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Automatic Control, IEEE Transactions on

Issue 6 • Date Jun 1994

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Displaying Results 1 - 25 of 36
  • Numerical solution of the discrete-time periodic Riccati equation

    Publication Year: 1994 , Page(s): 1197 - 1210
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    In this paper we present a method for the computation of the periodic nonnegative definite stabilizing solution of the periodic Riccati equation. This method simultaneously triangularizes by orthogonal equivalences a sequence of matrices associated with a cyclic pencil formulation related to the Euler-Lagrange difference equations. In doing so, it is possible to extract a basis for the stable deflating subspace of the extended pencil, from which the Riccati solution is obtained. This algorithm is an extension of the standard QZ algorithm and retains its attractive features, such as quadratic convergence and small relative backward error. A method to compute the optimal feedback controller gains for linear discrete time periodic systems is dealt with View full abstract»

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  • H2-optimal zeros

    Publication Year: 1994 , Page(s): 1298 - 1301
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Although the problem of pole placement has received enormous attention, the problem of zero placement has been relatively neglected. The latter, however, could be of substantial importance in some design problems, such as actuators and sensors positioning. In this paper, the authors characterize the zeros that ensure H2-optimality of transfer functions and analyze qualitative properties of the resulting systems View full abstract»

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  • Robust control of robot manipulators with parametric uncertainty

    Publication Year: 1994 , Page(s): 1230 - 1233
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    This paper proposes a robust control law for n-link robot manipulators with parametric uncertainty whose upper bound is not assumed to be known. The proposed robust control based on the Corless-Leitmann approach includes a simple estimation law for the upper bound on the parametric uncertainty and an additional control input to be updated as a function of the estimated value. Using the Lyapunov stability theory, the uniform ultimate boundedness of the tracking error is proved View full abstract»

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  • A robust algorithm for random parameter tracking

    Publication Year: 1994 , Page(s): 1211 - 1221
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    An algorithm for tracking time-varying parameters is studied. It is shown to be exponentially stable independently of the choice of algorithm parameters. We derive some useful nonasymptotic estimates for the tracking error and develop the asymptotically optimal version of the method View full abstract»

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  • H control of systems under norm bounded uncertainties in all system matrices

    Publication Year: 1994 , Page(s): 1320 - 1322
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    This paper concerns H control of systems under norm bounded uncertainties in all the system matrices. This is an extension of the work by Xie et al.(1992), where only the A matrix is allowed to be uncertain. It is found that the problem shares the same formulation with the H control problem for systems without uncertainties. It can also be viewed as reducing the problem of dealing with systems with both structured uncertainties and unstructured uncertainties to one with unstructured uncertainties only View full abstract»

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  • The Kalman-Bucy filter in the guaranteed estimation problem

    Publication Year: 1994 , Page(s): 1282 - 1286
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The optimal guaranteed a priori estimation problem is considered. The Kalman-Bucy filter is used for the approximate solving of this problem. The analytical estimate for the nonoptimality degree of the Kalman-Bucy filter is obtained. This estimate is determined by the Kalman-Bucy filter characteristics only. Thus the Kalman-Bucy filter efficiency can be established without accurate solving of the difficult optimal guaranteed estimation problem View full abstract»

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  • A ripple free sampled-data robust servomechanism controller using exponential hold

    Publication Year: 1994 , Page(s): 1287 - 1291
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    In a general command tracking and disturbance rejection problem, it is known that a sampled-data controller using zero-order hold may only guarantee the asymptotic tracking at the sampling instances, but cannot smooth out the ripples between the sampling instances. In this paper, a sampled-data robust servomechanism controller using exponential hold is developed for guaranteeing the asymptotic tracking not only at, but also between, the sampling instances. In this development, a so called “internally-reducible” condition to characterize a class of robust servomechanism controllers is derived first, then the proposed controller is shown to be contained in this class. Generally speaking, a sampled-data structure using exponential hold can provide more design freedoms so that it tends to simplify the construction of a robust servomechanism controller and facilitate the implementation on digital computers. An example for a DC motor control is presented to illustrate the advantages of this approach View full abstract»

