By Topic

Automatic Control, IEEE Transactions on

Issue 7 • Date July 1998

Filter Results

Displaying Results 1 - 25 of 30
  • Comments on "Robust tracking control for rigid robotic manipulators"

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (28 KB)  

    In the original paper by M. Zhihong and M. Palaniswami (ibid., vol.39, p.154-9, 1994), a robust tracking control using a nominal feedback controller and a variable structure compensator for a rigid robotic manipulator with uncertain dynamics was presented. It is assumed that the model uncertainty is bounded. The author claims that this assumption is not necessarily correct and that the results obtained are therefore untenable. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hedging policies for failure-prone manufacturing systems: optimality of JIT and bounds on buffer levels

    Page(s): 953 - 957
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    The authors consider multiple part-type single-machine manufacturing systems subject to failures. They provide necessary and sufficient conditions for the optimality of just-in-time (JIT) manufacturing, and further show that the necessary and sufficient conditions coincide when the backlog costs for all the parts are equal. In general, finding optimal hedging policies for multiple part-type problems is extremely difficult. They provide bounds on the optimal hedging points and also prove that, under an optimal hedging policy, the buffer levels will be upper bounded View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust stabilization for continuous-time systems with slowly time-varying uncertain real parameters

    Page(s): 987 - 992
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    The authors construct a class of parameter-dependent Lyapunov functions to guarantee robust stability in the presence of time-varying rate restricted plant uncertainty. Extensions to a class of time-varying nonlinear uncertainty that generalize the multivariable Popov criterion are also considered. These results are then used for controller synthesis to address the problem of robust stabilization in the presence of slowly time-varying real parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal release times in a single server: an optimal control perspective

    Page(s): 998 - 1002
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    The paper is concerned with the basic structure of optimal control of discrete-event dynamic processes defined over a max-plus algebra. Only a simple system is considered, namely a single server processing a given sequence of jobs, but the structural conditions that are discovered may lead to extensions to more general systems. The problem in question is how to optimally control the completion (output) times of the jobs by assigning their release (input) times, so as to minimize a measure of the discrepancy between the completion times and given desired due dates. The concept of the costate is applied to the discrete dynamics to identify structural optimality conditions, and, in the case of quadratic cost measures, the optimal control is shown to be computable by a state-feedback law that is linear in the max-plus algebra View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Controller approximation: approaches for preserving H performance

    Page(s): 858 - 871
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    Investigates the design of reduced-order controllers using an H framework. Given a stabilizing controller which satisfies a prespecified level of closed-loop H performance, sufficient conditions are derived for another controller to be stabilizing and satisfy the same level of H, performance. Such controllers are said to be (P,γ)-admissible, where P is the model of the plant under consideration and γ is the required level of prespecified H performance. The conditions are expressed as norm bounds on particular frequency-weighted errors, where the weights are selected to make a specific transfer function a contraction. The design of reduced-order (P,γ)-admissible controllers is then formulated as a frequency-weighted model reduction problem. It is advantageous for the required weights to be large in some sense. Solutions which minimize either the trace, or the determinant, of the inverse weights are characterized. We show that the procedure for minimizing the determinant of the inverse weights always gives a direction where the weights are the best possible. To conclude, we demonstrate by way of a numerical example, that when used in conjunction with a combined model reduction/convex optimization scheme, the proposed design procedures are effective in substantially reducing controller complexity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust estimation without positive real condition

    Page(s): 938 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The strictly positive real (SPR) condition on the noise model is necessary for a discrete-time linear stochastic control system with unmodeled dynamics, even so for a time-invariant ARMAX system, in the past robust analysis of parameter estimation. However, this condition is hardly satisfied for a high-order and/or multidimensional system with correlated noise. The main work in this paper is to show that for robust parameter estimation and adaptive tracking, as well as closed-loop system stabilization, the SPR condition is replaced by a stable matrix polynomial. The main method is to design a “two-step” recursive least squares algorithm with or without a weighted factor and with a fixed lag regressive vector and to define an adaptive control with bounded external excitation and with randomly varying truncation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • H∞-output feedback controller design for linear systems with time-varying delayed state

    Page(s): 971 - 974
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    This paper considers the H∞-controller design problem for linear systems with time-varying delays in states. The authors obtain sufficient conditions for the existence of H∞ controllers in terms of three linear matrix inequalities (LMIs). These sufficient conditions are dependent on the maximum value of the time derivative of time-varying delay. Furthermore, they briefly explain how to construct such controllers from the positive-definite solutions of their LMIs and give an example View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal state-space partition for control of discrete-event systems with static specifications

    Page(s): 1013 - 1016
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    The sensors distinguish among elements of the observation space, which is a partition of the state space, and the controller assigns a control pattern to each observation value. We study the coarsest partition to satisfy the static specification. If the sensors are reliable, then we can reduce the sensor cost by implementing the coarsest partition as the observation space. We show that, unfortunately, the coarsest partition does not uniquely exist in general. We then present a necessary and sufficient condition for the unique existence of the coarsest partition View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Passivity and disturbance attenuation via output feedback for uncertain nonlinear systems

    Page(s): 992 - 997
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    The authors address the problem of disturbance attenuation with internal stability via output feedback for a class of passive systems with uncertainties. The problem is approached by means of adaptive output feedback control which does not require any state observer. The results obtained extend an earlier result of Steinberg and Corless (1985). Sufficient conditions are proposed under which a nonlinear system can be made locally or globally passive via output feedback View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive state regulation in the presence of disturbances of known frequency range

    Page(s): 872 - 880
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Adaptive state regulation via adaptive observation and asymptotic feedback matrix synthesis in the presence of bounded disturbances of known frequency range is considered. The adaptive observer uses a filtered output error to adapt parameter and state estimates. The filter is designed to attenuate in the disturbance frequency range. It is shown that, with persistent excitation, parameter and feedback gain errors are bounded by a quantity which is proportional directly to the attenuated disturbance magnitudes and inversely to the degree of persistent excitation. Closed-loop stability is proven when the ratio of filtered disturbance magnitude to degree of persistent excitation is sufficiently small. A computer simulation demonstrates the method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A paradigm of ill-posedness with respect to time delays

    Page(s): 964 - 967
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    The authors present a simple general model of an infinite-dimensional control system which is stabilized by a velocity feedback, but then destabilized by “small” or “large” time delays in the feedback. This model is in some sense generic for boundary-stabilized conservative hyperbolic linear partial differential equations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive control of a class of nonlinearly parameterized plants

    Page(s): 930 - 934
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A stable adaptive control method is developed for a class of first-order nonlinearly parameterized plants. The method is based on modified adaptive algorithms that yield a stable system in which the output errors are guaranteed to converge to zero. The stability analysis is carried out using suitably constructed Lyapunov functions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The asymptotic stability of nonlinear (Lur'e) systems with multiple slope restrictions

    Page(s): 979 - 982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    The authors present the analysis of the asymptotic stability of multiple slope-restricted nonlinear (Lur'e) systems. By providing a Lyapunov function, they obtain a matrix-language criterion in terms of algebraic Riccati equations and linear matrix inequalities, which are discussed at the point of computational issues. Additionally, they consider the frequency-domain interpretation of the result View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On consistency of Bayes estimates in a certainty equivalence adaptive system

    Page(s): 943 - 947
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The authors analyze a control problem with data generated by the linear regression model where intercept and slope coefficients are unknown. They propose a certainty equivalence control rule based on Bayes estimates of the intercept and slope coefficients. It is shown that the control rule converges to the optimal control rule, which requires complete knowledge of intercept and slope coefficients. Furthermore, under the proposed control rule, if the total control cost tends to infinity, they show that the Bayes estimates for slope and intercept are consistent View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Filtering on sampled-data systems with parametric uncertainty

    Page(s): 1022 - 1027
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The paper is concerned with the problem of robust H filtering for a class of systems with parametric uncertainties and unknown time delays under sampled measurements. The parameter uncertainties considered are real time-varying and norm-bounded, appearing in the state equation. An approach has been proposed for the designing of H filters, using sampled measurements, which would guarantee a prescribed H performance in the continuous-time context, irrespective of the parameter uncertainties and unknown time delays. Both cases of finite and infinite horizon filtering are studied. It has been shown that the above robust H-filtering problem can be solved in terms of differential Riccati inequalities with finite discrete jumps View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Generalization of integral constraints on sensitivity to time-delay systems

    Page(s): 1008 - 1012
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Extends results on integral constraints to time-delay systems. Key technical issues in this extension include properties of nonminimum phase zeros, the convergence of Blaschke products, and the Poisson integral. The results have implications for scalar and multivariable control system design as well as in filtering problems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Connections between Razumikhin-type theorems and the ISS nonlinear small gain theorem

    Page(s): 960 - 964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    A Razumikhin-type theorem that guarantees input-to-state stability for functional differential equations with disturbances is established using the nonlinear small-gain theorem. The result is used to show that input-to-state stabilizability for nonlinear finite-dimensional control systems is robust, in an appropriate sense, to small time delays at the input. Also, relaxed Razumikhin-type conditions guaranteeing global asymptotic stability for differential difference equations are given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Global positioning of robot manipulators via PD control plus a class of nonlinear integral actions

    Page(s): 934 - 938
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Deals with the position control of robot manipulators. Proposed is a simple class of robot regulators consisting of a linear proportional-derivative (PD) feedback plus an integral action of a nonlinear function of position errors. By using Lyapunov's direct method and LaSalle's invariance principle, the authors characterize a class of such nonlinear functions, and they provide explicit conditions on the regulator gains to ensure global asymptotic stability. These regulators offer an attractive alternative to global regulation compared with the well-known partially model-based PD control with gravity compensation and PD control with desired gravity compensation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stabilizing receding-horizon control of nonlinear time-varying systems

