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Automatic Control, IEEE Transactions on

Issue 2 • Date Feb. 2000

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Displaying Results 1 - 25 of 29
  • Comments on "On the structure of digital controllers with finite word length consideration"

    Publication Year: 2000
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    In the above-mentioned paper by Li (ibid. vol.43 (1998)), a condition is presented as necessary and sufficient to give the optimal realization of state space controllers for minimal sensitivity of all closed-loop eigenvalues subject to finite word-length effects. The condition is shown here not to be sufficient. In addition, the condition for minimal sensitivity of a single closed-loop eigenvalue presented in the above-mentioned paper is not complete. The complete conditions are presented in this paper. View full abstract»

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  • Adaptive distributed parameter systems identification with enforceable identifiability conditions and reduced-order spatial differentiation

    Publication Year: 2000 , Page(s): 203 - 216
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    Presents the synthesis of adaptive identifiers for distributed parameter systems (DPS) with spatially varying parameters described by partial differential equations (PDEs) of parabolic, elliptic, and hyperbolic type. The features of the PDE setting are utilized to obtain the not directly intuitive parameter estimation algorithms that use spatial derivatives of the output data with the order reduced from that of the highest spatial plant derivative. The tunable identifier parameters are passed through the integrator block, which forms their orthogonal expansions. The latter are shown to be pointwise plant parameter estimates. In this regard, the approach of the paper is in the spirit of finite-dimensional observer realization in integrating rather than differentiating the output data, only applied to the spatial rather than temporal domain. The constructively enforceable identifiability conditions, formulated in terms of the sufficiently rich input signals referred to as generators of persistent excitation, are shown to guarantee the existence of a unique zero steady state for the parameter errors. Under such inputs, the tunable parameters in the adaptive identifiers proposed are shown to converge to plant parameters in L2 and the orthogonal expansions of these tunable parameters-pointwise View full abstract»

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  • Locally optimal and robust backstepping design

    Publication Year: 2000 , Page(s): 260 - 271
    Cited by:  Papers (40)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    For a class of nonlinear systems, a robust backstepping design achieves both local optimality and global inverse optimality. The design is robust in the sense that it achieves a prescribed level of disturbance attenuation with stability margins. An analytic example illustrates the performance of the locally optimal control design View full abstract»

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  • Just-in-time policies for single-machine manufacturing flow controllers

    Publication Year: 2000 , Page(s): 336 - 339
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    Single, unreliable machine producing n part types is considered. Using a continuous flow model, conditions are found for the optimality of a just-in-time, or zero-inventory, policy via a stochastic coupling analysis. These conditions are proven to be necessary and conjectured to be sufficient for optimality. This correspondence extends the results of Veatch and Caramanis, in which necessary and sufficient conditions are found for a single machine producing two part types, and it strengthens the results of Perkins and Srikant, in which sufficient conditions are found for n part types View full abstract»

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  • Nonoptimality of static-priority policies in unreliable two-part-type manufacturing systems

    Publication Year: 2000 , Page(s): 309 - 311
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    In this note, we show that for the two-part-type, one-machine continuous flow model, a static-priority policy cannot be optimal when the hedging point of the part of highest priority is positive. This result was previously conjectured by Veatch and Caramanis View full abstract»

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  • A note on H2 optimal control problems with passivity constraints

    Publication Year: 2000 , Page(s): 286 - 290
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    Considers the problem of determining the closest function that has a positive real part on the unit disk to a given function in H2 . An explicit characterization of the projection is given, remarks on potential applications using this projection result to control synthesis and system identification problems are made View full abstract»

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  • Stochastic sampling algorithms for state estimation of jump Markov linear systems

    Publication Year: 2000 , Page(s): 188 - 202
    Cited by:  Papers (54)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Jump Markov linear systems are linear systems whose parameters evolve with time according to a finite-state Markov chain. Given a set of observations, our aim is to estimate the states of the finite-state Markov chain and the continuous (in space) states of the linear system. The computational cost in computing conditional mean or maximum a posteriori (MAP) state estimates of the Markov chain or the state of the jump Markov linear system grows exponentially in the number of observations. We present three globally convergent algorithms based on stochastic sampling methods for state estimation of jump Markov linear systems. The cost per iteration is linear in the data length. The first proposed algorithm is a data augmentation (DA) scheme that yields conditional mean state estimates. The second proposed scheme is a stochastic annealing (SA) version of DA that computes the joint MAP sequence estimate of the finite and continuous states. Finally, a Metropolis-Hastings DA scheme based on SA is designed to yield the MAP estimate of the finite-state Markov chain. Convergence results of the three above-mentioned stochastic algorithms are obtained. Computer simulations are carried out to evaluate the performances of the proposed algorithms. The problem of estimating a sparse signal developing from a neutron sensor based on a set of noisy data from a neutron sensor and the problem of narrow-band interference suppression in spread spectrum code-division multiple-access (CDMA) systems are considered View full abstract»

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  • On ℋ control for dead-time systems

    Publication Year: 2000 , Page(s): 272 - 285
    Cited by:  Papers (70)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A mixed sensitivity ℋ problem is solved for dead-time systems. It is shown that for a given bound on the ℋ-norm causal stabilizing controllers exist that achieve this bound if and only if a related finite-dimensional Riccati equation has a solution with a certain nonsingularity property. In the case of zero time delay, the Riccati equation is a standard Riccati equation and the nonsingularity condition is that the solution be nonnegative definite. For nonzero time delay, the nonsingularity condition is more involved but still allows us to obtain controllers. All suboptimal controllers are parameterized, and the central controller is shown to be a feedback interconnection of a finite-dimensional system and a finite memory system, both of which can be implemented. Some ℋ problems are rewritten as pure rational ℋ , problems using a Smith predictor parameterization of the controller View full abstract»

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  • A stability condition of zeros of sampled multivariable systems

    Publication Year: 2000 , Page(s): 295 - 299
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    This note derives a new condition for zeros of sampled multivariable systems to be stable for sufficiently small sampling periods. It is a natural extension of Hagiwara's result for single-input-single-output systems (1993) to multivariable systems View full abstract»

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  • Robust control via concave minimization local and global algorithms

    Publication Year: 2000 , Page(s): 299 - 305
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    This paper is concerned with the robust control problem of linear fractional representation (LFT) uncertain systems depending on a time-varying parameter uncertainty. Our main result exploits a linear matrix inequality (LMI) characterization involving scalings and Lyapunov variables subject to an additional essentially nonconvex algebraic constraint. The nonconvexity enters the problem in the form of a rank deficiency condition or matrix inverse relation on the scalings only. It is shown that such problems, but also more generally rank inequalities and bilinear constraints, can be formulated as the minimization of a concave functional subject to LMI constraints. First of all, a local Frank and Wolfe (1956) feasible direction algorithm is introduced in this context to tackle this hard optimization problem. Exploiting the attractive concavity structure of the problem, several efficient global concave programming methods are then introduced and combined with the local feasible direction method to secure and certify global optimality of the solutions. Computational experiments indicate the viability of our algorithms, and in the worst case, they require the solution of a few LMI programs View full abstract»

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  • On “Evaluating the bounded-input-bounded-output stability integral for second-order systems”

    Publication Year: 2000 , Page(s): 311 - 312
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    It is shown that the value of this integral is easily calculated by using the nastiest disturbance switch curve in spiral coordinates View full abstract»

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  • Service gap minimization in G/D/1/B+1 queues

    Publication Year: 2000 , Page(s): 290 - 294
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    When a G/D/1/B1 queue's B position buffer overflows, arriving or buffered jobs must be dropped. Assuming a nonbatch arrival process with bounded increments, we use sample path arguments to identify the overflow dropping policy that minimizes the average number of consecutively dropped jobs (the average service gap). This policy, which creates gaps whenever possible, as close to the front of the buffer as possible, remains optimal drop-by-drop for batch arrivals, blocking servers, and time-varying buffer sizes View full abstract»

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  • A new approach to the solution of the l1 control problem: the scaled-Q method

