279 research outputs found
Formal synthesis of analytic controllers for sampled-data systems via genetic programming
No full textThis paper presents an automatic formal controller synthesis method for nonlinear sampled-data systems with safety and reachability specifications. Fundamentally, the presented method is not restricted to polynomial systems and controllers. We consider a periodically switched controllers based on a Control Lyapunov Barrier-like function. The proposed method utilizes genetic programming to synthesize these function in analytic form, as well as the controller modes. Correctness of the controller are subsequently verified by means of a Satisfiability Modulo Theories solver. Effectiveness of the proposed methodology is demonstrated on multiple systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Tamas Keviczk
Formal synthesis of analytic controllers: An evolutionary approach
No full textControl design for modern safety-critical cyber-physical systems still requires significant expert-knowledge, since for general hybrid systems with temporal logic specifications there are no constructive methods. Nevertheless, in recent years multiple approaches have been proposed to automatically synthesize correct-by-construction controllers. However, typically these methods either result in enormous look-up tables, require online optimization, or are highly dependent on expert-knowledge. The goal of this thesis is to propose a novel approach that overcomes these limitations, i.e. to propose a framework for automatic controller synthesis, capable of synthesizing closed-form controllers for hybrid systems with temporal logic specifications, without a heavy reliance on expert-knowledge. To this end, we draw inspiration from the human design process and utilize two methods that show great similarities to it, namely evolutionary algorithms and counterexample-guided inductive synthesis (CEGIS). Specifically, we use genetic programming (GP), an evolutionary algorithm capable of evolving entire programs. This makes it possible to automatically discover the structure of a solution. Moreover, it enables the synthesis of compact closed-form controllers, circumventing the need for look-up tables or online optimization. In combination with GP, we use the concept of CEGIS to refine candidate solutions based on counterexamples, until the controller is guaranteed to satisfy the desired specification. In this thesis we propose two CEGIS-based synthesis frameworks, which differ in the employed verification paradigms, namely utilizing either (co-synthesized) Lyapunov-like functions or reachability analysis. Both frameworks result in correct-by-construction compact closed-form controllers, where the use of expert-knowledge is optional. Both frameworks are capable of synthesizing sampled-data controllers, enabling implementation in embedded hardware with limited memory and computation power, forming a stepping stone towards faster automation.Team Tamas Keviczk
De Suzanne Verdier a Anna Barbauld: Una revolución ecofeminista de las Geórgicas
No full textThis article explores how the tradition of georgic writing in the early 19th century is reinvented through strong ecofeminist standpoints in France and in England. It focuses on the works of two poets: Suzanne Verdier’s Géorgiques du Midi (Georgics of Southern France, 1799-1812) and Anna Barbauld’s English poem “The Caterpillar” (1815). Through a comparative analysis, this article will question the connections between French and English traditions of the Georgic and observe how female voices emerge at the dawn of Romanticism, with specific ecopolitical claims and poetic representations. Indeed, Verdier dedicates the first canto of her French georgics, “The Silkworm”, to sericulture, an exclusively female practice, which is initially denounced as a form of repressive biopolitics, but later becomes a model of female empowerment and ecological awareness. The author plays with the tradition of Georgics to turn them into an ecofeminist plea. As for Barbauld, she was a friend of Erasmus Darwin, whose essay Phytologia, though not openly political, was connected to radicalism. Both Darwin’s and Barbauld’s work imply, as Verdier’s poem does, that reforming agriculture would lead to a global social and political change. Barbauld prolonged this reflection by questioning the place of women in this new world in a context of political turmoil with the Napoleonic wars. Yet, despite the hostility between France and England during this period, this inaugural ecological reflection may also constitute a social and poetical network propitious to the inter-fertilization of revolutionary ideas, knitting secret silk threads of peace between the two countries, and the promise of a fertile future.Este artículo explora cómo la tradición de la escritura de las geórgicas a principios del siglo XIX se reinventa a través de puntos de vista ecofeministas en Francia e Inglaterra. Se centra en las obras de dos poetas: las Géorgiques du Midi (Geórgicas del Sur de Francia, 1799-1812) de Suzanne Verdier y el poema en inglés de Anna Barbauld "The Caterpillar" (“La Oruga”, 1815). A