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Automatic Control, IEEE Transactions on

Issue 2 • Date Feb. 1994

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Displaying Results 1 - 25 of 33
  • Comments on two methods for designing a digital equivalent to a continuous control system

    Publication Year: 1994 , Page(s): 420 - 421
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (213 KB)  

    Rattan (1984, 1989) suggests two methods for designing a digital control system to match the performance of a given continuous control system as closely as possible. In this note, two main points are made. First, there are a number of errors in the paper by Rattan (1989) that significantly affect its conclusions. Second, neither of the methods is guaranteed to produce a stable closed-Loop system, even if the original closed-loop system is stable. In fact, the two methods will generally lead to unstable closed-loop systems when the number of free parameters in the compensator design process is large.<> View full abstract»

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  • Comments on "On a property of compensators designed by the separation principle" /spl lsqb/with reply/spl rsqb/

    Publication Year: 1994 , Page(s): 447 - 448
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    In the above paper by B. Friedland et al. (ibid., vol.38, no.2, p.370-3 (1993)), a proof is given that, in a control system designed with a full-state observer and state feedback control, the compensator transfer function is the same no matter how the closed-loop poles are distributed between the observer and the controller. The present author points out that a technique is known for computing the observer and controller feedback gains corresponding to all possible distributions of closed-loop poles between the observer and the controller. He further points out that the way the closed-loop poles are distributed can make an important difference to the closed-loop system behavior. In reply, Friedland et al. are grateful for the citation of the two references given and they point out further advantage of the controller-observer implementation.<> View full abstract»

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  • A parameterization for the class of all stabilizing controllers for linear minimum phase plants

    Publication Year: 1994 , Page(s): 433 - 434
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    This note gives a simple parameterization for the class of stabilizing controllers for linear single-input single-output minimum phase plants. This result is the dual of the well-known parameterization for the class of all stabilizing controllers for linear single-input single-output stable plants View full abstract»

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  • Supervisory control of timed discrete-event systems

    Publication Year: 1994 , Page(s): 329 - 342
    Cited by:  Papers (90)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    The Ramadge-Wonham framework for control of discrete event systems is augmented with timing features by use of Ostroff's semantics for timed transition models. It is shown that the RW concept of controllability and the existence of maximally permissive supervisory controls can be suitably generalized. The enhanced setting admits subsystem composition and the concept of forcible event as an event that preempts the tick of a global clock. An example of a simple manufacturing cell illustrates how the new framework can be used to solve synthesis problems which may include logic-based, temporal and quantitative optimality specifications View full abstract»

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  • Time complexity of a path formulated optimal routing algorithm

    Publication Year: 1994 , Page(s): 385 - 391
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A detailed analysis of convergence rate is presented for an iterative path formulated optimal routing algorithm. In particular, it is quantified, analytically, how the convergence rate changes as the number of nodes in the underlying graph increases. The analysis is motivated by a particular path formulated gradient projection algorithm that has demonstrated excellent convergence rate properties through extensive numerical studies. The analytical result proven in this note is that the number of iterations for convergence depends on the number of nodes only through the network diameter View full abstract»

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  • On stability of interval matrices

    Publication Year: 1994 , Page(s): 368 - 371
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    New sufficient, and sometimes necessary and sufficient conditions, are obtained for Schur- and Hurwitz-stability of interval matrices by relying on the concept of connective stability and M-matrices. The necessity part is broadened to include interval matrices with mixed signs of the off-diagonal elements, provided the sign patterns follow that of the Morishima matrix. The obtained results are extended to cover convex combinations of interval matrices View full abstract»

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  • A new Smith predictor for controlling a process with an integrator and long dead-time

    Publication Year: 1994 , Page(s): 343 - 345
    Cited by:  Papers (94)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    A new Smith predictor for control of a process with an integrator and long dead-time is proposed in this note. The controller decouples the setpoint response from the load response. This simplifies both design and tuning. Simulation results obtained by controlling a typical process show that the new controller has superior performance compared to previous algorithms View full abstract»

