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Automatic Control, IEEE Transactions on

Issue 7 • Date July 1994

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Displaying Results 1 - 25 of 32
  • Comments on "Least squares methods for H/spl infin/ control oriented system identification"

    Publication Year: 1994
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    In the above paper by Helmicki-Jacobson (ibid. vol.38, no.5, p.819-26 (1993)), the authors present two sets of convergent least squares algorithms for identification in H/spl infin/. In this paper we: (1) point out an error in the proof of convergence for the first set; (2) show that the first set of optimization problems is really equivalent to a special case of the second set; and (3) provide a small correction to the derivation of the error bounds for the second set of algorithms.<> View full abstract»

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  • Routing with limited state information in queueing systems with blocking

    Publication Year: 1994 , Page(s): 1492 - 1497
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Proves the optimality of routing policies with limited state information that are employed in queueing systems with finite capacities and customers arriving at arbitrary instants. Using sample path arguments it is shown that, on one hand, when service times are exponential and capacities are equal, the round robin policy minimizes the expected number of losses by any time t and at the same time, maximizes the expected number of departures by t, over all policies that use no state information. On the other hand, when service times are deterministic, a modified round robin policy that makes use of limited state information outperforms stochastically all dynamic policies that have richer state information, in terms of the number of losses and the number of departures by t View full abstract»

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  • Controllability distributions and systems approximations: a geometric approach

    Publication Year: 1994 , Page(s): 1473 - 1476
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Given a nonlinear system we determine a relation at an equilibrium between controllability distributions defined for a nonlinear system and a Taylor series approximation of it. The value of such a relation is appreciated if we recall that the solvability conditions as well as the solutions to some control synthesis problems can be stated in terms of geometric concepts like controlled invariant (controllability) distributions. The relation between these distributions at the equilibrium will help us to decide when the solvability conditions of this kind of problems are equivalent for the nonlinear system and its approximation View full abstract»

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  • Criteria for choosing the horizon in extended horizon predictive control

    Publication Year: 1994 , Page(s): 1467 - 1470
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    This paper presents some simple criteria for choosing the prediction horizon in extended horizon predictive control (EHPC) so that the closed-loop system is stable. In these criteria, the horizon is selected according to some characteristics of the impulse response of the plant View full abstract»

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  • A recursive Schur-based solution of the four-block problem

    Publication Year: 1994 , Page(s): 1476 - 1481
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    We describe a new solution to the four-block problem using the method of generalized Schur analysis. We first reduce the general problem to a simpler one by invoking a coprime factorization with a block-diagonal inner matrix. Then, using convenient spectral factorizations, we are able to parameterize the unknown entry in terms of a Schur-type matrix function, which is shown to satisfy a finite number of interpolation conditions of the Hermite-Fejer type. All possible interpolating functions are then determined via a simple recursive procedure that constructs a transmission-line (or lattice) cascade of elementary J-lossless sections. This also leads to a parameterization of all solutions of the four-block problem in terms of a linear fractional transformation View full abstract»

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  • Convergence of the signed output error adaptive identifier

    Publication Year: 1994 , Page(s): 1387 - 1399
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    This paper considers an adaptive output error identifier with a signum function in its update kernel. It is shown that the classical strict positive real (SPR) condition required for the convergence of traditional adaptive identifiers does not suffice for the convergence of this signed identifier. Instead, what is needed is a stronger operator condition called the strict dominant passive (SDP) condition. We give an analog of the Kalman-Yakubovic-Popov Lemma for the SDP conditions and, using it, give a convergence proof under the assumptions of persistent excitation and SDP View full abstract»

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  • Nonlinear controllers for positive real systems with arbitrary input nonlinearities

    Publication Year: 1994 , Page(s): 1513 - 1517
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Input nonlinearities such as saturation can severely degrade closed-loop performance due to integrator windup and other effects. For positive real plants with positive real controllers, we propose a nonlinear controller modification that effectively counteracts the effects of arbitrary input nonlinearities. For this class of problems, we prove global asymptotic stability of the closed-loop system and demonstrate closed-loop performance by means of system simulation View full abstract»

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  • Control of asynchronous sampled data systems

    Publication Year: 1994 , Page(s): 1451 - 1455
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    This paper is concerned with the problem of controller design in the case of asynchronous sampled data systems. Optimal LQG controllers are obtained for the class of two-rate systems where all the control inputs are held at a rate which is asynchronously related to the rate with which all of the outputs are sampled. Furthermore for this class, a parameterization of all stabilizing controllers is provided View full abstract»

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  • On the convergence and ODE limit of a two-dimensional stochastic approximation

    Publication Year: 1994 , Page(s): 1439 - 1442
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    We consider a two-dimensional stochastic approximations scheme of the Robbins-Monro type which naturally arises in the study of steering policies for Markov decision processes. Making use of a decoupling change of variables, we establish its almost sure convergence by ad-hoc arguments that combine standard results on one-dimensional stochastic approximations with a version of the law of large numbers for martingale differences. We use this direct analysis to guide us in selecting the test function which appears in standard convergence results for multidimensional schemes. Furthermore, although a blind application of the ordinary differential equation (ODE) method is not possible here due to a lack of regularity properties, the aforementioned change of variables paves the way for an interpretation of the behavior of solutions to the associated limiting ODE View full abstract»

