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European control Conference (ECC)

作者： Hamid Reza Shaker Rafael Wisniewski Department of Electronic Systems Section of Automation and Control Aalborg University Aalborg Ø Denmark

In this paper, a general method for model order reduction of switched linear dynamical systems is presented. The proposed technique is based on the generalized gramian framework for model reduction. It is shown that different classical reduction methods can be developed into generalized gramian framework. Balanced reduction within specified frequency bound is developed within this framework. In order to avoid numerical instability and also to increase the numerical efficiency, generalized gramian based Petrov-Galerkin projection is constructed instead of the similarity transform approach for reduction. The method preserves the stability of the original switched system under arbitrary switching signal and is applicable to both continuous and discrete time systems. The performance of the proposed method is illustrated by numerical examples.

关键词： Reduced order systems Switched systems Switches Mathematical model Numerical stability Stability analysis Equations

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Design of a small satellite for performing measurements in a ground station network

Design of a small satellite for performing measurements in a...

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International Workshop on Satellite and Space Communications (IWSSC)

作者： Bastian Preindl Lars Mehnen Frank Rattay Jens Dalsgaard Nielsen Institute of Analysis and Scientific Computing University of Technology Vienna Austria Institute of Biomedical Ingineering FH Technikum Wien Austria Section of Automation and Control University of Aalborg Denmark

Small satellites gain more and more interests from both educational and academic institutions, but also from the industry. They constitute a cheap alternative to large, more expensive and more complex satellites. A consequence of their small form factor is the lack of space for secondary payload, like advanced communication facilities. These deficiencies make it difficult to apply quality assurances concerning satellite communication links on the ground segment. Previous approaches have been primarily passive and focused only on the bit error rate of receiving links at ground stations. The results therefor covered only one direction of a bidirectional link and even if they were quite accurate in common, they were nevertheless only approximations. In this paper a novel design solution based on a small satellite cluster is going to be proposed to offer quality assurance for the ground segment in both sending and receiving directions in multiple amateur frequency bands based on high-accurate error rate information.

关键词： Performance evaluation Satellite ground stations Bit error rate Space vehicles Satellite broadcasting Telecommunication network reliability Performance analysis Scientific computing Educational technology Satellite communication

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Uninterrupted production of metal coils by making successive joints with roll bonding technique

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Materials Transactions 2009年第8期50卷 2124-2126页

作者： Huang, Chin-Chuan Chiang, Mao-Hsiung Jeffrey Kuo, C.-F. Chen, Yih-Nan Yeh, An-Chou Graduate Institute of Automation and Control National Taiwan University of Science and Technology Keelung Rd. Taipei 106 Taiwan Department of Engineering Science and Ocean Engineering National Taiwan University Roosevelt Road Taipei 10617 Taiwan Department of Mechanical Engineering Tatung University 40 Zhongshan North Road 3rd Section Taipei 104 Taiwan Metal Industries Research and Development Centre 1001 Kaonan Highway Kaohsiung 81160 Taiwan

The aim is to develop an uninterrupted processing route to manufacture metal coils, so that the efficiency of production, as well as the quality of the product and the cost-efficiency can be improved. The traditional method of joining two metal sheets is by welding;however the welding process itself can easily introduce additional processing steps and pile up the cost of production. In the past, joining two metal sheets with identical composition by the rolling process has not been easy. The present study induces dissimilarity between two sheets, i.e. pre-heat treatment for one plate to result grain growth. Experimental results indicate that such introduction of dissimilarity between two metal parts can significantly improve the roll bonding process, not only making the joint much stronger than the traditional welding technique, this newly developed method can enhance the efficiency of the production of metal coils in industries. © 2009 The Japan Institute of Metals doi:10.2320/matertrans.M2009153.

关键词： Processing

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Fault detection for shipboard monitoring - Volterra kernel and hammerstein model approaches

Fault detection for shipboard monitoring - Volterra kernel a...

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7th IFAC International Symposium on Fault Detection, Supervision and Safety of Technical Systems, SAFEPROCESS'09

作者： Lajic, Zoran Blanke, Mogens Nielsen, Ulrik Dam Technical University of Denmark Department of Mechanical Engineering Section of Coastal Maritime and Structural EngBuild. 403 2800-Kgs. Lyngby Denmark Technical University of Denmark Department of Electrical Engineering Automation and Control Group Build. 326 2800-Kgs. Lyngby Denmark Norwegian University of Technology and Science Centre for Ships and Ocean Structures 7491 Trondheim Norway

ISBN: (纸本)9783902661463

In this paper nonlinear fault detection for in-service monitoring and decision support systems for ships will be presented. The ship is described as a nonlinear system, and the stochastic wave elevation and the associated ship responses are conveniently modelled in frequency domain. The transformation from time domain to frequency domain has been conducted by use of Volterra theory. The paper takes as an example fault detection of a containership on which a decision support system has been installed. © 2009 IFAC.

关键词： Fault detection

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Fault Detection for Shipboard Monitoring – Volterra Kernel and Hammerstein Model Approaches

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IFAC Proceedings Volumes 2009年第8期42卷 24-29页

作者： Zoran Lajic Mogens Blanke Ulrik Dam Nielsen Technical University of Denmark Department of Mechanical Engineering Section of Coastal Maritime and Structural Eng.Build. 403 2800-Kgs. Lyngby Denmark Technical University of Denmark Department of Electrical Engineering Automation and Control Group Build. 326 2800-Kgs. Lyngby Denmark Norwegian University of Technology and Science Centre for Ships and Ocean Structures 7491 Trondheim Norway

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Input shaping for helicopter slung load swing reduction

Input shaping for helicopter slung load swing reduction

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作者： Bisgaard, Morten La Cour-Harbo, Anders Bendtsen, Jan Dimon Aalborg University Department of Electronic Systems Section for Control and Automation Denmark Department of Electronic Systems Section for Control and Automation Fredrik Bajers Vej 7C DK-9220 Aalborg East Denmark

ISBN: (纸本)9781563479458

This paper presents a feedforward swing reducing control system for augmenting already existing helicopter controllers and enables slung load flight with autonomous helicopters for general cargo transport. The feedforward controller is designed to avoid excitation of the lightly damped modes of the system by shaping the reference trajectory using robust input shaping. It is developed together with a slung load state estimator capable of estimating the slung load swing frequency. This means that the control system can adapt to an unknown wire length for the slung load. Simulations and flight tests show the effectiveness of the input shaping applied to a small scale autonomous helicopter slung load system. Both simulations and flight verifications shows significant slung load swing reduction using the proposed trajectory shaping over flight without. Indeed it is shown how the system is capable of performing almost completely swing free maneuvers using the designed input shaper. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Helicopters

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A Piecewise affine hybrid systems approach to fault tolerant satellite formation control

A Piecewise affine hybrid systems approach to fault tolerant...

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3rd International Symposium on Formation Flying, Missions and Technologies, ESA-ESTEC

作者： Grunnet, Jacob D. Larsen, Jesper A. Bak, Thomas Wisniewski, Rafael Department of Electronic Systems Section for Automation and Control Aalborg University Frb. Vej. 7C 9220 Aalborg SOø Denmark

ISBN: (纸本)9789292212186

In this paper a procedure for modelling satellite formations including failure dynamics as a piecewiseaffine hybrid system is shown. The formulation enables recently developed methods and tools for control and analysis of piecewise-affine systems to be applied leading to synthesis of fault tolerant controllers and analysis of the system behaviour given possible faults. The method is illustrated using a simple example involving two satellites trying to reach a specific formation despite of actuator faults occurring.

关键词： Fault tolerance

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Discrete game abstraction for fault tolerant control synthesis

Discrete game abstraction for fault tolerant control synthes...

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IEEE International Symposium on Computer Aided control System Design (CACSD)

作者： Jacob D. Grunnet Thomas Bak Jan D. Bendtsen Jesper A. Larsen Department of Electronic Systems Section for Automation and Control University of Aalborg Denmark

ISBN: (纸本)9781424422210

The focus of this paper is on the generation of controllers for fault tolerant control. Active off-line fault tolerant control design relies on a pool of controllers designed to handle different failure modes. Designing this pool of controllers remains a challenge and this paper hence investigates automatic control synthesis for a specific class of systems by abstracting the control problem to a set of combinatorial objects or a state machine. Next, a discrete game is formulated, in which the objective is to reach a goal set representing a desired (reference) state, and faults are treated as moves by a malignant opponent. Assuming that a winning strategy exists for this game, it forms a rule base that determines which control law to use under a given fault condition.

关键词： control systems USA Councils

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Combinatorial hybrid systems

Combinatorial hybrid systems

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IEEE International Symposium on Computer Aided control System Design (CACSD)

作者： Jesper A. Larsen Rafal Wisniewski Jacob D. Grunnet Institute of Electronic Systems Section of Automation and Control University of Aalborg Aalborg Denmark

ISBN: (纸本)9781424422210

As initially suggested by E. Sontag, it is possible to approximate an arbitrary nonlinear system by a set of piecewise linear systems. In this work we concentrate on how to control a system given by a set of piecewise linear systems defined on simplices. By using the results of L. Habets and J. van Schuppen, it is possible to find a controller for the system on each of the simplices thus guaranteeing that the system flow on the simplex only will leave the simplex through a subset of its faces. Motivated by R. Forman, on the triangulated state space we define a combinatorial vector field, which indicates for a given face the future simplex. In the suggested definition we allow nondeterminacy in form of splitting and merging of solution trajectories. The combinatorial vector field gives rise to combinatorial counterparts of most concepts from dynamical systems, such as duals to vector fields, flow, flow lines, fixed points and Lyapunov functions. Finally it will be shown how this theory extends to switched dynamical systems and an algorithmic overview of how to do supervisory control will be shown towards the end.

关键词： control systems USA Councils

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Combinatorial Vector Fields for Piecewise Affine control Systems

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IFAC Proceedings Volumes 2008年第2期41卷 7961-7966页

作者： Rafał Wiśniewski Jesper Abildgaard Larsen Department of Electronic Systems Section of Automation and Control Aalborg University Fredrik Bajers Vej 7 9220 Aalborg Ø Denmark

This paper is intended to be a continuation of Habets and van Schuppen [2004] and Habets et al. [2006], which address the control problem for piecewise-affine systems on an arbitrary polytope or a family of these. Our work deals with the underlying combinatorics of the underlying discrete system. Motivated by Forman [1998], on the triangulated state space we define a combinatorial vector field, which indicates for a given face the future simplex. In the suggested definition we allow nondeterminacy in form of splitting and merging of solution trajectories. The combinatorial vector field gives rise to combinatorial counterparts of the flow lines. The main result is then an algorithm for synthesis of supervisory control.

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