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Automatic Control, IEEE Transactions on

Issue 1 • Date Jan. 1988

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Displaying Results 1 - 20 of 20
  • On the phase portrait of a class of large nonlinear dynamic systems such as the power system

    Page(s): 4 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1378 KB)  

    Complete results are presented on the phase portrait of a class of large nonlinear dynamic systems that includes the power system. The connection between the constant energy surface and the stability boundary of the power system is explored. This gives valuable insight into classical stability tests, which are based on the constant energy surface. An approach to stability monitoring of the power system derived from these results is outlined.<> View full abstract»

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  • Stability regions of nonlinear autonomous dynamical systems

    Page(s): 16 - 27
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    A topological and dynamical characterization of the stability boundaries for a fairly large class of nonlinear autonomous dynamic systems is presented. The stability boundary of a stable equilibrium point is shown to consist of the stable manifolds of all the equilibrium points (and/or closed orbits) on the stability boundary. Several necessary and sufficient conditions are derived to determine whether a given equilibrium point (or closed orbit) is on the stability boundary. A method for finding the stability region on the basis of these results is proposed. The method, when feasible, will find the exact stability region, rather than a subset of it as in the Lyapunov theory approach. Several examples are given to illustrate the theoretical prediction.<> View full abstract»

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  • A perturbation analysis of interactive static and dynamic bifurcations

    Page(s): 28 - 41
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    The instability behavior of a nonlinear autonomous system in the vicinity of a coincident critical point, which leads to interactions between static and dynamic bifurcations, is studied. The critical point considered is characterized by a simple zero and a pair of pure imaginary eigenvalues of the Jacobian, and the system contains two independent parameters. The static and dynamic bifurcations and quasiperiodic motions resulting from the interaction of the bifurcation modes and the associated invariant tori are analyzed by a novel unification technique that is based on an intrinsic perturbation procedure. Divergence boundary, dynamic bifurcation boundary, secondary bifurcations, and invariant tori are determined explicitly. Two illustrative examples concerning control systems are presented.<> View full abstract»

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  • Optimal control of a queueing system with two interacting service stations and three classes of impatient tasks

    Page(s): 42 - 49
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    The problem of task selection and service priority is studied for a queueing network with two interacting service stations and three classes of impatient tasks. By using stochastic dynamic programming, a functional equation for the optimal, state-dependent priority assignment policy is derived. Properties of the optimal cost-to-go functions and the optimal policy are established through inductive proofs. It is shown that the optimal policy is governed by two switching surfaces in the three-dimensional state space (one dimension for each task class). For the infinite-time-horizon case, the optimal policy is shown to be stationary. In this case, the optimal cost-to-go function and switching surfaces are obtained numerically by using the overrelaxed Gauss-Seidel method. Sensitivities of the optimal policy with respect to key system parameters are also investigated.<> View full abstract»

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  • Design issues in adaptive control

    Page(s): 50 - 58
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    An integrated approach to the design of practical adaptive control algorithms is presented. Many existing ideas are brought together, and the effect of various design parameters available to a user is explored. The theory is extended by showing how the problem of stabilizability of the estimated model can be overcome by running parallel estimators. It is shown how asymptotic tracking of deterministic set points can be achieved in the presence of unmodeled dynamics.<> View full abstract»

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  • Robust control with structure perturbations

    Page(s): 68 - 78
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    The problem of making a given stabilizing controller robust so that the closed-loop system remains stable for prescribed ranges of variations of a set of physical parameters in the plant. The problem is treated in the state-space and transfer-function domains. In the state-space domain a stability hypersphere is determined in the parameter space using Lyapunov theory. The radius of this hypersphere is iteratively increased by adjusting the controller parameters until the prescribed perturbation ranges are contained in the stability hypersphere. In the transfer-function domain a corresponding stability margin is defined and optimized on the basis of the recently introduced concept of the largest stability hypersphere in the space of coefficients of the closed-loop characteristic polynomial. The design algorithms are illustrated by examples.<> View full abstract»

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  • The experimental computer control of a two-dimensional hyperbolic system

    Page(s): 79 - 87
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    The system treated consists of a 5-foot gold-coated rubber membrane mounted on a circular cylindrical drum. Seven electrodes reside on a command surface located behind the membrane inside the drum, serving as capacitive sensors and electrostatic force actuators of transverse membrane deflection. The membrane is modeled as flat, isotropic, and uniformly tensioned. Controllers regulating membrane deflection are designed using aggregation and design procedures based on sensor and actuator influence functions. The resulting control laws are implemented on a minicomputer in two sets of experiments. The first set studies modal pole placement and direct regulation of simulated model noise. The second set investigates the indirect regulation of simulated noise in a residual mode via spillover at different synthesized spillover levels. The study shows that spillover can be made a beneficial source of damping in residual systems.<> View full abstract»

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  • Decentralized structures for parallel Kalman filtering

    Page(s): 88 - 94
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    Various multisensor network scenarios with signal processing tasks that are amenable to multiprocessor implementation are described. The natural origins of such multitasking are emphasized, and novel parallel structures for state estimation using the Kalman filter are proposed that extend existing results in several directions. In particular, hierarchical network structures are developed that have the property that the optimal global estimate based on all the available information can be reconstructed from estimates computed by local processor nodes solely on the basis of their own local information and transmitted to a central processor. The algorithms potentially yield an approximately linear speedup rate, are reasonably failure-resistant, and are optimized with respect to communication bandwidth and memory requirements at the various processors.<> View full abstract»

