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Donkers M.C.F.,TU Eindhoven | Heemels W.P.M.H.,TU Eindhoven | Van De Wouw N.,TU Eindhoven | Hetel L.,Laboratoire dAutomatique
IEEE Transactions on Automatic Control

In this paper, we study the stability of networked control systems (NCSs) that are subject to time-varying transmission intervals, time-varying transmission delays, and communication constraints. Communication constraints impose that, per transmission, only one node can access the network and send its information. The order in which nodes send their information is orchestrated by a network protocol, such as, the Round-Robin (RR) and the Try-Once-Discard (TOD) protocol. In this paper, we generalize the mentioned protocols to novel classes of so-called "periodic" and "quadratic" protocols. By focusing on linear plants and controllers, we present a modeling framework for NCSs based on discrete-time switched linear uncertain systems. This framework allows the controller to be given in discrete time as well as in continuous rime. To analyze stability of such systems for a range of possible transmission intervals and delays, with a possible nonzero lower bound, we propose a new procedure to obtain a convex overapproximation in the form of a poly topic system with norm-bounded additive uncertainty. We show that this approximation can be made arbitrarily tight in an appropriate sense. Based on this overapproximation, we derive stability results in terms of linear matrix inequalities (LMIs). We illustrate our stability analysis on the benchmark example of a batch reactor and show how this leads to tradeoffs between different protocols, allowable ranges of transmission intervals and delays. In addition, we show that the exploitation of the linearity of the system and controller leads to a significant reduction in conservatism with respect to existing approaches in the literature. © 2011 IEEE. Source

Tofighi E.,University of Newcastle | Faulwasser T.,Laboratoire dAutomatique | Faulwasser T.,Karlsruhe Institute of Technology | Kellett C.M.,University of Newcastle
2015 Australian Control Conference, AUCC 2015

In this paper the design of nonlinear model predictive control (NMPC) for multi-mega watt wind turbines is addressed. In an attempt to minimize energy production costs, we propose an NMPC scheme to maximize the wind energy harvest while mitigating structural loads. The proposed controller relies on noisy look-ahead wind field information obtained via LIDAR measurements. By means of simulations we demonstrate the advantages of the proposed NMPC approach. © 2015 Engineers Australia. Source

Bogaerts Ph.,Roosevelt University | Vande Wouwer A.,Laboratoire dAutomatique | Cuvelier A.,Roosevelt University | Hanus R.,Roosevelt University
European Control Conference, ECC 1999 - Conference Proceedings

Although the temperature distribution inside a condenser could in principle be described by a set of partial differential equations (PDEs) for the energy and mass balances of both fluid phases, the resulting distributed parameter model would be difficult to handle in practical applications. In this study, a simplified model of an industrial condenser is derived by assuming that the temperature profile in the condensed phase possesses an a-priori known functional representation. This assumption, which is justified by physical arguments, allows the PDE describing the energy balance of the cooling water to be solved analytically. Based on industrial temperature and flow measurements, an optimization algorithm is used to estimate the numerical values of unknown model parameters, e.g., heat transfer coefficient and characteristics of the condensed phase temperature profile. The resulting model can be used for simulation or fault detection purposes. © 1999 EUCA. Source

Atlan M.,University Pierre and Marie Curie | Atlan M.,Institut Universitaire de France | Bigerelle M.,Laboratoire dAutomatique | Larreta-garde V.,Laboratoire ERRMECe | And 2 more authors.
Aesthetic Plastic Surgery

Abstract: Several companies offer anatomically shaped breast implants but differences among manufacturers are often misunderstood. The shell texture is a crucial parameter for anatomically shaped implants to prevent rotation and to decrease the risk of capsular contracture, even though concerns have recently been raised concerning the complications associated with textured breast implants. The aim of this study was to characterize differences in terms of texture, cell adhesion, shape, and stiffness between some commonly used anatomically shaped implants from three different manufacturers. Methods: Five commercially available anatomically shaped breast implants from 3 different manufacturers (Allergan, Mentor, and Sebbin) were used. Scanning electron microscopy, X-ray microtomography, and scanning mechanical microscopy were used to characterize the shell texture. Human fibroblast adhesion onto the shells was evaluated. 3D models of the implants were obtained using CT-scan acquisitions to analyze their shape. Implant stiffness was evaluated using a tractiometer. Results: Major differences were observed in the topography of the textures of the shells, but this was not conveyed by a statistically significant fibroblast adhesion difference. However, fibroblasts adhered better on anatomically shaped textured implants than on smooth implants (p < 0.01). Our work pointed out differences in the Biocell® texture in comparison with older studies. The 3D analysis showed significant shape differences between the anatomically shaped implants of the 3 companies, despite similar dimensions. Implant stiffness was comparable among the 3 brands. Conclusions: Each texture had its specific topography, and this work is the first description of Sebbin anatomic breast implant texturation. Moreover, major discrepancies were found in the analysis of the Biocell® texture when comparing our results with previous reports. These differences may have clinical implications and are discussed. This study also highlighted major shape differences among breast implants from different manufacturers, which is quite counterintuitive. The clinical impact of these differences however needs further investigation. No Level Assigned: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266. © 2016, Springer Science+Business Media New York and International Society of Aesthetic Plastic Surgery. Source

De Souza C.E.,Laboratorio Nacional Of Computacao Cientifica Lncc Mct | Coutinho D.F.,Laboratoire dAutomatique | Fu M.,University of Newcastle
2009 European Control Conference, ECC 2009

In this paper we investigate the stability of discrete-time linear time-invariant systems subject to finite-level logarithmic quantized feedback. Both state feedback and output feedback are considered. We develop an LMI approach to estimate, for a given controller and a given finite-level quantizer, a set of admissible initial states and an associated attractor set in a neighborhood of the origin such that all state trajectories starting in the first set will converge to the attractor in a finite time and will never leave it. Furthermore, when these two such sets are a priori specified, we develop sufficient conditions for designing a suitable state or output feedback controller, along with a finite-level logarithmic quantizer. © 2009 EUCA. Source

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