8 research outputs found
Mitigating Software-Instrumentation Cache Effects in Measurement-Based Timing Analysis
Measurement-based timing analysis (MBTA) is often used to determine the timing behaviour of software programs embedded in safety-aware real-time systems deployed in various industrial domains including automotive and railway. MBTA methods rely on some form of instrumentation, either at hardware or software level, of the target program or fragments thereof to collect execution-time measurement data. A known drawback of software-level instrumentation is that instrumentation itself does affect the timing and functional behaviour of a program, resulting in the so-called probe effect: leaving the instrumentation code in the final executable can negatively affect average performance and could not be even admissible under stringent industrial qualification and certification standards; removing it before operation jeopardizes the results of timing analysis as the WCET estimates on the instrumented version of the program cannot be valid any more due, for example, to the timing effects incurred by different cache alignments. In this paper, we present a novel approach to mitigate the impact of instrumentation code on cache behaviour by reducing the instrumentation overhead while at the same time preserving and consolidating the results of timing analysis
Fine-Grain Iterative Compilation for WCET Estimation
Compiler optimizations, although reducing the execution times of programs, raise issues in static WCET estimation techniques and tools. Flow facts, such as loop bounds, may not be automatically found by static WCET analysis tools after aggressive code optimizations. In this paper, we explore the use of iterative compilation (WCET-directed program optimization to explore the optimization space), with the objective to (i) allow flow facts to be automatically found and (ii) select optimizations that result in the lowest WCET estimates. We also explore to which extent code outlining helps, by allowing the selection of different optimization options for different code snippets of the application
Semi-Clairvoyance in Mixed-Criticality Scheduling
In the Vestal model of mixed-criticality systems, jobs are characterized by multiple different estimates of their actual, but unknown, worst-case execution time (WCET) parameters. Prior work on mixed-criticality scheduling theory assumes that the execution duration of a job is only revealed by actually executing the job through to completion. We consider a different *semi-clairvoyant* model here, in which it is assumed that upon arrival a job reveals which of its WCET parameters it will respect. We identify circumstances under which this is a reasonable model, and design and evaluate scheduling algorithms appropriate for this model. We show that such semi-clairvoyance yields a significant quantifiable benefit over non-clairvoyance, in terms of both the complexity of schedulability analysis and the speedup needed to ensure schedulability
Proceedings of Junior Researcher Workshop on Real-Time Computing
It is our great pleasure to welcome you to Junior Researcher Workshop on Real-Time Computing 2007, which is held conjointly with the 15th conference on Real-Time and Network Systems (RTNS'07). The first successful edition was held conjointly with the French Summer School on Real-Time Systems 2005 (http://etr05.loria.fr). Its main purpose is to bring together junior researchers (Ph.D. students, postdoc, ...) working on real-time systems. This workshop is a good opportunity to present our works and share ideas with other junior researchers and not only, since we will present our work to the audience of the main conference. In response to the call for papers, 14 papers were submitted and the international Program Committee provided detailed comments to improve these work-in-progress papers. We hope that our remarks will help the authors to submit improved long versions of theirs papers to the next edition of RTNS. JRWRTC'07 would not be possible without the generous contribution of many volunteers and institutions which supported RTNS'07. First, we would like to express our sincere gratitude to our sponsors for their financial support : Conseil Général de Meuthe et Moselle, Conseil Régional de Lorraine, Communauté Urbaine du Grand Nancy, Université Henri Poincaré, Institut National Polytechnique de Lorraine and LORIA and INRIA Lorraine. We are thankful to Pascal Mary for authorizing us to use his nice picture of “place Stanislas” for the proceedings and web site (many others are available at www.laplusbelleplacedumonde.com). Finally, we are most grateful to the local organizing committee that helped to organize the conference
Urubu: energy scavenging in wireless sensor networks
For the past years wireless sensor networks (WSNs) have been coined as one of the most
promising technologies for supporting a wide range of applications. However, outside the
research community, few are the people who know what they are and what they can offer.