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  • Identification of alternating renewal electric load models from energy measurements

    Publication Year: 1994 , Page(s): 1184 - 1196
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    In statistical load modeling methodologies, aggregate electric load behavior is derived by propagating the ensemble statistics of an individual load process which is representative of the loads in the aggregate. Such a modeling philosophy tends to yield models whereby if physical meaning is present at the elemental level, it is preserved at the aggregate level. This property is essential for applications involving direct control of power system loads. The potential applicability of statistical load models is a strong function of one's ability to limit the volume of unusual data required to build those. An identification algorithm for a previously proposed stochastic hybrid-state Markov model of individual heating-cooling loads is presented. It relies only on data routinely gathered in power systems (device energy consumption over constant time intervals). It exploits an alternating renewal viewpoint of the load dynamics. After deriving some general results on the occupation statistics of time homogeneous alternating renewal processes, the analysis is focused on the specific model. In the process, however, some intriguing features likely to be shared by a wide class of alternating renewal processes are revealed View full abstract»

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  • A counterexample on continuous coprime factors

    Publication Year: 1994 , Page(s): 1262 - 1263
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    In Georgiou and Smith (1992), the following question was raised: Consider a linear, shift-invariant system on L2[0, ∞). Let the graph of the system have Fourier transform (MN)H2 (i.e., the system has a transfer function P=N/M) where M, N are elements of CA={f∈H: f is continuous on the compactified right-half plane}. Is it possible to normalize M and N (i.e., to ensure |M|2+|N|2=1) in CA? The author shows by example that this is not always possible View full abstract»

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  • Modified extended Kalman filtering

    Publication Year: 1994 , Page(s): 1322 - 1326
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    In this paper we compare the performance of the extended Kalman filter (EKF) with that of a proposed filter called modified extended Kalman filter (MEKF), in terms of the actual state and the estimated state as a function of time and the integral-squared error as a function of noise intensity both for dynamics and measurement noise. All the simulation results indicate that the performance of the MEKF is better than EKF. For illustration, numerical examples are presented using both EKF and MEKF View full abstract»

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  • Stabilization of oscillations by a nonnegative feedback control

    Publication Year: 1994 , Page(s): 1273 - 1276
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    The feedback stabilization of m-dimensional nonlinear systems is studied in this note. The Jacobian is assumed to possess 2q purely imaginary eigenvalues and m-2q eigenvalues with negative real parts. The feedback control law is assumed to be nonnegative and given by the square of a linear function. The direct and indirect control systems are investigated. In both cases stabilizability is proved and explicit formulas for the feedback functions are obtained. Lyapunov's direct method is employed View full abstract»

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  • Steady-state behavior in the vibrational control of a class of nonlinear systems by AP-forcing

    Publication Year: 1994 , Page(s): 1255 - 1258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Vibrational control is an open-loop control technique that uses zero mean parametric vibrations for shaping the response of a linear or nonlinear dynamical system. Several theoretical results are available, based on averaging techniques, assuring the possibility of modifying the equilibrium properties of a system. For nonlinear systems, computational difficulties arise and theoretical results cannot easily be applied. In this note, the stationary behavior of a class of nonlinear systems vibrationally controlled by AP-forcing is investigated. A practical formula linking the amplitude and the frequency of the vibration and the amplitude of the steady-state oscillation in the controlled variable is obtained. As test cases, the well-known Rayleigh equation, a catalytic reactor equation, and the phase locked loop equation are considered View full abstract»

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  • Adaptively controlling nonlinear continuous-time systems using multilayer neural networks

    Publication Year: 1994 , Page(s): 1306 - 1310
    Cited by:  Papers (105)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Multilayer neural networks are used in a nonlinear adaptive control problem. The plant is an unknown feedback-linearizable continuous-time system. The control law is defined in terms of the neural network models of system nonlinearities to control the plant to track a reference command. The network parameters are updated online according to a gradient learning rule with dead zone. A local convergence result is provided, which says that if the initial parameter errors are small enough, then the tracking error will converge to a bounded area. Simulations are designed to demonstrate various aspects of theoretical results View full abstract»

