Iterative algorithm for lane reservation problem on transportation network

International audienceIn this paper, we study an NP-hard lane reservation problem on transportation network. By selecting lanes to be reserved on the existing transportation network under some special situations, the transportation tasks can be accomplished on the reserved lanes with satisfying the condition of time or safety. Lane reservation strategy is a flexible and economic method for traffic management. However, reserving lanes has impact on the normal traffic because the reserved lanes can only be passed by the special tasks. It should be well considered choosing reserved lanes to minimize the total traffic impact when applying the lane reservation strategy for the transportation tasks. In this paper, an integer linear program model is formulated for the considered problem and an optimal algorithm based on the cut-and-solve method is proposed. Some new techniques are developed for the cut-and-solve method to accelerate the convergence of the proposed algorithm. Numerical computation results of 125 randomly generated instances show that the proposed algorithm is much faster than a MIP solver of commercial software CPLEX 12.1 to find optimal solutions on average computing time

Dispositif innovant de frein automobile par le volant, intégré à un système de direction de type Steer-by-Wire (dédié aux personnes paraplégiques)

La réflexion portée par cette thèse vise l amélioration de l accès à la conduite automobile aux personnes paraplégiques. Il s agit de développer une solution innovante pour l assistance à la conduite automobile, en employant la technologie X-by-Wire. Une expertise a été réalisée afin d évaluer l existant dans ce domaine et identifier le manquant. A l issue de cette étape cruciale, un nouveau concept de frein par action sur le volant, couplé à un système de direction filo-commandé Steer-by-Wire a été proposé. Nous avons pu mettre en évidence les avantages apportés en matière de sécurité et d ergonomie, en étalant l utilisation même aux conducteurs valides. La partie dominante de cette thèse a été orientée vers une étude théorique approfondie, touchant à la modélisation, simulation et validation de quelques processus dynamiques, qui interviennent dans le fonctionnement du concept proposé. Dans ce contexte, un modèle dynamique du buste en situation de conduite a été établi et validé expérimentalement. L influence du mouvement de tangage du véhicule a été également abordée. Un modèle dynamique d un système de direction Steer-by-Wire a été proposé et expérimenté pour reproduire un retour haptique au volant assez réaliste. Afin de concrétiser l idée, un démonstrateur a été fabriqué, doté de deux servomoteurs pour la création et la gestion des retours d efforts freinage et volant. La solution mécanique retenue, nous a permis d intégrer une assistance active au freinage d urgence. Enfin, un banc d essai avec acquisition de données sur PC en temps réel a été réalisé avec le démonstrateur. Des résultats théoriques et expérimentaux concluants et prometteurs ont été dévoilésReflection carried by this thesis aims to improve access to automotive driving for paraplegics people. That consists to develop an innovative solution for driving assistance by using X-by-Wire technology. Expertise has been achieved beforehand in order to evaluate the existing devices in this field and explore new open ways. After this crucial step, a new concept of braking handwheel coupled to a steering-by-wire system was proposed. We showed the relevant advantages provided by the proposed device in the safety and ergonomics domains, by spreading its use also to the valid drivers. The main axis of this thesis was dedicated to a detailed theoretical study, involving modeling, simulation and validation of some dynamic processes, influencing operation of the proposed concept. In this context, a dynamic model of the driver's bust in driving situation has been established and validated experimentally. The influence of the pitching movement of the vehicle was also discussed. A dynamic model for a steering-by-wire system was developed and tested to reproduce a realistic handwheel feedback. In order to concretize our idea, a demonstrator has been designed and created, by using two DC engines to provide and manage feedbacks of braking and steering on handwheel. The chosen mechanical solution allowed us to integrate an active assistance in emergency braking. Finally, experiments were realized with prototype by using data acquisition on PC in real time. Interesting and promising theoretical and experimental results were exposed.EVRY-Bib. électronique (912289901) / SudocSudocFranceF

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Commande multivariable robuste par les approches LQG/LTR et H-infini. Application a un helicoptere

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 84498 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Experimental vehicle longitudinal control using a second order sliding mode technique

International audienceThis paper presents an experimental implementation of a shared vehicle longitudinal controller at low speed. The main objective is the increase of traffic capacity while improving safety and comfort. The longitudinal control method used is based on a second order sliding mode technique. The central controller is based on the management of inter-vehicular spacing in relation to vehicle speed. Results are presented both by simulation and by use of an experimental process with a vehicle prototype which is equipped with the required sensors and actuators. A number of scenarios are tested under usual traffic conditions such as stop-and-go, stopping at obstacles and car-following with merging/overtaking. Finally, the positive impact of such a system is given in terms of traffic capacity enhancement and collision gravity reduction

Design of a class of reduced order unknown inputs nonlinear observer for fault diagnosis

International audienceIn this paper the problem of fault detection in non-linear systems is considered. Our goal is to extend the unknown inputs observer approach to nonlinear systems. The approach consists of two stages. At first stage, a change of coordinates is found that decoupages the nonlinear system into two subsystems: one which is independent of the unknown inputs and another with the states that can be expressed as linear combinations of the outputs and the states of the first subsystem. Secondly a nonlinear observer is designed for the former. The use of such observer in robust fault detection purposes is then discussed, and finally illustrated by a numerical example

