Browsing by Subject "Optimal control systems"
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Item Open Access Designing emergency response networks for hazardous materials transportation(2007) Berman O.; Verter V.; Kara, B.Y.Undesirable consequences of dangerous goods incidents can be mitigated by quick arrival of specialized response teams at the accident site. We present a novel methodology to determine the optimal design of a specialized team network so as to maximize its ability to respond to such incidents in a region. We show that this problem can be represented via a maximal arc-covering model. We discuss two formulations for the maximal arc-covering problem, a known one and a new one. Through computational experiments, we establish that the known formulation has excessive computational requirements for large-scale problems, whereas the alternative model constitutes a basis for an efficient heuristic. The methodology is applied to assess the emergency response capability to transport incidents, that involve gasoline, in Quebec and Ontario. We point out the possibility of a significant improvement via relocation of the existing specialized teams, which are currently stationed at the shipment origins. © 2005 Elsevier Ltd. All rights reserved.Item Open Access Discrete-time LQ optimal repetitive control(IEEE, 1999) Köroğlu, Hakan; Morgül, ÖmerLQ optimal repetitive control is developed in single-input single-output discrete-time signal/system framework. For a given plant and a stabilizing controller, the LQ optimal repetitive control system can be obtained by the addition of a plug-in unit to the existing control system. The overall behaviour (stochastic behaviour, stability robustness etc.) of the new system can be improved by the appropriate choice/tuning of the design parameters.Item Open Access Fixed zeros of decentralized control systems(IEEE, 2000) ÜÜnyelioglu, K. A.; Özgüner, Ü.; Özgüler, A. B.This paper considers the notion of decentralized fixed zeros for linear, time-invariant, finite-dimensional systems. For an N-channel plant that is free of unstable decentralized fixed modes, an unstable decentralized fixed zero of Channel i (1 ≤ i ≤ N) is defined as an element of the closed right half-plane, which remains as a blocking zero of that channel under the application of every set of N - 1 controllers around the other channels, which make the resulting single-channel system stabilizable and detectable. This paper gives a complete characterization of unstable decentralized fixed zeros in terms of system-invariant zeros.Item Open Access LQ optimal design at finitely many frequencies(Institute of Electrical and Electronics Engineers, 1998) Köroğlu, H.; Morgül, Ö.The notion of Linear Quadratic (LQ) optimality at a single frequency is developed in single-input single-output (SISO) linear time-invariant (LTI) system/quasi-stationary signal framework and the optimality condition is given. LQ optimal design at finitely many frequencies is then shown to be reducible to an interpolation problem.Item Open Access Minimizing Lmax for the single machine scheduling problem with family set-ups(Taylor & Francis, 2004) Schultz, S. R.; Hodgson, T. J.; King, R. E.; Taner, M. R.A procedure for the single machine-scheduling problem of minimizing the maximum lateness for jobs with sequence independent set-ups is presented. The procedure provides optimal/near-optimal solutions over a wide range of problems. It performs well compared with other heuristics, and it is effective in finding solutions for large problems.Item Open Access Optimal control for a class of partially observed bilinear stochastic systems(IEEE, 1990) Dabbous, Tayel E.An alternative formulation is presented for a class of partially observed bilinear stochastic control problems which is described by three sets of stochastic differential equations: one for the system to be controlled, one for the observer, and one for the control process which is driven by the observation process. With this formulation, the stochastic control problem is converted to an equivalent deterministic identification problem of control gain matrices. Using standard variation arguments, the necessary conditions of optimality on the basis of which the optimal control parameters can be determined are obtained.Item Open Access Optimal control of a two-stage stochastic hybrid manufacturing system with Poisson arrivals and exponential service times(IEEE, 2005) Gökbayrak, Kağan; Selvi, ÖmerExtending earli'er work on single-stage stochastic hybrid system models, we consider a two-stage stochastic hybrid system where the job arrivals are represented through a Poisson process, and the service times required to attain a desired physical state are exponentially distributed dependent