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  • On regularizing descriptor systems by output feedback

    Publication Year: 1994 , Page(s): 1507 - 1509
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    In this paper, linear time-invariant descriptor-variable systems are considered which are either nonregular or, if they are regular, they have impulsive modes. It is shown that if a certain necessary and sufficient condition is satisfied, then both regularity can be established and impulsive modes can be eliminated by output feedback. We have also considered the problem of achieving structural properties of the regularized system View full abstract»

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  • Necessary and sufficient conditions for the controllability and observability of a class of linear, time-invariant systems with interval plants

    Publication Year: 1994 , Page(s): 1443 - 1447
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    We establish necessary and sufficient conditions for the controllability of single-input/multi-output linear time-invariant systems with interval plants and for the observability of multi-input/single-output linear time-invariant systems with interval plants. In arriving at our results, we determine allowable plant uncertainty bounds for controllability and observability. Two specific examples are considered to demonstrate the applicability of our results View full abstract»

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  • Cycle time of stochastic event graphs: evaluation and marking optimization

    Publication Year: 1994 , Page(s): 1482 - 1486
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    Addresses the performance evaluation and optimization of a strongly connected event graph with random firing times. The authors proposed an upper bound and a lower bound for the average cycle time of event graphs knowing the initial marking. The authors then prove that, under some weak conditions on the firing time distributions, it is possible to reach, on average, a cycle time smaller than any given value C* with a finite marking, assuming that C* is greater than the greatest firing time. Finally, the authors propose an heuristic algorithm to reach such an average cycle time while minimizing a p-invariant criterion View full abstract»

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  • Robust parametric classical control design

    Publication Year: 1994 , Page(s): 1524 - 1530
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    This paper extends well-known graphical design tools such as the Nyquist plot, Bode plot, and Nichols charts to the domain of control systems containing parameter uncertainty. We have specifically considered linear interval control systems, namely those where the uncertain parameters appear linearly in the characteristic polynomial and vary in intervals, because in these cases exact construction of frequency envelopes is possible. Using these developments, we calculate various extremal stability margins for such systems, and these are used with standard classical control design techniques to deal with robustness with respect to parametric uncertainty. In addition, we give an effective technique to iteratively select values of the design parameters within given ranges so that the closed loop system produces improved gain or phase margin View full abstract»

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  • Stochastic optimization of regenerative systems using infinitesimal perturbation analysis

    Publication Year: 1994 , Page(s): 1400 - 1410
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB)  

    We consider the problem of optimizing the steady-state mean of a controlled regenerative process using a stochastic optimization algorithm driven by infinitesimal perturbation analysis (IPA) derivative estimates. We derive IPA derivative estimates for our problem and prove almost sure convergence of the algorithm. The generality of our formulation should encompass a wide variety of practical systems. We illustrate our framework and results via several examples View full abstract»

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  • A direct approach to decentralized control of service rates in a closed Jackson network

    Publication Year: 1994 , Page(s): 1460 - 1463
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    In this note, we consider a problem of decentralized control of service rates in a closed Jackson network under the long-run time-average expected cost criterion. We use a direct approach to solving the problem. The approach is based on an intrinsic property of the product-form solution: if the cost function is an affine function of a service rate, then the long-run average expected cost is always monotone in that service rate. This intrinsic property leads immediately to the optimality of bang-bang or threshold policies. The result extends the existing result obtained by linear programming, to more general cost functions View full abstract»

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  • Analysis on the Laguerre formula for approximating delay systems

    Publication Year: 1994 , Page(s): 1517 - 1521
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    This paper provides a detailed analysis on the commonly employed Laguerre formula for approximating delay systems. Convergence proofs are provided, and error bounds are constructed with respect to the L∞ and L2 norms View full abstract»

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  • New approach to block-diagonalization of singularly perturbed systems by Taylor expansion

    Publication Year: 1994 , Page(s): 1429 - 1431
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Block-diagonalization of a singularly perturbed system requires the solution of the Riccati equation and the Lyapunov equation. A new approach is suggested for both equations, using Taylor expansions. The convergence is studied in detail; it is shown that it is ensured under restrictions which are less restrictive than the case of previously suggested methods View full abstract»

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  • A computational scheme for H∞ model reduction

    Publication Year: 1994 , Page(s): 1447 - 1451
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    In this paper, a computational scheme for the H∞ model reduction problem is introduced. The scheme is illustrated by three examples. The algorithm is based on the recent characterization of the solution to the H∞ model reduction problem. A suboptimal computational procedure for the general multivariable continuous-time rth order optimal H model reduction problem is developed View full abstract»

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  • Hysteresis switching adaptive control of linear multivariable systems

    Publication Year: 1994 , Page(s): 1360 - 1375
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1228 KB)  

