摘要:

Asymptotic stability in the sense of min–max theory is developed for a class of uncertain variable structure systems. Based on this unification between the theories, a min–max controller with predescribed sliding motion is designed. The proposed design method simplifies the one previously obtained for this purpose.

ISSN:0020-7721    

DOI:10.1080/00207728908910328

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

There are many algorithms currently available to approximate solutions to the ‘travelling salesman’ problem of finding the shortest route connecting n points in a complete tour. Conley (1988) presents a multi–stage simulation on a rank ordered distance array to solve a one vehicle problem forn = 20. A modification of that approach is presented here to deal with sending out two delivery trucks (or one truck making two trips) to touch allnpoints and return. An example forn = 33 is developed. The multi–stage simulation approach is then compared with other techniques.

ISSN:0020-7721    

DOI:10.1080/00207728908910329

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A dither is a high frequency signal introduced into a non-linear system in order to improve its performance. It is shown that the stability of a dithered system can be predicted rigorously by establishing the stability of its corresponding smoothed system when the dither has a sufficiently large amplitude as well as high–enough frequency, and the transfer function of the ‘linearized’ feedback system has a high-frequency attenuation property. A generally parametrized controller, advanced by Youlaet al., and a dither as its auxiliary are simultaneously introduced to augment the stability of the non–linear feedback system, where the controlled plant are not necessarily stable. The main feature of this study is that the technique of robustness optimization is used to find a lower bound on the dither amplitude for stabilization of the non–linear feedback system. Furthermore, there arc no stable, square, and minimum-phase constraints on the controlled plant.

ISSN:0020-7721    

DOI:10.1080/00207728908910330

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The stochastic optimal control problem is considered for a class of noisy discrete-time linear systems with markovian jumping parameters and quadratic cost. It is assumed that the controller has complete access to the jumping parameters. Using a dynamic programming technique, an optimal control policy is derived, together with an explicit expression for the optimal cost. Besides the intrinsic theoretical interest in its own right, the results derived here may have an important bearing on the study of the partially observable situation (no access to the jumping parameter),inter alia.

ISSN:0020-7721    

DOI:10.1080/00207728908910331

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Optimum software release policies are considered, minimizing the expected software cost simultaneously with the reliability requirement. Cost here also includes the penalty cost which is incurred by the manufacturer for not delivering the software at scheduled delivery time. The underlying software reliability growth models (SRGMs) are based on the non-homogeneous Poisson process (NHPP). Numerical results are also presented.

ISSN:0020-7721    

DOI:10.1080/00207728908910332

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The communication efficiency associated with the problems of transmitting information in space and time is known to be dependent upon the characteristics of the transmission medium. Notably Turin (1977), Kailath (1961), and Bello (1963) have considered the temporal channel response as a function of the channel time and delay spread processes. The physics of the medium have not been considered. Middleton and Groginsky (1965) and Wittwer (1980) have attempted to incorporate the physics of the medium in a strictly temporal channel model. This paper presents a theory that generalizes the earlier work for characterizing medium-induced effects upon deterministic and random space-time fields, and the theory is applicable to any frequency band in the electromagnetic spectrum. For a linear medium, a space-time system field function (S-TSFF) is introduced as a system model for an arbitrary (turbulent or material) medium (Lo 1988). The unified system field theory states that the output space-time field is related to the input space-time field and the S-TSFF through a set of space-time superposition integrals. The geometry between the energy source, the medium, and the observed world-point area or volume is dependent on the chosen coordinate system, and is implicitly expressed by the space-time superposition integrals. (The term world-point was used by Minkowski (1908) to denote a point in a four-dimensional space-time coordinate system. To distinguish our approach from the analysis of arbitrary events in a space-time manifold, the terms world-area and world-volume are chosen to denote the ‘simultaneity in space’ as opposed to the notation of world-line and world-space used in the theory of relativity.) For a deterministic input space-time field, the statistics of the output field are solely dependent on the S-TSFF. For a random input space-time field, the statistics of the output field are related to the statistics of the input field and the S-TSFF. In either case, the statistical characterization can be expressed in terms of a space-time correlation function, or, equivalentIy, the space-time power spectral density of the input-output fields and of the S-TSFF. The space-time correlation function of the S-TSFF generalizes the concept of the mutual coherence function (MCF) used in statistical optics (Born and Wolf 1970). A dual property for the S-TSFF is observed and it is shown to be consistent with the duality principle in physics and the linear system theory in engineering. This space-time duality concept leads to the conclusion that fundamental properties of matter are imbedded in all physically realizable systems. This conclusion has far reaching implications in many detection, instrumentation, and measurement systems—for example, the uncertainty principle can be applied to analyse the stability of atomic clocks and trap ion frequency standards. The medium's response to an applied field is dependent upon whether the observed field is due to a space-time point source, a space-time plane wave, or something in-between. The space-time system field theory has numerous applications in system engineering, e.g. communications, radar, sonar, optics, and various imaging systems.