on the controllable process rates. For the case where the costs associated with the process rates and the inventory levels are non-decreasing convex, and the process rates take values from finite sets, we show that there exist threshold policies on both inventory levels for selecting the optimal process rates at each station.Item Open Access Optimal pattern of technology adoptions under embodiment: a multi-stage optimal control approach(John Wiley & Sons Ltd., 2011) Saglam, C.By deriving the necessary conditions for a multi-stage optimal control problem where the endogenous switching instants appear as an argument of the state equation, we analyze the optimal pattern of technology adoptions under embodiment with a finite planning horizon. We show that the optimal pattern of technology adoptions depends crucially on how the growth rate advantage compares to the adjustment and the obsolescence costs inherent to embodiment. We obtain non-stationary lifetimes for the adopted technologies due to finite planning horizon. We analyze numerically the effects of planning horizon, speed of adjustment to the new technology, growth rate of technology and the impatience rate on the optimal pattern. Copyright © 2010 John Wiley & Sons, Ltd.Item Open Access Parameter identification for partially observed diffusions(Kluwer Academic Publishers-Plenum Publishers, 1992) Dabbous, T.E.; Ahmed, N.U.In this paper, we consider the identification problem of drift and dispersion parameters for a class of partially observed systems governed by Ito equations. Using the pathwise description of the Zakai equation, we formulate the original identification problem as a deterministic control problem in which the unnormalized conditional density (solution of the Zakai equation) is treated as the state, the unknown parameters as controls, and the likelihood ratio as the objective functional. The question of existence of elements in the parameter set that maximize the likelihood ratio is discussed. Further, using variational arguments and the Gateaux differentiability of the unnormalized density on the parameter set, we obtain the necessary conditions for optimal identification. © 1992 Plenum Publishing Corporation.Item Open Access Robust LQ control for harmonic reference/disturbance signals(IEEE, 2000) Köroğlu, Hakan; Morgül, ÖmerLinear Quadratic (LQ) controller design is considered for continuous-time systems with harmonic signals of known frequencies and it is shown that the design is reducible to an interpolation problem. All LQ optimal loops are parametrized by a particular solution of this interpolation problem and a (free) stable/proper transfer function. The appropriate choice of this free parameter for optimal stability robustness is formulated as a multiobjective design problem and reduced to a Nevanlinna-Pick interpolation problem with some interpolation points on the boundary of the stability domain. Using a related result from the literature, it is finally shown that, if there is sufficient penalization on the power of the control input, the level of optimum stability robustness achievable with LQ optimal controllers is the same as the level of optimum stability robustness achievable by arbitrary stabilizing controllers.Item Open Access Sensitivity minimization by stable controllers: an interpolation approach for suboptimal solutions(IEEE, 2007) Gümüşsoy, S.; Özbay, HitayWeighted sensitivity minimization is studied within the framework of strongly stabilizing (stable)H∞controller design for a class of infinite dimensional systems. This problem has been solved by Ganesh and Pearson, [8], for finite dimensional plants using Nevanlinna-Pick interpolation. We extend their technique to a class of unstable time delay systems. Moreover, we illustrate suboptimal solutions, and their robust implementation.Item Open Access Short time series microarray data analysis and biological annotation(IEEE, 2008) Sökmen, Z.; Atalay, V.; Çetin-Atalay, RengülSignificant gene list is the result of microarray data analysis should be explained for the purpose of biological functions. The aim of this study is to extract the biologically related gene clusters over the short time series microarray gene data by applying unsupervised methods and automatically perform biological annotation of those clusters. In the first step of the study, short time series microarray expression data is clustered according to similar expression profiles. After that, several biological data sources are integrated to get information related with the genes in one of those clusters and new sub-clusters are created by using this unified information. As a last step, biological annotation of gene sub-clusters is performed by using information related with those sub-clusters.