摘要:

A new method for deriving minimum-order dynamic equivalents of power networks is developed. The approach starts with a linearized model in polynomial matrix form of the external power network, seen from its boundary nodes with the study system. Then, the concept of structural dynamic equivalent is introduced as a generalized definition of equivalent related to the order reduction that may occur when deriving the transfer function matrix of the external system and due to pole-zero cancellations. In this case, necessary and sufficient conditions are given for determining systematically the existence of structural equivalents of external systems, their order and exact mathematical representation. Furthermore, the above-mentioned theoretical results are used to develop an algorithm for constructing approximate reduced models, called nearly structural dynamic equivalents, which takes into account the more realistic event of near pole-zero cancellation. Indications about the error bounds of the approximate model are also provided. The capability and usefulness of the proposed method are illustrated by carrying out simulation studies on a sample power network.

ISSN:0020-7721    

DOI:10.1080/00207729208949185

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A real-time expert system is developed to support efficient operation and management of the No. 2 ironmaking reactor (blast furnace) in the China Steel Corporation. The expert system integrates the deep theoretical knowledge represented in reactor models with the practical experience of sophisticated field engineers. Fuzzy logic reasoning is applied in the expert system to deal with inherent indeterminacy of the operators‘ in-field knowledge of furnace heat levels. This expert system is divided into ‘information’ and ‘reasoning’ sub-systems. The information sub-system receives operational data from the process computer and executes the model calculations relevant to ironmaking. The sensory data and computation results of various models are then displayed on the operator's terminal by way of attractive diagrams and tables to help field engineers to comprehend the furnace conditions as an integrated whole. The treated data afforded by the information sub-system are then periodically extracted by a reasoning sub-system for judging furnace conditions and for inferring adequate control strategies according to linguistic rules derived from expert operators. The expert system is currently under test in the No. 2 blast furnace of the China Steel Corporation. So far results have shown that the expert system can effectively reproduce the control strategies of experienced engineers and can reinforce the operation abilities of less experienced field engineers.

ISSN:0020-7721    

DOI:10.1080/00207729208949186

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Our aim is to show that for a saturated state feedback regulator for which the open-loop system is asymptotically stable, it is always possible to find a feedback matrixFwhich guarantees its global asymptotic stability. An algorithm allowing easy computation of a suitable state feedback matrix F is given. The dynamics of the regulator is studied with respect to that of the open-loop system; conditions allowing the characterization of a dynamically faster regulator are also proposed. Finally, the results obtained are illustrated by some examples.

ISSN:0020-7721    

DOI:10.1080/00207729208949187

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A linear time-invariant discrete-time state regulator problem is addressed, where the weighting to the control input in the performance index tends to zero. It has been shown that this type of so-called discrete cheap control problem possesses a singular perturbation property in the closed-loop system. Using the discrete singular perturbation technique, an asymptotic series solution of the Kalman gain matrix is obtained and it has been shown that the feedback gain matrix can be obtained by solving the reduced order problems of the singularly perturbed system. Asymptotic solutions up to the second order approximation terms are developed and their closeness with the exact solution are compared using suitable examples.

ISSN:0020-7721    

DOI:10.1080/00207729208949188

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An algorithm is described for the standard fixed-interval smoothing problem in which the system is linear, time-varying discrete-time. The present smoother which is called the forward-pass Bryson-Frazier smoother here is shown to be a dual version of the well-known Bryson-Frazier smoother. The algorithm is less attractive in the numerical implementation of time-varying systems than that of Bryson and Frazier, because it involves inversion of the state transition matrix. However, the mechanization of this new algorithm allows the smoothed estimate or error covariance to be readily updated in response to a change in the initial statistics. A numerical example of a fourth-order tracking system illustrates the characteristics of both Bryson-Frazier smoothers. Thus, the present result together with the usual Bryson-Frazier smoother give a set of two solutions to the fixed-interval smoothing problem using a Lagrange multiplier method.

ISSN:0020-7721    

DOI:10.1080/00207729208949189

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The ‘generalized predictive control’ (GPC) law is derived in a tutorial presentation which includes critical analysis of the steps in the solution and of the resulting controller. The advantages and difficulties inherent in the approach are discussed and alternative means of implementing the controllers are considered. The relationship between GPC and the popular ‘generalized minimum variance’ optimal control law is also investigated.

ISSN:0020-7721    

DOI:10.1080/00207729208949190

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An algebraic approach to eigenstructure assignment in a class of continuous time singular systems Ex = Ax + Bu via state variable feedback u = Fx is developed. This constitutes an extension of the respective approach for linear multivariable regular systems. This method not only assigns eigenvalues to the closed-loop system, but assigns also part of the closed-loop eigenvector structure. Three cases are examined depending on the rank (E), compared to the number of inputs.

ISSN:0020-7721    

DOI:10.1080/00207729208949191

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Organizations that are divided into a certain number of groups are said to have an atomized structure. Group approach to organization is recently gaining popularity. There are a number of techniques that can be used to study and develop mathematical models of group functioning. This technique originates from what is called cybernetic design of organization and they are based on the systems approach, mathematical modelling and simulation. The tools developed so far, however, are applied to the groups that have already been denned as parts of a larger organization. What is still needed is a technique upon which the decision concerning creation of groups may be based. The intent of this paper is to propose a graph-based approach for atomized organization structure development. The depth-first search algorithm versus matrix based technique is discussed. It is shown that the group retrieval process may be carried out using easily programmable operations on an adjacency matrix.

ISSN:0020-7721    

DOI:10.1080/00207729208949192

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Relational database operations (selection, projection, join, etc.) can be implemented with 100% parallelism if each relation is stored as a set of bit vectors containing projections on subsets of the bits of a tuple (Ullmann 1988, 1990). This representation is approximate in that spurious tuples, called false drops, may be recovered along with the genuine tuples. In small-scale experiments, the number of projections required to maintain the expected number of false drops at a low, constant value was reported to be linearly proportional to the number of tuples stored in the database (Ullmann 1988). We show that a previous estimate for the number of false drops (Roberts 1979), given in the context of Bloom filters (Bloom 1970), also demonstrates a near-linear behaviour, but seriously underestimates the number of false drops, due to an assumption of independence between the projections which is no longer valid for the parallel database hardware. We give an improved estimate for the number of false drops which agrees well with the experimental results. This allows us to determine optimal parameters for the parallel database hardware.

ISSN:0020-7721    

DOI:10.1080/00207729208949193

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The M/G/m queueing system in the steady state is discussed. We refine a diffusion approximation model incorporating the constraint of traffic conservation for general queueing systems. An approximate expression for the distribution of the number of customers is presented. Numerical results indicate that the refined model provides improved performance.

ISSN:0020-7721    

DOI:10.1080/00207729208949194

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor