摘要:

The problem of approximate realisation is described and various methods are discussed. A new method is then given which directly identifies the system poles from pulse response data by finding the local minima of a real function of a complex variable. These estimates of the poles are then refined using a new iterative nonlinear least-squares algorithm. Finally, these methods are applied to a ‘seismic wavelet’, and are shown to give good qualitative and quantitative information on the system being modelled.

DOI:10.1049/piee.1979.0140

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper is concerned with certain aspects of modelling dynamical systems. This problem can be divided into two parts; first, there is the question of identifying the system structure, and secondly of identifying the parameters defining the structure. Realisation theory provides a framework in which models of dynamical systems can be analysed mathematically, and in particular affects the structural identification problem. This paper is an expository paper devoted to surveying the main results. Three main areas are treated, those of linear, bilinear and nonlinear systems, providing a natural progression of technique and applicability. The complexities of the nonlinear theory have been minimised as far as possible, so that the results can be applied with a limited knowledge of calculus and algebra. Examples on Hamiltonian and polynomic systems are included to show how realisation theory is used in structural identification.

DOI:10.1049/piee.1979.0141

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper gives a selective review of the results obtained by applying the methods of functional analysis to stability problems in dynamical system theory.

DOI:10.1049/piee.1979.0142

出版商:IEE    

年代:1979

数据来源: IET

摘要:

In the paper, multivariable input/output stability criteria of a graphical nature for nonlinear multivariable feedback systems are developed. The derived stability criteria, which are of the circle type, use the frequency plots of the eigenvalues of a normal transfer-function matrix which approximates the linear part of the nonlinear feedback system. An iterative design procedure is introduced which reduces the error of approximation and the feedback systems sensitivity to disturbances, while ensuring the stability of the closed-loop system.

DOI:10.1049/piee.1979.0143

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The Hopf bifurcation theorem is used by physicists, biologists and others interested in oscillations in systems described by differential equations. This paper presents a version of the theorem applicable directly to feedback systems, using the method of characteristic loci in an interpretation which looks rather like a multiple-loop version of the graphical describing function method. Frequency, amplitude and stability of oscillations about an equilibrium state are predicted by an iterative process which starts with a 2nd-order harmonic balance and successively increases the number of harmonics taken into account. The results from each stage of the process are used to define a curve in the complex plane from which the results of the next stage can be read off; consequently, the user has a visual indication of the accuracy and rate of convergence. The main theoretical limitation is that the nonlinear elements in the system must be continuously differentiable at least once more than the order of the highest harmonic used, whereas the main practical limitation is that the formula for the curve becomes extremely complicated if more than about six harmonics are considered.

DOI:10.1049/piee.1979.0144

出版商:IEE    

年代:1979

数据来源: IET

摘要:

Self tuning is an important new branch of control which is attracting increasing theoretical and practical interest. The objective of self tuning is to control systems with unknown constant or slowly varying parameters, so theoretical interest is concerned with the stability, performance and convergence of the recursive algorithms involved, while practical interest derives from its potential as a simple controller commissioning tool, both as a method for controlling time-varying or nonlinear plant over a range of operating points, and for dealing with batch problems where the plant or materials vary over successive batches. This paper summarises and expands previous work on the design of self-tuning controllers. It discusses the closed-loop properties of various classes of self tuner, convergence concepts and results, and some of the technical problems involved with implementing self tuners on small computers or microprocessors.

DOI:10.1049/piee.1979.0145

出版商:IEE    

年代:1979

数据来源: IET

摘要:

The paper considers some control problems for systems described on infinite-dimensional spaces. A mathematical framework in terms of semigroups is developed which enables the generalisation of the finite-dimensional results to infinite dimensions, and which includes partial differential equations and delay equations as special cases. After first surveying some finite-dimensional results, abstract dynamical systems are introduced and the systems theory concepts of stability, controllability, observabiity and the linear quadratic problem are analysed. Throughout the paper the abstract theory is applied to a number of examples to obtain specific results.

DOI:10.1049/piee.1979.0146

出版商:IEE    

年代:1979

数据来源: IET