    Page(s): 1030 - 1036
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    A receding horizon control scheme for nonlinear time-varying systems is proposed which is based on a finite-horizon optimization problem with a terminal state penalty. The penalty is equal to the cost that would be incurred over an infinite horizon by applying a (locally stabilizing) linear control law to the nonlinear system. Assuming only stabilizability of the linearized system around the desired equilibrium, the new scheme ensures exponential stability of the equilibrium. As the length of the optimization horizon goes from zero to infinity, the domain of attraction moves from the basin of attraction of the linear controller toward the basin of attraction of the infinite-horizon nonlinear controller. Stability robustness in the face of system perturbations is also established View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ordinal optimization for a class of deterministic and stochastic discrete resource allocation problems

    Page(s): 881 - 900
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1244 KB)  

    The authors consider a class of discrete resource allocation problems which are hard due to the combinatorial explosion of the feasible allocation search space. In addition, if no closed-form expressions are available for the cost function of interest, one needs to evaluate or (for stochastic environments) estimate the cost function through direct online observation or through simulation. For the deterministic version of this class of problems, the authors derive necessary and sufficient conditions for a globally optimal solution and present an online algorithm which they show to yield a global optimum. For the stochastic version, they show that an appropriately modified algorithm, analyzed as a Markov process, converges in probability to the global optimum, An important feature of this algorithm is that it is driven by ordinal estimates of a cost function, i.e., simple comparisons of estimates, rather than their cardinal values. They can therefore exploit the fast convergence properties of ordinal comparisons, as well as eliminate the need for “step size” parameters whose selection is always difficult in optimization schemes. An application to a stochastic discrete resource allocation problem is included, illustrating the main features of their approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Active diagnosis of discrete-event systems

    Page(s): 908 - 929
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    The need for accurate and timely diagnosis of system failures and the advantages of automated diagnostic systems are well appreciated. However, diagnosability considerations are often not explicitly taken into account in the system design. In particular, design of the controller and that of the diagnostic subsystem are decoupled, and this may significantly affect the diagnosability properties of a system. The authors present an integrated approach to control and diagnosis. More specifically, they present an approach for the design of diagnosable systems by appropriate design of the system controller. This problem, which they refer to as the active diagnosis problem, is studied in the framework of discrete-event systems (DESs); it is based on prior and new results on the theory of diagnosis for DESs and on existing results in supervisory control under partial observations. They formulate the active diagnosis problem as a supervisory control problem where the legal language is an “appropriate” regular sublanguage of the regular language generated by the system. They present an iterative procedure for determining the supremal controllable, observable, and diagnosable sublanguage of the legal language and for obtaining the supervisor that synthesizes this language. This procedure provides both a controller that ensures diagnosability of the closed-loop system and a diagnoser for online failure diagnosis. The procedure can be implemented using finite-state machines and is guaranteed to converge in a finite number of iterations. The authors illustrate their approach using a simple pump-valve system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust controller synthesis via shifted parameter-dependent quadratic cost bounds

    Page(s): 1003 - 1007
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Parameterized Lyapunov bounds and shifted quadratic guaranteed cost bounds are merged to develop shifted parameter-dependent quadratic cost bounds for robust stability and robust performance. Robust fixed-order (i.e., full- and reduced-order) controllers are developed based on new shifted parameter-dependent bounding functions. A numerical example is presented to demonstrate the effectiveness of the proposed approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On an estimate of the decay rate for applications of Razumikhin-type theorems

    Page(s): 958 - 960
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    A decay estimate is established for solutions of a class of Razumikhin-type functional differential equations (FDEs). The FDEs investigated here are general enough to satisfy the requirement of applications of Razumikhin-type theorems. With the help of an application of our result, it is illustrated that the method presented in this paper is adaptable to quantitative stability analysis of the retarded functional differential equations encountered in engineering View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Output error convergence of adaptive filters with compensation for output nonlinearities

    Page(s): 975 - 978
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    Output error convergence of a Wiener model-based nonlinear stochastic gradient algorithm is analyzed. The normalized scheme estimates the parameters of a linear finite impulse response model in cascade with a known output nonlinearity. The algorithm can be interpreted as a normalized least mean square algorithm with compensation for an output nonlinearity. Linearizing inversion of the nonlinearity is not utilized. Global output error convergence is then proved, provided that the nonlinearity is monotone (not strictly monotone), and provided that a previously observed mechanism resulting in deadlock does not occur. The algorithm and the analysis include important practical cases like sensor saturation and dead zones that must be excluded when global parametric convergence is studied View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A generalization of the structured singular value and its application to model validation

    Page(s): 901 - 907
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    The structured singular value μ gives a means of assessing the stability and performance of a system under a class of norm-bounded structured perturbations. This paper introduces a generalization of μ which guarantees stability with respect to perturbations, where some elements of the perturbation structure are bounded from above and some are bounded from below. This generalization is used to solve the frequency domain robust control model validation problem. Model validation determines whether or not there exist a model in the model set and a bounded noise signal that are consistent with the experimental input-output measurements. A computable convex upper bound to the generalized μ problem is presented, and the relationship between the generalized μ problem and the standard μ and model validation problems is discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
P. J. Antsaklis
Dept. Electrical Engineering
University of Notre Dame