Some Issues In Model-Based Development for Embedded Control Systems

Abstract This presentation aims to discuss the needs for better and more solid foundations of model-based development in embedded control systems. Three particular points are discussed: a comparison between modelbased development in control and in computer sciences, the need for a sampling theory of discrete event systems and the need for precise implementation methods based on preemptive scheduling

A Unifying View of Loosely Time-Triggered Architectures

Cyber-Physical Systems require distributed architectures to support safety critical real-time control. Hermann Kopetz' Time-Triggered Architecture (TTA) has been proposed as both an architecture and a comprehensive paradigm for systems architecture, for such systems. TTA offers the programmer a logical discrete time compliant with synchronous programming, together with timing bounds. A clock synchronization protocol is required, unless the local clocks used themselves provide the recquired accuracy. To relax the strict requirements on synchronization imposed by TTA, Loosely Time-Triggered Architectures (LTTA) have been proposed. In LTTA, computation and communication units are all triggered by autonomous, unsynchronized, clocks. Communication media act as shared memories between writers and readers and communication is non blocking. This is at the price of communication artifacts (such as duplication or loss of data), which must be compensated for by using some "LTTA protocol". In this paper we pursue our previous work by providing a unified presentation of the two variants of LTTA (token- and time-based), with simplified analyses. We compare these two variants regarding performance and robustness and we provide ways to combine them. This report was prepared for a lecture in Gérard Berry's seminar series at the Collège de France, March 5, 2014; it is a corrected version of a paper, which appeared at Emsoft'2010. It is dedicated to our close friend Paul Caspi who died in April 2012.Les infrastructures de calcul distribuées pour le contrôle des systèmes embarqués critiques requièrent des propriétés particulières destinées à préserver les caractéristiques attendues du contrôleur. Les architectures TTA (Time-Triggered Architectures) ont été proposées par Hermann Kopetz, à la fois comme une architecture de calcul et comme une méthodologie de conception des systèmes. TTA offre au programmeur un temps logique conforme à celui de la programmation synchrone, avec en outre un contrôle strict du temps. Il requiert un protocole de synchronisation entre les horloges du système réparti. Pour affaiblir ces hypothèses, les architectures LTTA (Loosely Time-Triggered Architectures) ont été proposées récemment. Dans LTTA, les calculs et les communications sont rythmées par des horloges locales, non synchronisées. Les supports de communication se comportent comme des mémoires partagées. La communication est donc non-bloquante. Ce type de communiccation crée évidemment des artefacts à combattre par un protocole dit "LTTA". Dans cet article nous présentons une approche unifiée des deux techniques connues pour ce type de protocole, reposant sur l'usage, soit de jetons, soit du temps. On compare ces deux variantes et on étudie leur performance. Le présent rapport est une version corrigée d'un article paru à Emsoft'2010. Il est dédié à notre très cher ami Paul Caspi, décédé en Avril 2012

A Unifying View of Loosely Time-Triggered Architectures

Cyber-Physical Systems require distributed architectures to support safety critical real-time control. Hermann Kopetz' Time-Triggered Architecture (TTA) has been proposed as both an architecture and a comprehensive paradigm for systems architecture, for such systems. TTA offers the programmer a logical discrete time compliant with synchronous programming, together with timing bounds. A clock synchronization protocol is required, unless the local clocks used themselves provide the recquired accuracy. To relax the strict requirements on synchronization imposed by TTA, Loosely Time-Triggered Architectures (LTTA) have been proposed. In LTTA, computation and communication units are all triggered by autonomous, unsynchronized, clocks. Communication media act as shared memories between writers and readers and communication is non blocking. This is at the price of communication artifacts (such as duplication or loss of data), which must be compensated for by using some "LTTA protocol". In this paper we pursue our previous work by providing a unified presentation of the two variants of LTTA (token- and time-based), with simplified analyses. We compare these two variants regarding performance and robustness and we provide ways to combine them. This report was prepared for a lecture in Gérard Berry's seminar series at the Collège de France, March 5, 2014; it is a corrected version of a paper, which appeared at Emsoft'2010. It is dedicated to our close friend Paul Caspi who died in April 2012.Les infrastructures de calcul distribuées pour le contrôle des systèmes embarqués critiques requièrent des propriétés particulières destinées à préserver les caractéristiques attendues du contrôleur. Les architectures TTA (Time-Triggered Architectures) ont été proposées par Hermann Kopetz, à la fois comme une architecture de calcul et comme une méthodologie de conception des systèmes. TTA offre au programmeur un temps logique conforme à celui de la programmation synchrone, avec en outre un contrôle strict du temps. Il requiert un protocole de synchronisation entre les horloges du système réparti. Pour affaiblir ces hypothèses, les architectures LTTA (Loosely Time-Triggered Architectures) ont été proposées récemment. Dans LTTA, les calculs et les communications sont rythmées par des horloges locales, non synchronisées. Les supports de communication se comportent comme des mémoires partagées. La communication est donc non-bloquante. Ce type de communiccation crée évidemment des artefacts à combattre par un protocole dit "LTTA". Dans cet article nous présentons une approche unifiée des deux techniques connues pour ce type de protocole, reposant sur l'usage, soit de jetons, soit du temps. On compare ces deux variantes et on étudie leur performance. Le présent rapport est une version corrigée d'un article paru à Emsoft'2010. Il est dédié à notre très cher ami Paul Caspi, décédé en Avril 2012

Distributing Automata for Asynchronous Networks of Processors

This paper addresses the problem of distributed program synthesis. In the first part, we formalize the distribution process and prove its correctness, i.e. that the initial centralized program's behavior is equivalent to the corresponding distributed's one. In order to achieve that, we first represent the program by a finite transition system, labeled by the program's actions. Then we derive an independence relation over the actions from the control and data dependencies. This leads to represent the program by an order-automaton, whose transitions are labeled partial orders coding for an action and its dependencies with other actions. In the second part, we show how such an order-automaton can be practically used to derive a distributed program

First NuSTAR Limits on Quiet Sun Hard X-Ray Transient Events

We present the first results of a search for transient hard X-ray (HXR) emission in the quiet solar corona with the \textit{Nuclear Spectroscopic Telescope Array} (\textit{NuSTAR}) satellite. While \textit{NuSTAR} was designed as an astrophysics mission, it can observe the Sun above 2~keV with unprecedented sensitivity due to its pioneering use of focusing optics. \textit{NuSTAR} first observed quiet Sun regions on 2014 November 1, although out-of-view active regions contributed a notable amount of background in the form of single-bounce (unfocused) X-rays. We conducted a search for quiet Sun transient brightenings on time scales of 100 s and set upper limits on emission in two energy bands. We set 2.5--4~keV limits on brightenings with time scales of 100 s, expressed as the temperature T and emission measure EM of a thermal plasma. We also set 10--20~keV limits on brightenings with time scales of 30, 60, and 100 s, expressed as model-independent photon fluxes. The limits in both bands are well below previous HXR microflare detections, though not low enough to detect events of equivalent T and EM as quiet Sun brightenings seen in soft X-ray observations. We expect future observations during solar minimum to increase the \textit{NuSTAR} sensitivity by over two orders of magnitude due to higher instrument livetime and reduced solar background.Comment: 11 pages, 7 figures; accepted for publication in The Astrophysical Journa

A Cost-Effective Design for a Neutrino Factory

There have been active efforts in the U.S., Europe, and Japan on the design of a Neutrino Factory. This type of facility produces intense beams of neutrinos from the decay of muons in a high energy storage ring. In the U.S., a second detailed Feasibility Study (FS2) for a Neutrino Factory was completed in 2001. Since that report was published, new ideas in bunching, cooling and acceleration of muon beams have been developed. We have incorporated these ideas into a new facility design, which we designate as Study 2B (ST2B), that should lead to significant cost savings over the FS2 design.Comment: 46 pages, 38 figures; to be submitted to Physical Review Special Topics: Accelerators and Beam

First Results for Solar Soft X-ray Irradiance Measurements from the Third Generation Miniature X-Ray Solar Spectrometer

Three generations of the Miniature X-ray Solar Spectrometer (MinXSS) have flown on small satellites with the goal "to explore the energy distribution of soft X-ray (SXR) emissions from the quiescent Sun, active regions, and during solar flares, and to model the impact on Earth's ionosphere and thermosphere". The primary science instrument is the Amptek X123 X-ray spectrometer that has improved with each generation of the MinXSS experiment. This third generation MinXSS-3 has higher energy resolution and larger effective area than its predecessors and is also known as the Dual-zone Aperture X-ray Solar Spectrometer (DAXSS). It was launched on the INSPIRESat-1 satellite on 2022 February 14, and INSPIRESat-1 has successfully completed its 6-month prime mission. The INSPIRESat-1 is in a dawn-dusk, Sun-Synchronous Orbit (SSO) and therefore has 24-hour coverage of the Sun during most of its mission so far. The rise of Solar Cycle 25 (SC-25) has been observed by DAXSS. This paper introduces the INSPIRESat-1 DAXSS solar SXR observations, and we focus the science results here on a solar occultation experiment and multiple flares on 2022 April 24. One key flare result is that the reduction of elemental abundances is greatest during the flare impulsive phase and thus highlighting the important role of chromospheric evaporation during flares to inject warmer plasma into the coronal loops. Furthermore, these results are suggestive that the amount of chromospheric evaporation is related to flare temperature and intensity.Comment: 43 pages including 19-page Appendix A, 8 figures, 7 table

Avoiding Irrational NeuroLaw Exuberance: A Plea for Neuromodesty

In a 2002 editorial published in The Economist, the following warning was given: Genetics may yet threaten privacy, kill autonomy, make society homogeneous and gut the concept of human nature. But neuroscience could do all of these things first. The genome was fully sequenced in 2001, and there has not been one resulting major advance in therapeutic medicine since. Thus, even in its most natural applied domain-medicine-genetics has not had the far-reaching consequences that were envisioned. The same has been true for various other sciences that were predicted to revolutionize the law, including behavioral psychology, sociology, psychodynamic psychology, and others. This will also be true of neuroscience, which is simply the newest science on the block. Neuroscience is not going to do the terrible things The Economist fears, at least not for the foreseeable future. Neuroscience has many things to say but not nearly as much as people would hope, especially in relation to law. At most, in the near to intermediate term, neuroscience may make modest contributions to legal policy and case adjudication. Nonetheless, there has been irrational exuberance about the potential contribution of neuroscience, an issue I have addressed previously and referred to as Brain Overclaim Syndrome. I first consider the law\u27s motivation and the motivation of some advocates to turn to science to solve the very hard normative problems that law addresses. Part III discusses the law\u27s psychology and its concepts of the person and responsibility. The next Part considers the general relation of neuroscience to law, which I characterize as the issue of translation. Part V canvasses various distractions that have bedeviled clear thinking about the relation of scientific, causal accounts of behavior to responsibility. The following Part examines the limits of neurolaw and Part VII considers why neurolaw does not pose a genuinely radical challenge to the law\u27s concepts of the person and responsibility. Part VIII makes a case for cautious optimism about the contribution neuroscience may make to law in the near and intermediate term. A brief conclusion follows..