    Publication Year: 2000 , Page(s): 180 - 187
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    We explore an approach for solving multiple input-multiple output (MIMO) l1 optimal control problems. This approach, which we refer to as the scaled-Q approach, is introduced to alleviate many of the difficulties facing the numerical solution of optimal l1 control problems. In particular, the computations of multivariable zeros and their directions are no longer required. The scaled-Q method also avoids the pole-zero cancellation difficulties that existing methods based on zero-interpolation face when attempting to recover the optimal controller from an optimal closed-loop map. Because the scaled-Q approach is based on solving a regularized auxiliary problem for which the solution is always guaranteed to exist, it can be used no matter where the system zeros are (including the stability boundary). Upper and lower bounds that converge to the optimal cost are provided, and all solutions are based on finite dimensional linear programming for which efficient software exists View full abstract»

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  • Some contributions to fixed-distribution learning theory

    Publication Year: 2000 , Page(s): 217 - 234
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    We consider some problems in learning with respect to a fixed distribution. We introduce two new notions of learnability; these are probably uniformly approximately correct (PUAC) learnability which is a stronger requirement than the widely studied PAC learnability, and minimal empirical risk (MER) learnability, which is a stronger requirement than the previously defined notions of “solid” or “potential” learnability. It is shown that, although the motivations for defining these two notions of learnability are entirely different, these two notions are in fact equivalent to each other and, in turn, equivalent to a property introduced here, referred to as the shrinking width property. It is further shown that if the function class to be learned has the property that empirical means converge uniformly to their true values, then all of these learnability properties hold. In the course of proving conditions for these forms of learnability, we also obtain a new estimate for the VC-dimension of a collection of sets obtained by performing Boolean operations on a given collection; this result is of independent interest. We consider both the case in which there is an underlying target function, as well as the case of “model-free” (or agnostic) learning. Finally, we consider the issue of representation of a collection of sets by its subcollection of equivalence classes. It is shown by example that, by suitably choosing representatives of each equivalence class, it is possible to affect the property of uniform convergence of empirical probabilities View full abstract»

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  • Parametric generalized singular perturbation approximation for model order reduction

    Publication Year: 2000 , Page(s): 339 - 343
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    A new model reduction technique for the approximation of balanced realization is introduced. The method involves a further generalization of the generalized singular perturbation approximation by adding several parameters that can be tuned according to a specified performance criterion. An a priori bound can be computed guaranteeing the quality of the approximated model in the whole range of parameter variations. Two numerical examples conclude this paper View full abstract»

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  • Input-output block decoupling of linear time-varying singular systems

    Publication Year: 2000 , Page(s): 312 - 318
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The input-output block decoupling problem by state feedback is studied for linear time-varying singular systems. First, an algorithm, the regularization algorithm, is developed such that the system can be made by state feedback to have a unique impulse-free solution. Second, another algorithm, the block decoupling algorithm, is proposed, which provides sufficient conditions for the solvability of the input-output block decoupling problem. Then, a decoupling feedback law is constructed such that the corresponding closed-loop system is regular, impulse-free, and noninteractive. Finally, an example is given to illustrate the applicability of the algorithms View full abstract»

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  • The disturbance decoupling problem for time-delay nonlinear systems

    Publication Year: 2000 , Page(s): 305 - 309
    Cited by:  Papers (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    In this paper, the disturbance decoupling problem (DDP) for a class of SISO nonlinear systems with multiple delays in the input and the state is studied. A pioneering mathematical approach is introduced for this class of systems and is claimed to be the cornerstone of the problem. Necessary and sufficient conditions are given for the existence of a bicausal feedback that solves the DDP. Sufficient conditions for the existence of a solution within other classes of compensators are included as well View full abstract»

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  • On the control of complementary-slackness juggling mechanical systems

    Publication Year: 2000 , Page(s): 235 - 246
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Studies the feedback control of a class of complementary-slackness hybrid mechanical systems. Roughly, the systems we study are composed of an uncontrollable part (the “object”) and a controlled one (the “robot”), linked by a unilateral constraint and an impact rule. A systematic and general control design method for this class of systems is proposed. The approach is a nontrivial extension of the one degree-of-freedom (DOF) juggler control design. In addition to the robot control, it is also useful to study some intermediate controllability properties of the object's impact Poincare mapping, which generally takes the form of a nonlinear discrete-time system. The force input mainly consists of a family of dead-beat feedback control laws, introduced via a recursive procedure, and exploiting the underlying discrete-time structure of the system. The main goal of the paper is to highlight the role of various physical and control properties characteristic of the system on its stabilizability properties and to propose solutions in certain cases View full abstract»