ISSN:0020-7721    

DOI:10.1080/00207728908910333

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Based on the unified concept of space-time system field theory, a general space-time channel model can be constructed from the statistics of the space-time system field function (S-TSFF) for an arbitrary medium. This statistical characterization of the medium (channel) can be expressed in terms of the space-time correlation function, or, equivalently, the space-time power spectral density of the S-TSFF. The space-time correlation function of the S-TSFF generalizes the concept of the mutual coherence function (MCF) for a random electric field to an arbitrary space-time field. There are three different geometrical channel models depending on the choice of the coordinate systems, e.g. rectangular, cylindrical, and spherical. Using the notions of channel correlation time and correlation distance— i.e. doppler spread and delay spread—various geometrical tap-delay channel models are derived. From a system point of view, the space-time correlation parameters can be interpreted as a measure of the spatial and temporal memory of the channel. It is further demonstrated that the rectangular space-time channel model reduces to the two-dimensional randomly time-varying tap-delay line models introduced by Kailath (1961) and Bello (1963). A dual property for the S-TSFF is observed. This system duality principle shows that the channel response can manifest as a space-time filter put forth by linear system theory (convolution integral in space-time), or as a space-time aperture put forth by optics (convolution integral in space-time spectrum).

ISSN:0020-7721    

DOI:10.1080/00207728908910334

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The design problem of decentralized robust controllers is considered for a class of large-scale systems. The system considered in this paper is composed of interconnected subsystems with time-varying uncertainties. For such large-scale uncertain systems, we give a simple und new method whereby we can derive the sufficient conditions for asymptotically stabilizing the overall system using decentralized feedback robust controllers. An illustrative example is given to demonstrate the design procedure of the decentralized feedback robust controllers, in the light of the method developed in this paper.

ISSN:0020-7721    

DOI:10.1080/00207728908910335

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Estimating the frequency of one or more sinusoidal waves is a problem belonging to the field of signal analysis. The frequency characteristics of sinusoidal waves can be measured by peaks or troughs of the waves. Because of (he limit of the sampling frequency, the peaks or troughs of sinusoidal and EEG waves in the sampling usually deviate from their original ones in the time domain. Starting from a sinusoidal wave analysis, we present a correction formula with which the deviation time tdcan be calculated so as to detect the position of the real peak or trough of the data as fast and as accurately as possible on the time axis. The wave of the sleep spindle in the EEG can be considered as an asymmetrical sinusoid. Then after the waves have been filtered, the formula can also be applied to analyse the spindle of EEG waves and it is shown to be useful in the measurement of the frequency of the spindle wave. Error analysis and practical examples are presented.

ISSN:0020-7721    

DOI:10.1080/00207728908910336

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A robust tracking control algorithm based mainly on the theory of variable structure systems and Lyapunov's direct method is developed in this paper, to treat the tracking control problem of a class of non-linear time-varying systems with uncertain dynamics. A nominal model is used instead of an exact one. together with a description of the bounds of plant uncertainty. The objective is to design a control law such that all the plants lying within a specified band of uncertainly will be driven to reach the goal. The modelling error, time-varying system dynamics, system uncertainties, and disturbances are all treated as general disturbances to the nominal system. This algorithm greatly eases the difficulties present in requiring a precise model of the physical system for the control purpose and for handling the non-linear time-varying system. The non-linear time-varying system is first linearized to a linear time-varying system (with time-varying coefficients completely defined) via the method of variable structure systems. The control method is then switched to the Lyapunov-direct method, to eliminate the control chattering problem caused by the method of variable structure systems and to complete the tracking of the nonlinear time-varying system.

ISSN:0020-7721    

DOI:10.1080/00207728908910337

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor