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Automatic Control, IEEE Transactions on

Issue 5 • Date May 1994

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Displaying Results 1 - 25 of 47
  • Comments on "Block multirate input-output model for sampled-data control systems"

    Page(s): 1145 - 1147
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (295 KB)  

    In the above paper, Albertos (1990) presents a modeling technique to model linear, time-invariant systems with synchronous sampling. The model is derived from both the discrete transfer function and state-space representation of a given system and yields two similar expressions. Albertos equates the two in Lemma 2.1; there is, however, an inconsistency in Lemma 2.1, and this is discussed further.<> View full abstract»

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  • Comments on "Two necessary conditions for a complex polynomial to be strictly Hurwitz and their applications in robust stability analysis" [with reply]

    Page(s): 1147 - 1148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (93 KB)  

    In the original paper, Y. Q. Shi, K. K. Yen, and C. M. Chen (IEEE Trans. Automat. Contr., vol. 38, no. 1, p. 125-8, 1993) present two simple necessary conditions for a polynomial with complex coefficients to be strictly Hurwitz. They claim that this is an extension and refinement of a result of Xie and Xie (1988). Polyak and Tsypkin comment that the second condition is well known and that the first one is a direct corollary of Newton's test for a polynomial to have only real roots. The original authors express their appreciation for certain points but state that their intention was to point out two conditions for use in stability analysis.<> View full abstract»

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  • Comments on "Stabilization via static output feedback

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (79 KB)  

    In the above paper (Trofino-Neto and Kucera, 1993) the proof given for theorem (3.1) is inconsistent; in this note a modified proof is suggested.<> View full abstract»

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  • Computational complexity of μ calculation

    Page(s): 1000 - 1002
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The structured singular value μ measures the robustness of uncertain systems. Numerous researchers over the last decade have worked on developing efficient methods for computing μ. This paper considers the complexity of calculating μ with general mixed real/complex uncertainty in the framework of combinatorial complexity theory. In particular, it is proved that the μ recognition problem with either pure real or mixed real/complex uncertainty is NP-hard. This strongly suggests that it is futile to pursue exact methods for calculating μ of general systems with pure real or mixed uncertainty for other than small problems View full abstract»

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  • Achievable closed-loop properties of systems under decentralized control: conditions involving the steady-state gain

    Page(s): 932 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1092 KB)  

    The question of the existence of decentralized controllers for open-loop stable multivariable systems which provide particular closed-loop properties is investigated. In particular, we study the existence of decentralized controllers which provide integral action (Type I closed-loop performance) and also demonstrate one or more of: unconditional stability, integrity with respect to actuator and sensor failure, and decentralized unconditional stability. Necessary, sufficient, and, in some cases, necessary and sufficient conditions on the open-loop steady-state gain are derived such that there exists a controller which provides these desired closed-loop characteristics. These results provide the basis for a systematic approach to control structure selection for decentralized controller design View full abstract»

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  • A normality theorem for decentralized control of discrete-event systems

    Page(s): 1089 - 1093
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Derives a necessary condition, formulated as a normality theorem, for decentralized control of discrete event systems. The result is of practical interest since it can be tested to determine whether decentralization is possible. This result is applied to the classical coordination problem of the “dining philosophers” for illustrative purposes View full abstract»

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  • Heuristics, rules of thumb, and the 80/20 proposition

    Page(s): 1025 - 1027
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    The author discusses perspectives in the quest for optimality in design. The author provides a perspective, indicates a new direction for optimization research, and supplies a rationale for the use of heuristics in decision making. The author submits that it pays to ask a softer question in a large category of complex problems. However, the author is not advocating a license to be sloppy and to stop the search for good heuristics. Indeed, the author's intentions are to point out the possibility of quantifying heuristics View full abstract»

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  • On the general solution of the state deadbeat control problem

    Page(s): 1002 - 1006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    In this note, the state deadbeat control problem is considered. It is shown that, after appropriate change of basis of input and state spaces, the general solution of the state deadbeat control problem can be expressed completely by the rows of the powers of system matrix. This result yields a very simple procedure for the calculation of a state feedback deadbeat control gain. It also provides the number of free parameters which could be used for further design purposes. The results are illustrated by an example at the end of the note View full abstract»

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  • Sampled-data controller design for uncertain systems

    Page(s): 1036 - 1042
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    Presents a sampled-data controller design methodology for uncertain systems. A continuous system with bounded time-varying uncertainty is sampled at intervals of length T. The controller is designed using a Riccati equation approach by neglecting O(T2) uncertainty terms in the discretized system. Stability is verified for this choice of T with the U(T2) terms included. If there exists a stabilizing continuous controller, then there also exists a stabilizing sampled-data controller for a sufficiently small choice of T View full abstract»

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  • On the connection between nonlinear differential-algebraic equations and singularly perturbed control systems in nonstandard form

    Page(s): 1079 - 1084
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    Considers a class of control systems represented by nonlinear differential equations depending on a small parameter. The systems are not in the standard singularly perturbed form, and therefore, one of the challenges is to show that the control systems do represent singularly perturbed two-time-scale systems. Assumptions are introduced which guarantee that an equivalent representation for the systems can be obtained in the standard singularly perturbed form, thereby justifying the two-time-scale property. The equations for the slow dynamics are characterized by a set of differential-algebraic equations which have been studied previosly in the literature. The fast dynamics are characterized by differential equations. Both the slow and the fast dynamics are easily derived and are defined in terms of variables that define the original control system. Control design for the class of systems being considered is studied using the composite control approach View full abstract»

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  • Properties of a low-frequency approximation balancing method of model reduction

    Page(s): 1135 - 1141
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    This correspondence describes a balancing technique of model reduction which is characterized by exactness at zero frequency. Various interesting properties and error bounds of the reduced-order model are derived in a rigorous manner. A critical comparison is made to Moore's reduced model (1981) obtained by direct truncation. An illustrative numerical example is included View full abstract»

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  • On the elastic mode estimation aspect of a class of multibody flexible systems

    Page(s): 1016 - 1020
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    An investigation pertaining to estimation of the elastic generalized coordinates for a given class of flexible structures is presented. To begin with, a model for studying nonlinear dynamics of the structure is described. The governing equations of motion are obtained using the Lagrangian procedure with modal discretization. Next, deformations caused by rapid slewing maneuvers are estimated using the least square estimation approach. As an alternative, a procedure based on the operator spline technique is proposed and its potential assessed. It is motivated by the need for achieving an on-line estimation procedure permitting real time control. Finally, a comparative performance study of the two procedures is undertaken using a simplified model of the flexible system View full abstract»

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  • Bounded error identification of time-varying parameters by RLS techniques

    Page(s): 1106 - 1110
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The performance of the recursive least squares algorithm with constant forgetting factor in the identification of time-varying parameters is studied in a stochastic framework. It is shown that the mean square tracking error keeps bounded if and only if the so-called covariance matrix of the algorithm is L1-bounded. Then, a feasibility range for the forgetting factor is worked out in correspondence of which the covariance matrix (and therefore the tracking error) keeps bounded View full abstract»

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  • Vibrational control of nonlinear time lag systems with bounded delay: averaging theory, stabilizability, and transient behavior

    Page(s): 898 - 912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1168 KB)  

    This paper develops the theory of vibrational control of nonlinear time lag systems with arbitrarily large but bounded delay. Averaging theory for fast oscillating, differential delay equations is presented and then applied to vibrational control. Conditions are given which ensure the existence of parametric vibrations that stabilize nonlinear time lag systems. Transient behavior is also discussed. Illustrative examples are given which show 1) the feasibility of the theory to important applications and 2) the differences in the theory presented and the existing known theory for vibrational control of ordinary differential equations View full abstract»

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  • Modeling and control of a floating platform

    Page(s): 1075 - 1078
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    A platform with a rotating crane resting on three adjustable floats in a tub has been built on laboratory scale. Controller design is studied to prevent the platform from leaning due to crane movements. The system dynamics can be described primarily by a simple sixth order linear model. Model errors are then due mainly to unmodeled effects of waves that are essentially linear transfers. It is precisely under these conditions that H design should perform well. Actual design and tests show that H controllers do not substantially outperform LQG designs combined with feedforward controllers, but the combination of both feedforward and feedback controllers can easily be obtained by H design techniques View full abstract»

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  • Stationarity and reciprocity in stochastic multipoint boundary value systems

    Page(s): 1114 - 1116
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    Investigates certain statistical properties of the state vector in a stochastic multipoint boundary value system. The authors give necessary and sufficient conditions for the state vector to be stationary, and prove that the state vector is locally reciprocal View full abstract»

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  • On the rate of convergence of a distributed asynchronous routing algorithm

    Page(s): 1123 - 1129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    We analyze a distributed asynchronous algorithm, proposed by Tsitsiklis and Bertsekas (1986), for optimal routing in a virtual-circuit data network. We show that, under a strict convexity assumption on the link delay functions, the sequence of routings generated by the algorithm converges in the space of path flows and the convergence rate is linear. Our analysis is based on estimating the distance from a routing to the set of optimal routings and, for the synchronous case, it gives an explicit estimate of the convergence ratio in terms of the network parameters View full abstract»

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  • Approximate solution of large sparse Lyapunov equations

    Page(s): 1110 - 1114
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    Describes a simple method for efficiently estimating the dominant eigenvalues and eigenvectors of the solution to a Lyapunov equation, without first solving the equation explicitly. The method is based on the power method and matrix-vector multiplications and is particularly suitable for problems where those multiplications can be done efficiently, such as where the coefficient matrices are large and sparse or low-rank. The same idea is directly applicable to balanced-truncation order reduction of linear systems View full abstract»

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  • The discrete-time q-Markov cover models with improved low-frequency approximation

    Page(s): 1102 - 1105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A new method of obtaining q-Markov cover models for linear discrete systems based on singular perturbation technique is proposed. The reduced-order models obtained not only match initial Markov parameters and high-frequency power moments like conventional q-Markov covers, but also match the initial time moments and low-frequency power moments of the original system View full abstract»

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  • Eigenstructure assignment by decentralized output feedback-a complete parametric approach

    Page(s): 1009 - 1014
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The problem of eigenstructure assignment in multivariable linear systems by decentralized output feedback is considered. By using a complete parametric solution of a generalized Sylvester matrix equation, parametric representations of both the left and right closed-loop eigenvectors and generalized eigenvectors as well as the feedback gains with respect to the closed-loop eigenvalues and two series of partially free parameter vectors are established. The obtained result does not require any conditions on the closed-loop eigenvalues, and generalizes some previous results in this area. An example shows the effect of the proposed approach View full abstract»

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  • A fundamental notion of equivalence for linear multivariable systems

    Page(s): 1141 - 1145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A fundamental form of equivalence of polynomial matrix descriptions of linear multivariable systems is defined, based on the existence of a bijective map between the finite and infinite solution sets of the differential equations describing the two systems. The connection with the system matrix relationship of full system equivalence is established View full abstract»

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  • Avoiding stick-slip through PD control

    Page(s): 1094 - 1097
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Addresses the question of how to achieve steady motion at very low velocities using proportional-derivative (PD) control. Most prior work in control has used friction models which depend only on the current value of velocity. This type of analysis indicates that stick-slip can be avoided only through velocity feedback. The tribology literature, however, indicates that friction also depends on the history of motion. By including this dependence, a second regime of stable motion is revealed which is associated with position feedback gains above a critical value. Two experimentally-based dynamic friction models are compared using a linearized stability analysis. In accord with experiment, a state variable friction model exhibits asymptotically stable motion for any system stiffness (position feedback gain) exceeding a critical value. This property is not exhibited by a time-lag friction model View full abstract»

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  • On the time complexity of worst-case system identification

    Page(s): 944 - 950
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    In this paper we treat a general worst-case system identification problem. This problem is worst-case with respect to both noise and system modeling uncertainty. We consider this problem under various a priori information structures. We determine bounds on the minimum duration identification experiment that must be run to identify the plant to within a specified guaranteed worst-case error bound. Our results are algorithm independent. We show that this minimum duration is prohibitively long. Based on our results, we suggest that worst-case (with respect to noise) system identification requires unrealistic amounts of experimental data View full abstract»

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  • Design of robust controllers for time-delay systems

    Page(s): 995 - 999
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The problem of stabilizing linear dynamical time-delay systems subject to bounded uncertainties is investigated. Two memoryless feedback controllers are considered. It is established that when the matching conditions are met and certain bounding relations are satisfied, then the linear controller renders the zero-response of the system asymptotically stable. Saturation-type controllers are shown to guarantee that all system responses are uniformly ultimately bounded View full abstract»

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  • Distributed algorithms with random processor failures

    Page(s): 1032 - 1036
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Examines a distributed algorithm where the processors may fail in a random fashion. This results in a model with random communication delays. Convergence conditions are derived. Extensions of the analysis and results to cases where the random processor failures are perceived and corrected within random time intervals are possible. For the sake of simplicity, the analysis is presented for a two processor model for solving a system of linear equations View full abstract»

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Aims & Scope

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