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Decision and Control, 1995., Proceedings of the 34th IEEE Conference on

Date 13-15 Dec 1995

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Displaying Results 1 - 25 of 215
  • Stability analysis and control parameter optimization of an inventory system with order variation limits

    Page(s): 4200 - 4201 vol.4
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    This paper considers an one-item inventory system subject to random order lead times and random demand. The key parameter of the control policy is the objective inventory level. In each period, the order to be placed brings the inventory position as close as possible to the objective inventory level, and the variation of the quantity to be ordered from one period to the next one is kept bounded by some given upper and lower variation limits. We show that the inventory level remains finite along the time provided that the variation limits are positive. The average inventory cost is shown to be a convex function of the objective inventory level. A simulation-based approach is proposed for the determination of the optimal objective inventory. A method of dichotomy with derivative is then used to determine the optimal objective inventory level. Thanks to the particular structure of the problem, the average costs and the derivatives needed in various iterations of this method are estimated using a single sample path with respect to a given objective inventory View full abstract»

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  • Using an adaptive autopilot for flight control system performance improvement

    Page(s): 3759 - 3762 vol.4
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    Classically designed interceptor autopilots which use proportional and integral controllers with rate and position feedback have traditionally been the standard design approach. Although adequate for most situations, there are certain scenarios where the body bending effects of the divert thrusters and the mass property variation due to divert thruster firings reduce the effectiveness of these traditional control laws. Under such conditions, second order body bending filters and associated synthetic feedback techniques need to be added in the loop in order to maintain adequate body stability and gain margin. In this effort, we propose augmenting the classical controller and associated filters with a direct adaptive control system to ameliorate the effects of body bending, system delay, and changes in interceptor dynamics View full abstract»

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  • MIMO optimal control design: the interplay of the ℋ2 and the l1 norms

    Page(s): 3682 - 3687 vol.4
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    We consider the problem of minimizing the ℋ2 performance of the closed loop subject to a l1 constraint. The development is devoted to multi-input multi-output (MIMO) systems. It is shown that approximating solutions to the optimal within any a priori given tolerance can be obtained via a finite dimensional quadratic optimization problem whose dimension is known a priori View full abstract»

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  • A necessary and sufficient condition for the solvability of perturbed Nevanlinna-Pick interpolation problems

    Page(s): 4341 - 4342 vol.4
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    This paper gives a necessary and sufficient condition for the solvability of a family of Nevanlinna-Pick interpolation problems with polytopes of uncertain functional values. Similar to Kharitonov's extreme point test, the condition given requires all vertex Pick matrices to be positive definite View full abstract»

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  • Global synchronous scheduling policies for flexible manufacturing systems

    Page(s): 4190 - 4195 vol.4
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    In this paper, we consider global approaches to scheduling flexible manufacturing systems (FMS) of the type considered by Perkins and Kumar (1989). We call the class of global scheduling policies that we consider global synchronous clearing (GSC) policies because they operate by synchronizing the flow of parts through sections (which we call paths) of the FMS. We provide sufficient conditions for the stability of two GSC policies, and we provide some guidelines for the choice of GSC policies vs. distributed policies View full abstract»

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  • Regulator theory for switched systems

    Page(s): 3712 - 3718 vol.4
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    In this paper the exact output tracking problem for systems with parameter jumps is considered. Necessary and sufficient conditions are derived for the elimination of switching-introduced output transient. Previous works have studied this problem for minimum-phase systems. In contrast, our approach, which is also applicable for nonminimum-phase systems, obtains bounded but possibly noncausal solutions. A major advantage, when reference trajectories are generated by an exosystem, is that a feedback-control based solution is obtained. As in standard regulator theory, we obtain a linear map from the states of the exosystem to the desired system state which is defined via a matrix differential equation. The constant solution of this differential equation provides asymptotic tracking, and coincides with the feedback law used in standard regulator theory. The obtained results are applied to a simple flexible manipulator with jumps in the pay-load mass View full abstract»

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  • Finite singularities of nonlinear systems. Output stabilization, observability and observers