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  • Necessary and sufficient conditions for the Hurwitz and Schur stability of interval matrices

    Publication Year: 1994 , Page(s): 1251 - 1255
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Establishes a set of new sufficient conditions for the Hurwitz and Schur stability of interval matrices. The authors use these results to establish necessary and sufficient conditions for the Hurwitz and Schur stability of interval matrices. The authors relate the above results to the existence of quadratic Lyapunov functions for linear time-invariant systems with interval-valued coefficient matrices. Using the above results, the authors develop an algorithm to determine the Hurwitz and the Schur stability properties of interval matrices. The authors demonstrate the applicability of their results by means of two specific examples View full abstract»

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  • Stabilizing controller design for linear systems with sensor or actuator failures

    Publication Year: 1994 , Page(s): 1224 - 1230
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    In this paper, the stability of the standard linear, time-invariant, multi-input multi-output unity-feedback system is investigated in the presence of either sensor or actuator failures. Any diagonal stable perturbation is included in the failure descriptions. Stabilizing controllers are synthesized for two failure classes: the first class allows at most one failure at a time; the second class requires at least one connection without failure. A parameterization of all stabilizing controllers is achieved with prior knowledge of the failure. A controller design method requiring no knowledge of the failure is also presented; this method is restricted to plants for which certain closed-loop transfer functions can be made diagonal View full abstract»

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  • Robust Kalman filtering for uncertain discrete-time systems

    Publication Year: 1994 , Page(s): 1310 - 1314
    Cited by:  Papers (107)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    This paper is concerned with the problem of a Kalman filter design for uncertain discrete-time systems. The system under consideration is subjected to time-varying norm-bounded parameter uncertainty in both the state and output matrices. The problem addressed is the design of a linear filter such that the variance of the filtering error is guaranteed to be within a certain bound for all admissible uncertainties. Furthermore, the guaranteed cost can be optimized by appropriately searching a scaling design parameter View full abstract»

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  • Feedback control of linear systems by multirate pulse-width modulation

    Publication Year: 1994 , Page(s): 1292 - 1297
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    In this note, sampled-data methods for modeling and control design of pulse-width modulated systems are examined. Both single-rate and multirate approaches are considered. Local controllability and observability analyses of the sampled-data models are performed, and feedback linearizability conditions for the sampled-data models are derived. Multirate nonlinear state and output feedback designs are presented that permit asymptotic regulation or tracking View full abstract»

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  • Coordinating locomotion and manipulation of a mobile manipulator

    Publication Year: 1994 , Page(s): 1326 - 1332
    Cited by:  Papers (69)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    A mobile manipulator in this study is a manipulator mounted on a mobile platform. Assuming the end point of the manipulator is guided, e.g., by a human operator to follow an arbitrary trajectory, it is desirable that the mobile platform is able to move as to position the manipulator in certain preferred configurations. Since the motion of the manipulator is unknown a priori, the platform has to use the measured joint position information of the manipulator for its own motion planning. This paper presents a control algorithm for the platform so that the manipulator is always positioned at the preferred configurations measured by its manipulability. Simulation results are presented to illustrate the efficacy of the algorithm. The algorithm is also implemented and verified on a real mobile manipulator system. The use of the resulting algorithm in a number of applications is also discussed View full abstract»

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  • The nonlinear interactor and its application to input-output decoupling

    Publication Year: 1994 , Page(s): 1246 - 1250
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The solvability of the input-output decoupling problem via pure dynamic state feedback, a special type of dynamic compensator without zeros at infinity, is investigated. A necessary and sufficient condition for the solvability of this problem is established in terms of a nonlinear interactor, a new concept in the theory of nonlinear control View full abstract»

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  • System identification using Kautz models

