摘要:

The behaviour of model reference adaptive controllers (MRAC) designed in a deterministic framework is analysed in a stochastic framework. The case of discrete time linear single-input single-output minimum phase systems is considered. The analysis is based on the ordinary differential equation method developed by Ljung. New schemes are also introduced in order to achieve minimal variance tracking in a stochastic environment.

ISSN:0020-7179    

DOI:10.1080/00207178208922653

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper investigates the conditions for existence and the characterization of fixed modes in decentralized multivariable control systems employing local controllers. It is shown that for scalar local controllers in the diagonal control structure, the necessary and sufficient condition for a system polo ats= λ to be a fixed mode is thats= λ be a transmission zero of all subsystems formed by selecting the same inputs and outputs of the system. The results are applied to scalar controllers in any arbitrary control structure and also to non-scalar local controllers and similar conditions are obtained. Examples are discussed for illustration.

ISSN:0020-7179    

DOI:10.1080/00207178208922654

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Maxwell's manuscripts held at Cambridge University Library contain several items of interest from a control or stability point of view. Extracts are reproduced dealing with (i) a speed governor designed by Maxwell at the age of fifteen, and (ii) the stability of fluid motion (1855).

ISSN:0020-7179    

DOI:10.1080/00207178208922655

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The structural dominance method of Litz is generalized to aid in determining not only the dominant modes, as in the original method, but also the most sensitive state variables and the most effective inputs of a linear, large-scale system. Through the addition or modification of a number of features, the utility of the method to the control system designer has been greatly enhanced. These include: (a) avoiding the gain normalization procedure of the original method (which eliminates information on input/output sensitivity), (b) definition of input- and state-variable normalization elements (so as to permit evaluation of variable sensitivities by direct numerical comparison), and (c) generalization of a time-weighting technique (to assist in determining minimum order of the reduced system model). With the range of measures provided in the generalized method, the system designer can now introduce both subjective and objective criteria quite naturally into the selection of a control structure (choice of measured and manipulated variables) and into the analysis and synthesis of a reduced model for control system design.

ISSN:0020-7179    

DOI:10.1080/00207178208922656

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Six of the most commonly-used modal reduction techniques are represented by means of signal flow diagrams connecting inputs and state variables. In this representation, the derivation and the cross-comparison of the various methods are greatly facilitated. Each method is then analysed to determine key characteristics, i.e. (i) steady-state agreement, (ii) initial-value agreement, (iii) independence of the reduced model on the choice of retained state variables and inputs, and (iv) eigen vector orientation. Realistic, large-scale systems are used to evaluate the static and dynamic characteristics of each model reduction method numerically. These studies reveal some important, and often unrecognized, weaknesses of several traditional techniques and confirm the strength of the newly-developed technique of Litz.

ISSN:0020-7179    

DOI:10.1080/00207178208922657

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper treats the problem of time-optimal decoupled control for multi-input multi-output systems subject to constraints on the controls. The problem is to determine a control vector which transfers one state variable from a given initial steady state to a given final steady state in minimum time, whilst holding the remaining state variables constant. The solution is obtained using an extension of Pontryagin's maximum principle to problems in which thestate-controlspace is subject to additional non-differential inequality constraints. By an appropriate reformulation of the problem it is shown that the optimal solution requires that one of the controls be set at its extreme (saturated) value, while the other controls arc determined from the constraints on the state variables which are held constant. The controls behave continuously without switching, but the choice of the control which is held at saturation is changed at certain points. The optimal solutions are easily represented by phase-plane diagrams and the synthesis of the controls can be obtained for the whole of the admissible state space, depending on the direction of motion required of the output.

ISSN:0020-7179    

DOI:10.1080/00207178208922658

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Necessary conditions are derived for an optimal control problem in which the states are governed by integral or integro differential equations. The results are obtained by showing that corresponding necessary conditions hold for a sequence of optimal control problems in which the states are governed by differential equations involving delays, the solutions of which converge uniformly to the solution of the given problem.

ISSN:0020-7179    

DOI:10.1080/00207178208922659

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Optimum synthesis procedures for systems containing plants subject to large parameter variations require that bounds (or boundaries) specifying the magnitude of these variations be produdec at each frequency of interest. This paper presents a direct method (the ‘ dominant chord ’ approach) of determining these (‘ strong ’) bounds, with little or no approximation, for a large class of plants. Additionally, it is shown that an extension of this method to produce ‘ weak ’ bounds can result in substantial reductions in loop gain requirements.

ISSN:0020-7179    

DOI:10.1080/00207178208922660

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

We propose a unified description of several so-called fast, algorithms. The projection operator technique is used to derive least-squares ladder (or lattice) algorithms in the filter and the predictor forms. This technique, usually associated with orthogonal projection operations, is extended to oblique projections. The first application is an easy derivation of the ‘ exact ’ instrumental variable ladder algorithm which, to our knowledge, has not previously been described in the literature. A second application is a new derivation, based on the operator technique, of an algorithm for the fast calculation of gain matrices for recursive estimation schemes.

ISSN:0020-7179    

DOI:10.1080/00207178208922661

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor