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  • 251.
    Fredriksson, Albin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. RaySearch Labs, Stockholm, Sweden..
    Hårdemark, Björn
    RaySearch Labs, Stockholm, Sweden..
    ROBUST OPTIMIZATION ACCOUNTING FOR ORGAN MOTION, RANGE ERRORS, AND SETUP ERRORS IN IMPT2011In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 99, p. S100-S100Article in journal (Other academic)
  • 252.
    Jönsson, Ulf T.
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Cantoni, Michael
    Robust stability analysis for feedback interconnections of unstable time-varying systems2011In: 2011 AMERICAN CONTROL CONFERENCE, 2011, p. 3734-3741Conference paper (Refereed)
    Abstract [en]

    We consider the problem of robust stability analysis for feedback interconnections of causal linear systems that are potentially time-varying with unbounded gain over the space of finite-energy inputs. To this end, a combination of nu-gap metric and integral-quadratic-constraint based analysis is employed. The main results are developed in an abstract setting using generalized Wiener-Hopf and Hankel operators and the Fredholm index. Underlying assumptions are then verified for two important classes of system: multiplication by constantly proper Callier-Desoer transfer functions; and stabilizable and detectable finite-dimensional state-space systems with coefficients of bounded and continuous variation across time.

  • 253. Khong, S. Z.
    et al.
    Cantoni, M.
    Jönsson, Ulf
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Robust stability properties of the v-gap metric for time-varying systems2011In: Proc IEEE Conf Decis Control, 2011, p. 2028-2033Conference paper (Refereed)
    Abstract [en]

    The stability of uncertain feedback interconnections of causal time-varying linear systems is studied in terms of a recently established generalisation of the v-gap metric. In particular, a number of robustness results from the well-known linear time-invariant theory are extended. The time-varying generalisations include: sufficient conditions for robust stability; a bound on robust performance; and two-sided bounds on the induced norm of the variation in a closed-loop mapping as an open-loop component of the feedback interconnection is perturbed. Underlying assumptions are verified for causal systems that exhibit linear periodically time-varying behaviour. This includes a class of sampled-data systems as a special case. Within the periodic context considered, it can be shown that a robust stability condition is also necessary.

  • 254.
    Avventi, Enrico
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Spectral Moment Problems: Generalizations, Implementation and Tuning2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Spectral moment interpolation find application in a wide array of use cases: robust control, system identification, model reduction to name the most notable ones. This thesis aims to expand the theory of such methods in three different directions. The first main contribution concerns the practical applicability. From this point of view various solving algorithm and their properties are considered. This study lead to identify a globally convergent method with excellent numerical properties. The second main contribution is the introduction of an extended interpolation problem that allows to model ARMA spectra without any explicit information of zero’s positions. To this end it was necessary for practical reasons to consider an approximated interpolation insted. Finally, the third main contribution is the application to some problems such as graphical model identification and ARMA spectral approximation.

  • 255.
    Briat, Corentin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Seuret, A.
    Stability criteria for asynchronous sampled-data systems - A fragmentation approach2011In: IFAC Proc. Vol. (IFAC-PapersOnline), 2011, no PART 1, p. 1313-1318Conference paper (Refereed)
    Abstract [en]

    The stability analysis of asynchronous sampled-data systems is studied. The approach is based on a recent result which allows to study, in an equivalent way, the quadratic stability of asynchronous sampled-data systems in a continuous-time framework via the use of peculiar functionals satisfying a necessary boundary condition. The method developed here is an extension of previous results using a fragmentation technique inspired from recent advances in time-delay systems theory. The approach leads to a tractable convex feasibility problem involving a small number of finite dimensional LMIs. The approach is then finally illustrated through several examples.

  • 256.
    Möller, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Engineering Sciences (SCI), Centres, Center for Industrial and Applied Mathematics, CIAM.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Blomgren, Mats
    Gunnarsson, Fredrik
    Stability of Rate and Power Control Algorithms in Wireless Cellular Networks2011In: 2011 50th IEEE Conference On Decision And Control And European Control Conference (CDC-ECC), IEEE , 2011, p. 4535-4541Conference paper (Refereed)
    Abstract [en]

    In radio resource management for cellular networks a trade-off has to be made between the congestion level, related to cell coverage and intercell interference, and the Quality of Service (QoS) or data rates of the users. This is implemented by using a fast inner power control loop and an outer rate control algorithm, working on a slower time scale. Due to the distributed nature of the network, both information and control is distributed. Measurements of congestion and QoS are used in the control loops and this introduces a nonlinear feedback. Another complicating factor is that filtering, computations and information exchange in the network introduce time delays. In this paper we propose a general high order model as a cascade system with an outer and inner control loop. The control algorithms use distributed information available in the network. The full system model includes the nonlinear feedback from congestion and QoS measurements, time delays and time scale modelling. We provide sufficient conditions for stability and convergence of the system. Our primary analysis tool is input output theory.

  • 257.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Stability of systems interconnected over circular graphs2011In: IFAC Proc. Vol. (IFAC-PapersOnline), 2011, no PART 1, p. 3378-3383Conference paper (Refereed)
    Abstract [en]

    Primal and dual stability criteria based on multiplier descriptions are considered for systems interconnected over circular graphs. The resulting stability conditions scale gracefully with the size of the graph and gives rise to criteria with simple primal or dual interpretations. The criteria can be combined which results in a powerful framework.