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  • Adaptive parameter estimation for a constrained low-pass system

    Page(s): 109 - 112
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    A novel algorithm is presented for adaptive parameter estimation for a constrained low-pass Butterworth system model. The algorithm will estimate the system cutoff frequency and gain online. When it is known that the true system has a low-pass Butterworth structure or some transfer function similar to it and its true order is used, the algorithm will lead to a substantial savings in computation and more accurate results than unconstrained algorithms. Potential applications include filter design and adaptive decision on Nyquist rate for systems View full abstract»

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  • Stability conditions for multisequence systems with cyclic service

    Page(s): 102 - 103
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    The conditions under which several multiqueue systems with cyclic service (also referred to as polling systems) will be stable are investigated. The stability conditions established are more general than those established by other authors. In particular, both station stability and system stability are considered for polling systems for which an exact analysis has been obtained and for those for which an exact analysis has not yet been obtained View full abstract»

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  • Independent parameterization of two-degree-of-freedom compensators in general robust tracking systems

    Page(s): 59 - 67
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    Consideration is given to a general robust tracking problem in which the controlled object is a linear multivariable system having measured variables that are not necessary coincident with the output variables to be controlled. A necessary and sufficient condition for the two-degree-of-freedom compensator to achieve a robust tracking system with internal stability is given. An existence condition is derived for such a compensator, and the class of all such compensators is parameterized, so that two specifications with respect to responses for reference commands and feedback properties can be satisfied independently by the two free parameters View full abstract»

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  • Generalization of Monopoli's error augmentation and an application

    Page(s): 117 - 118
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    A frequently used adaptive control signal processing technique often called error augmentation is generalized. A broader class of adaptive control structures is now allowed. As an illustration, a sensitivity- and robustness-specifying structure is given that requires the generalization View full abstract»

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  • On L2- and L-stability approaches for the robust control of robot manipulators

    Page(s): 118 - 122
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    Robustness results were recently obtained for the linear and nonlinear control of robot manipulators using the L2- and L -stability approaches, respectively. Critical remarks on these approaches and further investigations are presented. In order to investigate L2-stability, it is shown that additional assumptions have to be made and a reformulation of the control problem has to be carried out View full abstract»

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  • Saddle point conditions for a class of stochastic dynamical games with imperfect information

    Page(s): 98 - 101
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    Nonlinear dynamical games are considered in which one player has full (causal) information on the state and the opponent's measurements and control, while the other one only has partial, possibly noise-corrupted, state information. A dynamic-programming-like algorithm in an extended space is given that, when successful, yields, a saddle point, usually in mixed strategies. This result is used to provide an equilibrium in safe strategies for the case in which both players are restricted to imperfect state information View full abstract»

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  • Persistency of excitation results for structured nonminimal models

    Page(s): 112 - 116
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    It is frequently convenient to use specially structured nonminimal models for parameter estimation such as in the case of direct adaptive control where the model is parameterized in terms of the desired control law parameters. This is done, for example, in direct model reference adaptive control and in direct pole assignment adaptive control algorithms. It is shown that the parameters appearing in these nonminimal models can be uniquely estimated if and only if a certain design identity has a unique solution. The result is used to develop persistency of excitation results for these models View full abstract»

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  • Simultaneous eigenvalue lower bounds for the Lyapunov matrix equation

    Page(s): 126 - 128
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    Simultaneous eigenvalue lower bounds for the solution of the Lyapunov equation are presented. The n-summation and the n -product bounds generalize existing bounds such as those for the trace and the determinant. These bounds are stronger than the majority of the relevant bounds shown in the literature View full abstract»

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  • Frequency domain conditions for the solvability of the multivariable disturbance decoupling problem

    Page(s): 122 - 126
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    Given a plant description in terms of its transfer matrices, necessary and sufficient conditions are derived in the frequency domain for the solvability of the multivariable disturbance decoupling problem with independent controlled and measured outputs View full abstract»

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  • Extension of the optimality of the threshold policy in heterogeneous multiserver queueing systems

    Page(s): 104 - 109
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    The authors extend the validity of some results on the optimal control of two-server queueing models with service times of unequal distribution, operating in continuous or discrete time. The distribution of arrivals can be arbitrary subject to some conditions. Both discounted and long-run average costs are considered. Dynamic programming and probabilistic arguments are used to establish the assertion that the optimal policy is of threshold type, i.e. the slower server should be utilized only when the queue length exceeds a certain threshold value View full abstract»

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  • On tracking characteristics of weighted least squares estimators applied to nonstationary system identification

    Page(s): 96 - 98
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    The parameter-tracking abilities of weighted-least-squares (WLS) estimators are characterized in terms of a suitably defined variability matrix and associated frequency characteristics. Using these concepts, the conflict arising between the estimation variance and estimation bandwidth is easily explained and quantified View full abstract»

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  • First-order tracking properties of weighted least squares estimators

    Page(s): 94 - 96
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    The first-order tracking properties (evolution of the mean tracking error) of weighted-least-squares (WLS) estimators applied to nonstationary system identification are investigated. The expected path of the parameter estimates is evaluated. The concept of the impulse response associated with the WLS estimator is introduced 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