Un algorithme hors-ligne en temps linéaire pour calculer les vitesses du processeur qui minimisent la consommation d'énergie

International audienc

Design of a Hybrid Controller for Autonomous Vehicles Driving on Automated Highways

In this paper we address the problem of the hybrid control of autonomous vehicles driving on automated highways. Vehicles are autonomous, so they do not communicate with each other nor with the infrastructure. Two problems have to be dealt with: A vehicle driving in a single-lane highway must never collide with its leading vehicle; and a vehicle entering the highway at a designated entry junction mustb e able to merge from the merging lane to the main lane, again without any collision. To solve these problems we propose to equip each vehicle with a hybrid controller, consisting of several continuous control laws embedded inside a finite state automaton. The automaton specifies when a given vehicle must enter the highway, merge into the main lane, yield to other vehicles, exit from the high way, and soon. The continuous control laws specify what acceleration the vehicle must have in order to avoid collisions with nearby vehicles. Bycarefully designing these control laws and the conditions guarding the automaton transitions, we are able to demonstrate three important results. Our first result states the initial conditions guaranteeing that a following vehicle never collides with its leading vehicle. Oursecond result extends the first one to a lane of autonomous vehicles.Our third result states that if all the vehicles are equipped with our hybrid controller, then no collision can ever occur and all vehicleseither merge successfully or are forced to drop out when they reach the end of their merging lane. Finally we show the out come of ahighway microsimulation conducted with the SHIFT hybrid simulator developed at UC Berkeley by the PATH group

A formal approach for the synthesis and implementation of fault-tolerant industrial embedded systems

International audienceWe demonstrate the feasibility of a complete workflow to synthesize and implement correct-by-construction fault tolerant distributed embedded systems consisting of real-time periodic tasks. Correct-by-construction is provided by the use of discrete controller synthesis (DCS), a formal method thanks to which we are able to guarantee that the synthesized controlled system guarantees the functionality of its tasks even in the presence of processor failures. For this step, our workflow uses the Heptagon domain specific language and the Sigali DCS tool. The correct implementation of the resulting distributed system is a challenge, all the more since the controller itself must be tolerant to the processor failures. We achieve this step thanks to the libDGALS real-time library (1) to generate the glue code that will migrate the tasks upon processor failures, maintaining their internal state through migration, and (2) to make the synthesized controller itself fault-tolerant

Stability Analysis of a Longitudinal Control Law for Autonomous Vehicles

We focus in this article on the analysis of an existing acceleration law for a following autonomous vehicle with constant time headway goal. We first define a function that measures the positioning of the following vehicle compared to the leading vehicle with respect to the desired time headway. We study the convergence and bounds of this positioning function and prove some key results in an ideal case, i.e., when all accelerations are unbounded. Then we conduct several simulations that validate our theoretical results and show their limitations in real cases, i.e., when the accelerations are technologically bounded. Finally we use decoupling and feedback linearization techniques to derive a new acceleration law whose convergence is always exponential in the ideal case, and we compare both laws

Méthodes logico-numériques pour la vérification des systèmes discrets et hybrides

Cette thèse étudie la vérification automatique de propriétés de sûreté de systèmes logico-numériques discrets ou hybrides. Ce sont des systèmes ayant des variables booléennes et numériques et des comportements discrets et continus. Notre approche est fondée sur l'analyse statique par interprétation abstraite. Nous adressons les problèmes suivants : les méthodes d'interprétation abstraite numériques exigent l'énumération des états booléens, et par conséquent, ils souffrent du probléme d'explosion d'espace d'états. En outre, il y a une perte de précision due à l'utilisation d'un opérateur d'élargissement afin de garantir la terminaison de l'analyse. Par ailleurs, nous voulons rendre les méthodes d'interprétation abstraite accessibles à des langages de simulation hybrides. Dans cette thèse, nous généralisons d'abord l'accélération abstraite, une méthode qui améliore la précision des invariants numériques inférés. Ensuite, nous montrons comment étendre l'accélération abstraite et l'itération de max-stratégies à des programmes logico-numériques, ce qui aide à améliorer le compromis entre l'efficacité et la précision. En ce qui concerne les systèmes hybrides, nous traduisons le langage de programmation synchrone et hybride Zelus vers les automates hybrides logico-numériques, et nous étendons les méthodes d'analyse logico-numérique aux systèmes hybrides. Enfin, nous avons mis en oeuvre les méthodes proposées dans un outil nommé ReaVer et nous fournissons des résultats expérimentaux. En conclusion, cette thèse propose une approche unifiée à la vérification de systèmes logico-numériques discrets et hybrides fondée sur l'interprétation abstraite qui est capable d'intégrer des méthodes d'interprétation abstraite numériques sophistiquées tout en améliorant le compromis entre l'efficacité et la précision.This thesis studies the automatic verification of safety properties of logico-numerical discrete and hybrid systems. These systems have Boolean and numerical variables and exhibit discrete and continuous behavior. Our approach is based on static analysis using abstract interpretation. We address the following issues: Numerical abstract interpretation methods require the enumeration of the Boolean states, and hence, they suffer from the state space explosion problem. Moreover, there is a precision loss due to widening operators used to guarantee termination of the analysis. Furthermore, we want to make abstract interpretation-based analysis methods accessible to simulation languages for hybrid systems. In this thesis, we first generalize abstract acceleration, a method that improves the precision of the inferred numerical invariants. Then, we show how to extend abstract acceleration and max-strategy iteration to logico-numerical programs while improving the trade-off between efficiency and precision. Concerning hybrid systems, we translate the Zelus hybrid synchronous programming language to logico-numerical hybrid automata and extend logico-numerical analysis methods to hybrid systems. Finally, we implemented the proposed methods in ReaVer, a REActive System VERification tool, and provide experimental results. Concluding, this thesis proposes a unified approach to the verification of discrete and hybrid logico-numerical systems based on abstract interpretation, which is capable of integrating sophisticated numerical abstract interpretation methods while successfully trading precision for efficiency.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Circuit Generation for Verification of ESTEREL Programs

