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Automatic Control, IEEE Transactions on

Issue 11 • Date Nov. 1999

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Displaying Results 1 - 25 of 45
  • On approximate pulse transfer functions

    Publication Year: 1999 , Page(s): 2062 - 2067
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB)  

    A systematic approach to a class of approximations to the pulse transfer function of a system consisting of a zero-order hold and a linear continuous-time plant is presented. It is based on the asymptotic result of Astrom, Hagander, and Sternby (1984) on zeros of sampled systems at high sampling rates, and on the bilinear transformation. Since the number of intrinsic parameters does not change in the discretization process, model matching control, robust control, and identification are suggested as possible areas of application. Superiority of the approximations considered over a δ-operator based truncated approximation is shown. The results are illustrated by an example. View full abstract»

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  • Decentralized adaptive regulation with unknown high-frequency-gain signs

    Publication Year: 1999 , Page(s): 2072 - 2076
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    We propose for the first time a decentralized adaptive control scheme without requiring a priori information on subsystem high-frequency-gain signs. This is achieved by introducing Nussbaum-type functions in local adaptive controllers, and developing a new analysis approach which is quite different from the conventional one used in centralized adaptive control involving a Nussbaum-type function. With the help of integrator backstepping, the decentralized control scheme can also be applied to high-relative-degree systems. The results of this paper enlarge the class of uncertain large-scale systems for which decentralized adaptive control can be designed View full abstract»

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  • The Kharitonov theorem with degree drop

    Publication Year: 1999 , Page(s): 2218 - 2220
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The purpose of this paper is to present a proof of the Kharitonov theorem based on Bezoutians. An interesting consequence of this proof is that it shows the validity of Kharitonov's result in the presence of a degree drop View full abstract»

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  • Polyhedral regions of local stability for linear discrete-time systems with saturating controls

    Publication Year: 1999 , Page(s): 2081 - 2085
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    The study and the determination of polyhedral regions of local stability for linear systems subject to control saturation is addressed. The analysis of the nonlinear behavior of the closed-loop saturated system is made by dividing the state space in regions of saturation. Inside each of these regions, the system evolution can be represented by a linear system with an additive disturbance. From this representation, a necessary and sufficient condition relative to the contractivity of a given convex compact polyhedral set is stated. Consequently, the polyhedral set can be associated with a Lyapunov function and the local asymptotic stability of the saturated closed-loop system inside the set is guaranteed. Furthermore, it is shown how, in some particular cases, the compactness condition can be relaxed in order to ensure the asymptotic stability in unbounded polyhedra. Finally, an application of the contractivity conditions is presented in order to determine local asymptotic stability regions for the closed-loop saturated system View full abstract»

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  • Conditional densities for continuous-time nonlinear hybrid systems with applications to fault detection

    Publication Year: 1999 , Page(s): 2164 - 2169
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Continuous-time nonlinear stochastic differential state and measurement equations, all of which have coefficients capable of abrupt changes at a random time, are considered; finite-state jump Markov chains are used to model the changes. Conditional probability densities, which are essential in obtaining filtered estimates for these hybrid systems, are then derived. They are governed by a coupled system of stochastic partial differential equations. When the Q matrix of the Markov chain is either lower or upper diagonal, it is shown that the system of conditional density equations is finite-dimensional computable. These findings are then applied to a fault detection problem to compute state estimates that include the failure time View full abstract»

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  • ISS property for time-varying systems and application to partial-static feedback stabilization and asymptotic tracking

    Publication Year: 1999 , Page(s): 2179 - 2184
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A concept of input-to-state stability (ISS) for time-varying control systems is introduced that constitutes extension of the well-known notion concerning the autonomous case. We use this concept to derive sufficient conditions for global stabilization of triangular systems by means of a time-varying smooth feedback and to achieve asymptotic tracking of unbounded signals View full abstract»

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  • Stochastic control of discrete systems: a separation principle for Wiener and polynomial systems

    Publication Year: 1999 , Page(s): 2125 - 2130
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A new separation principle is established for systems represented in discrete frequency-domain Wiener or polynomial forms. The LQG or H 2 optimal controller can be realized using an observer based structure estimating noise free output variables that are fed back through a dynamic gain control block. Surprisingly, there are also two separation principle theorems, depending upon the order in which the ideal output optimal control and the optimal observer problems are solved View full abstract»

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  • H control for linear time-varying systems: controller parameterization

    Publication Year: 1999 , Page(s): 2058 - 2062
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    In this correspondence, the H control problem is studied for finite-dimensional linear time-varying (FDLTV) systems. State-space formulas are derived for all FDLTV controllers solving the problem. These controllers are parameterized by the interconnection of the “central controller” with an exponentially stable, free system having H norm strictly less than γ. Our approach is drawn from some changes of variables, a time-varying version of a strict bounded real lemma, and Youla parameterization; thus, the proofs given are simple and clear View full abstract»

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  • A model-based probabilistic approach for fault detection and identification with application to the diagnosis of automotive engines