  • 258. Wang, L.
    et al.
    Wang, X.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Synchronization of multi-agent systems with topological interaction2011In: IFAC Proc. Vol. (IFAC-PapersOnline), 2011, no PART 1, p. 14642-14647Conference paper (Refereed)
    Abstract [en]

    The recent research by a group of European scientists shows that, each starling bird adjusts its flight in the light of topological interaction, that according to a fixed number of its nearest neighbors, rather than all agents within a fixed Euclidean distance. A theoretical study to understand such topological interaction is given in this paper, and a sufficient synchronization condition imposing only on the initial states is developed. Furthermore, the number of neighbors needed for the synchronization is discussed, which shows that for the sake of connectivity the number of neighbors should increase as the density of group increasing. Keywords: network topologies, distributed non-linear elements, synchronization.

  • 259. Liu, Zhixin
    et al.
    Han, Jing
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    The proportion of leaders needed for the expected consensus2011In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 47, no 12, p. 2697-2703Article in journal (Refereed)
    Abstract [en]

    In order to have a self-organized multi-agent system exhibit some expected collective behavior, it is necessary to add some special agents with information (called leaders) to intervene the system. Then a fundamental question is: how many such leaders are needed? Naturally the answer depends on the model to be studied. In this paper a typical model proposed by Vicsek et al. is used for answering the question. By estimating the characteristics concerning the initial states of all agents and analyzing the system dynamics, we provide lower bounds on the ratio of leaders needed to guarantee the expected consensus.

  • 260.
    Hartikainen, Markus
    et al.
    University of Jyväskylä, Finland.
    Miettinen, Kaisa
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    A Computationally Inexpensive Approach in Multiobjective Heat Exchanger Network Synthesis2010In: Proceedings of the 2nd International Conference on Applied Operational Research / [ed] M. Collan, 2010, p. 99-109Conference paper (Refereed)
  • 261. Lovisari, E.
    et al.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    A Nyquist criterion for synchronization in networks of heterogeneous linear systems2010In: 2nd IFAC Workshop on Distributed Estimation and Control in Networked Systems, IFAC Papers Online, 2010, p. 103-108Conference paper (Refereed)
    Abstract [en]

    We study the synchronization of a set of SISO subsystems interconnected via a time-invariant Laplacian matrix. By synchronization we mean that the outputs of all subsystems must be asymptotically equal to each other and behave in the same manner. We assume that the subsystems can be represented as the sum of a common nonzero transfer function plus a perturbation. A Nyquist-type criterion is established which ensures synchronization provided that the convex hull of the frequency responses of the subsystems does not intersect a certain region defined by the spectrum of the interconnection matrix. The result is applied to a variety of examples of different nature for which synchronization takes place. A counter example for which complete synchronization is impossible is also presented.

  • 262.
    Nikulin, Yury
    et al.
    University of Turku.
    Miettinen, Kaisa
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Mäkelä, M. M.
    A Parametrized Achievement Scalarizing Function for Multiobjective Optimization2010Report (Other academic)
  • 263.
    Hartikainen, Markus
    et al.
    University of Jyväskylä, Finland.
    Miettinen, Kaisa
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Wiecek, Margaret M
    Clemson University.
    A Pareto Front Approximation with Inherent Nondominance and the Delaunay Triangulation2010Report (Other academic)
  • 264.
    Jönsson, Ulf T.
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, Chung-Yao
    A Scalable Robust Stability Criterion for Systems With Heterogeneous LTI Components2010In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 55, no 10, p. 2219-2234Article in journal (Refereed)
    Abstract [en]

    A scalable robust stability criterion for interconnected systems with heterogeneous linear time-invariant components is presented in this paper. The criterion involves only the properties of individual components and the spectrum of the interconnection matrix, which can be verified with relatively low computational effort, and more importantly maintains scalability of the analysis. Our main result shows that if the components are single-input-single-output (SISO), then the criterion has an appealing graphical interpretation which resembles the classical Nyquist criterion.

  • 265.
    Siegbahn, Patrick
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Hearn, Donald
    A Study of Fairness in Fourball Golf Competition2010In: Optimal strategies in sports economics and management, BERLIN: SPRINGER-VERLAG BERLIN , 2010, p. 143-170Chapter in book (Other academic)
    Abstract [en]

    The golf handicap system is designed to be fair in single player games. The same system is also applied to team games with two or more players per team. In this study the fairness of the particular team golf game known as fourball match play was analyzed as well as measures to improve it. By using historical player data, software was produced to simulate games. The level of fairness was estimated given the handicaps of the players. It was determined that: Players with high handicap have high variance and therefore also an advantage. Teams should seek to optimize the spread in handicaps by pairing with someone as close to 11 or 29 handicap strokes apart and as far from 0 or 18 as possible. The handicap allowance introduced by the United States Golf Association to penalize high handicappers in team golf is not an effective tool to handle the unfairness. The tiebreaker rule is a simple way to lower the general unfairness by roughly 70%.

