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Automatic Control, IEEE Transactions on

Issue 6 • Date June 2003

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Displaying Results 1 - 25 of 29
  • Book review

    Publication Year: 2003 , Page(s): 1116 - 1117
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    Freely Available from IEEE
  • On the control of asynchronous machines with races

    Publication Year: 2003 , Page(s): 1073 - 1081
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (433 KB) |  | HTML iconHTML  

    The problem of eliminating the effects of critical races on asynchronous machines is considered in a control theoretic context. State feedback controllers that eliminate the effects of critical races are developed. The results include necessary and sufficient conditions for the existence of such controllers and algorithms for their design. When the controllers exist, they eliminate the race effects and control the machine to match a given race-free model. View full abstract»

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  • Sparse kernel regression modeling using combined locally regularized orthogonal least squares and D-optimality experimental design

    Publication Year: 2003 , Page(s): 1029 - 1036
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (459 KB) |  | HTML iconHTML  

    The note proposes an efficient nonlinear identification algorithm by combining a locally regularized orthogonal least squares (LROLS) model selection with a D-optimality experimental design. The proposed algorithm aims to achieve maximized model robustness and sparsity via two effective and complementary approaches. The LROLS method alone is capable of producing a very parsimonious model with excellent generalization performance. The D-optimality design criterion further enhances the model efficiency and robustness. An added advantage is that the user only needs to specify a weighting for the D-optimality cost in the combined model selecting criterion and the entire model construction procedure becomes automatic. The value of this weighting does not influence the model selection procedure critically and it can be chosen with ease from a wide range of values. View full abstract»

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  • Stabilization of nonlinear systems with moving equilibria

    Publication Year: 2003 , Page(s): 1036 - 1040
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    This note provides a new method for the stabilization of nonlinear systems with parametric uncertainty. Unlike traditional techniques, our approach does not assume that the equilibrium remains fixed for all parameter values. The proposed method combines different optimization techniques to produce a robust control that accounts for uncertain parametric variations, and the corresponding equilibrium shifts. Comparisons with analytical gain scheduling are provided. View full abstract»

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  • Additional dynamics for general class of time-delay systems

    Publication Year: 2003 , Page(s): 1060 - 1063
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    In this note, some recent results on additional dynamics introduced by transformations of time-delay systems are extended to the case of general time-varying systems with delay. Sufficient stability conditions for the additional dynamics are also given. View full abstract»

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  • Asymptotic stabilization via output feedback for lower triangular systems with output dependent incremental rate

    Publication Year: 2003 , Page(s): 1103 - 1108
    Cited by:  Papers (101)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    We study the global asymptotic stabilization by output feedback for systems whose dynamics are in a feedback form and where the nonlinear terms admit an incremental rate depending only on the measured output. The output feedback we consider is of the observer-controller type where the design of the controller follows from standard robust backstepping. The novelty is in the observer which is high-gain such as with a gain coming from a Riccati equation. View full abstract»

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  • General interpolation in MPC and its advantages

    Publication Year: 2003 , Page(s): 1092 - 1096
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    Linear terminal control laws in model predictive control imply the need to compromise between performance and size of terminal region. A remedy allows the control law to vary with time, but requires very large online computation. Here, use is made of nonlinear terminal laws comprising an interpolation between predefined laws, each with its own precomputed terminal set. This reduces the online computation significantly, yet results in large terminal sets defined by the convex hull of invariant ellipsoids. The use of a different prediction class also produces significant benefits with respect to performance. View full abstract»

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  • Minimal communication in a distributed discrete-event system

    Publication Year: 2003 , Page(s): 957 - 975
    Cited by:  Papers (38)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1339 KB) |  | HTML iconHTML  

    This paper deals with distributed discrete-event systems, in which agents (or local sites) are required to communicate in order to perform some specified tasks. Associated with each agent is a finite-state automaton that captures the required tasks to be performed at that site. The problem considered is that each agent must be able to distinguish between the states of its automaton. To help it disambiguate states, an agent uses a combination of direct observation (obtained from sensor readings available to that agent) and communicated information (obtained from sensor readings available to another agent). Since communication may be costly, a strategy to minimize communication between sites is developed. The complexity of the solution reflects the interdependence of the agents' communication protocols. That is, the decision to communicate the occurrence of an event relies on which event sequences are indistinguishable to an agent, which, in turn, is a result of what has already been communicated to that agent. View full abstract»