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  • Relationship between availability of states and pole/zero cancellations in H-control

    Publication Year: 1994 , Page(s): 379 - 381
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    This note compares servo systems designed with three methods of H -control, that is, output feedback control, state feedback control and partial state feedback control. The three kinds of control use different information of the plant to generate the control input. We show that if more states are used, then the number of the pole/zero cancellations can be reduced View full abstract»

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  • A large deviations analysis of range tracking loops

    Publication Year: 1994 , Page(s): 360 - 364
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    Large deviations theory is applied to the analysis of a discrete time range tracking loop. It is shown that the resulting asymptotics differ from those of the continuous time diffusion limit View full abstract»

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  • Accuracy and stability of discrete-time filters generated by higher-order s-to-z mapping functions

    Publication Year: 1994 , Page(s): 435 - 441
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    This note compares several different approaches to selecting an s-to-z mapping function for the purpose of converting a continuous-time transfer function F(s) to an “equivalent” discrete-time transfer function FD(z). The primary bases of comparison are stability and accuracy. Secondary bases of comparison include: 1) the amount of computation needed to process one input to produce one output, 2) the ease with which the coefficients of FD(z) can be determined, in particular, as the sampling period T is varied, 3) the ease of determining stability, in particular, the maximum value of T for stability, 4) the self-starting capability, and 5) compatibility with decomposition in the s-domain View full abstract»

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  • Lyapunov stability of a class of discrete event systems

    Publication Year: 1994 , Page(s): 269 - 279
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    Discrete event systems (DES) are dynamical systems which evolve in time by the occurrence of events at possibly irregular time intervals. “Logical” DES are a class of discrete time DES with equations of motion that are most often nonlinear and discontinuous with respect to event occurrences. Recently, there has been much interest in studying the stability properties of logical DES and several definitions for stability, and methods for stability analysis have been proposed. Here the authors introduce a logical DES model and define stability in the sense of Lyapunov and asymptotic stability for logical DES. Then the authors show that more conventional analysis of stability which employs appropriate Lyapunov functions can be used for logical DES. The authors provide a general characterization of the stability properties of automata-theoretic DES models, Petri nets, and finite state systems. Furthermore, the Lyapunov stability analysis approach is illustrated on a manufacturing system that processes batches of N different types of parts according to a priority scheme (to prove properties related to the machine's ability to reorient itself to achieve safe operation) and a load balancing problem in computer networks (to study the ability of the system to achieve a balanced load to minimize underutilization) View full abstract»

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  • Unified formulation of variable structure control schemes for robot manipulators

    Publication Year: 1994 , Page(s): 371 - 376
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A general target model is proposed in the task space to represent motion trajectory, interaction force trajectory, and second-order function relating the motion errors and the interaction force errors. Using variable structure model reaching control (VSMRC) strategy, the model is achieved in the sliding mode with robust performance. Reaching transient can be eliminated or guaranteed with prescribed quality. By choosing a suitable model for the application, robust motion control, impedance control, hybrid position/force control, or constrained motion control are achieved, respectively View full abstract»

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  • Argument conditions for Hurwitz and Schur polynomials from network theory

    Publication Year: 1994 , Page(s): 345 - 346
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    The monotonicity conditions, recently given, for the arguments of Hurwitz polynomials, as well as some of their associated polynomials, are, very simply, derived using well-established results in network theory. Corresponding results for Schur polynomials may also be obtained View full abstract»

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  • A reduced order observer based controller design for H-optimization

    Publication Year: 1994 , Page(s): 355 - 360
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    In this note the H control problem with measurement feedback is investigated. It is well-known that for this problem, in general, we need controllers of the same dynamic order as the given system. However, in the case that some entries of the measurement vector are not noise-corrupted, we show that one can find dynamic compensators of a lower dynamical order. Note that this implies that the standard assumptions on the direct feedthrough matrices, as made in most papers on H control, are not satisfied. Our result can be derived by using reduced order observer based controllers. View full abstract»