  • 266.
    Sasane, Amol
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    An abstract Nyquist criterion containing old and new results2010In: Journal of Mathematical Analysis and Applications, ISSN 0022-247X, E-ISSN 1096-0813, Vol. 370, no 2, p. 703-715Article in journal (Refereed)
    Abstract [en]

    We prove an abstract Nyquist criterion in a general set up. As applications, we recover various versions of the Nyquist criterion, some of which are new.

  • 267. Haanpaa, T
    et al.
    Aittokoski, T
    Miettinen, Kaisa
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Hakanen, Jussi
    University of Jyväskylä.
    An Approach to Minimize the Number of Function Evaluations in Global Optimization2010In: 24th Mini EURO Conference on Continuous Optimization and Information-Based Technologies in the Financial Sector, Proceedings / [ed] R. Kasimbeyli, C. Dincer, S. Ozpeynirci, L. Sakalauskas, Vilnius Gediminas Technical University Publishing House 'Technika' , 2010, p. 161-166Conference paper (Refereed)
  • 268.
    Karasalo, Maja
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Martin, Clyde
    An estimated general cross validation function for periodic control theoretic smoothing splines2010In: Lecture notes in control and information sciences, ISSN 0170-8643, E-ISSN 1610-7411, Vol. 398, p. 95-104Article in journal (Refereed)
    Abstract [en]

    In this paper, a method is developed for estimating the optimal smoothing parameter for periodic control theoretic smoothing splines.The procedure is based on general cross validation (GCV) and requires no a priori information about the underlyingcurve or level of noise in the measurements.The optimal smoothin parameter is the minimizer of a GCV cost function, which is derived based on a discretizationof the L2 smoothing problem for periodic control theoretic smoothing splines.

  • 269.
    Thunberg, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Ögren, Petter
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    An Iterative Mixed Integer Linear Programming Approach to Pursuit Evasion Problems in Polygonal Environments2010In: 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA)  / [ed] Rakotondrabe M; Ivan IA, 2010, p. 5498-5503Conference paper (Refereed)
    Abstract [en]

    In this paper, we address the multi pursuer version of the pursuit evasion problem in polygonal environments. It is well known that this problem is NP-hard, and therefore we seek efficient, but not optimal, solutions by relaxing the problem and applying the tools of Mixed Integer Linear Programming (MILP) and Receding Horizon Control (RHC). Approaches using MILP and RHC are known to produce efficient algorithms in other path planning domains, such as obstacle avoidance. Here we show how the MILP formalism can be used in a pursuit evasion setting to capture the motion of the pursuers as well as the partitioning of the pursuit search region into a cleared and a contaminated part. RHC is furthermore a well known way of balancing performance and computation requirements by iteratively solving path planning problems over a receding planning horizon, and adapt the length of that horizon to the computational resources available. The proposed approach is implemented in Matlab/Cplex and illustrated by a number of solved examples.

  • 270. Pardalos, P. M.
    et al.
    Yatsenko, V. A.
    Messo, Alexandre
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Chinchuluun, A.
    Xanthopoulos, P.
    An optimization approach for finding a spectrum of lyapunov exponents2010In: Springer Optimization and Its Applications, Springer, 2010, p. 285-303Conference paper (Refereed)
    Abstract [en]

    In this chapter, we consider an optimization technique for estimating the Lyapunov exponents from nonlinear chaotic systems. We then describe an algorithm for solving the optimization model and discuss the computational aspects of the proposed algorithm. To show the efficiency of the algorithm, we apply it to some well-known data sets. Numerical tests show that the algorithm is robust and quite effective, and its performance is comparable with that of other well-known algorithms.

  • 271. Mariethoz, Sebastien
    et al.
    Almer, Stefan
    Baja, Mihai
    Beccuti, Andrea Giovanni
    Patino, Diego
    Wernrud, Andreas
    Buisson, Jean
    Cormerais, Herve
    Geyer, Tobias
    Fujioka, Hisaya
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, Chung-Yao
    Morari, Manfred
    Papafotiou, Georgios
    Rantzer, Anders
    Riedinger, Pierre
    Comparison of Hybrid Control Techniques for Buck and Boost DC-DC Converters2010In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 18, no 5, p. 1126-1145Article in journal (Refereed)
    Abstract [en]

    Five recent techniques from hybrid and optimal control are evaluated on two power electronics benchmark problems. The benchmarks involve a number of practically interesting operating scenarios for fixed-frequency synchronous dc-dc converters. The specifications are defined such that good performance can only be obtained if the switched and nonlinear nature of the problem is accounted for during the design phase. A nonlinear action is featured in all methods either intrinsically or as external logic. The designs are evaluated and compared on the same experimental platform. Experiments show that the proposed methods display high performances, while respecting circuit constraints, thus protecting the semiconductor devices. Moreover, the complexity of the controllers is compatible with the high-frequency requirements of the considered application.

  • 272.
    Jönsson, Ulf
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, ChungYao
    Consensus of Heterogeneous Linear Agents Applied to a Formation Control Problem2010In: Proceedings of the IEEE Conference on Decision and Control, NEW YORK: IEEE , 2010, p. 6902-6907Conference paper (Other academic)
    Abstract [en]

    Robustness to dynamic uncertainty is considered for consensus algorithms. The purpose of such algorithms is to use distributed control to reach an agreement regarding a certain quantity of interest that depends on the state of all systems. In distinction to the standard consensus problem where the dynamics of all individual agents are the same and of low dimension, the convergence criterion now depends on the full spectrum of the communication graph and not only the largest nonzero eigenvalue. The new consensus criterion is posed as an inverse Nyquist criterion that provides a clear separation between the individual dynamics and the spectrum of the graph. A formation control problem for a target encircling task is considered as an application.