    Publication Year: 1994 , Page(s): 1276 - 1282
    Cited by:  Papers (67)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    In this paper, the problem of approximating a linear time-invariant stable system by a finite weighted sum of given exponentials is considered. System identification schemes using Laguerre models are extended and generalized to Kautz models, which correspond to representations using several different possible complex exponentials. In particular, linear regression methods to estimate this sort of model from measured data are analyzed. The advantages of the proposed approach are the simplicity of the resulting identification scheme and the capability of modeling resonant systems using few parameters. The subsequent analysis is based on the result that the corresponding linear regression normal equations have a block Toeplitz structure. Several results on transfer function estimation are extended to discrete Kautz models, for example, asymptotic frequency domain variance expressions View full abstract»

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  • Efficient algorithm for a class of least squares estimation problems

    Publication Year: 1994 , Page(s): 1241 - 1243
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A computationally efficient algorithm for solving least squares estimation problems is proposed. It is well suited for problems with the normal equation matrix factorizable in terms of Kronecker's products. Three classes of identification problems factorizable in this sense are pointed out. Computational complexity of the algorithm and its robustness against round off errors is also discussed View full abstract»

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  • An algorithm for computing value sets of uncertain transfer functions in factored real form

    Publication Year: 1994 , Page(s): 1268 - 1273
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    An algorithm is given for the fast computation of the value sets of uncertain transfer functions, including parametric uncertainty in factored real form and multiplicative unstructured uncertainty. The uncertain parameters are assumed to belong to compact intervals. Elementary value sets are computed for each factor. Vector addition and edge detection in the logarithmic complex plane are used to compute the complete value set. The algorithm is meant for robust control system design View full abstract»

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  • Discrete-time compensators with loop transfer recovery

    Publication Year: 1994 , Page(s): 1259 - 1262
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Loop transfer recovery (LTR) has gained some prominence over the last years. In this paper, the authors briefly overview the main design features of the LQG/LTR controller both at the input and at the output of the plant, using the delta operator formulation developed in Middleton and Goodwin (1990). Two discrete-time compensators with LTR capability are then derived following the LTR design approach proposed in Chen, Saberi, and Sannuti (1991) for the continuous-time case. These compensators are shown to outperform their underlying LQG/LTR controllers from the perspective of recovery error. Of particular importance, they share the same degree of recovery as the continuous time compensators of the above papers when the sampling period goes to zero View full abstract»

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  • An input normal form homotopy for the L2 optimal model order reduction problem

    Publication Year: 1994 , Page(s): 1302 - 1305
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    In control system analysis and design, finding a reduced-order model, optimal in the L2 sense, to a given system model is a fundamental problem. The problem is very difficult without the global convergence of homotopy methods, and a homotopy based approach has been proposed. The issues are the number of degrees of freedom, the well posedness of the finite dimensional optimization problem, and the numerical robustness of the resulting homotopy algorithm. A homotopy algorithm based on the input normal form characterization of the reduced-order model is developed here and is compared with the homotopy algorithms based on Hyland and Bernstein's optimal projection equations. The main conclusions are that the input normal form algorithm can be very efficient, but can also be very ill conditioned or even fail View full abstract»

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  • A cyclic switching strategy for parameter-adaptive control

    Publication Year: 1994 , Page(s): 1172 - 1183
    Cited by:  Papers (39)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    This paper introduces a new strategy, called “cyclic switching,” to deal with the well-known certainty equivalence control synthesis problem which arises in the design of identifier-based adaptive controllers because of the existence of points in parameter space where the design model ΣD, upon which certainty equivalence synthesis is based, loses stabilizability. Unlike most previously suggested methods for handling this problem, the technique proposed here can be employed with or without process excitation. For the technique to work it is not necessary for there to be a mechanism for moving tuned parameters away from values at which ΣD loses stabilizability, and no such mechanism is used 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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Editor-in-Chief
P. J. Antsaklis
Dept. Electrical Engineering
University of Notre Dame