinaire en environnement virtuel. Le système retenu est une direction assistée électrique qui permet au conducteur de réduire les efforts nécessaires à produire pour le maniement du volant en virage. Une défaillance d'un tel système peut produire une perte soudaine et permanente d'assistance et rendre ainsi le volant plus difficile à tourner. L'objectif de cette étude est de déterminer l'impact de ce type d'évènement sur les performances du conducteur. Seront considérés en particulier la performance visuelle et la production de stress. Il a été constaté que lorsque cet évènement apparaît avant l'entrée en virage, les conducteurs sont capables de s'y adapter. De plus, une augmentation de la raideur des muscles du bras a été observée lors de manoeuvres de changement de file, ce qui rend le contrôle du volant plus robuste à des perturbations extérieures. Enfin, il semble que les conducteurs sont capables de gérer un stress soudain et de courte durée. L'expérimentation a été réalisée sur le simulateur de conduite dynamique ULTIMATE développé au Centre Technique de Simulation de RENAULT. Le simulateur s'est vu doté d'un nouveau restituteur d'effort pour le volant, offrant des performances dynamiques supérieures au précédent restituteur. L'installation et la validation de ce nouveau matériel sera présentée dans de plus amples détails. Le comportement des conducteurs a été étudié au travers de questionnaires afin d'évaluer la production de stress lors des différentes situations. La détection et/ou la reconnaissance d'objets dans la scène virtuelle procure des indices quant aux effets sur l'attention visuelle du conducteur de la défaillance du système d'assistance. Dans le but de quantifier la performance de conduite, des indicateurs tels que le Steering Reversal Rate, le Steering Entropy et le Time-to-Line-Crossing ont été utilisés. Malgré que l'évènement soit inattendu, tous les conducteurs ont réussi à terminer leur tâche de conduite sans quitter la route. Les résultats montrent une augmentation du stress lorsque cet évènement apparaît. Remarquons aussi l'altération de l'attention visuelle des conducteurs de part leur difficulté à reconnaître les objets de l'environnement. Cette étude suggère que les simulateurs de conduite à hautes performances autorisent l'évaluation des effets sur la performance de conduite d'évènements critiques en termes de sécurité

From Driving Simulation to Virtual Reality

Driving simulation from the very beginning of the advent of VR technology uses the very same technology for visualization and similar technology for head movement tracking and high end 3D vision. They also share the same or similar difficulties in rendering movements of the observer in the virtual environments. The visual-vestibular conflict, due to the discrepancies perceived by the human visual and vestibular systems, induce the so-called simulation sickness, when driving or displacing using a control device (ex. Joystick). Another cause for simulation sickness is the transport delay, the delay between the action and the corresponding rendering cues. Another similarity between driving simulation and VR is need for correct scale 1:1 perception. Correct perception of speed and acceleration in driving simulation is crucial for automotive experiments for Advances Driver Aid System (ADAS) as vehicle behavior has to be simulated correctly and anywhere where the correct mental workload is an issue as real immersion and driver attention is depending on it. Correct perception of distances and object size is crucial using HMDs or CAVEs, especially as their use is frequently involving digital mockup validation for design, architecture or interior and exterior lighting. Today, the advents of high resolution 4K digital display technology allows near eye resolution stereoscopic 3D walls and integrate them in high performance CAVEs. High performance CAVEs now can be used for vehicle ergonomics, styling, interior lighting and perceived quality. The first CAVE in France, built in 2001 at Arts et Metiers ParisTech, is a 4 sided CAVE with a modifiable geometry with now traditional display technology. The latest one is Renault’s 70M 3D pixel 5 sides CAVE with 4K x 4K walls and floor and with a cluster of 20 PCs. Another equipment recently designed at Renault is the motion based CARDS driving simulator with CAVE like 4 sides display system providing full 3D immersion for the driver. The separation between driving simulation and digital mockup design review is now fading though different uses will require different simulation configurations. New application domains, such as automotive AR design, will bring combined features of VR and driving simulation technics, including CAVE like display system equipped driving simulators

Synthesis and luminescence properties of ZnO/Zn2SiO4/SiO2 composite based on nanosized zinc oxide-confined silica aerogels

International audienceLuminescence properties of crystalline Zn2SiO4 greatly depend on the method of elaboration. A new protocol of sol-gel processing technique was used to prepare zinc orthosilicate willemite crystals incorporated in silica host matrix containing ZnO nanoparticles (ZnO/ Zn2SiO4/SiO2). Hydrolysis and condensation of tetraethylorthosilicate have been achieved in the presence of 25 nm-sized nanocrystalline ZnO particles. Supercritical drying and annealing in the range 1423-1473 K in air atmosphere yielded a new photoluminescence band centred at around 760 nm and observed for the first time. Photoluminescence excitation measurements show different origins in the recombination mechanism of this emission band. Different possible attributions of the 760 nm emission band will be discussed. (c) 2006 Elsevier B.V. All rights reserved

Spontaneous and stimulated emission of vertically aligned ZnO nanorods of different lengths

International audienceThe effect of the length of zinc oxide nanorods on their photoluminescence (PL) has been studied in the visible through UV spectral region. Hexagonally faceted columnar nanorods grown on (100) Si substrates have been shown to be aligned almost vertically. The chemistry of point defects in the nanorods depends on their position in the reactor during growth. The room-temperature PL spectrum of the nanorods shows narrow peaks due to stimulated free-exciton emission. The threshold optical pump power density for lasing in the longer ZnO nanorods is 8000 kW/cm(2), and the laser radiation is directed predominantly along their axis