  • 273. Anisi, David A.
    et al.
    Ögren, Petter
    Swedish Defence Research Agency (FOI), Sweden.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative Minimum Time Surveillance With Multiple Ground Vehicles2010In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 55, no 12, p. 2679-2691Article in journal (Refereed)
    Abstract [en]

    In this paper, we formulate and solve two different minimum time problems related to unmanned ground vehicle (UGV) surveillance. The first problem is the following. Given a set of surveillance UGVs and a polyhedral area, find waypoint-paths for all UGVs such that every point of the area is visible from a point on a path and such that the time for executing the search in parallel is minimized. Here, the sensors' field of view are assumed to have a limited coverage range and be occluded by the obstacles. The second problem extends the first by additionally requiring the induced information graph to be connected at the time instants when the UGVs perform the surveillance mission, i.e., when they gather and transmit sensor data. In the context of the second problem, we also introduce and utilize the notion of recurrent connectivity, which is a significantly more flexible connectivity constraint than, e.g., the 1-hop connectivity constraints and use it to discuss consensus filter convergence for the group of UGVs.

  • 274.
    Wendin, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Lawphongpanich, Siriphong
    Yin, Yafeng
    FINDING BOUNDEDLY RATIONAL USER EQUILIBRIUM FLOWS2010In: TRANSPORTATION AND URBAN SUSTAINABILITY, HONG KONG: HONG KONG SOC TRANSPORTATION STUDIES LTD , 2010, p. 327-334Conference paper (Refereed)
    Abstract [en]

    Models for transportation network analysis in the literature typically assume that users always choose shortest or least-cost routes to reach their destinations regardless of the saving these routes offer. Under this assumption, users are perfectly or unboundedly rational and a flow distribution is in equilibrium when users cannot improve their travel time or cost by unilaterally changing routes. However, users in practice often switch to alternative routes only when they offer significant time or cost saving, i.e., users are boundedly rational. This paper addresses the problem of finding an equilibrium flow distribution when users are boundedly rational. Because link-based conditions for boundedly rational user equilibrium only identities a subset of such distributions, the formulation herein is path-based and contains complementarity constraints, a class of constraints that violates standard regularity conditions. The proposed algorithm is distinct from other path-generating schemes because it generates paths for two purposes, one to make the current solution feasible and the other to find an improved solution.

  • 275.
    Avventi, Enrico
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Lindquist, Anders
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Graphical Models of Autoregressive Moving-Average Processes2010In: The 19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010), 2010Conference paper (Refereed)
    Abstract [en]

    Consider a Gaussian stationary stochastic vector process with the property that designated pairs of components are conditionally independent given the rest of the components. Such processes can be represented on a graph where the components are nodes and the lack of a connecting link between two nodes signifies conditional independence. This leads to a sparsity pattern in the inverse of the matrix-valued spectral density. Such graphical models find applications in speech, bioinformatics, image processing, econometrics and many other fields, where the problem to fit an autoregressive (AR) model to such a process has been considered. In this paper we take this problem one step further, namely to fit an autoregressive moving-average (ARMA) model to the same data. We develop a theoretical framework which also spreads further light on previous approaches and results.

  • 276.
    Hartikainen, Markus
    et al.
    University of Jyväskylä, Finland.
    Miettinen, Kaisa
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Wiecek, Margaret M
    Clemson University.
    Inherent Nondominance - Pareto Front Approximations for Decision Making2010Report (Other academic)
  • 277.
    Möller, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Input-Output Analysis of Power Controlin Wireless Networks2010In: Proceedings of the IEEE Conference on Decision and Control, 2010, p. 6451-6456Conference paper (Refereed)
    Abstract [en]

    In a wireless communication network different users share a common resource. An objective of radio resource management is to assign the resources in an effective way between the users. Power control is an important component in this setting that has been extensively studied over the last two decades. In many real networks there are inherent time delays due to filtering of signals and control signaling. Time delays can affect stability and convergence properties of the power control algorithms. We therefore consider power control laws of higher order to include models with delays and delay compensation. The main contribution of this paper is to prove less conservative conditions for system stability. Our primary tool to reduce conservativeness is to use scalings in an input-output framework for stability analysis.

  • 278. Aleman, Dionne M.
    et al.
    Glaser, Daniel
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Romeijn, H. Edwin
    Dempsey, James F.
    Interior point algorithms: guaranteed optimality for fluence map optimization in IMRT2010In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 55, no 18, p. 5467-5482Article in journal (Refereed)
    Abstract [en]

    One of the most widely studied problems of the intensity-modulated radiation therapy (IMRT) treatment planning problem is the fluence map optimization (FMO) problem, the problem of determining the amount of radiation intensity, or fluence, of each beamlet in each beam. For a given set of beams, the fluences of the beamlets can drastically affect the quality of the treatment plan, and thus it is critical to obtain good fluence maps for radiation delivery. Although several approaches have been shown to yield good solutions to the FMO problem, these solutions are not guaranteed to be optimal. This shortcoming can be attributed to either optimization model complexity or properties of the algorithms used to solve the optimization model. We present a convex FMO formulation and an interior point algorithm that yields an optimal treatment plan in seconds, making it a viable option for clinical applications.

