Etude de l'impact des contraintes aéronautiques sur les systèmes d'isolation des moteurs de conditionnement d'air

Notre étude s'inscrit dans le cadre d'un projet régional de collaboration entre le laboratoire LAPLACE, les sociétés Liebherr Aerospace et Technofan et les PMEs Delty, ADN et Cirtem. Son sujet principal est l'étude des systèmes d'isolation électrique des machines tournantes de classe thermique 180°C, alimentés par onduleur MLI et fonctionnant en environnement aéronautique. La première partie de ce travail se focalise d'une part sur la quantification expérimentale des risques encourus par les systèmes d'isolation électriques des futures générations de moteurs employés dans la pressurisation des avions plus électriques et d'autre part sur la sélection des fils émaillés envisagés pour concevoir leur système d'isolation. La seconde partie est consacrée à une nouvelle solution visant à protéger des moteurs basse tension soumis aux contraintes fonctionnelles et environnementales sévères. Cette solution repose sur l'utilisation de particules de silice (micro-particules ou nano-particules) dispersés dans le vernis d'imprégnation. Afin d'évaluer les propriétés correspondantes du vernis ainsi réalisé, différentes expériences sont détaillées et analysées en fonction de la taille des particules. L'objectif consiste en effet à accroitre la tenue aux décharges du vernis sans pour autant détériorer ses autres propriétés diélectriques (conductivité électrique et rigidité diélectrique) et sa tenue mécanique.This study falls within the framework of a cooperation project between the Laplace Laboratory, the companies Liebherr Aerospace and Technofan and the SMEs Delty, ADN and Cirtem. The principal theme is the study of electrical insulation systems of rotating machines (thermal class 180°C), fed by PWM inverter and operating in a aeronautic environment. The first part of this work focuses on the one hand on the experimental quantification of risks associated with the electrical insulation systems of the future motors used in the pressurization of the ''more electric'' aircrafts, and on the other hand on the selection of enamelled wires considered to design their insulation system. The second part is dedicated to a new solution to protect low voltage motors subject to severe functional and environmental constraints. This solution is based on the use of silica particles (micro-particles or nano-particles) dispersed in the impregnation varnish. In order to estimate the corresponding properties of such varnishes, different experimental investigation are detailed and analyzed in accordance with the size of particles. The goal is to inscrease the resistance to partial discharges of varnish but without deterioration of its other dielectric properties (electric conductivity and dielectric strength) and its mechanical strength

Entrepreneurial Finance: Insights from English Language Training Market in Vietnam

Entrepreneurship plays an indispensable role in the economic development and poverty reduction of emerging economies like Vietnam. The rapid development of technologies during the Fourth Industrial Revolution (Industry 4.0) has a significant impact on business in every field, especially in the innovation-focused area of entrepreneurship. However, the topic of entrepreneurial activities with technology applications in Vietnam is under-researched. In addition, the body of literature regarding entrepreneurial finance tends to focus on advanced economies, while mostly neglecting the contextual differences in developing nations. Therefore, this research contributes to these topics by investigating the main characteristics of a high potential market for entrepreneurs in Vietnam, which is the English language training market (ELTM). It also aims at indicating the impacts of technology on the entrepreneurial firms within this market, with an emphasis on financing sources. To answer the research questions, this study employs a qualitative analysis and conducts 12 in-depth, semi-structured interviews with entrepreneurs and researchers in the field. The key findings in our study highlight the main contributing factors to the growth of the market, both universally and context-specific for a developing nation like Vietnam. It also lists the leaders in each market segment and the industry’s potential profit margin. The results also show that most entrepreneurs in the ELTM utilized private sources of finance rather than external ones, such as bank loans. It again confirms the idea from previous works that even with the rapid development of the economic and technological landscape, entrepreneurial activities in general barely benefit from additional sources of funding. However, it also points out the distinct characteristics of the ELTM that may influence these financing issues; for example, English training services usually collect revenues from customers before delivering their classes. This is of advantage for entrepreneurs in this area and helps significantly reduce the financial barriers. These findings, which are among the first attempts to contribute to a better understanding of entrepreneurial opportunities in the Industry 4.0 in Vietnam, provide valuable insights for policymakers and entrepreneurs, as well as investors