    This paper presents a model reference adaptive control scheme for deterministic continuous-time multivariable systems represented by square, strictly proper, minimum-phase transfer function matrices. A typical requirement of existing algorithms is to assume that the zero structure at infinity and the high-frequency gain matrix are fully (or at least partially) known. It is well known that these requirements may be very restrictive, since, in general, both the zero structure at infinity and the high-frequency gain matrix depend on plant parameters. In this paper we show that these restrictive assumptions may be considerably weakened using Morse et al.'s hysteresis switching control strategy (1992). The strategy entails running a finite number of parameter estimators in parallel and using a switching algorithm to select between candidate estimators based on their associated prediction errors. Hysteresis in the switching algorithm precludes switching arbitrarily rapidly between estimators, and all switching ceases within a finite time. The results represent a significant step forward in understanding the minimal amount of prior knowledge necessary to design a stabilizing controller for a linear multivariable system View full abstract»

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  • Rational ℒ1 suboptimal compensators for continuous-time systems

    Publication Year: 1994 , Page(s): 1487 - 1492
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The persistent disturbance rejection problem (L1 optimal control) for continuous time-systems leads to nonrational compensators, even for single input/single output systems. As noted in Dahleh and Pearson (1987), the difficulty of physically implementing these controllers suggests that the most significant application of the continuous time L1 theory is to furnish achievable performance bounds for rational controllers. In this paper the authors use the theory of positively invariant sets to provide a design procedure, based upon the use of the discrete Euler approximating system, for suboptimal rational L1 controllers with a guaranteed cost. The main results of the paper show that (i) the L 1 norm of a continuous-time system is bounded above by the l 1 norm of an auxiliary discrete-time system obtained by using the transformation z=1+rs and (ii) the proposed rational compensators yield L1 cost arbitrarily close to the optimum, even in cases where the design procedure proposed in the above mentioned paper fails due to the existence of plant zeros on the stability boundary View full abstract»

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  • Extreme-point robust stability results for discrete-time polynomials

    Publication Year: 1994 , Page(s): 1470 - 1472
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    This paper provides some new extreme-point robust-stability results for discrete-time polynomials with special uncertainties in the coefficient space. The proofs, obtained using the bilinear transformation, are simple, and the results specialize to existing robust-stability results View full abstract»

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  • Optimal choice of time-scaling factor for linear system approximations using Laguerre models

    Publication Year: 1994 , Page(s): 1463 - 1467
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Clowes (1965) illustrated how to select the optimal time-scaling factor for approximations of rational transfer functions using a series expansion of Laguerre functions. The present paper extends this result to approximations for general, L2 stable, linear systems. As a direct application of this extended result, we are able to obtain approximations for irrational transfer functions which minimize the frequency domain error in the L2 sense. Also, we give empirical solutions for the optimal time-scaling factor for approximations of first order plus delay systems which can then be applied to a larger class of overdamped systems View full abstract»

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  • On a robust nonlinear servomechanism problem

    Publication Year: 1994 , Page(s): 1510 - 1513
    Cited by:  Papers (59)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A notion of kth-order robust control for the nonlinear servomechanism problem is introduced. A transmission zeros condition is given for the existence of a kth-order robust control law such that, regardless of small parameter perturbations of the plant and control law, the closed-loop system will induce a stable invariant manifold with the error map zero up to kth-order at each point of the manifold. Such a control law incorporates an internal model of up to k subsystems determined by the exosystem. A special case of the result of this paper recovers the well-known linear robust servomechanism result View full abstract»

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  • Feedback control of quantized constrained systems with applications to neuromorphic controllers design

    Publication Year: 1994 , Page(s): 1497 - 1502
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    During the last few years there has been considerable interest in the use of trainable controllers based upon the use of neuron like elements, with the expectation being that these controllers can be trained, with relatively little effort, to achieve good performance. Good performance, however, hinges on the ability of the neural net to generate a “good” control law even when the input does not belong to the training set, and it has been shown that neural nets do not necessarily generalize well. It has been proposed that this problem can be solved by essentially quantizing the state space and then using a neural net to implement a table lookup procedure. There is little information on the effect of this quantization upon the controllability properties of the system. In this paper The authors address this problem by extending the theory of control of constrained systems to the case where the controls and measured states are restricted to finite or countably infinite sets. These results provide the theoretical framework for previously suggested neuromorphic controllers, but they are also valuable for analyzing the controllability properties of computer-based control systems View full abstract»

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  • An algorithm for the computation of 2-D eigenvalues

    Publication Year: 1994 , Page(s): 1436 - 1439
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    In this paper, a definition for the eigenvalues of two-dimensional (2-D) general discrete state-space models is proposed. This definition is consistent with that known for 2-D Roesser models. Also, a programmable algorithm is developed to compute the 2-D eigenvalues View full abstract»

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In the IEEE Transactions on Automatic Control, the IEEE Control Systems Society publishes high-quality papers on the theory, design, and applications of control engineering.  Two types of contributions are regularly considered

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Meet Our Editors

Editor-in-Chief
P. J. Antsaklis
Dept. Electrical Engineering
University of Notre Dame