  • 279. Witrant, Emmanuel
    et al.
    Di Marco, Piergiuseppe
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Park, Pan Gun
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Briat, Corentin
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Limitations and performances of robust control over WSN: UFAD control in intelligent buildings2010In: IMA Journal of Mathematical Control and Information, ISSN 0265-0754, E-ISSN 1471-6887, Vol. 27, no 4, p. 527-543Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to propose a model-based feedback control strategy for indoor temperature regulation in buildings equipped with underfloor air distribution. Supposing distributed sensing and actuation capabilities, a zero-dimensional model of the ventilation process is derived, based on the thermodynamics properties of the flow. A state-space description of the process is then inferred, including discrete events and non-linear components. The use of a wireless sensor network and the resulting communication constraints with the IEEE 802.15.4 standard are discussed. Both synchronous and asynchronous transmissions are considered. Based on the linear part of the model, different H-infinity robust multiple-input multiple-output (MIMO) controllers are designed, first with a standard mixed-sensitivity approach and then by taking into account the network-induced delay explicitly. The impact of the communication constraints and the relative performances of the controllers are discussed based on simulation results.

  • 280.
    Briat, Corentin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Sename, O.
    GIPSA-Lab, Department of Control Systems (Former LAG), Grenoble Universités.
    Lafay, J. F.
    IRCCyN - Centrale de Nantes.
    Memory-resilient gain-scheduled state-feedback control of uncertain LTI/LPV systems with time-varying delays2010In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 59, no 8, p. 451-459Article in journal (Refereed)
    Abstract [en]

    The stabilization of uncertain LTI/LPV time-delay systems with time-varying delays by state-feedback controllers is addressed. Compared to other works in the literature, the proposed approach allows for the synthesis of resilient controllers with respect to uncertainties on the implemented delay. It is emphasized that such controllers unify memoryless and exact-memory controllers usually considered in the literature. The solutions to the stability and stabilization problems are expressed in terms of LMIs which allow us to check the stability of the closed-loop system for a given bound on the knowledge error and even optimize the uncertainty radius under some performance constraints; in this paper, the H-infinity performance measure is considered. The interest of the approach is finally illustrated through several examples.

  • 281. Hu, Jiangping
    et al.
    Hu, Xiaoming
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Nonlinear filtering in target tracking using cooperative mobile sensors2010In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 46, no 12, p. 2041-2046Article in journal (Refereed)
    Abstract [en]

    Collaborative signal processing and sensor deployment have been among the most important research tasks in target tracking using networked sensors In this paper the mathematical model is formulated for single target tracking using mobile nonlinear scalar range sensors Then a sensor deployment strategy is proposed for the mobile sensors and a nonlinear convergent filter is built to estimate the trajectory of the target.

  • 282. Hu, J.
    et al.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Nonlinear shift estimation and optimal sensor deployment for target tracking2010In: 2010 8th IEEE International Conference on Control and Automation, ICCA 2010, IEEE , 2010, p. 773-778Conference paper (Refereed)
    Abstract [en]

    In this paper, the mathematical model for target tracking using nonlinear scalar range sensors is formulated first. Sensors are classified into active sensors and submissive sensors according to the relative distances with the target. Then two different estimation algorithms accompanying with an optimal sensor deployment strategy are proposed for both active and submissive sensors to estimate the trajectory of the target. Finally, some numerical examples are given to validate the proposed tracking algorithm.

  • 283.
    Briat, Corentin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jönsson, Ulf
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nonlinear state-dependent delay modeling and stability analysis of internet congestion control2010In: 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), 2010, p. 1484-1491Conference paper (Refereed)
    Abstract [en]

    It is shown that the queuing delay involved in the congestion control algorithm is state-dependent and does not depend on the current time. Then, using an accurate formulation for buffers, networks with arbitrary topologies can be built. At equilibrium, our model reduces to the widely used setup by Paganini et al. Using this model, the delay-derivative is analyzed and it is proved that the delay time-derivative does not exceed one for the considered topologies. It is then shown that the considered congestion control algorithm globally stabilizes a delay-free single buffer network. Finally, using a specific linearization result for systems with state-dependent delays from Cooke and Huang, we show the local stability of the single bottleneck network.

  • 284.
    Wang, Jinhuan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Hebei University of Technology, Tianjin, China.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Observer-based tracking problem of leader-follower multi-agent systems2010In: Proceedings of the 29th Chinese Control Conference, CCC'10, 2010, p. 5821-5826Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider the tracking problem for leader-follower multi-agent systems moving in the plane. In our model, the system matrix of the leader can be of any form and the control input of the leader is not known to the followers even if they are connected to the leader. To track such a leader, an observer-based decentralized feedback controller is designed for each follower. We show that if the adjacent graph of the system is connected, with the proposed control law, all the followers can track the leader eventually. At last, we generalize the result to the higher dimension case for some special system matrix of the leader.