Robust Handling Improvement of Four Wheel Steering Vehicles

International audienceThis paper presents coprime factors and LFT based feedforward and feedback H1 control of four wheel steering vehicle handling improvement. Control synthesis uses a linear vehicle model which includes the yaw motion and disturbance input with road adhesion variations. The synthesis procedure allows the separate processing of the robust yaw damping, disturbance rejection and side slip angle minimization or model matching. The control is applied to the rear wheels by combination of the driver input and feedback of the yaw rate. The synthesized controller is tested on a nonlinear model in both disturbance rejection and driver imposed yaw reference tracking maneuvers

Estimate Based Hinfini Compensator: Application to Robust Automatic Steering

International audienceUsing the results of the linear sub-state estimation and of the linear matrix inequality (LMI), we develop a Luenberger low - order unknown input observer/controller, which gives full unbiased state estimation and H∞ disturbance attenuation. This method is designed in a nonstandard case: an output-disturbance free system, it's based on the bounded real lemma, and the resultant design algorithms are two Riccati inequalities

Système d'assistance à la conduite pour véhicules à deux-roues motorisés

À l'heure actuelle, le deux-roues motorisé (DRM) constitue un moyen de transport de plus en plus convoité, notamment pour les possibilités qu'il offre d'esquiver les engorgements de trafic. Ce constat est justifié par le nombre de DRM circulant quotidiennement et impliquant un trafic de plus en plus croissant. Néanmoins, ce phénomène conduit à l'explosion du nombre d accidents et par conséquent un grand nombre de victimes classant ainsi, les DRM dans la catégorie des modes de transport particulièrement dangereux et ses utilisateurs dans celle des usagers très vulnérables. A première vue, le développement des aides à la conduite actives pourrait résoudre le problème de contrôlabilité du véhicule mais cette solution n'est plus envisageable dès lors qu'il s'agit de pertes de contrôle irréversibles qui constituent, par ailleurs un pourcentage très important des accidents de DRM en tant que véhicule seul. En effet, ce type de système intervient, alors que le véhicule se trouve déjà dans une situation dégradée. De plus, l adaptabilité des aides actives sur les véhicules à deux roues motorisés reste problématique. Actuellement, l'accent est mis sur le développement des systèmes de sécurité prévenant le conducteur de DRM suffisamment en amont d'un danger pour éviter la situation conflictuelle, c'est le cas des aides préventives. Ce travail de thèse s'inscrit dans ce cadre et y contribue au niveau de la modélisation, l'identification, l'estimation d'état, l'analyse de la dynamique limite et la mise en place d'une plate-forme expérimentale. Ainsi, plusieurs points ont été traités: Modélisation du système Véhicule-Infrastructure-Conducteur (V-I-C). Développement d observateurs pour l estimation des variables d états et des entrées inconnues. Mise en place d un modèle vitesse limite, servant de référence pour l unité d avertissement, qui tient compte de plusieurs critères (dynamique du véhicule, comportement du conducteur, géométrie de la route). Identification d'un modèle mathématique propre au véhicule prototype (Scooter). Mise en place d une plate-forme expérimentale qui s'articule autour de l'instrumentation d'un scooter par un ensemble de capteurs et centrale d'enregistrement.Nowadays, the use of Powered Two Wheeled (PTW) vehicles is constantly growing, upsetting driving practices and road traffic. Unfortunately, this expansion is also inflected by an important increase of motorcycle's fatalities (20 times higher when driving a car). Recent statistics confirm this observation and consider riders as the most vulnerable road users. In 2010, the French Agency of Road Safety made a finding of around 1000 deaths (25% of traffic fatalities), while the traffic proportion of motorcycles does not exceed 1%. Several research programs are launched to answer this issue and to find solutions in term of preventive and / or active security systems. At first sight, the development of active driving assistance could solve the problem of motorcycle's controllability. The safety systems are not enough or efficient when situations are irreversible. Example of poor cornering which is responsible for most bike accidents involving single-vehicle motorcycle crashes. Indeed, this type of system occurs while the vehicle is still in a degraded situation. In addition, the adaptability of active assistance of PTW vehicles remains dangerous. Currently, the focus is on the development of safety systems warning riders sufficiently before hazardous situations.The present PhD thesis aims into this framework and gives several contributions in terms of: modeling, identification, state estimation and study of dynamic limit applied to an experimental benchmark. Thus, several points were studied: Modeling of System Driver-Vehicle-Infrastructure (D-V-I). Development of observers to estimate the state variables and unknown inputs. Establishment of a model of limit speed, as a reference for the unity of warning, which takes into account several criteria (vehicle dynamics, driver behavior, road geometry). Identification of a mathematical model specific to the prototype vehicle (Scooter). Establishment of an experimental platform which is based on the instrumentation of a Scooter with a set of sensors and central registration.EVRY-Bib. électronique (912289901) / SudocSudocFranceF