través de un análisis comparativo, este artículo cuestionará las conexiones entre las tradiciones francesa e inglesa de las geórgicas y observará cómo emergen las voces femeninas en los albores del Romanticismo, con reclamos ecopolíticos específicos y nuevas representaciones poéticas. De hecho, Verdier dedica el primer canto de sus geórgicas francesas, "El gusano de seda", a la sericultura, una práctica exclusivamente femenina, que inicialmente se presenta como una forma de biopolítica represiva, pero luego se convierte en un modelo de empoderamiento femenino y conciencia ecológica. En cuanto a Barbauld, era amiga de Erasmus Darwin, cuyo ensayo Phytologia, aunque no abiertamente político, estaba relacionado con el radicalismo. El trabajo de Darwin y Barbauld implica, así como lo hace el poema de Verdier, que reformar la agricultura conduciría a un cambio social y político. Barbauld prolongó esta reflexión para cuestionar el lugar de las mujeres en este nuevo mundo en un contexto de agitación política con las guerras napoleónicas. Sin embargo, a pesar de la hostilidad entre Francia e Inglaterra durante este período, esta reflexión ecológica inaugural también puede constituir una red social y poética propicia para el intercambio de ideas revolucionarias, tejiendo hilos secretos de paz entre los dos países, y la promesa de un futuro fértil
Geometric control of an under-actuated balancing robot
No full textBall-balancing robots, or Ballbots, are under-actuated omni-directional mobile robots that balance on top of a single ball. The under-actuated nature arises from the fact that both position and attitude of the robot are actuated by the same actuators. This thesis introduces a geometric approach to the control of ball-balancing robots. In this approach, a new full 3D model is derived using screw theory. Based on this model, a geometric observer and geometric controller are proposed. Two methodologies are implemented, a computed torque controller and a sliding mode controller, that can track the attitude of the robot on either the special orthogonal group SO(3) or the 2-sphere S^2. Position control is achieved through the use of the relation between the desired linear acceleration and the attitude of the robot. The resulting desired attitude is tracked by one of the geometric attitude controllers. Simulation results show the effectiveness of the proposed controllers. The proposed sliding mode controller is shown to be more robust to model uncertainties. The position controller is shown to be able to control the position and follow trajectories, but overall global stability is not guaranteed. Recommendations are made to improve the performance. For the geometric observer, stability is shown under a set of assumptions. The work is concluded with a set of experiments on a real platform.Systems and ControlDelft Center of Systems and ControlMechanical, Maritime and Materials Engineerin
The New Corporation in Europe. Bruegel Policy Brief 2008/07, September 2008
Get PDFThis Policy Briefing examines how Europe’s corporations are changing the way they do business since the 2004 EU Enlargement. Dalia Marin argues that firms are adapting to heightening global competition by shifting decision-making processes. The author gives policy recommendations in the areas of EU neighbourhood and trade policies
Formes d'entreprises et innovations relationnelles : conséquences pour l'intervention publique
No full textÉric Verdier, Unternehmensformen und Neuerungen in den sozio-ökonomischen Beziehungen : Folgen für den staatlichen Eingriff (Fallstudie eines Wirtschaftsweiges).
Die verhältnismässig bessere Widerstandsfähigkeit der Klein- und Mittelunternehmen gegen die Krise in ihrer ersten Phase wird oft als eine Rehabilitation des Kleinunternehmens betrachtet, wegen seiner Unabhängigkeit gegenüber den bürokratischen Betriebsregeln, welche die Schwerindustrie kennzeichen wurden. Auf einem Gegenbeispiel basierend (dem französischen Metall-Werkzeugmaschinenbau, in dem die Klein- und Mittelunternehmen bei weitem vorherrschen), will der Verfasser zeigen, dass die Beseitigung des gegenwärtigen Disfunktionen teilweise auf dem Aufbau neuer Formen der wirtschaftlichen Koordinierung beruht.
Tatsächlich kann das durch eine sehr persönliche Geschäftsführung gekennzeichnete Kleinunternehmen auf mittlerer und langer Frist bedeutende Schwierigkeiten treffen, um sich der Entwicklung des Marktes anzupassen und sie vor allem vorauszuschätzen. Dagegen scheint das Mitwirken unterschiedlicher Investitionen ein Pfand für die Flexibilität und gleichzeitig für die Einheitlichkeit der Industrie zu bestellen, wie einige Vergleiche mit auslândischen Beispielen es sehen lassen. Noch mehr als die Automatisierung steht dann auf dem Spiel die Neufassung nicht nur der Funktionsstrukturen der Klein- und Mittelbetriebe, insbesondere im kaufmännischen Bereich, sondern auch der Beziehungen mit der sozio-ökonomischen Umwelt : die auf der Kooperation (anstatt der Anweisung) beruhende Verbindung zu den Zulieferern, der bessere Zugang zu den Mitteln des Schul-, Finanz-und Forschungswesens, besonders anhand von überbetrieblichen Einrichtungen.
Der staatliche Eingriff kann den Übergang von einem Organisationsmodell zu dem anderen wesentlich fördem, unter der Bedingung, dass er die allgemeinen Lösungen bzw. die von den spezifischen Kennzeichen der Kleinunternehmen zu entfernten Formeln ausschliesst.Éric Verdier, Types of firms and relational innovations : Effects on State intervention.
The better resistance of small and medium sized firms to the first phase of the crisis is often attributed to a rehabilitation of the kind of small firm free from the bureaucratic rules of operation characterizing major industries. Using an example that disproves this tendency - the French metal-working machine tool sector, where small firms predominate - the author attempts to show that the present disorders have been overcome, partly, by building up new forms of economic coordination.
Indeed, small firms, characterized by highly personalized management, may, on a middle or long-term basis, encounter serious difficulties in keeping up with changes in the market, and particularly in anticipating them. On the other hand, the simultaneous existence of varied investments (as suggested by comparison with examples found abroad) seems to be a sign both of flexibility and of industrial coherence. Even more than automation, reorganization is involved, not only of the operational structures of the small firm, especially on the sales side, but also of relationships with the economic and social environnement : sub-contracting based on cooperation rather than on orders, easier access to the resources of educational, financial and research organizations, particularly via the support of interfirm services.
State intervention may considerably favour the transition from one type of organization to the other, as long as it keeps away from general rules that are too far removed from the specific needs of small, personal firms.La meilleure résistance des PME à la première phase de la crise est souvent assimilée à une réhabilitation du modèle de la petite entreprise dégagée des règles de fonctionnement bureaucratiques qui caractériseraient la grande industrie - s'appuyant sur un contre exemple, le secteur français de la machine-outil à métaux où prédominent très largement les PME -, l'auteur s'attache à montrer que le dépassement des dérèglements actuels repose, partiellement, sur la construction de nouvelles formes de coordination économique.
En effet, la PME, caractérisée par une gestion très personnalisée peut sur le moyen ou long terme rencontrer de graves difficultés à suivre les évolutions du marché et surtout à les anticiper. Par contre, la co-occurence d'investissements diversifiés semble constituer, ainsi que le suggèrent des comparaisons avec des exemples étrangers, un gage tout à la fois de flexibilité et de cohésion du tissu industriel. Plus encore que l'automatisation, est alors en jeu une refonte, non seulement des structures fonctionnelles de la PME, en particulier dans le domaine commercial, mais aussi des relations avec l'environnement économique et social : rapports de sous-traitance fondés sur la coopération plutôt que sur la prescription, meilleur accès aux ressources des systèmes éducatif, financier et de recherche, grâce en particulier à l'appui d'institutions inter-entreprises.
L'intervention publique peut considérablement favoriser le passage d'un modèle d'organisation à l'autre, à la condition de s'écarter de formules générales et donc trop éloignées des spécificités d'entreprises personnelles de faible taille.Verdier Éric. Formes d'entreprises et innovations relationnelles : conséquences pour l'intervention publique. In: Formation Emploi. N.15, 1986. pp. 3-17
The new corporation in Europe
Get PDFThis Policy Brief examines how Europeâ??s corporations are changing the way they do business since the 2004 EU Enlargement. Dalia Marin argues that firms are adapting to heightening global competition by shifting decision-making processes. The author gives policy recommendations in the areas of EU neighbourhood and trade policies.
L'efficacité de la formation continue dans les PME
No full textThe author forcusses on discrepancies between legal resources and small firms meeds in permanent training : misadaptation to their industrial organization, their specific capacities and absences of industrial strategy. Regrouping users more flexibility in legal norms, decompartmentalizing assistance are some of the solutions for greater efficiency.L'auteur examine l'incidence des dispositifs institutionnels de formation continue sur l'efficacité de leur utilisation par les PME. Les modes d'utilisation des dispositifs légaux s'ajustent mal à la situation des PME : inadaptation à leur organisation industrielle et aux modalités de constitution de leurs compétences, manque de stratégie industrielle d'ensemble. Des formules sont recherchées pour regrouper les utilisateurs, assouplir les normes légales, décloisonner les aides afin d'en obtenir une meilleure efficacité.Verdier Eric. L'efficacité de la formation continue dans les PME. In: Sociologie du travail, 32ᵉ année n°3, Juillet-septembre 1990. pp. 295-320
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