  • 285.
    Fallgren, Mikael
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    On the complexity of maximizing the minimum Shannon capacity in wireless networks by joint channel assignment and power allocation2010In: 2010 18th International Workshop on Quality of Service (IWQoS), IEEE , 2010, p. 5542766-Conference paper (Refereed)
    Abstract [en]

    We consider wireless telecommunications systems with orthogonal frequency bands, where each band is referred to as a channel, e.g., orthogonal frequency-division multiple access (OFDMA). For a given snap-shot in time, two joint channel assignment and power allocation optimization problems are presented, one in downlink and one in uplink. The objective is to maximize the minimum total Shannon capacity of any mobile user in the system, subject to system constraints. The corresponding decision problems are proved to be NP-hard. We also show that for any constant ρ > 0, a sufficiently large number of channels ensure that the optimization problems are not ρ-approximable, unless P is equal to NP.

  • 286.
    Byrnes, Christopher
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Engineering Sciences (SCI), Centres, Center for Industrial and Applied Mathematics, CIAM. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lindquist, Anders
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Engineering Sciences (SCI), Centres, Center for Industrial and Applied Mathematics, CIAM. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the Stability and Instability of Padé Approximants2010In: Lecture notes in control and information sciences, ISSN 0170-8643, E-ISSN 1610-7411, Vol. 398, p. 165-175Article in journal (Refereed)
    Abstract [en]

    Over the past three decades there has been interest in using Pade approximants K with n = deg(K) < deg(G) = N as "reduced-order models" for the transfer function G of a linear system The attractive feature of this approach is that by matching the moments of G we can reproduce the steady-state behavior of G by the steady-state behavior of K. for certain classes of Inputs Indeed, we illustrate this by finding a first-order model matching a fixed set of moments for G. the causal inverse of a heat equation A key feature of this example is that the heat equation is a minimum phase system, so that its inverse system has a stable transfer function G and that K can also be chosen to be stable On the other hand, elementary examples show that both stability and instability can occur in reduced order models of a stable system obtained by matching moments using Pade approximants and, in the absence of stability, it does not make much sense to talk about steady-state responses nor does it make sense to match moments In this paper, we review Pack approximains. and their intimate relationship to continued fractions and Riccati equations, in a historical context that underscores why Pade approximation, as useful as it is, is not an approximation in any sense that reflects stability. Our main results on stability and instability states that if N >= 2 and l, r >= 0 with 0<l+r=n<N there is a non-empty open set U-lr of stable transfer functions G, having infinite Lebesque measure, such that each degree n proper rational function K matching the moments of G has e poles lying in C- and r poles lying in C+ The proof is constructive.

  • 287.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Primal and Dual Criteria for Robust Stability and Their Application to Systems Interconnected Over a Bipartite Graph2010In: 2010 AMERICAN CONTROL CONFERENCE , 2010, p. 5458-5464Conference paper (Refereed)
    Abstract [en]

    A dual formulation of a standard stability criterion from robust control is derived and investigated. The dual provides additional insight into the stability criterion and is sometimes easier to use than the primal. This is illustrated for a class of systems interconnected over a bipartite graph. The dual criterion reveals structural properties of the interconnection which in some cases are easy to investigate using low complexity tests.

  • 288.
    Karasalo, Maja
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Gustavi, Tove
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Robust Formation Control using Switching Range Sensors2010In: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 58, no 8, p. 1003-1016Article in journal (Refereed)
    Abstract [en]

    In this paper, control algorithms are presented for formation keeping and path followingfor non-holonomic platforms. The controls are based on feedback from onboard directional range sensors, and a switching Kalman filter is introduced for active sensing.Stability is analyzed theoretically and robustness isdemonstrated in experiments and simulations.

  • 289. Mortini, R.
    et al.
    Sasane, Amol
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Some algebraic properties of the Wiener-Laplace algebra2010In: Journal of Applied Analysis, ISSN 1425-6908, Vol. 16, no 1, p. 79-94Article in journal (Refereed)
    Abstract [en]

    We denote by W +(ℂ +) the set of all complex-valued functions defined in the closed right half plane ℂ + D {s ∈ ℂ | Re(s) ≥ 0} that differ from the Laplace transform of functions from L 1(0, ∞) by a constant. Equipped with pointwise operations, W +(C +) forms a ring. It is known that W +(ℂ +) is a pre-Bézout ring. The following properties are shown for W +(ℂ +): W +(ℂ +) is not a GCD domain, that is, there exist functions F 1, F 2 in W +(ℂ +) that do not possess a greatest common divisor in W +(ℂ +). W +(ℂ +) is not coherent, and in fact, we give an example of two principal ideals whose intersection is not finitely generated. We will also observe that W +(ℂ +) is a Hermite ring, by showing that the maximal ideal space of W +(ℂ +), equipped with the Gelfand topology, is contractible.

  • 290. Qi, H.
    et al.
    Cheng, D.
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Stabilization of random boolean networks2010In: 2010 8th World Congress on Intelligent Control and Automation (WCICA), IEEE , 2010, p. 1968-1973Conference paper (Refereed)
    Abstract [en]

    This paper considers the stabilization of random Boolean networks. We first give a survey on the semi-tensor product approach to Boolean (control) networks, which is a new technique developed by us. Particularly, the stability and stabilization of Boolean (control) networks are reviewed. Then, under the same framework, the topological structure of the random Boolean networks is investigated and revealed. Using it the stabilization of random Boolean networks is considered. A sufficient condition is provided. A stabilizer design method is proposed.