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  • Decentralized stable factors and a parameterization of decentralized controllers

    Publication Year: 1994 , Page(s): 347 - 351
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Decentralized stable factors (DSF) are used to extend the stable factorization approach to the design of decentralized controllers. The DSF allow a parameterization of all the stabilizing decentralized controllers in the form of a Youla parameterization. A decentralized controller serves as the central controller, and the Youla parameter has a particular structure and must satisfy an interaction constraint. This parameterization encompasses several other parameterization results on decentralized control systems View full abstract»

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  • H-optimal control for singularly perturbed systems. II. Imperfect state measurements

    Publication Year: 1994 , Page(s): 280 - 299
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1404 KB)  

    For pt.I, see ibid., vol. 29, no. 2, p 401-423 (1993). In this paper we study the H-optimal control of singularly perturbed linear systems under general imperfect measurements, for both finite- and infinite-horizon formulations. Using a differential game theoretic approach, we first show that as the singular perturbation parameter (say, ε>0) approaches zero, the optimal disturbance attenuation level for the full-order system under a quadratic performance index converges to a value that is bounded above by (and in some cases equal to) the maximum of the optimal disturbance attenuation levels for the slow and fast subsystems under appropriate “slow” and “fast” quadratic cost functions, with the bound being computable independently of E and knowing only the slow and fast dynamics of the system. We then construct a controller based on the slow subsystem only and obtain conditions under which it delivers a desired performance level even though the fast dynamics are completely neglected. The ultimate performance level achieved by this “slow” controller can be uniformly improved upon, however, by a composite controller that uses some feedback from the output of the fast subsystem. We construct one such controller, via a two-step sequential procedure, which uses static feedback from the fast output and dynamic feedback from an appropriate slow output, each one obtained by solving appropriate ε-independent lower dimensional H-optimal control problems under some informational constraints. We provide a detailed analysis of the performance achieved by this lower-dimensional ε-independent composite controller when applied to the full-order system and illustrate the theory with some numerical results on some prototype systems View full abstract»

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  • On residual generation by observer and parity space approaches

    Publication Year: 1994 , Page(s): 441 - 447
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A unifying framework for observer design by eigenstructure assignment is described. A new technique for structured residual generation, based on this framework, is proposed. One of the main features of this technique is that the equivalence between residual generation by means of observers or parity space devices are made conspicuous. More precisely, from a computational point of view, the equations to solve in both cases are shown to be similar, and for implementation, both devices are shown to be identical. A necessary and sufficient condition for the existence of structured residuals is given. Finally the sensitivity of structured residuals to nondecoupled failures is studied and a procedure for maximizing this sensitivity is described View full abstract»

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  • Eigenvalues of tridiagonal symmetric interval matrices

    Publication Year: 1994 , Page(s): 377 - 379
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    An algorithm for the determination of the eigenvalues of tridiagonal symmetric interval matrices is presented. The intervals of the eigenvalues are not overestimated, but exactly calculated. The algorithm is an efficient one, because it only needs twice as many operations as the Sturm algorithm, which is used for real matrices View full abstract»

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  • Robust D-stability for linear uncertain discrete time-delay systems

    Publication Year: 1994 , Page(s): 425 - 428
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    We propose criteria which guarantee robust pole location within a specified circular region for a linear uncertain discrete time-delay system. The perturbations are treated with structured and unstructured information. Examples are given to demonstrate the result View full abstract»

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  • Suboptimal perfect model matching for a plant with measurement noise and its application to MRACS

    Publication Year: 1994 , Page(s): 422 - 425
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    This note describes a method for the design of discrete time model matching control systems for a plant with measurement noise, and the application of this method to model reference adaptive control systems. This method uses the free parameters of the controller. Simulation results are presented which confirm the validity of the design method View full abstract»

