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Automatic Control, IEEE Transactions on

Issue 2 • Date Feb. 1999

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Displaying Results 1 - 25 of 33
  • Electronic submissions now accepted

    Publication Year: 1999 , Page(s): 238
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    Freely Available from IEEE
  • Robust controller design for matrix second-order systems with structured uncertainty

    Publication Year: 1999 , Page(s): 401 - 405
    Cited by:  Papers (2)
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    Matrix second-order systems arise frequently in the formulation of dynamic systems in classical mechanics, robotics, aerodynamics and many others. Though formulation of the control design problem in matrix second-order form has many advantages, there is very little literature available on this topic-even for nominal case. In this paper, we design controller gains directly in matrix second-order formulation for robust stability in a specified range of parameter variations. The stabilizing controller gains for the entire parameter variations range are obtained from only two given extreme matrices without formulating or checking the stability of other vertex matrices of the family. The design algorithm is computationally efficient and simple. View full abstract»

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  • State observers for discrete-time linear systems with unknown inputs

    Publication Year: 1999 , Page(s): 397 - 401
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    In the paper the problem of designing a full-order state observer for a general discrete-time linear system with unknown inputs is analyzed. Necessary and sufficient conditions for the existence either of an asymptotic or of a deadbeat observer are provided, and a constructive design procedure, together with some examples, are discussed. Finally, the equivalence of these conditions for problem solvability with those derived in previous contributions by means of different approaches is explicitly proved View full abstract»

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  • Parametrization and optimization of reduced-order filters

    Publication Year: 1999 , Page(s): 418 - 422
    Cited by:  Papers (5)
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    This paper deals with the design of reduced-order filters for linear signal models to ensure that the transfer function from the noise to the filtering error is not only stable but also has a minimum H2 norm. One of the major results in the paper is the discovery and parametrization of a set of filters of fixed order which lead to stable filtering error transfer functions. Such a parametrization is given in terms of an arbitrary orthogonal projection matrix and a given full-order filter. As a consequence, the problem of minimizing the H2 norm of the filtering error transfer function over the set of reduced-order filters can be formulated as an equivalent unconstrained parametric optimization problem over a compact manifold. A gradient flow-based algorithm is proposed to find an optimal solution to the problem. Nice properties of the algorithm including the convergence property are established theoretically as well as demonstrated numerically with an example View full abstract»

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  • A characterization of parity space and its application to robust fault detection

    Publication Year: 1999 , Page(s): 337 - 343
    Cited by:  Papers (49)
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    Deals with problems related to the parity relation-based residual generation. A characterization of parity vectors and a relationship between the order of parity relations and the dimension of the parity space are derived. The achieved results are used to determine the degree of freedom for designing parity relation-based residual generators and to study the robustness problem View full abstract»

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  • Further properties of optimal hedging points in a class of manufacturing systems

    Publication Year: 1999 , Page(s): 379 - 382
    Cited by:  Papers (1)
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    For single-part-type manufacturing systems with homogeneous irreducible Markov machine failure rates, it is known that simple feedback control policies, called hedging point policies, are optimal, and the stationary probability distribution of the part surplus can be obtained analytically for given tentative values of hedging points. In this paper, the authors extend previous work on the ordering of optimal hedging points, and some better results are obtained View full abstract»

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  • Steady-state performance analysis of serial transfer lines subject to machine and buffer failure

    Publication Year: 1999 , Page(s): 319 - 325
    Cited by:  Papers (3)
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    In modern automated production lines, it is common to connect adjacent machines with buffers. Since these buffers are mechanical devices, they are prone to failure. Previous research concerning the steady-state analytical modeling of serial transfer lines assumed that buffers are completely reliable. The paper considers the unreliable buffer and presents a model of the serial transfer line incorporating this concept. A decomposition technique is developed for the general serial transfer line with unreliable buffers, and an algorithm for computing the solution of the model is presented View full abstract»

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  • A parametric extension of mixed time/frequency robust identification

    Publication Year: 1999 , Page(s): 364 - 369
    Cited by:  Papers (16)
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    A parametric extension to the time/frequency robust identification framework is presented. The results can be applied to stable linear time-invariant systems on which time and/or frequency experiments have been performed. The parametric portion of the model should be affine in the unknown parameters, which includes practical applications such as flexible structures. The consistency problem is cast as a constrained finite-dimensional convex optimization problem that can be formulated as a linear matrix inequality. The proposed procedure provides an interpolating identification algorithm, convergent and optimal up to a factor of two (with respect to central algorithms) View full abstract»

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  • A unifying approach of LTI discrete-time state observers by means of complementary matrices

    Publication Year: 1999 , Page(s): 422 - 426
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    This paper deals with the generalization of state observers in the framework of LTI deterministic discrete-time systems using complementary matrix formalism. Four necessary and sufficient general conditions have been established in the design of any type of state observer. Furthermore, necessary sufficient intrinsic conditions have been deduced. Respecting these intrinsic conditions guarantees satisfaction of the preceding general conditions. An illustrative example is also included View full abstract»

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  • A probabilistic language formalism for stochastic discrete-event systems

    Publication Year: 1999 , Page(s): 280 - 293
    Cited by:  Papers (28)
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    The formalism of probabilistic languages has been introduced for modeling the qualitative behavior of stochastic discrete-event systems. A probabilistic language is a unit interval-valued map over the set of traces of the system satisfying certain consistency constraints. Regular language operators such as choice, concatenation, and Kleene-closure have been defined in the setting of probabilistic languages to allow modeling of complex systems in terms of simpler ones. The set of probabilistic languages is closed under such operators, thus forming an algebra. It also is a complete partial order under a natural ordering in which the operators are continuous. Hence, recursive equations can be solved in this algebra. This is alternatively derived by using the contraction mapping theorem on the set of probabilistic languages which is shown to be a complete metric space. The notion of regularity, i.e., finiteness of automata representation, of probabilistic languages has been defined and it is shown that regularity is preserved under choice, concatenation, and Kleene-closure. We show that this formalism is also useful in describing system performance measures such as completion time, reliability, etc., and present properties to aide their computation View full abstract»

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  • On the synthesis of stable ℋ controllers

    Publication Year: 1999 , Page(s): 431 - 435
    Cited by:  Papers (44)
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    A sufficient condition is derived for the existence of a stable suboptimal ℋ controller. It is shown that if a certain algebraic Riccati equation, determined from a parameterization of all suboptimal ℋ controllers, has a positive definite stabilizing solution, then a stable ℋ controller of order 2n can be constructed, where n is the order of the generalized plant View full abstract»

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  • Convex methods for robust H2 analysis of continuous-time systems

    Publication Year: 1999 , Page(s): 239 - 252
    Cited by:  Papers (10)
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    Treats the robust H2 performance question of evaluating the rejection of continuous-time white noise, in the worst case over structured uncertainty in the system. A frequency domain convex condition for robust H2 analysis is presented, with analogous properties as in the discrete-time case. In particular, necessary and sufficient results are obtained introducing a continuous-time version of the methodology of set descriptions of white noise. In addition, a state-space test in terms of linear matrix inequalities is developed for the robust H2 problem in the case of constant uncertainty scalings, which apply to nonlinear or time-varying uncertainty. Thus the problem is rendered finite dimensional in the same situation in which robust H analysis is finite dimensional View full abstract»

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  • Decentralized control of robot manipulators: nonlinear and adaptive approaches

    Publication Year: 1999 , Page(s): 357 - 363
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    For robot arm tracking, the authors propose a nonlinear and adaptive approach based on decentralized system structure. Using the passive feature of robots and cubic feedback to treat the nonlinear couplings and quadratic interconnections, the decentralized adaptation is achieved by applying the linear-in-parameters property of the motion equation. The nonlinear feedback improves the performance of PD control from local to global stability and the adaptation reduces its tracking errors. The practical significance of the approaches lies in the fact that they can be implemented in most robots without hardware alteration View full abstract»

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  • Disturbance decoupled functional observers

    Publication Year: 1999 , Page(s): 382 - 386
    Cited by:  Papers (21)
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    If a state observer does not exist, it is possible to design a functional observer. Principally, this is also true for systems with unknown inputs (termed as disturbances). Necessary and sufficient conditions for the existence of disturbance decoupled functional observers for linear time-invariant systems are provided. A method for designing such observers is given. The analysis and design are based on a matrix pencil approach. The design can also be used to obtain functional observers for descriptor systems with or without unknown inputs View full abstract»

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  • Decoupling of structured systems by parameter-independent precompensation and state feedback

    Publication Year: 1999 , Page(s): 348 - 352
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    In this paper, structured systems described by state-space models are considered. For these systems, the entries of the state-space model matrices are assumed to be either fixed zeros or free independent parameters. We study the dynamic decoupling of structured linear systems. It turns out that a large class of systems which is not state feedback decouplable can be made decouplable by the addition of a simple structured precompensator. Such a precompensator then has the property to be independent of the system parameters. We give a necessary and sufficient condition for a structured system to be made feedback decouplable using a parameter independent precompensator. Furthermore, we prove that when such a solution exists, the precompensator can be chosen to be diagonal. In this case the precompensator is constructed via a simple combinatorial algorithm. Our approach is based on a graph representation of the structured system. All the results of this paper are related to some particular shortest sets of input-output paths in the graph associated with the structured system View full abstract»

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  • Wavelet-based system identification for nonlinear control

    Publication Year: 1999 , Page(s): 412 - 417
    Cited by:  Papers (42)
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    Compactly supported orthogonal wavelets have certain properties that are useful for system identification and learning control. Drawing on the rich theory of wavelets, we propose a system identification scheme based on orthogonal wavelets. Better accuracy of estimation can be obtained by adding more terms to the wavelet based identifier, and these terms do not alter the coefficients of the existing terms. These terms can be selectively added depending upon the region of interest, for example we may require more terms in regions where the identified functions vary rapidly. We illustrate the concepts by applying the procedure to determine a speed-controller for an electric vehicle View full abstract»

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  • LQ preview synthesis: optimal control and worst case analysis

    Publication Year: 1999 , Page(s): 352 - 357
    Cited by:  Papers (16)
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    A generalized LQ-control problem, which treats a mixed attenuation of stored disturbance and initial state uncertainty, is discussed in the infinite-horizon time setting. The posed problem covers a part of predictive control problems and enables one to deal with the LQ optimal preview servocontroller design. For the generalized LQ problem, we first derive an optimal preview control which minimizes the LQ cost functional and provide some interpretations on the structure of resulting control law. We then analyze worst case initial uncertainties, i.e., those of initial state and the shape of stored disturbance, which maximize the cost functional of the resulting closed-loop system View full abstract»

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  • Remarks on quantitative analysis for a family of scalar delay differential inequalities

    Publication Year: 1999 , Page(s): 334 - 336
    Cited by:  Papers (2)
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    A quantitative description for the stability of solutions is presented for a family of scalar time varying delay differential inequalities, here, the results proposed by Lehman and Shujaee (1994) are generalized View full abstract»

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  • Modeling and control of impact in mechanical systems: theory and experimental results

    Publication Year: 1999 , Page(s): 294 - 309
    Cited by:  Papers (53)
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    Considers the equations of motion of mechanical systems subject to inequality constraints, which can be obtained by looking for the stationary value of the action integral. Two different methods are used to take into account the inequality constraints in the computation of the stationary value of the action integral: the Valentine variables method and the penalty functions method. The equations of motion resulting from the application of the Valentine variables method, which introduces the concept of “nonsmooth” impacts, constitute the exact model of the constrained mechanical system; such a model is suitable to be employed when the impacting parts of the actual mechanical system are very stiff. The equations of motion resulting from the application of the penalty functions method, which introduces the concept of “smooth impacts,” constitute an approximate model of the constrained mechanical system; such a model is suitable to be employed when the impacting parts of the actual mechanical system show some flexibility. Various feedback control laws from the natural outputs and from their time derivatives are studied with reference to both models of impact; the closed-loop systems resulting from the application of the same control law to both models show pretty much the same global asymptotic stability properties. The proposed control laws are only concerned with regulation problems in the presence of possible contacts and impacts among parts of the mechanical system or with the external environment. The effectiveness of the proposed control structure has been tested experimentally with reference to a single-link robot arm, showing a valuable behavior View full abstract»