    Publication Year: 1999 , Page(s): 2200 - 2205
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A model based parameter and state estimation technique is presented toward fault diagnosis in dynamic systems. The methodology is based on the representation of the system dynamics in terms of transition probabilities between user-specified sets of magnitude intervals of system parameters and state variables during user-specified time intervals. These intervals may reflect noise in the monitored data, random changes in the parameters, or modeling uncertainties in general. The transition probabilities are obtained from a given system model that yields the current values of the state variables in discrete time from their values at the previous time step and the values of the system parameters at the previous time step. Implementation of the methodology on a simplified model of the air, inertial, fuel, and exhaust dynamics of the powertrain of a vehicle shows that the methodology is capable of estimating the system parameters and tracking the unmonitored dynamic variables within the user-specified magnitude intervals View full abstract»

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  • Adaptive internal model control: H optimization for stable plants

    Publication Year: 1999 , Page(s): 2130 - 2134
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    This paper considers the design of a robust adaptive H optimal controller based on the IMC structure. Specific attention is focused on the practically important class of stable plants with one open right half-plane zero. The certainty equivalence principle of adaptive control is used to combine a robust adaptive law with a robust H internal model controller to obtain an adaptive H internal model control scheme with provable guarantees of stability and robustness. The approach used earlier for designing and analyzing adaptive H2 optimal control schemes is seen to carry over in a natural fashion to the adaptive H optimal control case. This attests to the generality of that approach, which not only provides a theoretical basis for analytically justifying some of the reported industrial successes of existing adaptive internal model control schemes, but also opens up the possibility of synthesizing new ones by simply combining a robust adaptive law with a robust internal model controller structure View full abstract»

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  • Preservation of SPR functions and stabilization by substitutions in SISO plants

    Publication Year: 1999 , Page(s): 2171 - 2174
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    In this paper, we present sufficient conditions to preserve stability by rational function substitutions, It is proved that by making substitutions with strictly positive real (SPR) zero relative degree functions, it is possible to preserve the stability and coprime factorization of transfer functions. It is also proved that these functions are closed under function composition. Finally, we prove some results about robust stabilization using constant compensators, SPR robust functions, and robust stability, based on the result over closure of SPR functions View full abstract»

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  • Robust stability and design of linear discrete-time SISO systems under l1 uncertainties

    Publication Year: 1999 , Page(s): 2076 - 2080
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Shows how value sets and the zero exclusion principle can be used to obtain results on the robust stability and design of controllers against a special infinite-dimensional l1 norm bounded parametric uncertainty in both numerator and denominator of scalar discrete-time plants. This parametric uncertainty has properties of both parametric and unstructured uncertainty and allows standard H design tools to be used without conservatism View full abstract»

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  • Generalized (C, A, B)-pairs and parameter insensitive disturbance-rejection problems with dynamic compensator

    Publication Year: 1999 , Page(s): 2195 - 2200
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    In the so-called geometric approach, the notion of the generalized (C, A, B)-pairs is introduced for uncertain linear systems, and its properties are investigated. Further, the parameter insensitive disturbance-rejection problem with dynamic compensator is formulated and some sufficient conditions for the problem to be solvable are presented View full abstract»

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  • A discussion of Chaplin and Smith's patent for the cancellation of repetitive vibrations

    Publication Year: 1999 , Page(s): 2221 - 2225
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    This paper considers a method proposed by Chaplin and Smith for the cancellation of repetitive vibrations. Direct implementation of the concepts of the patent is not straightforward because of the lack of precise information regarding certain components, and because of the absence of guidelines for the design of a system with satisfactory stability and performance properties. This paper proposes a specific algorithm based on the concepts of the patent, and provides an approximate analysis which is found useful to obtain a closed-loop system with predictable dynamic characteristics. Simulations demonstrate the validity of the approximation and the success of the design. A tendency of the algorithm for convergence toward undesirable operating states is identified, and an improved version is derived. The algorithm is also compared to another algorithm proposed-for the same purposes View full abstract»

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  • Singular perturbation analysis of cheap control problem for sampled data systems

    Publication Year: 1999 , Page(s): 2209 - 2214
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    This paper studies the discrete-time cheap control problem for sampled data systems using the theory of singular perturbations. It is shown, by using the two time-scale property of singularly perturbed systems, that the problem can be solved in terms of two reduced-order subproblems for which computations can be done in parallel, thus increasing the computational speed. Similarly to the continuous-time case, the singular perturbation approach enables the decomposition of the algebraic Riccati equation into two reduced-order pure-slow and pure-fast continuous-time algebraic equations View full abstract»

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  • Adaptive variable structure set-point control of underactuated robots

    Publication Year: 1999 , Page(s): 2090 - 2093
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    Control of underactuated mechanical systems (robots) represents an important class of control problem. In this correspondence, a model-based adaptive variable structure control scheme is introduced, where the uncertainty bounds only depend on the inertia parameters of the system. Global asymptotic stability is established in the Lyapunov sense. Numerical simulations are conducted to validate the theoretical analysis View full abstract»

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  • Logic-based switching adaptive stabilization of feedforward nonlinear systems

    Publication Year: 1999 , Page(s): 2174 - 2178
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    For a class of feedforward nonlinear systems, we systematically solve the global adaptive stabilization problem. The proposed adaptive stabilizer consists of a nested saturation feedback and a tuning mechanism, which is constituted by a set of switching logics and is used to adaptively tune the saturation levels in a switching manner. It is proved that under the proposed control, global asymptotic regulation of states is achieved. The class of systems can be of arbitrary dynamic order, the contained uncertain nonlinearities need not be explicitly bounded, and even the form of nonlinearities can also be unknown View full abstract»

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  • A state observer for nonlinear systems

    Publication Year: 1999 , Page(s): 2098 - 2103
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    A state observer design methodology for a class of nonlinear systems is proposed. The nonlinear observer design methodology is, in fact, an extension of linear observer design techniques using transformations related to linear observability matrices View full abstract»

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  • An analysis of a class of neural networks for solving linear programming problems

    Publication Year: 1999 , Page(s): 1995 - 2006
    Cited by:  Papers (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A class of neural networks that solve linear programming problems is analyzed. The neural networks considered are modeled by dynamic gradient systems that are constructed using a parametric family of exact (nondifferentiable) penalty functions. It is proved that for a given linear programming problem and sufficiently large penalty parameters, any trajectory of the neural network converges in finite time to its solution set. For the analysis, Lyapunov-type theorems are developed for finite time convergence of nonsmooth sliding mode dynamic systems to invariant sets. The results are illustrated via numerical simulation examples View full abstract»

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  • Robust control of the output probability density functions for multivariable stochastic systems with guaranteed stability

    Publication Year: 1999 , Page(s): 2103 - 2107
    Cited by:  Papers (55)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    Presents two robust solutions to the control of the output probability density function for general multi-input and multi-output stochastic systems. The control inputs of the system appear as a set of variables in the probability density functions of the system output, and the signal available to the controller is the measured probability density function of the system output. A type of dynamic probability density model is formulated by using a B-spline neural network with all its weights dynamically related to the control input. It has been shown that the so-formed robust control algorithms can control the shape of the output probability density function and can guaranteed the closed-loop stability when the system is subjected to a bounded unknown input. An illustrative example is included to demonstrate the use of the developed control algorithms, and desired results have been obtained View full abstract»

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  • An alternative motivation for the indirect approach to closed-loop identification

    Publication Year: 1999 , Page(s): 2206 - 2209
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    Direct prediction error identification of systems operating in closed loop may lead to biased results due to the correlation between the input and the output noise. The authors study this error, what factors affect it, and how it may be avoided. In particular, the role of the noise model is discussed and the authors show how the noise model should be parameterized to avoid the bias. Apart from giving important insights into the properties of the direct method, this provides a nonstandard motivation for the indirect method View full abstract»

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  • The unreasonable effectiveness of neural network approximation

    Publication Year: 1999 , Page(s): 2043 - 2044
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    Results concerning the approximation rates of neural networks are of particular interest to engineers. The results reported in the literature have “slow approximation rates” O(1/√m), where m is the number of parameters in the neural network. However, many empirical studies report that neural network approximation is quite effective in practice. We give an explanation of this unreasonable effectiveness by proving the existence of approximation schemes that converge at a rate of the order of 1/m2 by using methods from number theory View full abstract»

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  • Iterative algorithm for parameter identification of Hammerstein systems with two-segment nonlinearities

    Publication Year: 1999 , Page(s): 2145 - 2149
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    This paper deals with parameter identification of Hammerstein systems having two-segment polynomial nonlinearities. The application of a simple decomposition technique and using switching sequences provide a special form of a Hammerstein model that is linear-in-parameters. This model is used in an iterative algorithm, enabling simultaneous estimation of all of the model parameters. To demonstrate the feasibility of the identification method, more illustrative examples are included View full abstract»

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  • Optimizing stability bounds of finite-precision PID controller structures

    Publication Year: 1999 , Page(s): 2149 - 2153
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    This paper investigates a recently derived lower bound stability measure for sampled-data controller structures subject to finite-wordlength (FWL) constraints. The optimal realization of the digital PID controller with FWL considerations is formulated as a nonlinear optimization problem, and an efficient strategy based on adaptive simulated annealing (ASA) is adopted to solve this complex optimization problem. A numerical example of optimizing the finite-precision PID controller structure for a simulated steel rolling mill system is presented to illustrate the effectiveness of the proposed strategy View full abstract»

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  • Global predictive regulation of null-controllable input-saturated linear systems

    Publication Year: 1999 , Page(s): 2226 - 2230
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    A predictive regulator is described for stabilizing linear plants subject to polyhedral input constraints. While the asymptotic stability of general linear plants is ensured subject to a set-membership condition on the initial state, global asymptotic and semiglobal exponential regulation is achieved for input-saturated plants which are asymptotically null controllable with bounded inputs. The design knobs of the regulator can be chosen off line so as to compromise between nonconservative regulation performance and computational complexity, and an online optimization problem of prequantifiable numerical burden results 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