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  • On the parametric H problems of weighted interval plants

    Publication Year: 2000 , Page(s): 332 - 335
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    In this paper, we consider the parametric H problems of weighted interval plants. A sufficient condition will be given on weighting function W(s) such that for any interval plant P(s, q, r) the maximal H norm of W(s)P(s, q, r) is achieved at one of the 16 so-called weighted Kharitonov plants. It is shown that for first-order and some high-order stable weighting functions, the extremality property is enjoyed generally by the maximal H norm of weighted interval plants View full abstract»

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  • Probabilistic data association avoiding track coalescence

    Publication Year: 2000 , Page(s): 247 - 259
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    For the problem of tracking multiple targets, the joint probabilistic data association (JPDA) approach has shown to be very effective in handling clutter and missed detections. The JPDA, however, tends to coalesce neighboring tracks and ignores the coupling between those tracks. Fitzgerald (1990) has shown that hypothesis pruning may be an effective way to prevent track coalescence. Unfortunately, this process leads to an undesired sensitivity to clutter and missed detections, and it does not support any coupling. To improve this situation, the paper follows a novel approach to combine the advantages of JPDA coupling, and hypothesis pruning into new algorithms. First, the problem of multiple target tracking is embedded into one filtering for a linear descriptor system with stochastic coefficients. Next, for this descriptor system, the exact Bayesian and new JPDA filters are derived. Finally, through Monte Carlo simulations, it is shown that these new PDA filters are able to handle coupling and are insensitive to track coalescence, clutter, and missed detections View full abstract»

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  • Robust triangular decoupling with application to 4WS cars

    Publication Year: 2000 , Page(s): 344 - 352
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The necessary and sufficient conditions for the problem of robust triangular decoupling are established for the case of a linear time-invariant system with a nonlinear uncertain structure. The general analytic expressions of the feedback matrices and the robust triangularly decoupled closed-loop system are derived. For the solution of the problem of robust triangular decoupling with simultaneous Hurwitz invariability, sufficient conditions are established. Finally, all of the above results are successfully applied to control four-wheel steering (4WS) cars View full abstract»

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  • Uncertainty, performance, and model dependency in approximate adaptive nonlinear control

    Publication Year: 2000 , Page(s): 353 - 358
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    We consider systems satisfying a matching condition that are functionally known up to weighted L2 and L measures of uncertainty. A modified LQ measure of control and state transient performance is given, and the performance of a class of approximate-model-based adaptive controllers is studied. An upper performance bound is derived in terms of the uncertainty models (the stability and state transient bounds require only the La uncertainty model; control effort bounds require both L2 and L uncertainty models) and various structural properties of the model basis. Sufficient conditions are given to ensure that the performance is bounded independently of the model basis size View full abstract»

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  • Smith's principle for congestion control in high-speed data networks

    Publication Year: 2000 , Page(s): 358 - 364
    Cited by:  Papers (39)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    In high-speed communication networks, large propagation delays could have an adverse impact on the stability of feedback control algorithms. In this paper, the classical control theory and Smith's principle are exploited to design an algorithm for controlling “best effort” traffic in high-speed asynchronous transfer mode (ATM) networks. The designed algorithm guarantees the stability of network queues, along with the fair and full utilization of network links, in a realistic traffic scenario in which multiple available bit rate connections, with different propagation delays, share the network with high priority traffic View full abstract»

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  • Geometric control theory

    Publication Year: 2000 , Page(s): 376 - 377
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (28 KB)  

    First Page of the Article
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  • Branch and bound computation of the minimum norm of a linear fractional transformation over a structured set

    Publication Year: 2000 , Page(s): 369 - 375
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The minimum norm of a linear fractional transformation (LFT) over a structured set is computed using a branch and bound algorithm. This is a global optimization problem caused by the possibility of local minima. Several computationally efficient lower bounds for the minimum norm of the LFT are developed, and it is demonstrated that the success of the optimization, as measured by time-to-converge, largely depends on the quality of these bounds 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