    Page(s): 3295 - 3299 vol.4
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    We consider observed, either controlled or uncontrolled analytic nonlinear systems having the property that the kth derivatives of the outputs can be smoothly expressed in terms of the outputs, their k-1 first derivatives, the inputs and their k first derivatives. We show that, in the uncontrolled case, the finiteness of the map which to the state associates the output with its first derivatives, with additional standard observability assumptions, implies this property. More generally, in both the controlled and uncontrolled cases, this property together with some observability assumptions allows the construction of asymptotic observers, even if the state is a continuous function only of the inputs, the outputs and their derivatives up to a certain order (at least in restriction to compacta). We show that our systems verifying the stated property, if state feedback stabilizable, are also dynamic output feedback stabilizable (with an additional assumption). Therefore, our result contains a number of previous ones. Proofs are not given View full abstract»

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  • Multi-objective aspects in lot-sizing in manufacturing systems

    Page(s): 4202 - 4205 vol.4
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    Deterministic timed event graphs (TEGs) are used in this paper to model manufacturing systems. The steady-state performance evaluation of such systems is carried out on the basis of simple results referred to TEGs. In this framework, a two-objective optimization problem joining the maximization of the system productivity and the minimization of the work-in-progress is formalized. The solution of this problem is sought by decomposing the overall problem in simpler subproblems whose structure turns out to be that of linear programming problems or linear mixed integer programming problems View full abstract»

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  • Bounded-input bounded-output stability of the Josephson junction represented by the perturbed Sine-Gordon equation

    Page(s): 3763 - 3764 vol.4
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    In this paper, the superconducting Josephson junction represented by the perturbed sine-Gordon equation is considered. The bounded-input bounded-output stability of this nonlinear system is established by showing that an energy-like (Lyapunov) function corresponding to the junction is bounded View full abstract»

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  • Pole placement for time-varying systems by gradient flows

    Page(s): 3688 - 3689 vol.4
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    An algorithm for pole-placement for time-varying systems is proposed. It is based on discretization of a gradient flow on symmetric realizations. We propose the algorithm, discuss convergence issues and demonstrate the approach by some examples View full abstract»

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  • Shortest 3-dimensional paths with a prescribed curvature bound

    Page(s): 3306 - 3312 vol.4
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    We present the solution of the three-dimensional case of a problem regarding the structure of minimum-length paths with a prescribed curvature bound and prescribed initial and terminal positions and directions. In particular, we disprove a conjecture, according to which every minimizer is a concatenation of circles and straight lines. We show that there are many minimizers-the “helicoidal arcs”-that are not of this form. These arcs are smooth and are characterized by the fact that their torsion satisfies a second-order ordinary differential equation. The solution is obtained by applying optimal control theory. An essential feature of the problem is that it requires the use of optimal control on manifolds. The natural state space of the problem is the product of three-dimensional Euclidean space and a two-dimensional sphere. Although the problem is obviously embeddable in 6-dimensional Euclidean space, the maximum principle for the embedded problem yields no information, whereas a careful application of the maximum principle on manifolds yields a very strong result, namely, that every minimizer is either a helicoidal arc or of the form C, S, CS, SC, CSC, CCC, where C, S stand for “circle” and “segment”, respectively View full abstract»

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  • A linear matrix inequality approach to the discrete time mixed l 1/ℋ control problem

    Page(s): 3670 - 3675 vol.4
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    This paper presents a solution method to the general mixed l1 /ℋ problem for discrete time linear time invariant systems. The problem formulation involves finding a stabilizing feedback controller that minimizes the l1 norm of a closed-loop transfer matrix subject to an ℋ norm constraint on another closed-loop transfer matrix. It is shown that for one-block problem the optimal solution can be approximated arbitrarily closely, in terms of the closed-loop l1 norm, by solving a sequence of finite dimensional convex optimization problems over linear matrix inequalities. For multi-block problem we have also obtained superoptimal and suboptimal solutions which give lower bounds and upper bounds convergent to the optimal closed-loop l1 norm. Numerical examples are provided to demonstrate the effectiveness of this approach View full abstract»

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  • Double band policy for a failure prone manufacturing system with alternate demand rates in heavy traffic