Even fewer are the ones that have seen these networks used in real world applications. The
main obstacle for the proliferation of these networks is energy, or the lack of it. Even
though renewable energy sources are always present in the networks environment,
designing devices that can efficiently scavenge that energy in order to sustain the operation
of these networks is still an open challenge.
Energy scavenging, along with energy efficiency and energy conservation, are the current
available means to sustain the operation of these networks, and can all be framed within
the broader concept of “Energetic Sustainability”. A comprehensive study of the several
issues related to the energetic sustainability of WSNs is presented in this thesis, with a
special focus in today’s applicable energy harvesting techniques and devices, and in the
energy consumption of commercially available WSN hardware platforms.
This work allows the understanding of the different energy concepts involving WSNs and
the evaluation of the presented energy harvesting techniques for sustaining wireless sensor
nodes. This survey is supported by a novel experimental analysis of the energy
consumption of the most widespread commercially available WSN hardware platforms.Há já alguns anos que as redes de sensores sem fios (do Inglês Wireless Sensor Networks -
WSNs) tĂŞm sido apontadas como uma das mais promissoras tecnologias de suporte a uma
vasta gama de aplicações. No entanto, fora da comunidade cientĂfica, poucas sĂŁo as
pessoas que sabem o que elas sĂŁo e o que tĂŞm para oferecer. Ainda menos sĂŁo aquelas que
já viram a sua utilização em aplicações do dia-a-dia. O principal obstáculo para a
proliferação destas redes é a energia, ou a falta dela. Apesar da existência de fontes de
energia renováveis no local de operação destas redes, continua a ser um desafio construir
dispositivos capazes de aproveitar eficientemente essa energia para suportar a operação
permanente das mesmas.
A colheita de energia juntamente com a eficiência energética e a conservação de energia,
sĂŁo os meios disponĂveis actualmente que permitem a operação permanente destas redes e
podem ser todos englobados no conceito mais amplo de “Sustentabilidade Energética”.
Esta tese apresenta um estudo extensivo das várias questões relacionadas com a
sustentabilidade energética das redes de sensores sem fios, com especial foco nas
tecnologias e dispositivos explorados actualmente na colheita de energia e no consumo
energético de algumas plataformas comercias de redes de sensores sem fios.
Este trabalho permite compreender os diferentes conceitos energéticos relacionados com as
redes de sensores sem fios e avaliar a capacidade das tecnologias apresentadas em suportar
a operação permanente das redes sem fios. Este estudo é suportado por uma inovadora
análise experimental do consumo energético de algumas das mais difundidas plataformas
comerciais de redes de sensores sem fios
Manipulador aéreo con brazos antropomórficos de articulaciones flexibles
[Resumen] Este artĂculo presenta el primer robot manipulador aĂ©reo con dos brazos antropomĂłrficos diseñado para aplicarse en tareas de inspecciĂłn y mantenimiento en entornos industriales de difĂcil acceso para operarios humanos. El robot consiste en una plataforma aĂ©rea multirrotor equipada con dos brazos antropomĂłrficos ultraligeros, asĂ como el sistema de control integrado de la plataforma y los brazos. Una de las principales caracterĂsticas del manipulador es la flexibilidad mecánica proporcionada en todas las articulaciones, lo que aumenta la seguridad en las interacciones fĂsicas con el entorno y la protecciĂłn del propio robot. Para ello se ha introducido un compacto y simple mecanismo de transmisiĂłn por muelle entre el eje del servo y el enlace de salida. La estructura en aluminio de los brazos ha sido cuidadosamente diseñada de forma que los actuadores estĂ©n aislados frente a cargas radiales y axiales que los puedan dañar. El manipulador desarrollado ha sido validado a travĂ©s de experimentos en base fija y en pruebas de vuelo en exteriores.Ministerio de EconomĂa y Competitividad; DPI2014-5983-C2-1-