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Automatic Control, IEEE Transactions on

Issue 5 • Date May 2000

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Displaying Results 1 - 25 of 33
  • Comments on "Robustifying nonlinear systems using high-order neural network controllers"

    Page(s): 1033 - 1036
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    *** PLEASE ASK ME ABOUT THIS (PHILIP) *** In the original paper by G.A. Rovithakis (ibid., vol.44, p.102-8, 1999), a nonlinear dynamical system is considered. The author indicates that Rovithakis overlooked some essential assumptions on the allowable perturbations, that the problem is therefore not well-posed, and that the controller derived is incorrect Rovithakis replies that it is well known that a system of the type considered can in some cases be decomposed into a controllable and an uncontrollable part and that it is obvious that in such a case the controller would apply only to the former. Rovithakis shows that Zhang's other results are incorrect. View full abstract»

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  • Author's reply

    Page(s): 1036
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (47 KB)  

    First Page of the Article
    View full abstract»

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  • Random iterative models [Book Reviews]

    Page(s): 1037 - 1039
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    Freely Available from IEEE
  • A state observer for nonlinear systems and its application to ball and beam system

    Page(s): 968 - 973
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    In this paper, we present a state observer for single-input/single-output nonlinear systems which fail to have well defined relative degree. It is shown that there exists a local state observer for a nonlinear system if it has robust relative degree n. The proposed observer utilizes the coordinate change which transforms a system into an approximate normal form. The proposed method is applied to a ball and beam system, and simulation results show that substantial improvement in the performance was achieved compared with other local observers View full abstract»

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  • Using scales in the multiobjective approach

    Page(s): 973 - 977
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    Scales are used to reduce the conservatism encountered in most multiobjective approaches to control design. The most general case (i.e., matrix scales) results in a nonconvex problem, though the use of scalar scales leads to convex searches in the analysis and state feedback problems. Output feedback synthesis and other extensions are discussed. Numerical examples are provided to show the effectiveness of the suggested approach. The article considers, in particular, H control View full abstract»

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  • An exponentially stable adaptive friction compensator

    Page(s): 977 - 980
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    This note presents a novel adaptive compensation scheme for Coulomb friction in a servocontrol system. An adaptive observer for estimating the unknown Coulomb friction coefficient is also derived on the basis of the Lyapunov technique. In addition, a linearizing control law is developed to compensate for the friction force and obtain the tracking objective. The proposed adaptive compensation guarantees an exponential convergence for state errors and parameter error, and known adaptive schemes guarantee only an asymptotic (or stable) convergence. Simulation results demonstrate the effectiveness of the proposed method for a single-mass servocontrol system View full abstract»

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  • Optimal adaptive control for estimation of parameters of ARX models

    Page(s): 964 - 968
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    The objective of this paper is to find an adaptive control strategy which would enable us to estimate the parameters of the ARX model as accurately as possible while keeping the output of the system below a specified level of variability. It turns out that this optimal experiment design problem can be solved by using the Astrom-Wittenmark self-tuning tracker (1973) with a specific choice of the reference signal View full abstract»

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  • On the design of a nonlinear adaptive variable structure derivative estimator

    Page(s): 1028 - 1033
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    Develops a derivative estimator using variable structure system (VSS) and adaptive techniques. The proposed nonlinear adaptive variable structure derivative estimator requires little knowledge about the observed signal source and is able to handle the observed signals that are the outputs of either linear or nonlinear dynamic systems with uncertainties. In the absence of system noise, the uniform boundedness of the proposed derivative estimation is guaranteed by means of the adaptive control approach. By virtue of VSS, the new derivative estimator is capable of adapting itself to the noise environment, especially the unpredictable changes in system noise View full abstract»

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  • Output feedback control of Markov jump linear systems in continuous-time

    Page(s): 944 - 949
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    This paper addresses the dynamic output feedback control problem of continuous-time Markovian jump linear systems. The fundamental point in the analysis is an LMI characterization, comprising all dynamical compensators that stabilize the closed-loop system in the mean square sense. The H2 and H-norm control problems are studied, and the H2 and H filtering problems are solved as a by product View full abstract»

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  • Robust and minimum norm pole assignment with periodic state feedback

    Page(s): 1017 - 1022
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    A computational approach is proposed to solve the minimum norm or robust pole assignment problem for linear periodic discrete-time systems. The proposed approach uses a periodic Sylvester-equation-based parametrization of the periodic pole assignment problem and exploits the nonuniqueness of the problem by imposing conditions on the norm of the resulting periodic state feedback or on the condition numbers of the periodic eigenvector matrices of the closed-loop system. The solution method relies on using gradient search methods on suitably defined cost functions. Explicit expressions of the gradients of cost functions are derived, and the efficient evaluation of the cost functions and gradients is discussed. Numerical examples illustrate the effectiveness of the proposed approach View full abstract»

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  • Nonlinear repetitive control

    Page(s): 949 - 954
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    Repetitive controllers are generally applied to reject periodic disturbances and to track periodic reference signals with a known period. Their design is based on the internal model principle, proposed by Francis and Wonham (1975). This paper describes a new finite-dimensional SISO repetitive controller for two different classes of nonlinear plants. Simulation results show asymptotic tracking of the periodic reference signal by the proposed repetitive controller in closed loop up to the Nth harmonic frequency. A proof of robustness of the repetitive control system to small nonlinearities, like actuator nonlinearities, is provided View full abstract»

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  • Extension of Parrott's theorem to nondefinite scalings

    Page(s): 937 - 940
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    In this paper, the matrix version of Parrott's theorem is extended to encompass nondefinite scalings. This extension can be used to relax the causality requirements for many linear matrix inequality based synthesis problems View full abstract»

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  • Observation control for discrete-continuous stochastic systems

    Page(s): 993 - 998
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    Presents a theoretical framework for the optimization of observations in partially observable linear discrete-continuous stochastic systems. The problem of achievement of the best quality of estimation with discrete and continuous observations is reduced to a deterministic one with impulse or generalized control. An approach based on the discontinuous time transformation is presented and used to reduce the original optimization problem with impulsive control to the standard one with bounded controls. The existence and description of the optimal generalized observation process are also discussed. The illustrative example of the observations optimal control is presented View full abstract»

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  • Stochastic approximation and user adaptation in a competitive resource sharing system

    Page(s): 844 - 853
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    This paper is motivated by the work of Altman and Shimkin (1998). Customers arrive at a service center and must choose between two types of service: a channel that is shared by all currently in it and a dedicated line. The mean service cost (or time) for any customer entering the shared resource depends on the decisions of all future arrivals up to the time of departure of that customer, and so has a competitive aspect. The decision rule of each arriving customer is based on its own immediate self-interest, given the available data on the past performance. If the current estimate of the cost for the shared resource equals that of the dedicated line, any decision is possible. The procedure is a type of learning algorithm. The convergence problem is one in asynchronous stochastic approximation, where the ODE may be a differential inclusion. It is shown that, asymptotically, the performance of the learning system is that for the symmetric Nash strategy, despite the allowed arbitrariness and lack of coordination View full abstract»

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  • Continuity of the solution of the Riccati equations for continuous time JLQP

    Page(s): 934 - 937
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    In this paper the continuity of the solution of the differential and algebraic Riccati equations for a continuous-time, Markovian, jump linear quadratic control problem as a function of coefficients is verified. The assumptions for this are stochastic stabilizability and observability View full abstract»

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  • Existence and design of functional observers for linear systems

    Page(s): 940 - 943
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    This paper presents straightforward derivations of the functional observers design for linear time-invariant multivariable systems. The order of these observers is equal to the dimension τ of the vector to be estimated. Necessary and sufficient conditions for the existence and stability of these observers are given. Illustrative examples are included View full abstract»

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  • Exponential stabilization of a class of unstable bilinear systems

    Page(s): 989 - 992
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    Considers the control design of bilinear systems with multiplicative control inputs. Previous control designs for such systems normally assume that the open-loop bilinear system is (neutrally) stable. In this paper, a nonlinear control design is proposed for open-loop unstable bilinear systems. The new control stabilizes the bilinear system globally and exponentially if a sufficient stability condition, which can be checked by off-line computer simulations in advance of the control, is satisfied View full abstract»

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  • Virtual reference direct design method: an off-line approach to data-based control system design

    Page(s): 954 - 959
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    This paper presents a direct model-reference approach to the off-line design of linear controllers, suited to deal with plants described by a single set of open-loop I/O measurements only. The method is direct inasmuch as the controller parameters are directly estimated with no preliminary identification of any model to describe the plant. The design can be carried out off-line and, in the present formulation, leads to a nonadaptive controller. The basic idea is that of interpreting the open-loop I/O measurements of the plant as closed-loop data produced by a “virtual” reference signal that can be computed by backpropagating the measured output of the plant through the reference model; thus, the controller design reduces to a standard identification problem, in which the “output” signal to be matched is the measured input of the plant. Both a deterministic (noise-free) and a stochastic setting, are considered View full abstract»

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  • Instantaneous impulse response of nonlinear system

    Page(s): 999 - 1001
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    Mathematical models for nonlinear systems, which admit both standard integrable and impulsive inputs are developed. It is shown that instantaneous response of a nonlinear system to an impulse is not, in general, single-valued, whereas a particular response can be selected through the construction of an auxiliary system. The complete integrability of the auxiliary system is proven to guarantee uniqueness of the impulse response View full abstract»

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  • Gaussian filters for nonlinear filtering problems

    Page(s): 910 - 927
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    We develop and analyze real-time and accurate filters for nonlinear filtering problems based on the Gaussian distributions. We present the systematic formulation of Gaussian filters and develop efficient and accurate numerical integration of the optimal filter. We also discuss the mixed Gaussian filters in which the conditional probability density is approximated by the sum of Gaussian distributions. A new update rule of weights for Gaussian sum filters is proposed. Our numerical tests demonstrate that new filters significantly improve the extended Kalman filter with no additional cost, and the new Gaussian sum filter has a nearly optimal performance View full abstract»

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  • Global output-feedback tracking for a benchmark nonlinear system

    Page(s): 1023 - 1027
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    The output-feedback global tracking problem is solved for the well-known nonlinear benchmark RTAC (rotational-translational actuator) system, in which one of the unmeasured states appears quadratically in the state equations. Our observer/controller backstepping design yields a nonlinear output-feedback controller that forces the translational displacement to globally asymptotically track an appropriate time-varying signal. The proposed solution is new even for the case of global output-feedback stabilization, namely when the reference signal is zero View full abstract»

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  • A two-step adaptive controller for a two-body system

    Page(s): 1011 - 1016
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A reduced-order adaptive control scheme using a direct state-feedback control law and an indirect feedforward compensation design is presented for a two-body system with joint flexibility and damping. A detailed stability analysis is given for such a two-step adaptive control design, which ensures closed-loop signal boundedness and asymptotic output tracking View full abstract»

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  • Admission control in stochastic event graphs

    Page(s): 854 - 867
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    We first show that the expectation of convex increasing functions of the workload (or waiting time) in (max, +) linear systems, under a single input sequence, is multi-modular. This is done using a coupling argument and a vectorial version of Lindley's equation. Next, we use this result and the optimization theory based on multi-modular costs to construct the optimal open-loop admission control in general (max, +) linear systems under admission rate constraints. This optimization result only requires stationarity assumptions on the arrival process and on the service times of the servers in the system View full abstract»

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  • Discontinuous unit feedback control of uncertain infinite-dimensional systems

    Page(s): 834 - 843
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Control systems, driven by a discontinuous unit feedback in a Hilbert space, are studied. The equation which describes a system motion, taking place in the discontinuity manifold and further referred to as a sliding mode, is derived by means of a special regularization technique. Based on the sliding mode equation, the procedure of synthesis of a discontinuous unit control signal is developed. Restricted to a class of infinite-dimensional systems with finite-dimensional unstable part, this procedure generates the control law which ensures desired dynamic properties as well as robustness of the closed-loop system with respect to matched disturbances. As an illustration of the capabilities of the procedure proposed, a scalar unit controller of an uncertain exponentially minimum phase dynamic system is constructed and applied to heat processes and distributed mechanical oscillators View full abstract»

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  • Computing efforts allocation for ordinal optimization and discrete event simulation

    Page(s): 960 - 964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Ordinal optimization has emerged as an efficient technique for simulation and optimization. Exponential convergence rates can be achieved in many cases. In this paper, we present a new approach that can further enhance the efficiency of ordinal optimization. Our approach intelligently determines the optimal number of simulation replications (or samples) and significantly reduces the total simulation cost. Numerical illustrations are included. The results indicate that our approach can obtain an additional 74% computation time reduction above and beyond the reduction obtained through the use of ordinal optimization for a 10-design example 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