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Automatic Control, IEEE Transactions on

Issue 1 • Date February 1975

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Displaying Results 1 - 25 of 60
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Comments on "Estimation in linear delayed discrete-time systems with correlated state and measurement noises"

    Page(s): 176 - 177
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    In a recent paper, equations were derived for the state estimation and the error covariance of a linear discrete-time delayed system involving correlated noises. However, there appears to be a fundamental mistake in the procedure given and this is corrected. View full abstract»

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  • Author's reply

    Page(s): 178
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    The author thanks Dr. Jury for his comments. The auxiliary constraints, based on evaluation of F(1) and F(-1), can be used to shorten the necessary computation, particularly in the singular cases. (In the nonsingular case, evaluation of F(1) and F(-1) is comparable to the steps saved in the tabular form.) It is to be noted, however, that the simplicity of the proposed method and the directness with which results are presented lend themselves to the assimilation of the auxiliary constraints and any other information incidental to a specific problem into the analysis. View full abstract»

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  • Comments on "On the Routh-Hurwitz criterion"

    Page(s): 178 - 179
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    First Page of the Article
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  • Author's reply

    Page(s): 179
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    First Page of the Article
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  • Author's reply

    Page(s): 180
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    First Page of the Article
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  • Author's reply

    Page(s): 181
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    The author appreciates very much the comments on his work and the commenter's supplement of other important references related to the subject of system order reduction. With respect to the comment on the physical basis of the criterion he describes, the author maintains he has clearly stated in his article that the criterion is based on the philosophy that the low order model L(s) is chosen to approximate the frequency response of the higher order system H(s). On the point of using a vector criterion instead of a scalar criterion, there is no doubt that the former is, in theory, more powerful than the latter. However, the former may easily lead to optimization problems which are more difficult to solve. The author fully agrees with the commentor's view that the "best model" is highly dependent on the specific application involved. Therefore, a more logical way for obtaining a specific model is to incorporate into the simplification criterion, a priori, elements measuring the performance of the resulting overall system. View full abstract»

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  • [Back cover]

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  • Least squares simulation of distributed systems

    Page(s): 75 - 83
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    This paper addresses the application of linear optimal control theory to the least squares functional approximation of linear initial-boundary value problems. The method described produces the optimal approximate solution by the realization of a linear quadratic servo configuration imposed on the Galerkin simulation for the problem. It is shown that appropriate formulation of the servo problem guarantees a stable numerical solution, even when the Galerkin simulation itself is unstable, a situation not uncommon with certain hyperbolic partial differential equations. Theoretical least squares and Galerkin properties are comparatively discussed, and numerical examples demonstrating least squares convergence in the face of Galerkin divergence are presented. View full abstract»

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  • Input regularity of cascaded systems

    Page(s): 120 - 123
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    Necessary and sufficient conditions for the input regularity of a tandem connection of two multivariable systems are given. The results are specialized to the case of state-space equations, in which case input regularity is equivalent to controllability. Also the problem is considered whether the composite system can be made input regular by means of a suitable connection of the two subsystems. View full abstract»

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  • Some new results in linear time-varying systems

    Page(s): 159 - 161
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    This correspondence presents some new results for linear time-varying systemsdot{x}(t)=A(t)x(t). These new results include, 1) an explicit necessary and sufficient condition of stability that can be determined directly by joint eigenvalues of two constant matrices, and 2) a new class of reducible systems which needs not be periodic, as is required in Floquet theory. View full abstract»

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  • On the computation of optimal stochastic observer gains

    Page(s): 145 - 146
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    The design of a reduced-order continuous-time optimal stochastic observer has been based on the solution of a full-order covariance equation which restricts the implementation benefits of the reduced-order estimator. In this correspondence, it is shown that the gains of the reduced-order observer can be obtained by solving a reduced-order covariance equation, thus gaining the benefits of the reduced-order estimator. View full abstract»

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  • On the global controllability of perturbed nonlinear systems

    Page(s): 170 - 172
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    Sufficient conditions for global controllability of certain types of perturbed nonlinear time-varying systems are given. The results are obtained by using Schauder's fixed-point theorem. View full abstract»

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  • On the calculation of the transfer function matrix

    Page(s): 134 - 135
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    Given the state space realization{A,B,C}of a linear time-invariant multivariable dynamic system, a computational algorithm for calculating elements of the corresponding transfer function matrix is presented. The algorithm neither requires cofactor calculation, nor applies any state transformation. The only requirement is calculation of the coefficients of characteristic equations of given matrices. Also, the Fortran subroutine based on the presented algorithm is included. View full abstract»

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  • Calculation of optimum feedback gains for output-constrained regulators

    Page(s): 164 - 166
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    The problem of numerical calculation of optimal output-constrained feedback regulators is considered. A new sequential computational procedure yields the regulator solution in several steps. The number of steps depends on the difference between the dimensions of the state and output vector. View full abstract»

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  • Sensitive decoupling control of linear disturbed-parameter systems