  • 291.
    Gustavi, Tove
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Dimarogonas, Dimos V.
    Laboratory for Information and Decision Systems, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
    Egerstedt, Magnus
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Sufficient conditions for connectivity maintenance and rendezvous in leader-follower networks2010In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 46, no 1, p. 133-139Article in journal (Refereed)
    Abstract [en]

    In this paper we derive a set of constraints that are sufficient to guarantee maintained connectivity in a leader-follower multi-agent network with proximity based communication topology. In the scenario we consider, only the leaders are aware of the global mission, which is to converge to a known destination point. Thus, the followers need to stay in contact with the group of leaders in order to reach the goal. In the paper we show that we can maintain the initial network structure, and thereby connectivity, by setting up bounds on the ratio of leaders-to-followers and on the magnitude of the goal attraction force experienced by the leaders. The results are first established for an initially complete communication graph and then extended to an incomplete graph. The results are illustrated by computer simulations.

  • 292.
    Karlsson, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Engineering Sciences (SCI), Centres, Center for Industrial and Applied Mathematics, CIAM. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Georgiou, Tryphon T.
    Department of Electrical Engineering, University of Minnesota.
    Lindquist, Anders
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    The Inverse Problem of Analytic Interpolation With Degree Constraint and Weight Selection for Control Synthesis2010In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 55, no 2, p. 405-418Article in journal (Refereed)
    Abstract [en]

    The minimizers of certain weighted entropy functionals are the solutions to an analytic interpolation problem with a degree constraint, and all solutions to this interpolation problem arise in this way by a suitable choice of weights. Selecting appropriate weights is pertinent to feedback control synthesis, where interpolants represent closed-loop transfer functions. In this paper we consider the correspondence between weights and interpolants in order to systematize feedback control synthesis with a constraint on the degree. There are two basic issues that we address: we first characterize admissible shapes of minimizers by studying the corresponding inverse problem, and then we develop effective ways of shaping minimizers via suitable choices of weights. This leads to a new procedure for feedback control synthesis.

  • 293.
    Hu, Xiaoming
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jönsson, UlfKTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.Wahlberg, BoKTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.Ghosh, BijoyTexas Tech University, USA.
    Three Decades of Progress in Control Sciences: Dedicated to Chris Byrnes and Anders Lindquist2010Collection (editor) (Other academic)
    Abstract [en]

    Features contributions from experts in  control research

    • Celebrates the 60th birthday of Chris Byrnes and Anders Lindquist
    • Has a celebrative flavor and at the same time contains reference material for researchers interested in control theory

    In this edited collection we commemorate the 60th birthday of Prof. Christopher Byrnes and the retirement of Prof. Anders Lindquist from the Chair of Optimization and Systems Theory at KTH. These papers were presented in part at a 2009 workshop in KTH, Stockholm, honoring the lifetime contributions of Professors Byrnes and Lindquist in various fields of applied mathematics.

  • 294. Mortini, Raymond
    et al.
    Rupp, Rudolf
    Sasane, Amol
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Wick, Brett D.
    Topological stable rank of H (a)(Omega) for circular domains Omega2010In: Analysis Mathematica, ISSN 0133-3852, E-ISSN 1588-273X, Vol. 36, no 4, p. 287-297Article in journal (Refereed)
    Abstract [en]

    Let Omega be a circular domain, that is, an open disk with finitely many closed disjoint disks removed. Denote by H (a)(Omega) the Banach algebra of all bounded holomorphic functions on Omega, with pointwise operations and the supremum norm. We show that the topological stable rank of H (a)(Omega) is equal to 2. The proof is based on Suarez's theorem that the topological stable rank of H (a)(D) is equal to 2, where D is the unit disk. We also show that for circular domains symmetric to the real axis, the Bass and topological stable ranks of the real-symmetric algebra H (a"e) (a) (Omega) are 2.

  • 295.
    Jönsson, Ulf T.
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, C. -Y
    Verification of consensus in networks of heterogeneous LTI agents2010In: Proceedings of SICE Annual Conference 2010, 2010, p. 2570-2575Conference paper (Refereed)
    Abstract [en]

    A framework for robust stability of large scale systems consisting of linear time-invariant systems interconnected over a network will be surveyed and applied to solve heterogeneous consensus problems. The purpose of distributed consensus algorithms is to reach an agreement regarding a certain quantity of interest that depends on the state of all systems. In most of consensus literature, dynamics of all agents in the network are assumed to be the same and of low dimensions. This simplifies the analysis and, for the most elementary networks, stability and the rate of convergence can be determined from the eigenvalues of the interconnection matrix. Here we discuss analogous results for the case where the individual dynamics are heterogeneous and possibly of infinite dimensions. Our criterion for consensus resembles the classical Nyquist criterion. An interesting aspect of this criterion is that in some instances a three-dimensional plot is required in order to make analysis accurate.