    Page(s): 4196 - 4197 vol.4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    We consider a manufacturing system with a single failure prone machine producing a single part type whose demand changes randomly and alternately between constant rates the successive periods of which are represented by i.i.d. random variables, as are the successive up and down periods of the machine state. We assume that the additional products can be bought with a zero lead time, and that the system operates in heavy traffic. The control objective is to minimise the expected discounted total cost. An asymptotically optimal policy is obtained using a diffusion approximation scheme View full abstract»

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  • Continuity properties of solutions to H2 and H Riccati equations

    Page(s): 4335 - 4340 vol.4
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    In H2 and H optimal control (semi-) stabilizing solutions of algebraic Riccati equations play an essential role. It is well-known that these solutions might have discontinuities as a function of the system parameters. The paper shows that these discontinuities are directly linked to nonleft-invertibility and, in contrast to what one might think, unrelated to zeros on the imaginary axis View full abstract»

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  • Identifying MIMO Wiener systems using subspace model identification methods

    Page(s): 4206 - 4211 vol.4
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    In this paper we show that the multivariable output-error state-space model (MOESP) class of sub-space model identification (SMI) schemes can be extended to identify Wiener systems, a series connection of a linear dynamic system followed by a static nonlinearity. In this paper, we restrict to present these extensions for the case the Taylor series expansion of the static nonlinearity contains odd terms. It is shown that the extension allows to identity the linear part of the Wiener systems as if the static nonlinearity is not present. In this way, it is related to cross-correlation analysis techniques View full abstract»

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  • Vehicle steering system state estimation using sliding mode observers

    Page(s): 3391 - 3396 vol.4
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    The increasing sophistication of the electronics package available on board the modern automobile, has made viable a number of new technologies that can greatly enhance the driveability and safety of the vehicle. One area that has received much attention is the use of drive by wire steering systems that partially or in some cases (such as in some envisaged IVHS systems) completely takes over the tasks of vehicle directional control. The vehicle handling dynamics are quite nonlinear (especially for severe maneuvers and over large variations in longitudinal speed). Most steering control algorithms require knowledge of the vehicle states and in many cases are quite sensitive to the values of various vehicle parameters such as tire cornering stiffness, tire-road coefficient of friction etc. Measuring the states is usually expensive and direct measurement of the parameters is often impossible. Thus, some means of estimating these variables becomes imperative. Recent advances in sliding mode control/estimation theory have demonstrated the effectiveness of such schemes when applied to nonlinear systems. This paper presents some extensions to the theory of sliding mode observers and an application to the problem of estimating vehicle steering system states View full abstract»

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  • Optimal location of controls for an acoustic problem

    Page(s): 3765 - 3766 vol.4
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    Investigates the optimal location of controllers to achieve reduction of noise field in an acoustic cavity. The author first formulates a linear quadratic tracking problem in a Hilbert space, and then considers the problem of optimization of an appropriate performance criterion with respect to the location of the controls. Numerical examples are presented to illustrate the author's theoretical results View full abstract»

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  • Frequency response of generalized sampled-data hold functions

    Page(s): 3596 - 3601 vol.4
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    Alternatives to the zero order hold known as generalized sampled-data hold functions have been proposed by several authors. More recently, it has been noticed that these new holds incur intersample behavior penalties in many cases. In studying such behavior, one of the issues of relevance is the “frequency response” of the hold; for example, it is known that “nonminimum phase” zeros of the hold impose design tradeoff in the continuous-time response to disturbances of the sampled-data system. This paper goes deeper into the analysis of the frequency response of these devices, and provides some preliminary results on zero location and integral constraints satisfied by the hold. We give a number of circumstances in which nonminimum phase zeros may occur and, furthermore, we show that holds with zeros off the jω-axis will tend to have poor frequency responses properties View full abstract»

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  • Theory and experiments in vision-based grasping

    Page(s): 4053 - 4058 vol.4
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    Flexible operation of a robotic agent requires interaction with an uncalibrated or partially calibrated environment through the use of sensing. Much of the recent work in robotics and computer vision has concentrated upon the active observation of dynamic targets by the robotic agent. This paper focuses on autonomous interaction with moving targets in the environment. In particular, the authors propose a system that performs autonomous grasping of a moving target in an uncalibrated environment. The proposed system is derived using the controlled active vision framework and provides the flexibility to robustly interact with the environment in the presence of uncertainty The proposed work is experimentally verified using the Minnesota Robotic Visual Tracker (MRVT) to select targets of interest, to derive estimates of unknown environmental parameters, and to supply a control vector based upon these estimates to guide the manipulator in both the tracking and the grasping of a target View full abstract»

