3,974 research outputs found

    Time-Based Estimator for Control Reconfiguration of Discrete Event Systems (DES)

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    International audienceIn this paper, we propose a Time-based estimator method to reconfigure manufacturing systems in case of sensor faults detection. The main idea is to replace the information lost by a timed one. In non-faulty behavior, each sensor is defined through two events: activation and deactivation. Our contribution is to define an estimator model of each event based on different clocks to maintain the same desired behavior of the system in a faulty mode (reconfigured)

    Supervisory control of fuzzy discrete event systems with applications to mobile robotics

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    Fuzzy Discrete Event Systems (FDES) were proposed in the literature for modeling and control of a class of event driven and asynchronous dynamical systems that are affected by deterministic uncertainties and vagueness on their representations. In contrast to classical crisp Discrete Event Systems (DES), which have been explored to a sufficient extent in the past, an in-depth study of FDES is yet to be performed, and their feasible real-time application areas need to be further identified. This research work intends to address the supervisory control problem of FDES broadly, while formulating new knowledge in the area. Moreover, it examines the possible applications of these developments in the behavior-based mobile robotics domain. An FDES-based supervisory control framework to facilitate the behavior-based control of a mobile robot is developed at first. The proposed approach is modular in nature and supports behavior integration without making state explosion. Then, this architecture is implemented in simulation as well as in real-time on a mobile robot moving in unstructured environments, and the feasibility of the approach is validated. A general decentralized supervisory control theory of FDES is then established for better information association and ambiguity management in large-scale and distributed systems, while providing less complexity of control computation. Furthermore, using the proposed architecture, simulation and real-time experiments of a tightly-coupled multi-robot object manipulation task are performed. The results are compared with centralized FDES-based and decentralized DES-based approaches. -- A decentralized modular supervisory control theory of FDES is then established for complex systems having a number of modules that are concurrently operating and also containing multiple interactions. -- Finally, a hierarchical supervisory control theory of FDES is established to resolve the control complexity of a large-scale compound system by modularizing the system vertically and assigning multi-level supervisor hierarchies. As a proof-of-concept example to the established theory, a mobile robot navigation problem is discussed. This research work will contribute to the literature by developing novel knowledge and related theories in the areas of decentralized, modular and hierarchical supervisory control of FDES. It also investigates the applicability of these contributions in the mobile robotics arena

    Advanced transport operating system software upgrade: Flight management/flight controls software description

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    The Flight Management/Flight Controls (FM/FC) software for the Norden 2 (PDP-11/70M) computer installed on the NASA 737 aircraft is described. The software computes the navigation position estimates, guidance commands, those commands to be issued to the control surfaces to direct the aircraft in flight based on the modes selected on the Advanced Guidance Control System (AGSC) mode panel, and the flight path selected via the Navigation Control/Display Unit (NCDU)

    A Decentralized Architecture for Active Sensor Networks

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    This thesis is concerned with the Distributed Information Gathering (DIG) problem in which a Sensor Network is tasked with building a common representation of environment. The problem is motivated by the advantages offered by distributed autonomous sensing systems and the challenges they present. The focus of this study is on Macro Sensor Networks, characterized by platform mobility, heterogeneous teams, and long mission duration. The system under consideration may consist of an arbitrary number of mobile autonomous robots, stationary sensor platforms, and human operators, all linked in a network. This work describes a comprehensive framework called Active Sensor Network (ASN) which addresses the tasks of information fusion, decistion making, system configuration, and user interaction. The main design objectives are scalability with the number of robotic platforms, maximum flexibility in implementation and deployment, and robustness to component and communication failure. The framework is described from three complementary points of view: architecture, algorithms, and implementation. The main contribution of this thesis is the development of the ASN architecture. Its design follows three guiding principles: decentralization, modularity, and locality of interactions. These principles are applied to all aspects of the architecture and the framework in general. To achieve flexibility, the design approach emphasizes interactions between components rather than the definition of the components themselves. The architecture specifies a small set of interfaces sufficient to implement a wide range of information gathering systems. In the area of algorithms, this thesis builds on the earlier work on Decentralized Data Fusion (DDF) and its extension to information-theoretic decistion making. It presents the Bayesian Decentralized Data Fusion (BDDF) algorithm formulated for environment features represented by a general probability density function. Several specific representations are also considered: Gaussian, discrete, and the Certainty Grid map. Well known algorithms for these representations are shown to implement various aspects of the Bayesian framework. As part of the ASN implementation, a practical indoor sensor network has been developed and tested. Two series of experiments were conducted, utilizing two types of environment representation: 1) point features with Gaussian position uncertainty and 2) Certainty Grid maps. The network was operational for several days at a time, with individual platforms coming on and off-line. On several occasions, the network consisted of 39 software components. The lessons learned during the system's development may be applicable to other heterogeneous distributed systems with data-intensive algorithms