  • 296.
    Thunberg, Johan
    et al.
    Department of Autonomous Systems, Swedish Defence Research Institute (FOI).
    Anisi, David
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Ögren, Petter
    Department of Autonomous Systems, Swedish Defence Research Institute (FOI).
    A comparative study of task assignment and path planning methods for multi-UGV missions2009In: OPTIMIZATION AND COOPERATIVE CONTROL STRATEGIES / [ed] Hirsch, MJ; Commander, CW; Pardalos, PM; Murphey, R, 2009, p. 167-180Conference paper (Refereed)
    Abstract [en]

    Many important problems involving a group of unmanned ground vehicles (UGVs) are closely related to the multi traviling salesman problem (m-TSP). This paper comprises a comparative study of a number of algorithms proposed in the litterature to solve m-TSPs occuring in robotics. The investigated algoritms include two mixed integer linear programming (MILP) formulations, a market based approach (MA), a Voronoi partition step (VP) combined with the local search used in MA, and a deterministic and a stocastic version of the granular tabu search (GTS). To evaluate the algoritms, an m-TSP is derived from a planar environment with polygonal obstacles and uniformly distributed targets and vehicle positions. The results of the comparison indicate that out of the decentralized approaches, the MA yield good solutions but requires long computation times, while VP is fast but not as good. The two MILP approaches suffer from long computation times, and poor results due to the decomposition of the assignment and path planning steps. Finally, the two GTS algorithms yield good results in short times with inputs from MA as well as the much faster VP. Thus the best performing centralized approach is the GTS in combination with the VP. Funded by the Swedish defence materiel administration (FMV) and the Swedish armed forces through the Technologies for Autonomous and Intelligent Systems (TAIS) project. 297316-LB704859

  • 297.
    Kuroiwa, Yohei
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    A Parameterization of Positive Real Residue Interpolants with McMillan Degree Constraint2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main body of this thesis consists of six appended papers.The papers are about the theory of the positive real interpolationwith McMillan degree constraint.In Paper A, a parameterization of the positive real residue interpolantswith McMillan degree constraint is given.For a given interpolation data and for each free parameter,a positive real interpolant, of which McMillan degree isequal to the McMillan degree of the maximum entropy interpolant, is obtained bysolving a nonlinear equation, which is homotopic to a nonlinear equation to determinethe maximum entropy interpolant.In Paper B,the state-space realization of the multivariable rational interpolant with bounded McMillan degreeis given by the block discrete-time Schwarz form.A characterization of the positive realness of the block discrete-time Schwarz form isgiven by a linear matrix inequality.In Paper C,a robust controller synthesis for the mismatch of delay in terms ofthe Nevanlinna-Pick interpolation is presented.In Paper D,a Smith predictor synthesis for unstable and minimum-phaseinput delay system and for a first orderunstable distributed delay system is given in terms of the Nevanlinna-Pick interpolation.In Paper E , we study an approximation of spectral density in termsof the generalized Kullback-Leibler distance minimization.For a given spectral density,we seek a spectraldensity by minimizingthe generalized Kullback-Leibler distance subject to a constraint onthe tangential second-orderstatistics.In Paper F, a property of Schur polynomial of real coefficientsand real Toeplitz matrix is given.Suppose that the vector of coefficients of a Schur polynomial annihilatesa Toeplitz matrix, then the Toeplitz matrix is in facta zero matrix.

  • 298.
    Kuroiwa, Yohei
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    A positive partial realization of time series2009In: 17th European Signal Processing Conference (EUSIPCO 2009), 2009, p. 413-416Conference paper (Refereed)
    Abstract [en]

    For a given partial covariance sequence (C 0,C 1,⋯,C n) and for each MA part of the ARMA modeling filter of degree n, an AR part of the ARMA modeling filter of degree n for the solution to the rational covariance extension problem is obtained by solving a nonlinear equation, which is homotopic to a nonlinear equation determining the maximum entropy AR filter.

  • 299.
    Jönsson, Ulf T.
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, Chung-Yao
    A Scalable Robust Stability Criterion for Systems with Heterogeneous LTI Components2009In: 2009 AMERICAN CONTROL CONFERENCE, 2009, p. 2898-2903Conference paper (Refereed)
    Abstract [en]

    A scalable robust stability criterion for networked interconnected systems with heterogeneous linear time-invariant components is presented in this paper. The criterion involves only the properties of individual components and the spectrum of the interconnection matrix, which can be verified with relatively low computational effort, and more importantly maintains scalability of the analysis. Moreover, if the components are single-input-single-output (SISO), the criterion has an appealing graphical interpretation which resembles the classical Nyquist criterion.

  • 300.
    Wang, Jinhuan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Cheng, Daizhan
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    An extension of LaSalle's Invariance Principle for a class of switched linear systems2009In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 58, no 10-11, p. 754-758Article in journal (Refereed)
    Abstract [en]

    In this paper LaSalle's Invariance Principle for switched linear systems is studied. Unlike most existing results in which each switching mode in the system needs to be asymptotically stable, in this paper the switching modes are allowed to be only Lyapunov stable. Under certain ergodicity assumptions, an extension of LaSalle's Invariance Principle for global asymptotic stability of switched linear systems is proposed provided that the kernels of derivatives of a common quadratic Lyapunov function with respect to the switching modes are disjoint (except the origin).

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