A switched LPV observer for actuator fault estimation

International audienceIn this paper, an actuator fault estimation problem is tackled, based on the LPV approach. First, the actuator fault is modeled in the form of a multiplicative fault by using a constant coefficient representing the loss of efficiency of the actuator's power α. Therefore, the estimation of a time varying faulty actuator can be transformed into the estimation of a constant coefficient α. Then, the faulty system is rewritten in the form of a switched LPV system. The coefficient α and the system states are estimated using an extended switched observer. The stability and performance of the observer is ensured considering a switched time-dependent Lyapunov function. The observer gains are derived based on LMI solutions for polytopic switched systems. Some simulation results are presented that show the effectiveness of this approach

A motion-scheduled LPV control of full car vertical dynamics

International audienceIn this paper, we present a new Linear Parameter Varying LPV/H ∞ motion adaptive suspension controller that takes into account the three main motions of the vehicle vertical dynamics: bounce, roll and pitch motions. The new approach aims, by using a detection of the vehicle motions, at designing a controller which is able to adapt the suspension forces in the four corners of the vehicle according to the dynamical motions, in order to mitigate these vertical dynamics which could be stimulated by the road-induced vibrations, making a tight turn or an evasive manoeuvre, braking or accelerating. The main idea of this strategy is to use three scheduling parameters, representative of the motion distribution in the car dynamics, to adapt and distribute efficiently the suspension actuators. The motion detection strategy is based on the supervison of load transfer distribution. A full 7 degree of freedom (DOF) vertical model is used to describe the body motion (chassis and wheels), and to synthesize the LPV controller. The controller solution is derived in the framework of the LPV/H ∞ and based on the LMI solution for polytopic systems. Some simulations are presented in order to demonstrate the effectiveness of this approach

Commande MIMO LPV /H ∞ de suspension semi-active

National audienceCet article présente une nouvelle commande LPV /H∞ de suspension semi-active qui prend en compte les trois mouvements principaux de la dynamique verticale du véhicule (rebond, roulis et tangage) qui affectent le confort des passagers. La nouvelle approche, utilisant la détection des mouvements du véhicule, a pour objectif de concevoir un contrôleur qui adapte les forces de suspension dans les quatre coins selon les mouvements du véhicule, pour atténuer les vibrations induites par la route. L' idée principale de cette stratégie est d'utiliser trois paramètres variants, représentant la distribution de mouvement dans la dynamique de la voiture, afin d'adapter et distribuer efficacement les actionneurs de suspension. La stratégie de détection du mouvement se base sur une méthode de calcul energétique [20]. Un modèle vertical à 7 degrés de liberté (DOF) du véhicule est utilisé pour décrire les mouvements du châssis et des roues, et de synthétiser le régulateur LPV. Ce régulateur est conçu dans le cadre H∞/LPV pour les systèmes polytopiques. Des résultats de simulation sont présentés pour valider l'approche proposée

Actuator fault estimation based on a switched LPV extended state observer

article en cours de soumission à une revueActuator fault estimation problem is tackled in this paper. The actuator faults are modeled in the form of multiplicative faults by using effectiveness factors representing the loss of efficiency of the actuators. The main contribution of this paper lies in the capability of dealing with the presented problem by using a switched LPV observer approach. The LTI system in the presence of faulty actuators is rewritten as a switched LPV system by considering the control inputs as scheduling parameters. Then, the actuator faults and the system states are estimated using a switched LPV extended observer. The observer gain is derived, based on the LMIs solution for the switched LPV systems. The presented actuator fault estimation approach is validated by two illustrative examples, the first one about a damper fault estimation of a semi-active suspension system, and the second one concerned to fault estimations on a multiple actuators system

An LPV Fault Tolerant control for semi-active suspension -scheduled by fault estimation

International audienceIn this paper, a novel fault tolerant control is proposed to accommodate damper faults (oil leakages) in a semi-active suspension system based on a quarter-car vehicle model. The fault accommodation is based on the Linear Parameter Varying (LPV) control strategy and involved in 2 steps. At first, a fast time-varying fault is estimated by using the fast adaptive fault estimation (FAFE) algorithm and based on an unknown input adaptive observer. Thanks to information about the estimated fault, the dissipativity domain of the semi-active suspension is adapted according to the fault. Then a single LPV fault tolerant controller is developed to manage the system performances. The controller solution, derived in the LPV/H ∞ framework, is based on the LMI solution for polytopic systems. Some simulation results are presented that show the effectiveness of this approach

Improving Bayesian statistics understanding in the age of Big Data with the bayesvl R package

The exponential growth of social data both in volume and complexity has increasingly exposed many of the shortcomings of the conventional frequentist approach to statistics. The scientific community has called for careful usage of the approach and its inference. Meanwhile, the alternative method, Bayesian statistics, still faces considerable barriers toward a more widespread application. The bayesvl R package is an open program, designed for implementing Bayesian modeling and analysis using the Stan language’s no-U-turn (NUTS) sampler. The package combines the ability to construct Bayesian network models using directed acyclic graphs (DAGs), the Markov chain Monte Carlo (MCMC) simulation technique, and the graphic capability of the ggplot2 package. As a result, it can improve the user experience and intuitive understanding when constructing and analyzing Bayesian network models. A case example is offered to illustrate the usefulness of the package for Big Data analytics and cognitive computing

Comparison of observer approaches for actuator fault estimation in semi-active suspension systems

International audienceIn this paper, the actuator fault estimation problem of semi-active suspension systems is considered. For instance, an oil leakage in the damper could cause a reduction of the damping force. The fault estimation requires a modeling of the damper fault (both multiplicative and additive fault models can be used). Three observer-based approaches are compared for fault estimation: an observer using fast adaptive fault estimation (FAFE) approach (used for estimation of additive faults), a parametric adaptive observer (AO) and a switched LPV observer (LPVO) (both intended to estimate mulplicative faults); Since the damper fault estimation is strongly affected by the unknown road disturbances, an H ∞ performance objective is used to reduce the effect of disturbances on the estimation error for performance assessment. Some simulations are performed on a quarter car model to validate these methodologies and a comparison is then given to shows the interest of each method. Keywords: Fault estimation, semi-active damper fault, adaptive observer, fast fault adaptive estimation, LPV observer

Healthcare consumers’ sensitivity to costs: a reflection on behavioural economics from an emerging market

Decision-making regarding healthcare expenditure hinges heavily on an individual's health status and the certainty about the future. This study uses data on propensity of general health exam (GHE) spending to show that despite the debate on the necessity of GHE, its objective is clear—to obtain more information and certainty about one’s health so as to minimise future risks. Most studies on this topic, however, focus only on factors associated with GHE uptake and overlook the shifts in behaviours and attitudes regarding different levels of cost. To fill the gap, this study analyses a dataset of 2068 subjects collected from Hanoi (Vietnam) and its vicinities using the baseline-category logit method. We evaluate the sensitivity of Vietnamese healthcare consumers against two groups of factors (demographic and socioeconomic-cognitive) regarding payment for periodic GHE, which is not covered by insurance. Our study shows that uninsured, married and employed individuals are less sensitive to cost than their counterparts because they value the information in reducing future health uncertainty. The empirical results challenge the objections to periodic health screening by highlighting its utility. The relevance of behavioural economics is further highlighted through a look at the bounded rationality of healthcare consumers and private insurance companies in using and providing the service, respectively