    Page(s): 151 - 153
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    The input-output decoupling control problem for a generalized multivariable linear model, covering most practical situations, is treated for the case where the model involves disturbances in the parameters. A sensitive decoupling controller is derived which maintains the decoupling conditions to first order in the parameter variations, about their nominal values. View full abstract»

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  • Estimation for rotational processes with one degree of freedom--Part I: Introduction and continuous-time processes

    Page(s): 10 - 21
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    A class of bilinear estimation problems involving single-degree-of-freedom rotation is formulated and resolved. Continuous-time problems are considered here, and discrete-time analogs will be studied in a second paper. Error criteria, probability densities, and optimal estimates on the circle are studied. An effective synthesis procedure for continuous-time estimation is provided, and a generalization to estimation on arbitrary Abelian Lie groups is included. Applications of these results to a number of practical problems including frequency demodulation will be considered in a third paper. View full abstract»

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  • Some notes on the inversion of confluent Vandermonde matrices

    Page(s): 154 - 157
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    The determination of the inverse of the confluent Vandermonde matrix stood often in the focus of attention. To achieve this aim many methods were elaborated. Based on the Leibniz rule of derivation, in this correspondence the elements of the inverse confluent Vandermonde matrix are computed, and, at the same time, a common explanation is given for the various methods seeming at the first sight quite different. View full abstract»

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  • Output feedback stabilization and related problems-solution via decision methods

    Page(s): 53 - 66
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    Given an unstable finite-dimensional linear system, the output feedback problem is, first, to decide whether it is possible by memoryless linear feedback of the output to stabilize the system, and, second, to determine a stabilizing feedback law if such exists. This paper shows how this and a number of other linear system theory problems can be simply reformulated so as to allow application of known algorithms for solution of the existence question, with the construction problem being solved by some extension of these known algorithms. The first part of the output feedback problem is solvable with a finite number of rational operations, and the second with a finite number of polynomial factorizations. Other areas of application of the algorithm are described: Stability and positivity tests, low-order observer and controller design, and problems related to output feedback. Alternative computational procedures more or less divorced from the known algorithms are also proposed. View full abstract»

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  • Eigenvalue and eigenfunction sensitivity of distributed-parameter systems (DPS)

    Page(s): 172 - 174
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    The first-and second-order eigenvalue/eigenfunction sensitivities to system parameter variations are studied for a class of linear distributed-parameter control systems having a discrete and distinct spectrum. An illustrative example is given. View full abstract»

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  • Superiority of transfer function over state-variable methods in linear time-invariant feedback system design

    Page(s): 84 - 97
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    The objectives and achievements of state-variable methods in linear time-invariant feedback system synthesis are examined. It is argued that the philosophy and objectives associated with eigenvalue realization by state feedback, with or without observers, are highly naive and incomplete in the practical context of control systems. Furthermore, even the objectives undertaken have not really been attained by the state-variable techniques which have been developed. The extremely important factors of sensor noise and loop bandwidths are obscured by the state-variable formulation and have been ignored in the state-variable literature. The basic fundamental problem of sensitivity in the face of significant plant parameter uncertainty has hardly received any attention. Instead, the literature has concentrated primarily on differential sensitivity functions and even those results are so highly obscured in the state-variable formation as to lead to incorrect conclusions. In contrast, the important practical considerations and constraints have been clearly revealed and considered in the transfer function formulation. Differential sensitivity results are simple and transparent. For single input-output systems, there exists an exact design technique for achieving quantitative sensitivity specifications in the face of significant parameter uncertainty, which is optimum in an important practical sense. This problem is much more difficult and has not been completely solved for multivariable systems, but it has at least been realistically attacked by some transfer function methods. Finally, the concepts of controllability and observability so much emphasized in the state-variable literature are examined. It is argued that their importance in this problem class has been greatly exaggerated. On the one hand, transfer function methods can be used to check for their existence. On the other hand, nothing is lost when they are ignored, if the synthesis problem is treated as one with parameter uncertainty by transfer function methods. View full abstract»

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  • A branching algorithm for discriminating and tracking multiple objects

    Page(s): 101 - 104
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    A recursive branching algorithm for multiple-object discrimination and tracking consists of a bank of parallel filters of the Kalman form, each of which estimates a trajectory associated with a certain selected measurement sequence. The measurement sequences processed by the algorithm are restricted to a tractable number by combining similar trajectory estimates, by excluding unlikely measurement/state associations, and by deleting unlikely trajectory estimates. The measurement sequence selection is accomplished by threshold tests based on the innovations sequence and state estimates of each filter. Numerical experiments performed using the algorithm illustrate how the accuracy of the a priori state estimates and trajectory model influences the selectivity of the algorithm. View full abstract»

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  • Algebraic approach to discrete linear control

    Page(s): 116 - 120
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    A new unified approach to the optimal control of discrete linear constant systems is presented. The approach is based exclusively on algebraic properties of polynomials and the synthesis procedure reduces to solving a linear polynomial Diophantine equation. This is believed to be conceptually simpler and computationally superior to existing methods. 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

Full Aims & Scope

Meet Our Editors

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