    IUC Independent Policy Report: At the End of the End of History

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    The IUC Independent Policy Report was drafted by the IUC Legal Standards Research Group, organized by a Steering Committee chaired by Ugo Mattei (International University College of Turin), coordinated by Edoardo Reviglio (International University College of Turin) and Giuseppe Mastruzzo (International University College of Turin), and composed by Franco Bassanini (University of Rome “La Sapienza”), Guido Calabresi (Yale University), Antoine Garapon (Institut des Hautes Etudes sur la Justice, Paris), and Tibor Varady (Central European University, Budapest). Contributors include Eugenio Barcellona (Eastern Piedmont University), Mauro Bussani (University of Trieste), Giuliano G. Castellano (Ecole Polytechnique Preg/CRG), Moussa Djir´e (Bamako University), Liu Guanghua (Lanzhou University), Golnoosh Hakimdavar (University of Turin), John Haskell (SOAS), Jedidiah J. Kroncke (Yale Law School), Andrea Lollini (Bologna University), Alberto Lucarelli (Federico II University), Boris N. Mamlyuk, (University of Turin), Alberto Monti (Bocconi University), Sergio Ariel Muro (Torquato di Tella University), Domenico Nicol`o (Mediterranean University of Reggio Calabria), and Nicola Sartori (University of Michigan). The IUC Independent Policy Report argues for a radical change of perspective, capable of restoring the supremacy of the law over the economic system. It is not only about finance, nor is it only about economics or policy. In this sense a transnational set of normative principles is needed in order to establish a global legal system capable of controlling economic processes, rather than being controlled by them. Within this framework a series of policy proposals are presented in order to effectively implement a new system of global standards. The current Western standard of living is unsustainable. Should the rest share the model of development of the West, our planet will simply not be capable of resisting the growth in consumption and pollution. Within this fundamental setting of scarcity in resources, using the rhetoric of the end of history as the polar star for growth, development and ultimately happiness of the whole world is simply a cynical lie. We argue here for the beginning of a necessary process aimed at the development of a legal system that is much less about creating an effcient backbone for an exploitive economy and much more about a vision of civilization, justice and respect where the laws of nature and those of humans converge in a sustainable long-term philosophy. Principles of justice, responsibility and long term environmental protection, rather than short term economic contingency and strong interests must set the legal agenda. A new governance and bottom-up inclusive integration of knowledge-based economies (wherever located), which is crucial to the very survival of humankind, cannot happen without defning new terms of a widely accepted standard of long term justice in the transnational context, hence the urgency to conceive legitimate transnational legal structures and possibly some apparatus of “superlegality.” The report is composed of fve sections. After having presented the pitfalls of the prevailing theoretical apparatus, an alternative cultural grid upon which policy actions should be shaped is presented. In this sense several normative proposals - revisiting the key characteristics of the current system - are offered aiming at acquiring a wider perspective over the actual global crisis

    Synthesis of communicating decentralized supervisors for discrete-event systems with application to communication protocol synthesis

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    A Discrete-Event Systems (DES) may be viewed as a dynamic system with a discrete state space and a discrete state-transition structure with an event-driven nature, which makes it different from the systems described by differential or difference equations. Given the desired behavior of a DES as a specification, decentralized supervisory control theory seeks to design for a (distributed) DES, consisting of a number of (geographically distant) sites, a set of supervisors, one for each site, such that the behavior of the DES always remains within the specification. If the specification is not coobservable, these supervisors need to communicate amongst each other. This thesis proposes a mathematical framework to formally model and synthesize such communicating decentralized supervisors. The framework provides a decentralized representation of the DES's centralized supervisor and captures its observational and control-related information as mappings, which are called updating and guard functions, respectively. This leads to a polynomial dynamical system, which serves to model the required communication and synthesize its rules. The systematic synthesis, obtained through this approach, characterizes the class of distributed control problems which are solvable only with communication, comes up with a finer partition of it, and addresses practical issues. The thesis ends with the application of the theoretical results to the modeling and synthesis of a communication protoco

    Cooperative Material Handling by Human and Robotic Agents:Module Development and System Synthesis

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    In this paper we present the results of a collaborative effort to design and implement a system for cooperative material handling by a small team of human and robotic agents in an unstructured indoor environment. Our approach makes fundamental use of human agents\u27 expertise for aspects of task planning, task monitoring, and error recovery. Our system is neither fully autonomous nor fully teleoperated. It is designed to make effective use of human abilities within the present state of the art of autonomous systems. It is designed to allow for and promote cooperative interaction between distributed agents with various capabilities and resources. Our robotic agents refer to systems which are each equipped with at least one sensing modality and which possess some capability for self-orientation and/or mobility. Our robotic agents are not required to be homogeneous with respect to either capabilities or function. Our research stresses both paradigms and testbed experimentation. Theory issues include the requisite coordination principles and techniques which are fundamental to the basic functioning of such a cooperative multi-agent system. We have constructed a testbed facility for experimenting with distributed multi-agent architectures. The required modular components of this testbed are currently operational and have been tested individually. Our current research focuses on the integration of agents in a scenario for cooperative material handling

    Supervisory control synthesis for large-scale infrastructural systems

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    Supervisory control synthesis for large-scale infrastructural systems

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