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  • Suboptimal receding horizon control for continuous-time systems

    Publication Year: 2003 , Page(s): 1081 - 1086
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    Solving a continuous-time optimal control problem under state and control constraints is known to be a very hard task. In this note, we propose a suboptimal solution based on the Euler auxiliary system (EAS). We show that we can determine a continuous-time stabilizing control whose cost not only converges to the optimal as the EAS time parameter vanishes, but it is also upper bounded by the discrete-time cost, no matter how such a parameter is chosen. In particular, continuous-time linear problems with convex cost can be solved by considering a fictitious receding-horizon scheme. Both stability and constraints satisfaction are guaranteed for the continuous-time system. This scheme turns out to be very useful when, due to unstable or poorly damped dynamics, the digital implementation of the control requires a very small (virtually zero) sampling time, since the "time parameter" of the EAS can be much greater than the sampling time, without compromising stability, with a strongly reduced computational burden. View full abstract»

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  • On the synthesis of safe control policies in decentralized control of discrete-event systems

    Publication Year: 2003 , Page(s): 1064 - 1068
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    State estimation and safe controller synthesis for a general form of decentralized control architecture for discrete-event systems is investigated. For this architecture, controllable events are assigned to be either "conjunctive" or "disjunctive." A new state estimator that accounts for past local control actions when calculating the set of estimated system states is presented. The new state estimator is applied to a previous general decentralized control law. The new control method generates a controlled language at least as large as that generated by the original method if a safety condition is satisfied. An algorithm for generating locally maximal control policies for a given state estimate is also discussed. The algorithm allows an amount of "steering" of the controlled system through an event priority mechanism. View full abstract»

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  • An approach to identification for robust control

    Publication Year: 2003 , Page(s): 1109 - 1115
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (431 KB) |  | HTML iconHTML  

    Given measured data generated by a discrete-time linear system, we propose a model consisting of a linear time-invariant system affected by norm-bounded perturbation. Under mild assumptions, the plants belonging to the resulting uncertain family form a convex set. The approach depends on two key parameters: an a priori given bound of the perturbation and the input used to generate the data. It turns out that the size of the uncertain family can be reduced by intersecting the model families obtained by making use of different inputs. The model validation problem in this identification scheme is analyzed. For a given energy level, the invalidation problem yields the family of those models which can never be invalidated for any possible input of fixed energy and any possible perturbation; this leads to the intersection of all uncertain families. A consequence of the invalidation problem is that for finite length measurements not all models can be invalidated, using fixed-energy inputs. View full abstract»

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  • Robust adaptive control of nonlinear systems represented by input-output models

    Publication Year: 2003 , Page(s): 1041 - 1045
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (350 KB) |  | HTML iconHTML  

    A robust adaptive control scheme is proposed for a class of nonlinear systems represented by input-output models with unmodeled dynamics. The scheme does not require the unknown parameters to satisfy the linear dependence condition and parameter estimation is not needed. With the proposed control scheme, all the variables in the closed-loop system are bounded in the presence of unmodeled dynamics and bounded disturbances. Moreover, the mean-square tracking error can be made arbitrarily small by choosing some design parameters appropriately. View full abstract»

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  • Quadratic stability and stabilization of dynamic interval systems

    Publication Year: 2003 , Page(s): 1007 - 1012
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    This note presents necessary and sufficient conditions for the quadratic stability and stabilization of dynamic interval systems. The results are obtained in terms of linear matrix inequalities (LMIs) and extended to the quadratic stability and stabilization of linear systems with uncertain parameters. With the powerful LMI toolbox, it is very convenient to solve these problems. The illustrative examples show that this method is effective and less conservative to check the robust stability and to design the stabilizing controller for dynamic interval systems. View full abstract»

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  • Reduction of future information required for optimal control of dynamic systems: a pseudostochastic model

    Publication Year: 2003 , Page(s): 1025 - 1029
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (295 KB) |  | HTML iconHTML  

    This note develops a pseudostochastic model for optimal control of dynamic systems over a given planning horizon. The obtained results reflect the extent to which reduction of future information impacts upon the performance and optimal control of dynamic systems. The main results indicate that, when using only partial information for determining optimal control, the performance of the dynamic system is almost identical to that when using full information. When ignoring the information expected beyond the planning horizon, a significant performance loss and a possible violation of feasibility of the optimal control can occur. View full abstract»

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  • Coordination of groups of mobile autonomous agents using nearest neighbor rules

    Publication Year: 2003 , Page(s): 988 - 1001
    Cited by:  Papers (2223)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB) |  | HTML iconHTML  

    In a recent Physical Review Letters article, Vicsek et al. propose a simple but compelling discrete-time model of n autonomous agents (i.e., points or particles) all moving in the plane with the same speed but with different headings. Each agent's heading is updated using a local rule based on the average of its own heading plus the headings of its "neighbors." In their paper, Vicsek et al. provide simulation results which demonstrate that the nearest neighbor rule they are studying can cause all agents to eventually move in the same direction despite the absence of centralized coordination and despite the fact that each agent's set of nearest neighbors change with time as the system evolves. This paper provides a theoretical explanation for this observed behavior. In addition, convergence results are derived for several other similarly inspired models. The Vicsek model proves to be a graphic example of a switched linear system which is stable, but for which there does not exist a common quadratic Lyapunov function. View full abstract»

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  • Global stability of congestion controllers for the Internet

    Publication Year: 2003 , Page(s): 1055 - 1060
    Cited by:  Papers (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    We consider a single link accessed by a single source which responds to congestion signals from the network. The design of controllers for such sources in the presence of feedback delay has received much attention recently. Here, we present conditions for the global, asymptotic stability and semiglobal exponential stability of congestion controllers. These conditions are natural extensions of conditions obtained through linearized analysis of such systems. Our result on exponential stability provides the missing link in the proof of how one obtains a single deterministic congestion control equation from a system with many congestion-controlled sources and random disturbances. Using numerical examples, we compare the conditions on the congestion-control parameters obtained using local and global stability analysis. View full abstract»

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  • On standard H control of processes with a single delay

    Publication Year: 2003 , Page(s): 1097 - 1103
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    This note presents a frequency domain method to solve the standard H control problem for processes with a single delay. For a given bound on the closed-loop H norm, there exist proper stabilizing controllers that achieve this bound if and only if both the corresponding delay-free H problem and an extended Nehari problem with a delay (or a one-block problem) are all solvable. The solvability of the extended Nehari problem (or the one-block problem) is equivalent to the nonsingularity of a delay-dependent matrix. The solvability conditions of the standard H control problem with a delay are formulated in terms of the existence of solutions to two delay-independent algebraic Riccati equations and a delay-dependent nonsingularity property. All suboptimal controllers solving the three problems are, respectively, parameterized as a structure incorporating a modified Smith predictor. View full abstract»

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  • Multitime scale Markov decision processes

    Publication Year: 2003 , Page(s): 976 - 987
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (822 KB) |  | HTML iconHTML  

    This paper proposes a simple analytical model called M time scale Markov decision process (MMDPs) for hierarchically structured sequential decision making processes, where decisions in each level in the M-level hierarchy are made in M different discrete time scales. In this model, the state-space and the control-space of each level in the hierarchy are nonoverlapping with those of the other levels, respectively, and the hierarchy is structured in a "pyramid" sense such that a decision made at level m (slower time scale) state and/or the state will affect the evolutionary decision making process of the lower level m+1 (faster time scale) until a new decision is made at the higher level but the lower level decisions themselves do not affect the transition dynamics of higher levels. The performance produced by the lower level decisions will affect the higher level decisions. A hierarchical objective function is defined such that the finite-horizon value of following a (nonstationary) policy at level m+1 over a decision epoch of level m plus an immediate reward at level m is the single-step reward for the decision making process at level m. From this we define "multi-level optimal value function" and derive "multi-level optimality equation." We discuss how to solve MMDPs exactly and study some approximation methods, along with heuristic sampling-based schemes, to solve MMDPs. View full abstract»

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  • Robust sliding-mode control for uncertain time-delay systems: an LMI approach

    Publication Year: 2003 , Page(s): 1086 - 1091
    Cited by:  Papers (105)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    This note is devoted to robust sliding-mode control for time-delay systems with mismatched parametric uncertainties. A delay-independent sufficient condition for the existence of linear sliding surfaces is given in terms of linear matrix inequalities, based on which the corresponding reaching motion controller is also developed. The results are illustrated by an example. View full abstract»

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  • Adaptive control of discrete time systems with concave/convex parametrizations

    Publication Year: 2003 , Page(s): 1069 - 1072
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    This note considers the adaptive control of a class of nonlinear discrete time system with concave/convex parametrizations. The solutions involved two tuning functions which are determined by a minmax optimization approach much like the continuous time counterparts found in the literature. Direct extension from the continuous time case do not work very well due to the premature termination of the adaptive algorithm before zero tracking error can be achieved. In this note, this problem is solved. The proposed algorithm is shown to be stable and achieves zero tracking error in steady state. View full abstract»

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  • Existence and computation of infinite horizon model predictive control with active steady-state input constraints

    Publication Year: 2003 , Page(s): 1002 - 1006
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (314 KB) |  | HTML iconHTML  

    This note addresses the existence and implementation of the infinite-horizon controller for the case of active steady-state input constraints. This case is important because, in many practical applications, controllers are required to operate at the boundary of the feasible region (for instance, in order to maximize global economic objectives). For this case, the usual finite horizon parameterizations with terminal cost cannot be applied, and optimal solutions are not generally available. We propose here an iterative algorithm that generates two finite-horizon approximations to the true infinite-horizon problem, where the solution to one of the approximations yields an upper bound on the true optimum, while the other approximation yields a lower bound. We show convergence of both bounding approximations to the optimal solution, as the horizon length in the approximations is increased. We outline a procedure, based on this result, to provide a solution to the infinite-horizon problem that is exact to within any user-specified tolerance. Finally, we present an example that includes a comparison between optimal and suboptimal controllers. View full abstract»

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  • Reachability analysis in T-invariant-less Petri nets

    Publication Year: 2003 , Page(s): 1019 - 1024
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB) |  | HTML iconHTML  

    An algorithm for reachability analysis in place/transition Petri nets having no transition invariants (T-invariants) is proposed. Given a Petri net with initial and target markings, a so-called complemented Petri net is created first that consists of the given Petri net and an additional complementary transition. Thereby, the reachability task is reduced to computation and investigation of those minimal-support and linearly combined T-invariants of the complemented Petri net, in which the complementary transition fires only once. Then, for each T-invariant with a single firing of the complementary transition, the algorithm will try to create a reachability path from the given initial marking to the target marking. View full abstract»

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  • A note on global output regulation of nonlinear systems in the output feedback form

    Publication Year: 2003 , Page(s): 1049 - 1054
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (375 KB) |  | HTML iconHTML  

    This note shows how the adaptive control method developed recently for nonlinearly parameterized systems can be used to solve the problem of global output regulation, for nonlinear systems in the so-called output-feedback form with unknown parameters and exogenous signals belonging to a compact set whose bound is also unknown. View full abstract»

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  • -multipliers for robust performance analysis

    Publication Year: 2003 , Page(s): 1016 - 1018
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    Linear systems subject to nonlinear time-varying sector-bounded uncertainties are considered. Robust performance is measured in terms of the worst-case ratio between the L-norms of the output and input signals. A new class of multipliers is introduced and characterized. The characterization can be used to compute an upper bound for robust performance, which tightens the bound obtained by the scaled small gain theorem. While the standard Popov multipliers and their extensions have been developed within the L2 framework, our multipliers are adapted to L. View full abstract»

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  • An example of a GAS system which can be destabilized by an integrable perturbation

    Publication Year: 2003 , Page(s): 1046 - 1049
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    A construction of a globally asymptotically stable time-invariant system which can be destabilized by some integrable perturbation is given. Besides its intrinsic interest, this serves to provide counterexamples to an open question regarding Lyapunov functions. 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