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  • Frequency-domain identification of linear systems using arbitrary excitations and a nonparametric noise model

    Publication Year: 1999 , Page(s): 343 - 347
    Cited by:  Papers (4)
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    Presents a generalized frequency domain identification method to identify single-input/single-output (SISO) systems combining two previously published extensions in one method: arbitrary but persistent excitations are allowed and a nonparametric noise model is extracted from the same data that are used to identify the system. The method is directly applicable to identification in feedback if an external persistently exciting reference signal is available View full abstract»

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  • Output-feedback stochastic nonlinear stabilization

    Publication Year: 1999 , Page(s): 328 - 333
    Cited by:  Papers (103)
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    The authors present the first result on global output-feedback stabilization (in probability) for stochastic nonlinear continuous-time systems. The class of systems that they consider is a stochastic counterpart of the broadest class of deterministic systems for which globally stabilizing controllers are currently available. Their controllers are “inverse optimal” and possess an infinite gain margin. A reader of the paper needs no prior familiarity with techniques of stochastic control View full abstract»

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  • An iterative learning controller with initial state learning

    Publication Year: 1999 , Page(s): 371 - 376
    Cited by:  Papers (62)
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    In iterative learning control (ILC), a common assumption is that the initial states in each repetitive operation should be inside a given ball centred at the desired initial states which may be unknown. This assumption is critical to the stability analysis, and the size of the ball will directly affect the final output trajectory tracking errors. In this paper, this assumption is removed by using an initial state learning scheme together with the traditional D-type ILC updating law. Both linear and nonlinear time-varying uncertain systems are investigated. Uniform bounds for the final tracking errors are obtained and these bounds are only dependent on the system uncertainties and disturbances, yet independent of the initial errors. Furthermore, the desired initial states can be identified through learning iterations View full abstract»

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  • Adaptive control of stochastic manufacturing systems with hidden Markovian demands and small noise

    Publication Year: 1999 , Page(s): 427 - 430
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    The adaptive production planning of failure-prone manufacturing systems is considered. In real manufacturing systems, the product demand is usually not known a priori. One of the major tasks in production scheduling is to estimate and predict the demand. In this paper, the authors consider the demand to be either the sum of an unknown rate and a small white noise or the sum of a hidden Markov chain and a small white noise. An algorithm is given to define a family of estimates for the unknown demand processes. Based on this family of estimates, adaptive controls are constructed, which are shown to be nearly optimal View full abstract»

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  • Set-valued observers and optimal disturbance rejection

    Publication Year: 1999 , Page(s): 253 - 264
    Cited by:  Papers (57)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    A set-valued observer (also called guaranteed state estimator) produces a set of possible states based on output measurements and models of exogenous signals. We consider the guaranteed state estimation problem for linear time-varying systems with a priori magnitude bounds on exogenous signals. We provide an algorithm to propagate the set of possible states based on output measurements and show that the centers of these sets provide optimal estimates in an l-induced norm sense. We then consider the utility of set-valued observers for disturbance rejection with output feedback and derive the following general separation structure. An optimal controller can consist of a set-valued observer followed by a static nonlinear function on the observed set of possible states. A general construction of this function is provided in the scalar control case. Furthermore, in the special case of full-control, i.e., the number of control inputs equals the number of states, optimal output feedback controllers can take the form of an optimal estimate of the full-state feedback controller View full abstract»

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  • Robustness of supervisors for discrete-event systems

    Publication Year: 1999 , Page(s): 376 - 379
    Cited by:  Papers (23)
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    Supervisory control in the context of ω-languages is considered. The nominal supervisor design problem is to find a non-blocking supervisor for a nominal plant such that the closed-loop infinite behavior equals a specified closed-loop behavior. The robustness of solutions to the nominal problem is defined with respect to variations in the plant. It is shown there exists a supervisor solving the nominal problem which maximizes the set of plants for which the closed-loop languages for all other plants in the set satisfy lower and upper bounds in the sense of language containment. Computational issues are discussed and the theoretical results are illustrated with an 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