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  • An entropy approach to queueing control

    Page(s): 3644 - 3645 vol.4
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    The problems of scheduling and routing of customers in queueing systems are examined from the point of view of entropy which is a measure of uncertainty in the context of the random experiment at hand. Two principles are developed, one of the maximum rate of entropy reduction which is equivalent to maximum speed of order in the system and one of minimum entropy which is equivalent to minimum uncertainty. The resulting controls are straightforward and easy to apply View full abstract»

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  • A dynamic inverse for nonlinear maps

    Page(s): 4218 - 4223 vol.4
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    We consider the problem of estimating the time-varying root of a time-dependent nonlinear map. We introduce a “dynamic inverse” of a map, another generally time-dependent map which composes with the original map to form a nonlinear vector-field. The flow of this vector field decays exponentially to the root. We then show how a dynamic inverse may be determined dynamically while being used simultaneously to find a root. We construct a continuous-time analog computational paradigm around the dynamic inverse View full abstract»

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  • The use of observability and controllability gramians or functions for optimal sensor and actuator location in finite-dimensional systems

    Page(s): 3319 - 3324 vol.4
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    In this paper, we discuss the optimal location of sensors and actuators for both linear and nonlinear dynamical systems, in both the continuous-time and discrete-time case, on the basis of observability and controllability functions. The optimal location of sensors can be viewed as the problem of maximizing the output energy generated by a given state. On the other hand, the optimal location of actuators can be viewed as the problem of minimizing the input energy required to reach a given state. Such design problems occur in many applications, such as the control of distributed parameter systems, arising in mechanical, hydraulic or chemical processes. In this paper, some new results on observability and controllability functions for nonlinear systems are also provided. Furthermore, we propose a general procedure for computing the optimal design parameters, based on both integer programming and a branch and bound method, suitable for large-scale systems. The effectiveness of this approach is demonstrated for a practical example View full abstract»

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  • Convexity vs. compensator order for the discrete-time, mixed-norm control problem

    Page(s): 3676 - 3681 vol.4
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    This paper address the issues of convexity and compensator order in mixed-norm optimization. The optimal H2/l1 control problem is formulated as a convex problem, and result in a compensator which is of arbitrarily high order. Because it is usually impractical to implement a very high order compensator, a fixed-order method is used to find compensators of a specifiable order. However, the fixed-order method results in a non-convex optimization problem in which there are local minima. The non-convexity and local minima resulting from the fixed-order problem are examined using the Pareto-optimal H2/l1 curves and compensator eigenvalue traces for varying compensator order. It is shown that it requires a discontinuous jump in the design variables to move from one local minimum to another. While these discontinuities can cause problems, several methods for dealing with them are suggested View full abstract»

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  • Nonlinear plant controller reduction

    Page(s): 4212 - 4217 vol.4
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    This paper extends the H balanced truncation approach of Mustafa and Glover (1991) for linear plants to input affine nonlinear plants. Nonlinear H balanced truncation is used to obtain a reduced order controller. Conditions which ensure that this controller stabilizes the full order plant are derived. In addition an upper bound on the performance of the closed loop system, with respect to the L2 gain, is obtained View full abstract»

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  • On the data based time varying LQG controllers via Cholesky factorisations

    Page(s): 3414 - 3419 vol.4
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    The linear quadratic Gaussian control (LQG) problem is considered for input output linear systems corrupted with noise. In a computer based environment it is reasonable to assume that the model is obtained from practical experiments and hence only is partially known. For that reason, it may be preferable to derive the optimal control law from the basis of a finite number of data. In the paper it is shown how Cholesky factorisations of the noise spectrum and of the weightings in the performance index gives the resulting LQG-controller as a direct output control law. Modifications of the performance index in order to reduce the complexity of the controller is proposed. Both the off-line and the on-line LQG problems are considered. In addition comparisons are made to generalised predictive control (GPC) and to the state space Kalman filter based control law View full abstract»

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