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Automatic Control, IEEE Transactions on

Issue 6 • Date December 1980

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Displaying Results 1 - 25 of 54
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Editorial: Short papers: A denouement

    Page(s): 1025 - 1026
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    Freely Available from IEEE
  • Announcement: Student paper competition

    Page(s): 1026
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    Freely Available from IEEE
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  • Comments on "On the selection of the dominant poles of a system to be retained in a low-order model"

    Page(s): 1253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (109 KB)  

    A limitation of the model order selection criterion as proposed in the above correspondence is pointed out. It is shown that the results obtained from the criterion are not generally unique and acceptable. View full abstract»

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  • Authors' reply

    Page(s): 1253
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    First Page of the Article
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  • Stochastic optimal control: The discrete time case [Book reviews]

    Page(s): 1254 - 1255
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    Freely Available from IEEE
  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE
  • A new algorithm for model reference adaptive control with variable adaptation gains

    Page(s): 1245 - 1248
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    Most of the model reference adaptive control (MRAC) systems use constant gains for the adaptation algorithms. In this paper a variable gain adaptation algorithm is presented for continuous-time systems. The property of global asymptotic stability of the closed-loop adaptive system is perserved. View full abstract»

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  • Bounds on estimation errors of discrete-time filters under modeling uncertainty

    Page(s): 1115 - 1121
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The performance of Kalman-type linear discrete-time filters in the presence of modeling errors is considered, and bounds are obtained for the performance index, the mean-squared error of estimates for suboptimal filters. The computation of these bounds requires information on only the model matrices and the range of errors for these matrices. Consequently, a designer can easily evaluate the performance of a suboptimal filter when only the range of errors in the elements of the model matrices is available. View full abstract»

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  • Asymptotic pole locations and nonlinear controllers

    Page(s): 1240 - 1241
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    This note generalizes a recently introduced method which produces nonlinear controllers by assigning suitable state dependence to a scalar parameter in an existing stable controller. The form of state dependence is guided by properties of the original controller. For example, variations inTof the modified receding horizon controller are guided by the fact, proved here, that the poles associated with that controller lie to the left of (-1/2T). Nonlinearization of the LQR is also described. View full abstract»

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  • Decoupling of invertible nonlinear systems with state feedback and precompensation

    Page(s): 1237 - 1239
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    For a class of nonlinear invertible systems considered by Hirschorn [1], a decoupling control synthesis using state feedback and precompensation is presented. Two examples which include decoupling of vertical and horizontal path angles of a terrain-following airplane are presented. View full abstract»

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  • Design of self-calibrating controllers for heliostats in a solar power plant

    Page(s): 1091 - 1097
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    A self-calibrating controller is developed for reducing installation and drive errors in a heliostat (steerable mirror used in solar/electric energy conversion). In this scheme, the heliostat periodically tracks the sun, which serves as a precision position reference. The difference between commanded and actual drive angles is used to estimate the coefficients of a model representing installation and drive errors. The calibrated model is then used to correct the drive actuator commands for these error sources when the heliostat is in a tracking mode (its principle mode of operation). Simulation results are given for a typical heliostat configuration with realistic errors. The algorithm is very effective in reducing beam steering errors. The concept is demonstrated using a prototype test apparatus and is shown to achieve an error reduction of more than 5:1. View full abstract»

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  • Team decision theory for linear continuous-time systems

    Page(s): 1154 - 1161
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    This paper develops a team decision theory for linear-quadratic (LQ) continuous-time systems. First, a counterpart of the well-known result of Radner on quadratic static teams is obtained for two-member continuous-time LQ static team problems when the statistics of the random variables involved are not necessarily Gaussian. An iterative convergent scheme is developed, which in the limit yields the optimal team strategies. For the special case of Gaussian distributions, the team-optimal solution is affine in the information available to each DM, and for the further special case when the team cost function does not penalize the intermediate values of state, the optimal strategies can be obtained by solving a Liapunov type time-invariant matrix equation. This static theory is then extended to LQG continuous-time dynamic teams with sampled observations under the one-step-delay observation sharing pattern. The unique solution is again affine in the information available to each DM, and further, it features a certainty-equivalence property. View full abstract»

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  • Asymptotic holdability

    Page(s): 1196 - 1198
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    Given an autonomous linear control system and a linear subspaceS subset R^{n}, we say that an initial state is asymptotically holdable inSif the trajectory can be held arbitrarily nearSon any specified compact initial interval, subject to an L1bound on input energy which depends on the initial state and the interval. It is shown that asymptotic holdability is equivalent to holdability obtaining under a certain impulse control process. A geometric characterization is given. View full abstract»

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  • Adaptive state estimation using MRAS techniques--Convergence analysis and evaluation

    Page(s): 1169 - 1182
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    Three adaptive state observers for discrete-time systems derived from MRAS techniques are presented. While in a deterministic environment all of these schemes converge toward the linear asymptotic observer, when used in a stochastic environment for adaptive state estimation their performances present noticeable differences. The schemes considered in the paper are analyzed both in a deterministic and stochastic environment using the "equivalent feedback representation" (EFR) method and "ordinary differential equation" (ODE) method, respectively. Conditions for the convergence of the estimated parameters to the desired ones in a stochastic environment are given. The connections with adaptive Kalman filters are discussed. A comparative evaluation of these schemes in a deterministic and stochastic environment based on simulations concludes the paper. View full abstract»

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  • Identification and model approximation for continuous-time systems on finite parameter sets

    Page(s): 1202 - 1206
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    Almost-sure convergence of the maximum likelihood and the maximum a posteriori probability estimates of unknown parameters of continuous-time stochastic dynamical linear time-invariant systems is investigated. The unknown parameter set is assumed to be finite. The situation where the ture parameter does not belong to the unknown parameter set is considered, as well as the situation where the true model is included in the unknown parameter set. View full abstract»

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  • Optimal and suboptimal control policies for a solar collector system

    Page(s): 1085 - 1091
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    An optimal control problem to maximize the net energy gathered by a flat-plate solar collector system by controlling the collector fluid flow rate is investigated. The problem is formulated in terms of a distributed parameter system and solved using the method of characteristics. It is shown that if the pump of the collector loop is such that its pumping power is greater than a linear function of the fluid velocity, then the optimal control policy is one in which the fluid flow is instantly switched between zero and maximum rates. Necessary conditions that determine the optimal switching times are derived. Because the resultant switching function of the optimal policy is shown to be decomposable into two parts, one that depends on the state of the system and another that requires a priori knowledge of the solar intensity over the entire period of operation, a suboptimal control policy that can be implemented by an on/off feedback controller with hysteresis is proposed. When this suboptimal policy is compared with the optimal policy, it is shown that on a clear day with sufficient solar insolation to dictate a two-switch optimal policy, the two policies are identical. Under other weather conditions, the feedback suboptimal controller will keep the pump off for a slightly shorter period of time than the time dictated by the optimal control. View full abstract»

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  • Sensitivity analysis and optimal control theory applied to corona charging of electrographic films

    Page(s): 1078 - 1085
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    Multiple-wire ac corona chargers are designed to charge film to a final voltage which is well regulated with respect to parameter variations. These low-sensitivity designs are optimal in the sense that they minimize a performance index which penalizes high dc bias voltages. To obtain low sensitivity to film capacitance, velocity, and charging efficiency, the film must be charged so that its surface voltage "overshoots" as it moves past the charger. For low sensitivity to film leakage resistance, however, an "undershooting" response is required. In experimental tests the optimally designed chargers perform nearly as expected. View full abstract»

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  • Instability of optimal-aim control

    Page(s): 1250 - 1252
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    It is shown that the so-called optimal-aim control strategy [1] might destabilize a controllable linear time-invariant system. This raises a serious question about the efficacy of this strategy when applied to a more complicated nonlinear power system. View full abstract»

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  • Frequency domain conditions for disturbance rejection

    Page(s): 1211 - 1213
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    The solvability conditions for the problems of nulling the disturbance transfer function in a linear time-invariant multivariable system by: 1) linear state feedback and 2) linear state feedback and disturbance feedforward control are known in geometric terms. In this paper it is shown that alternative necessary conditions for solvability are that the order of each row of the open-loop control transfer function: 1) strictly dominates and 2) dominates the order of the corresponding row of open-loop disturbance transfer function. Moreover, it is shown that when there are at least as many control inputs as outputs, these necessary conditions for solvability are generically sufficient, and that in other cases both problems are generically unsolvable. View full abstract»

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  • Estimation of images modeled by a two-dimensional separable autoegressive process

    Page(s): 1199 - 1201
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    This note considers the estimation of two-dimensional images that may be modeled by a separable autoregressive process. We first derive a one-dimensional vector stochastic model with multiple delays for images; the one-dimensional vector model is further decomposed into a set of nearly independent equations using the matrix factorization theorem and the orthogonal sine transform [10]. Then, applying the kalman filter, the approximate feasible estimation algorithm is obtained. View full abstract»

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  • An adaptive d-step ahead predictor based on least squares

    Page(s): 1161 - 1165
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    This paper examines the asymptotic properties of a least squares algorithm for adaptively calculating ad-step ahead prediction of a time series. It is shown that, with probability one, the sample mean-square difference between time recursive prediction and the optimal linear prediction converges to zero. Relatively weak assumptions are required regarding the underlying model of the time series. View full abstract»

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  • Analysis of stochastic approximation schemes with discontinuous and dependent forcing terms with applications to data communication algorithms

    Page(s): 1042 - 1058
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    A general convergence result is given for stochastic approximation schemes with (or without) equality constraints. The following features are taken into account. The forcing term is a strongly dependent sequence and may be discontinuous. Many examples are given to illustrate the applicability of the convergence theorem, both classical (recursive least squares scheme) and nonclassical ones (arising in the theory of self-adaptive eqnalizers). View full abstract»

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  • Control of constrained systems of controllability index two

    Page(s): 1102 - 1111
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    Many natural and man-made systems satisfy a strong controllability hypothesis which results from a natural partition of the state space into "position" and "velocity" coordinates. In particular, plane linkage systems used as biped locomotion models satisfy these conditions. Systems satisfying this hypothesis admit linear state-variable feedback, which can be used to position not only the poles of the system, but also (to a substantial extent) the corresponding eigenvectors. The resulting eigenstructures can be designed to stabilize and decouple systems in such a way that specified subspaces of the state-space are invariant under the dynamics of the closed loop system. Computations and simulations for several types of constrained motion arising in biped locomotion problems are presented. 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