Trajectory planning for autonomous vehicle in uncertain environment using evidential grid

International audienc

Pregled znanstvenih napredaka u učinskoj elektronici usmjerenih ka osiguravanju efikasnog rada i dužeg životnog vijeka PEMgorivih ćelija

This article focuses on the main issues that affect the lifetime and performance of proton-exchange membrane fuel cells. The short lifespans of these fuel cells represent a barrier to their massive commercialization and usage in mobile and stationary applications. As fuel cell is a very complex system, a lot of knowledge of different areas is required, such as chemistry, electricity and mechanics, in order to completely understand its operation and all the problems that can occur during it. It is for this reason that an interdisciplinary approach needs to be taken when designing fuel-cell energy systems. This paper focuses on identifying and solving those issues that negatively affect the lifetime and performance of fuel cells. It is hoped that this article would be a valuable aid for power electronics’ researchers and engineers for better understanding the presented issues and a useful guide for solving them with the use of proper power electronic-devices. Initially, the basic operation and structure of a proton-exchange membrane fuel cell is explained. Three main issues that can occur during operation of a mobile or stationary fuel cell energy system are pointed out and discussed in details, on the basis of the state-of-the-art on fuel cell technology. These issues are poor water management, reactant gas starvation and fuel cell current ripple. This article provides answers as to why they occur, how they affect the fuel cell, how they can be mitigated, and what are the future trends within this research field.Članak se osvrće na ključna pitanja koja utječu na vrijeme rada i performanse gorivih ćelija s polimernom membranom kao elektrolitom. Kratak životni vijek gorivih ćelija takve vrste prepreka je njihovoj komercijalizaciji i masovnoj upotrebi u mobilnim i stacionarnim stanicama. Budući da su gorive ćelije komplicirani sustavi potrebno je znanje iz raznih područja kemije, elektrotehnike i mehanike da bi se u potpunosti mogao razumjeti njihov način rada i problemi koji se događaju. Upravo je zbog toga multidisciplinarni pristup nužnost pri razvoju sustava koji koriste gorive ćelije. Ovaj je članak usmjeren prema identifikaciji i rješavanju onih problema koji negativno utječu na životni vijek i performanse gorivih ćelija. Autori se nadaju da će se članak pokazati kao korisna pomoć i vodič istraživačima i inženjerima u domeni učinske elektronike pri susretu s navedenim problemima. Objašnjen je način rada i struktura gorive ćelije s polimernom membranom kao elektrolitom. Izložena su, i diskutirana do u detalje, tri glavna problema sa stajališta trenutačnih spoznaja u području učinske elektronike. Ti problemi su: loše upravljanje vodom, nestanak reaktantnog plina i strujni trzaji u gorivim ćelijama. Objašnjeno je zašto se ovi problemi događaju, kako utječu na gorivu ćeliju, kako ih se može spriječiti i koje su buduće perspektive istraživanja

Thomas Jefferson and Maximilien Robespierre: Encountering Issues of Church and State

This thesis seeks to compare and contrast how Thomas Jefferson and Maximilien Robespierre encountered the issues of church and state during their lifetimes. Both figures were faced with revolution in an Age of Enlightenment and both were undoubtedly influential figures in their respective revolutions. In matters of church and state, both Jefferson and Robespierre argued that the basis of morality the freedom of conscience were essential matters to study. However, the two came to strikingly different conclusions about what role the state should play in religion. Jefferson concluded that there should be a separation of church and state. Robespierre, on the other hand, concluded that the state must be directly involved in religion. Though he praised religious freedom, Robespierre played a leading role in the creation of a state-lead religion. In order to understand these differences, this thesis explores the similarities and differences in their personal faith, geography, culture, and education

Panthéonizations and exhumations : ceremonial reburials in revolutionary France.

During the French Revolution, the Panthéon was created as a national mausoleum to house the remains of the grands hommes of France. Alongside the recently deceased heroes of the Revolution, the deputies of the National Assembly selected illustrious figures from French history to be transferred to the Panthéon. Only two of the selected figures were reburied within the monument: Voltaire and Rousseau. This thesis examines the significance of these ceremonial reburials on the French Revolution. Reburials, although largely ignored in the scholarship of the Revolution, were key to the creation of a modified culture of death which allowed the revolutionaries to move past the Catholic death culture of the ancien regime

Passivity of the Air Supply System of a PEM Fuel Cell Model and Robust PI Control

International audienc

Modélisation et commandes non linéaires du système d air des piles à combustible type PEM (Proton Exchange Membrane)

Le travail de thèse porte sur les systèmes d alimentation en air des piles à combustible type PEM (Proton Exchange Membrane). Une première étape du travail a porté sur la modélisation, et consistait à réduire le modèle dynamique d ordre 4 à un modèle plus simple d ordre 3. Ce dernier a été validé expérimentalement avec une erreur relative moins de 5%. Le modèle réduit a été décomposé en l interconnection de 3 sous-systèmes dont l un est strictement passif en sortie ; et une structure de commande en cascade a été conçue. Une étude de stabilité basée sur la passivité a permis d établir une méthodologie générale pour le réglage de tout type de contrôleur tout en garantissant la stabilité du système bouclé. De plus, une autre étude basée sur les caractéristiques de monotonicité du système a montré que le système est localement asymptotiquement stabilisable autour de tout point d équilibre, par un simple contrôleur proportionnel (p) ou proportionnel-intégral (pi), si la variable de retour est bien choisie. Plusieurs lois de commande ont été étudiées pour le réglage du débit d air du compresseur, et la stoechiométrie de la pile, comme le mode glissant, le rst, l ip, le backstepping, et l ors (output regulation subspaces). Des validations expérimentales ont mis en évidence les performances de la commande par mode glissant du second ordre, algorithme du super-twisting, avec gains variables.This thesis deals with the air supply system of PEM (Proton Exchange Membrane) fuel cells. The first part treats modelling, and consist on the reduction of the 4th order dynamical model into a simpler 3rd order one. The latter has been validated experimentally with a relative error less than 5%. The reduced model has been decomposed into the interconnection of 3 subsystems, with one of them being output strictly passive; and a cascaded control structure has been designed. A passivity based stability study results in a general methodology for tuning any controller, with guaranteed stability of the closed-loop system. Moreover, another stability study, based on the monotonicity characteristics of the system, shows that the system is locally asymptotically stabilisable around any equilibrium point, with a simple proportional or proportional-integral controller, if the feedback variable is well chosen. Many control laws have been designed to regulate the compressor air flow and the oxygen stoechiometry. The used controllers are higher order sliding mode, rst, ip, backstepping, and ors (output regulation subspaces). Experimental validation proves the performance of the second order sliding mode control, precisely, the super-twisting algoritm with variable gains.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Higher-Order Sliding Mode Control for Lateral Dynamics of Autonomous Vehicles, with Experimental Validation

International audienceThis paper presents design and experimental validation of a vehicle lateral controller for autonomous vehicle based on a higher-order sliding mode control. We used the super-twisting algorithm to minimize the lateral displacement of the autonomous vehicle with respect to a given reference trajectory. The control input is the steering angle and the output is the lateral displacement error. The particularity of such a strategy is to take advantage of the robustness of the sliding mode controller against nonlinearities and parametric uncertainties in the model, while reducing chattering, the main drawback of first order sliding mode. To validate the control strategy, the closed-loop system simulated on Matlab-Simulink has been compared to the experimental data acquired on our vehicle DYNA, a Peugeot 308, according to several driving scenarios. The validation shows robustness and good performance of the proposed control approach