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  • On the convergence of least squares estimates in white noise

    Publication Year: 1994 , Page(s): 364 - 368
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The problem of convergence of least squares (LS) estimates in a stochastic linear regression model with white noise is considered. It is well known that if the parameter estimates are known to converge, the convergence analysis for many adaptive systems can be rendered considerably less arduous. For an important case where the regression vector is a measurable function of the observations and the noise is Gaussian, it has been shown, by using a Bayesian embedding argument, that the LS estimates converge almost surely for almost all true parameters in the parameter space except for a zero-measure set. However, nothing can be said about a particular given system, which is usually the objective. It has long been conjectured that such a “bad” zero measure set in the parameter space does not actually exist. A conclusive answer to this important question is provided and it is shown that the set can indeed exist. This then shows that to provide conclusive convergence results for stochastic adaptive systems, it is necessary to resort to a sample pathwise analysis instead of the Bayesian embedding approach View full abstract»

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  • A bilinear formulation for the output feedback problem in linear systems

    Publication Year: 1994 , Page(s): 410 - 414
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    This note ties together a geometric theory and previous algebraic results for the closed-loop eigenstructure assignment by output feedback in multivariable systems. Necessary and sufficient conditions for the closed-loop stabilization, eigenstructure assignment are presented in terms of a bilinear Sylvester equation, the solutions of which completely characterize the closed-loop eigenstructure problem with output feedback. Some preliminary results for the solution of this bilinear equation are presented View full abstract»

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  • Positively invariant sets for constrained continuous-time systems with cone properties

    Publication Year: 1994 , Page(s): 401 - 405
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    This note deals with some properties of particular bounded sets w.r.t. linear continuous-time systems described by x˙(t)=A(0)x(t)+c(t), where c(t)∈Ω⊂Rn, Ω a compact set, and matrix etA(0) has the property of leaving a proper cone K positively invariant, that is etA(0)K⊂K. The considered bounded sets 𝒟(K; a, b) are described as the intersection of shifted cones. Necessary and sufficient conditions are given. They guarantee that such sets are positively invariant w.r.t. the considered system. The trajectories starting from x 0∈Rn/𝒟(K; a, b) (respectively to x0 ∈Rn) are studied in terms of attractivity and contractivity of the set 𝒟(K; a, b). The results are applied to the study of the constrained state feedback regulator problem View full abstract»

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  • Ultimate boundedness control for uncertain discrete-time systems via set-induced Lyapunov functions

    Publication Year: 1994 , Page(s): 428 - 433
    Cited by:  Papers (118)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    In this note, linear discrete-time systems affected by both parameter and input uncertainties are considered. The problem of the synthesis of a feedback control, assuring that the system state is ultimately bounded within a given compact set containing the origin with an assigned rate of convergence, is investigated. It is shown that the problem has a solution if and only if there exists a certain Lyapunov function which does not belong to a preassigned class of functions (e.g., the quadratic ones), but it is determined by the target set in which ultimate boundedness is desired. One of the advantages of this approach is that we may handle systems with control constraints. No matching assumptions are made. For systems with linearly constrained uncertainties, it is shown that such a function may be derived by numerically efficient algorithms involving polyhedral sets. The resulting compensator may be implemented as a linear variable-structure control View full abstract»

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  • Polynomial J-spectral factorization

    Publication Year: 1994 , Page(s): 315 - 328
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    Several algorithms are presented for the J-spectral factorization of a para-Hermitian polynomial matrix. The four algorithms that are discussed are based on diagonalization, successive factor extraction, interpolation, and the solution of an algebraic Riccati equation, respectively. The paper includes a special algorithm for the factorization of unimodular para-Hermitian polynomial matrices and deals with canonical, noncanonical, and nearly noncanonical factorizations View full abstract»

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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