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Automatic Control, IEEE Transactions on

Issue 1 • Date Jan. 2011

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Displaying Results 1 - 25 of 35
  • Table of contents

    Page(s): C1 - C4
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  • IEEE Control Systems Society

    Page(s): C2
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  • Scanning the issue

    Page(s): 1
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  • Disturbance Decoupling of Boolean Control Networks

    Page(s): 2 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    Disturbance decoupling problem (DDP) of Boolean control networks is considered. Using semi-tensor product of matrices and the matrix expression of logical functions, a working procedure is proposed to solve the problem. This procedure consists of two key design steps. First, how to convert a system into an output-friendly coordinate frame. An algorithm is provided to calculate the output-friendly subspaces. Secondly, it was shown how to find proper controllers to solve the problem if it is solvable. A state variable separation form is introduced to guide the design of controllers. Based on the design technique, necessary and sufficient conditions are obtained for the solvability of DDP. View full abstract»

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  • Stability Crossing Set for Systems With Three Delays

    Page(s): 11 - 26
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1216 KB) |  | HTML iconHTML  

    This article describes the stability crossing set for linear time-delay systems of arbitrary order with three delays. The crossing frequency set, which consists of all frequencies where a pair of zeros of the characteristic quasipolynomial may cross the imaginary axis, is partitioned to Grashof sets and Non-Grashof sets of various types. It was found that the general characteristics of the stability crossing set is completely determined by the partition structure of the crossing frequency set. With the exception of degenerate cases, this article provides a method of explicit and complete parameterization and geometric characterization of the stability crossing set of linear systems with three delays. With the well-known method of finding the crossing directions, this provides a powerful method of finding parameter regions of stable systems. Extension to systems with additional fixed delays is also discussed. View full abstract»

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  • Supervisory Control of Uncertain Linear Time-Varying Systems

    Page(s): 27 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    We consider the problem of adaptively stabilizing linear plants with unknown time-varying parameters in the presence of noise, disturbances, and unmodeled dynamics using the supervisory control framework, which employs multiple candidate controllers and an estimator based switching logic to select the active controller at every instant of time. Time-varying uncertain linear plants can be stabilized by supervisory control, provided that the plant's parameter varies slowly enough in terms of mixed dwell-time switching and average dwell-time switching, the noise and disturbances are bounded and small enough in terms of L-infinity norms, and the unmodeled dynamics are small enough in the input-to-state stability sense. This work extends previously reported works on supervisory control of linear time-invariant systems with constant unknown parameters to the case of linear time-varying uncertain systems. A numerical example is included, and limitations of the approach are discussed. View full abstract»

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  • Step Tracking in the Presence of Persistent Plant Changes

    Page(s): 43 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB) |  | HTML iconHTML  

    In this paper, we consider the use of periodic controllers for simultaneous stabilization and step tracking, including the case when there are occasional, though persistent, plant changes. We consider the case of a finite set of admissible models; we provide a design procedure that yields a controller which stabilizes each such model while providing near optimal LQR step tracking. We then demonstrate that this controller has the facility to tolerate occasional (but persistent) switches between these models without an undue effect on the performance. The controller is periodic with a slight nonlinearity. View full abstract»

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  • Optimal Gaits for Mechanical Rectifier Systems

    Page(s): 59 - 71
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (829 KB) |  | HTML iconHTML  

    The essential mechanism underlying animal locomotion can be viewed as mechanical rectification that converts periodic body movements to thrust force through interactions with the environment. This paper defines a general class of mechanical rectifiers as multi-body systems equipped with such thrust generation mechanisms. A simple model is developed from the Euler-Lagrange equation by assuming small body oscillations around a given nominal posture. The model reveals that the rectifying dynamics can be captured by a bilinear, but not linear, term of body shape variables. An optimal gait problem is formulated for the bilinear rectifier model as a minimization of a quadratic cost function over the set of periodic functions subject to a constraint on the average locomotion velocity. We prove that a globally optimal solution is given by a harmonic gait that can be found by generalized eigenvalue computation with a line search over cycle frequencies. We provide case studies of a chain of links for which snake-like undulations and jellyfish-like flapping gaits are found to be optimal. View full abstract»

