ISSN:0020-7721    

DOI:10.1080/00207729408949336

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A linear-quadratic output-feedback approach is given for designing digital servo-control systems of specified structure. The result is digital controllers that have a sensible structure based on classical control theory, in contrast to standard LQR design using state feedback plus an observer. The correct initial conditions for determining the LQ tracker output-feedback gains are not uniformly distributed as is traditionally assumed, but are shown to be explicitly given in terms of the step command magnitude. Both pole and zero placement are used to optimize the performance index. Arbitrary systems are treated, not only those with integrators in the forward paths, by adding a term to the performance index that weights the steady-state error. The approach works even if the system is non-minimum-phase. Necessary conditions are derived that may be used in a gradient-based routine to determine the optimal digital control gains. The approach does not rely on redesign of a continuous control system using techniques like the bilinear transformation, but uses direct discrete-time design. An aircraft digital command augmentation system is included as a sample design.

ISSN:0020-7721    

DOI:10.1080/00207729408949337

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In order to design tracking systems incorporating linear multivariable plants with more controlled outputs than manipulated inputs, it is shown that a more'general tracking concept than set-point tracking is necessary. The inclusion of inequalities in tracking conditions facilitates the characterization of tracking systems and linear multivariable plants. It is shown that the possibility of undertracking (i.e. tracking with non-negative errors) is characterized by the separation theorem of convex analysis, that linear multivariable plants can be classified into Class I and Class II plants based upon their steady-state transfer-function matrices, and that, in the case of Class I plants, undertracking is possible for any set-point commands. Furthermore, the necessary and/or sufficient conditions for Class I plants are given. Finally, it is shown that, in the case of Class 1 plants, undertracking is also possible for any set-point commands and any constant disturbances.

ISSN:0020-7721    

DOI:10.1080/00207729408949338

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The steady states of tracking systems incorporating self-selecting controllers and linear multivariable plants exhibit limit tracking when none of the plant outputs exceeds its corresponding set point (i.e. its limit value) and the number of pairs of equal plant outputs and set points is not less than the rank of the plant steady-state transfer-function matrix. The condition for the feasibility of limit tracking is given. An approach to the synthesis of limit-tracking systems is proposed that utilizes an order-reduction technique to reduce the number of separate set-point tracking controllers frompCmtop− m + 1 in the case ofm-input/p-output plants while guaranteeing the existence of the steady states of such tracking systems.

ISSN:0020-7721    

DOI:10.1080/00207729408949339

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Simplifications to the one-sided ‘one-block’ standard H∞ problem state space formulas are considered. These simplifications are then used lo solve a sum of sensitivities (also called ‘generalized WB’) problem as defined by Grimble (1987). Structural aspects of the controller and the feedback system are also revealed. A design example illustrating the closeness of results between the sum of sensitivities design and the mixed sensitivity is included.

ISSN:0020-7721    

DOI:10.1080/00207729408949340

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The paper discusses the principles of model-based fault detection and isolation (FDI) in nonlinear and time-varying uncertain dynamic systems. Such systems are typical for such complex plants as, for example, in the chemical process industries or in advanced transportation technology. For a model-based fault diagnosis in such situations, robust or even adaptive strategies are needed. In this paper the theory of robust linear observer-based residual generation for FDI is reviewed from a general point of view. The structural equivalence between the parity space approach and observer-based approach is shown in a new simple graphical way by showing that the observer-based FDI concept can easily be transformed into an equivalent extended parity space configuration, without claiming, however, equivalence of the underlying design techniques. The unknown input observer approach known as a most powerful and comprehensive framework for robust residual generation for FDI in uncertain linear systems is extended to classes of nonlinear and time-varying systems. For such plants an adaptive nonlinear unknown input observer scheme is proposed. Finally, appropriate residual evaluation techniques are outlined and suggestions are made to increase the robustness, for instance by using adaptive thresholds.

ISSN:0020-7721    

DOI:10.1080/00207729408949341

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

With the help of meter measuring systems, state estimation of water distribution systems can show not only the hydraulic properties of all system components, but it can also provide an estimate of errors to enhance engineers' confidence in the results. The number of meters as well as their topological distribution in networks strongly influences the accuracy of the estimates. The meter placement problem is formulated such that it results in a multi-objective optimization by seeking the best solution in terms of estimation accuracy and metering cost. A method employing a dynamic analysis of the co variance matrix of state variables and the decision-trees technique has been developed for the design of an optimal meter placement for state estimation of water distribution systems. The conjugate gradient technique is used to solve the non-linear least-squares problem of state estimation. Two test examples are presented to assist in the explanation of the algorithm.

ISSN:0020-7721    

DOI:10.1080/00207729408949342

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents a concise and straightforward formulation of the unknown input observer (UIO) problem based on the general structured observer. By employing the simplest generalized inverse of matrices, the {1}-inverse, we develop constructive design procedures for the UIO design that provide necessary and sufficient conditions for both full-order and reduced-order general structured UIOs. Moreover, corresponding configurations for continuous-time systems are also derived, and consequently this paper renders the complete solutions for general structured UIO design. Furthermore, we show that the general structured UIO is structurally and numerically equivalent to the UIO in the configuration of Luenberger observer. Examples are included to illustrate the validity of the proposed methodology.

ISSN:0020-7721    

DOI:10.1080/00207729408949343

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents a stable multirate output-feedback controller for digital control of a continuous-time input-delay system. It is shown that an arbitrary digital state feedback controller for an observable input-time-delay plant can be realized by using multirate sampled output data. The developed digital multirate-output feedback controller enables us to achieve results similar to those of the state feedback controller, without constructing an observer.

ISSN:0020-7721    

DOI:10.1080/00207729408949344

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper addresses three interrelated issues: a comparative analysis of the political risks for foreign direct investments in forty-nine countries located throughout the world; an adjusted present value procedure that incorporates political risk; and an application of the adjusted present value procedure to a numerical example in a sensitivity analysis. The comparative analysis relies on the statistical methods of mutliple regression analysis and discriminant analysis. The multiple regression models are estimated by the probit analysis procedure, whereas the discriminant analysis models are a four-group problem. Both methods give Switzerland the country least politically risky, followed by the United States; Iran ranks as the worst. Such a rating is essential for multinational corporations selecting countries for direct investment. The article then investigates how to make use of the adjusted present value and sensitivity analysis techniques to manage against political risk and evaluate overseas direct investments as well as to select countries.

ISSN:0020-7721    

DOI:10.1080/00207729408949345

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor