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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Youla parameterization in closed-loop vibrational control

    Publication Year: 1994 , Page(s): 1455 - 1459
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    In this paper, we give a parameterization of a class of stabilizing vibrational controllers for single-input single-output systems. In particular, we show that for the averaged system, Youla parameterization takes place, and we use this parameterization to design a controller that satisfies unit step response specifications for the original (nonaveraged) system View full abstract»

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  • An eigenstructure assignment algorithm for the design of fault detection filters

    Publication Year: 1994 , Page(s): 1521 - 1524
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    In this paper, we present an algorithm for the construction of detection spaces in a fault detection filter by direct eigenstructure assignment. The algorithm permits great flexibility and simplifies the process of designing fault detection filters View full abstract»

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  • New conditions for the exponential stability of evolution equations

    Publication Year: 1994 , Page(s): 1432 - 1436
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    New conditions for the exponential stability for both linear nonautonomous finite and a class of infinite-dimensional systems described by parabolic partial differential equations (PDEs) are derived. The results for the parabolic systems are derived via semigroup approach View full abstract»

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  • Superposition properties and performance bounds of stochastic timed-event graphs

    Publication Year: 1994 , Page(s): 1376 - 1386
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    This paper addresses the performance evaluation of stochastic timed-event graphs. The transition firing times are random variables with general distribution. We first consider a stochastic timed-event graph in which the firing times are generated by time superposition (or addition) of two sets of random variable sequences. Properties of this system are established. Chiefly, we prove that the average cycle time is subadditive, i.e., it is smaller than the sum of the average cycle times of the two stochastic timed-event graphs in which the firing times are generated by one of the two sets of random variable sequences, respectively. Based on these superposition properties, we derive various upper bounds of the average cycle time of a general stochastic timed-event graph. In particular, we obtain upper bounds which converge to the exact average cycle time as the standard deviations of the firing times decrease. Finally, we derive performance bounds for stochastic timed-event graphs with bounded firing times View full abstract»

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  • Polynomial solution of the standard multivariable ℋ2-optimal control problem

    Publication Year: 1994 , Page(s): 1502 - 1507
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    In this work The authors solve the standard multivariable ℋ 2-optimal control problem using polynomial matrix techniques View full abstract»

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  • Adaptive control of nonlinear systems with a triangular structure

    Publication Year: 1994 , Page(s): 1411 - 1428
    Cited by:  Papers (101)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB)  

    In this paper, we introduce two distinct types of nonlinear dynamical systems, 𝒯1 and 𝒯2, both of which possess a triangular structure. It is shown that all systems belonging to 𝒯1 can be made stable and that if they belong to a subclass 𝒯1s, the stability holds globally. A precise characterization of the general class of nonlinear systems transformable to 𝒯1 is carried out. The second class, 𝒯2, corresponds to a set of second-order nonlinear differential equations and is motivated by problems that occur in mechanical systems. It is shown that global tracking can be achieved for all systems in 𝒯2. A constructive approach is used in all cases to develop the adaptive controller, and both stabilization and tracking are shown to be realizable. Simple examples are given to illustrate the different classes of nonlinear systems as well as the idea behind the approach used to stabilize them 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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  • 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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  • 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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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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Editor-in-Chief
P. J. Antsaklis
Dept. Electrical Engineering
University of Notre Dame