We propose in this paper a method that takes external Boolean variables into account for the verification of ESTEREL programs. The intermediate code that we use is a circuit that drives an action table. The circuit represents the control of the program, and the action table manipulates its external variables. The method transforms the actions into Boolean gates and registers acting on nets instead of variables. This involves encoding the input variables into the circuit and decoding output variables. This expansion method has been implemented within the \scdata\ processor and can be used in conjunction with the ESTEREL compiler

Revisiting the bicriteria (length,reliability) multiprocessor static scheduling problem

Our starting point is a dependency task graph and an heterogeneous distributed memory target architecture. We revisit the well studied problem of bicriteria (length,reliability) multiprocessor static scheduling of this task graph onto this architecture. Our first criteria remains the static schedule's length: this is crucial to assess the system's real-time property. For our second criteria, we consider the global system failure rate, seen as if the whole system were a single task scheduled onto a single processor, instead of the usual reliability, because it does not depend on the schedule length like the reliability does (due to its computation in the classical reliability model of Shatz and Wang). Therefore, we control better the replication factor of each individual task of the dependency task graph given as a specification, with respect to the desired failure rate. To solve this bicriteria optimization problem, we take the failure rate as a constraint, and we minimize the schedule length. We are thus able to produce, for a given application task graph and multiprocessor architecture, a Pareto curve of non-dominated solutions, among which the user can choose the compromise that fits his requirements best

A novel bicriteria scheduling heuristics providing a guaranteed global system failure rate

International audienceWe propose a new framework for the (length,reliability) bicriteria static multiprocessor scheduling problem. Our first criterion remains the schedule's length, crucial to assess the system's real-time property. For our second criterion, we consider the global system failure rate, seen as if the whole system were a single task scheduled onto a single processor, instead of the usual reliability, because it does not depend on the schedule length like the reliability does (due to its computation in the classical exponential distribution model). Therefore, we control better the replication factor of each individual task of the dependency task graph given as a specification, with respect to the desired failure rate. To solve this bicriteria optimization problem, we take the failure rate as a constraint, and we minimize the schedule length. We are thus able to produce, for a given dependency task graph and multiprocessor architecture, a Pareto curve of non-dominated solutions, among which the user can choose the compromise that fits his requirements best. Compared to the other bicriteria (length,reliability) scheduling algorithms found in the literature, the algorithm we present here is the first able to improve significantly the reliability, by several orders of magnitude, making it suitable to safety critical systems

Water-Oil Partition Profiling of Ionized Drug Molecules Using Cyclic Voltammetry and a 96-Well Microfilter Plate System

Purpose. A new experimental set-up for studying partitioning of ionizable drugs at the interface between two immiscible electrolyte solutions (ITIES) by amperometry is presented. The method is quite general, as it can be applied to any charged drug molecule. Methods. The procedure is based on 96-well microfilter plates with microporous filters to support 96 organic liquid membranes. The new methodology is first validated using a series of tetra-alkylammonium ions and subsequently used to construct the ion partition diagrams of 3,5-N,N-tetramethylaniline and 2,4-dinitrophenol. The lipophilicity of these drugs was examined by potentiometry and cyclic voltammetry in the NPOE/water system. Results. Cyclic voltammetry resulted in potential-pH profiles of the studied drugs. When the aqueous phase pK a is already known, the logP NPOEof lipophilic drugs could be determined using a very little amount of solvents and drugs. The values of the partition coefficients for the neutral forms agree well with those obtained by potentiometry. Conclusions. The procedure based on commercially available 96-well microfilter plates is shown to be useful for determining logP of ionized drugs in a rapid and efficient wa