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  • Networked Predictive Control of Uncertain Constrained Nonlinear Systems: Recursive Feasibility and Input-to-State Stability Analysis

    Page(s): 72 - 87
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (890 KB) |  | HTML iconHTML  

    In this paper, the robust state feedback stabilization of uncertain discrete-time constrained nonlinear systems in which the loop is closed through a packet-based communication network is addressed. In order to cope with model uncertainty, time-varying transmission delays, and packet dropouts (typically affecting the performances of networked control systems), a robust control scheme combining model predictive control with a network delay compensation strategy is proposed in the context of non-acknowledged UDP-like networks. The contribution of the paper is twofold. First, the issue of guaranteeing the recursive feasibility of the optimization problem associated to the receding horizon control law has been addressed, such that the invariance of the feasible region under the networked closed-loop dynamics can be guaranteed. Secondly, by exploiting a novel characterization of regional Input-to-State Stability in terms of time-varying Lyapunov functions, the networked closed-loop system has been proven to be Input-to-State Stable with respect to bounded perturbations. View full abstract»

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  • Controllability and Observability of a Well-Posed System Coupled With a Finite-Dimensional System

    Page(s): 88 - 99
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    We consider coupled systems consisting of a well-posed and strictly proper (hence regular) subsystem and a finite-dimensional subsystem connected in feedback. The external world interacts with the coupled system via the finite-dimensional part, which receives the external input and sends out the output. Under several assumptions, we derive well-posedness, regularity, exact (or approximate) controllability and exact (or approximate) observability results for such coupled systems. View full abstract»

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  • How to Make Bias and Variance Errors Insensitive to System and Model Complexity in Identification

    Page(s): 100 - 112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (471 KB) |  | HTML iconHTML  

    Solutions to optimal input design problems for system identification are sometimes believed to be sensitive to the underlying assumptions. For example, a wide class of problems can be solved with sinusoidal inputs with the same number of excitation frequencies (over the frequency range ) as the number of model parameters. The order of the true system is in many cases unknown and, hence, so is the required number of frequencies in the input. In this contribution we characterize when and how the input spectrum can be chosen so that the (asymptotic) variance error of a scalar function of the model parameters becomes independent of the order of the true system. A connection between these robust designs and the solutions of certain optimal input design problems is also made. Furthermore, we show that there are circumstances when using this type of input allows some model properties to be estimated consistently even when the model order is lower than the order of the true system. The results are derived under the assumptions of causal linear time invariant systems operating in open loop and excited by an input signal having a rational spectral factor with all poles and zeros strictly inside the unit circle. View full abstract»

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  • Linear-Quadratic Optimal Actuator Location

    Page(s): 113 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    In control of vibrations, diffusion and many other problems governed by partial differential equations, there is freedom in the choice of actuator location. The actuator location should be chosen to optimize performance objectives. In this paper, we consider linear quadratic performance. Two types of cost are considered; the choice depends on whether the response to the worst initial condition is to be minimized; or whether the initial condition is regarded as random. In practice, approximations are used in controller design and thus in selection of the actuator locations. The optimal cost and location of the approximating sequence should converge to the exact optimal cost and location. In this work conditions for this convergence are given in the case of linear quadratic control. Examples are provided to illustrate that convergence may fail when these conditions are not satisfied. View full abstract»

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  • Necessary and Sufficient Conditions for BIBO-Stability of Some Fractional Delay Systems of Neutral Type

    Page(s): 125 - 128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB) |  | HTML iconHTML  

    In this note, bounded-input bounded-output (BIBO)-stability of a large class of neutral type fractional delay systems is investigated. Necessary and sufficient conditions of BIBO-stability are presented for the intended class of systems (the sufficient conditions have been provided for a more general case in the previous studies). Two lemmas are provided for checking a prerequisite imposed on the considered class of systems. Finally, two numerical examples are given to illustrate the obtained results. View full abstract»

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  • Adaptive Delta Modulation in Networked Controlled Systems With bounded Disturbances

    Page(s): 129 - 134
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    This technical note investigates the closed-loop properties of the differential coding scheme known as Delta Modulation (Δ - M) when used in feedback loops within the context of linear systems controlled through a communication network. We propose a new adaptive scheme with variable quantization step Δ, by defining an adaptation law exclusively in terms of information available at both the transmitter and receiver. With this approach, global asymptotic stability of the networked control system is achieved for a class of controllable (possibly unstable) linear plants. Moreover, thanks to the globally defined switching policy, this architecture enjoys a disturbance rejection property that allows the system to recover from any finite-time unbounded disturbance or communication loss. View full abstract»

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  • Optimal Control and Scheduling of Switched Systems

    Page(s): 135 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB) |  | HTML iconHTML  

    This technical note addresses optimal control and scheduling (controlled switching) of discrete-time switched linear systems. A receding-horizon control and scheduling (RHCS) problem is introduced and solved by dynamic programming, leading to a combinatorial optimization problem with exponential complexity. By relaxed dynamic programming, complexity is reduced while relaxing optimality within prespecified bounds. The resulting RHCS strategy is expressed explicitly as a piecewise linear state feedback control law defined over regions implied by quadratic forms. Closed-loop stability is not guaranteed inherently for the RHCS strategy. Therefore, a posteriori stability criteria based on piecewise quadratic Lyapunov functions are proposed. Finally, a region-reachability criterion is presented. View full abstract»

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  • Robust Stability via Sign-Definite Decomposition

    Page(s): 140 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (602 KB) |  | HTML iconHTML  

    This paper considers the problem of robust stability of a polynomial family whose coefficients are polynomial functions of the parameters of interests. The problem occurs in the design of a fixed order or fixed structure multivariable feedback controller , parametrized by a real design parameter vector , for a plant , containing a vector of uncertain parameters. The characteristic polynomials of such systems often contain coefficients which depend polynomially on and . Using results on sign-definite decomposition, a new stability test is developed that gives a sufficient condition for Hurwitz stability of the family of closed loop systems that result when and vary over prescribed boxes. This test is reminiscent of Kharitonov's Theorem, even though the family of polynomials considered here is certainly not restricted to be interval or even convex. Moreover the test does reduce to Kharitonov's Theorem for the special case of interval polynomials. Using this criterion recursively and modularly, sets of controllers that stabilize the family of uncertain plants are determined. View full abstract»

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  • Robust Consensus Controller Design for Nonlinear Relative Degree Two Multi-Agent Systems With Communication Constraints

    Page(s): 145 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    Robust static output-feedback controllers are designed that achieve consensus in networks of heterogeneous agents modeled as nonlinear systems of relative degree two. Both ideal communication networks and networks with communication constraints are considered, e.g., with limited communication range or heterogeneous communication delays. All design conditions that are presented are scalable to large and heterogeneous networks because the controller parameters depend only on the dynamics of the corresponding agent and its neighbors, but not on other agents in the network. View full abstract»

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  • Comments on "Improvement on Stability Analysis for Linear Systems Under State Saturation

    Page(s): 152 - 155
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    The purpose of this note is to correct some statements and numerical results in the above paper. In particular, we will show that the stability criterion in is equivalent to that in , rather than less conservative as claimed, and the criterion in does apply to the numerical example suggested in . View full abstract»

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  • Modular Adaptive Control of Uncertain Euler–Lagrange Systems With Additive Disturbances

    Page(s): 155 - 160
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    A novel adaptive nonlinear control design is developed which achieves modularity between the controller and the adaptive update law. Modularity between the controller/update law design provides flexibility in the selection of different update laws that could potentially be easier to implement or used to obtain faster parameter convergence and/or better tracking performance. For a general class of linear-in-the-parameters (LP) uncertain Euler-Lagrange systems subject to additive bounded non-LP disturbances, the developed controller uses a model-based feedforward adaptive term in conjunction with the recently developed robust integral of the sign of the error (RISE) feedback term. Modularity in the adaptive feedforward term is made possible by considering a generic form of the adaptive update law and its corresponding parameter estimate. This generic form of the update law is used to develop a new closed-loop error system and stability analysis that does not depend on nonlinear damping to yield the modular adaptive control result. View full abstract»

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  • A Structurally Stable Globally Adaptive Internal Model Regulator for MIMO Linear Systems

    Page(s): 160 - 165
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB) |  | HTML iconHTML  

    The problem of compensating an uncertain disturbance and/or tracking some reference signals for a general linear MIMO system is studied in this work using the robust regulation theory frame. The disturbances are assumed to be composed by a known number of distinct sinusoidal signals with unknown phases, amplitude and frequencies. Under suitable assumptions, an exponentially convergent estimator of the unknown disturbance parameters is proposed and introduced into the classical robust regulator design to obtain an adaptive controller. This controller guarantees that the closed-loop robust regulation is attained in some neighborhood of the nominal values of the parameters of system. A simulated example shows the validity of the proposed approach. View full abstract»

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  • Inference-Based Decentralized Prognosis in Discrete Event Systems

    Page(s): 165 - 171
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    For discrete event systems, we study the problem of predicting failures prior to their occurrence, also referred to as prognosis, in the inference-based decentralized framework where multiple decision-makers interact to make the global prognostic decisions. We characterize the class of systems for which there are no missed detections (all failures can be prognosed prior to their occurrence) and no false alarms (all prognostic decisions are correct) by introducing the notion of -inference-prognosability, where the parameter represents the maximum ambiguity level of any winning prognostic decision. An algorithm for verifying -inference-prognosability is presented. We also show that the notion of coprognosability introduced in our prior work is the same as 0-inference-prognosability, and as the parameter is increased, a larger class of prognosable systems is obtained. View full abstract»

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  • Adaptive Control for Plants in the Presence of Actuator and Sensor Uncertain Hysteresis

    Page(s): 171 - 177
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    This note discusses the output tracking control for a linear plant containing uncertain hysteresis nonlinearities in actuator and sensor devices simultaneously, where the hysteresis is described by Prandtl-Ishlinskii model. A new adaptive control scheme is developed to compensate the plant, the actuator and the sensor uncertainties and to generate an adaptive estimate of the plant output. The proposed control law ensures the uniform boundedness of all signals in the closed-loop system. Furthermore, the tracking error between the estimated plant output and the desired output is guaranteed to converge to zero asymptotically. View full abstract»

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  • Decentralized Fault Tolerant Control of a Class of Interconnected Nonlinear Systems

    Page(s): 178 - 184
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    A decentralized adaptive approximation design for the fault tolerant control of a class interconnected feedback linearizable nonlinear systems is considered in this technical note. Multiple faults may occur in the subsystems local dynamics as well as in the interconnections between the subsystems. Linearly parameterized neural networks are used to adaptively approximate the unknown interconnection effects and changes in model dynamics due to failures. A dead-zone modification in the adaptive laws is combined with an adaptive bounding method for addressing stability and robustness issues in the presence of residual approximation errors. Outside the coverage region of the approximators, a decentralized safety control scheme is designed to steer back the trajectory by using a sliding mode approach with adaptive bounds. A simulation example is presented for illustrating the effectiveness of the proposed fault tolerant control methodology. View full abstract»

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  • General Framework for Mobile Robot Navigation Using Passivity-Based MPC

    Page(s): 184 - 190
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    This technical note proposes a novel navigation planner for mobile robots based on an adapted version of passivity-based nonlinear model predictive control. The proposed framework extends the convergent dynamic window approach and can be considered a generalized navigation planning technique able to include the high complex models required to describe the dynamics of vehicles moving outdoor on rough terrains. Several case studies are discussed to illustrate the usage of the framework. View full abstract»

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  • Positivity Preservation Properties of the Rantzer Multipliers

    Page(s): 190 - 194
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    The Rantzer multipliers are known to preserve the positivity of certain aberrations of memoryless monotone positive nonlinearities. We show that if the nonlinearity input is constrained to be positive valued for all time instants, these multipliers are positivity preserving for a larger class of nonlinearities. As a result, it follows that the Rantzer multipliers are useful in reducing the conservatism inherent in the multiplier theoretic stability analysis of feedback systems featuring a larger class of nonlinearities than the one these multipliers were originally intended for, so long as the nonlinearity input is positive-valued for all time instants. 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