Bruno Jammes

Discriminating sensors for driver's impairment detection

In this work, the authors present a statistical analysis applied to different sensors on the drivers impairment detection problem. Their goal is to get a minimal number of discriminating sensors to match the requirements of an industrial prototype. The signals coming from these group of sensors are used to create artificial variables based on several mathematical transformations (wavelets, standard deviations) in order to fuse this information at a first level. The authors statistical study is based on several steps: 1) the observation of the variation of the mean and variance of the different variables, 2) the test of Hypothesis F concerning a populations variance and then, an hypotheses test based on Students t distribution for the means, 3) principal components analysis (PCA); and 4) general performance of the diagnosis system using or not the different variables. This study has been performed using experimental data coming from 10 drivers in real experiments involving fatigued drivers at a closed circuit and over a motorway. These experiments have been realised using the CopiTech demonstrator which is equipped with a group of sensors measuring physiologic, mechanical and environmental status in real time. The analysis is validated by the physical state of the driver based on EEG. Results stress that the better discriminating sensors are: a) lateral position, b) steering wheel angle, and c) vehicle speed.

Optimal sizing of a lithium battery energy storage system for grid-connected photovoltaic systems

This paper proposes a system analysis focused on finding the optimal operating conditions (nominal capacity, cycle depth, current rate, state of charge level) of a lithium battery energy storage system. The purpose of this work is to minimize the cost of the storage system in a renewable DC microgrid. Thus, main stress factors influencing both battery lifetime (calendar and cycling) and performances are described and modelled. Power and energy requirements are also discussed through a probabilistic analysis on some years of real data from the ADREAM photovoltaic building of the LAAS-CNRS in Toulouse, FRANCE.

Multi-objective methodology to find the optimal forward current to supply light emitting diode (LED) lightings

Light emitting diodes (LEDs) are commonly expected to be the future of lighting because of a high luminous efficacy, a long lifetime and a high color rendering index (CRI). Nevertheless, the performance and the reliability of an LED are strongly dependent on the LED junction temperature. This paper presents a multi-objective methodology to find the optimal forward current subject to the annualized cost of the luminaire (initial capital cost, replacement cost, operation and maintenance cost...) and the annualized energy consumption. A simple LED model based on empirical data has been developed and takes into account optical, electrical, thermal and ageing behaviour. Three different white LEDs have been evaluated through several combinations of forward currents and heatsinks to satisfy a given mission profile. A set of optimal solutions has been determined by Pareto optimization.

A characterization framework to optimize LED luminaire's luminous efficacy

Light Emitting Diodes (LED) are semiconductor devices which, combined to phosphors, emit white light with high efficacy surpassing conventional light sources. Elementary LED is not suffisant to light a piece. It need to be associated with others and combined to a power supply to constitute a complete luminaire. Actually, “wall-plug” efficacy drops a lot due to factors such as optical attenuation, electrical connections losses, thermal impact, ... To develop optimal electrical supply, a study was conducted to increase knowledge on interactions between LEDs technologies, their topology, current level supply and luminous efficacy..., A more precise electrical model than classical used for light was developed. Simulation results on original LED matrix with its new modeling are shown. An experimental board was developed to validate our approach with real electrical characterizations.