摘要:

This paper discusses methods for applying restrictions to qualitative models of physical systems in order to ensure more specific behaviour. Restriction is performed by adding constraints; directly on exogenous parameters, and indirectly on non-exogenous or dependent parameters. The former are calledprimaryrestrictions, and the latter are calledderivedrestrictions. We show the connection between primary and derived restrictions, and how to determine the consistency of multiple restrictions. Examples are given of how a specific model is augmented using restrictions.

DOI:10.1049/ise.1993.0013

出版商:IEE    

年代:1993

数据来源: IET

摘要:

To build model-based systems capable of emulating the scientist's or engineer's way of reasoning about a given physical domain requires methods for automating the formulation or selection of a model which adequately captures the knowledge needed for solving a specific problem. To find and exploit such models requires the use and integration of different kinds of knowledge, formalisms and methods. This paper describes a system which aims at reasoning automatically about visco-elastic materials from a mechanical point of view. It integrates both domain-specific and domain-independent knowledge in order to classify and analyse the mechanical behaviour of materials. The classification task is based on qualitative knowledge, whereas the analysis of a material is performed at a quantitative level and is based on numerical simulation. The key ideas of the work are to automatically generate a library of models of ideal materials and their corresponding qualitative responses to standard experiments; to classify an actual material by selecting from within the library a class of models whose simulated qualitative behaviours towards standard loads match the observed behaviours; to identify a quantitative model of the material, and then to analyse the material by simulating its behaviour on any load. Each model in the library is automatically generated in two different forms; at the lowest level, as a symbolic description and, at a mathematical level, as an ordinary differential equation. This paper mainly concentrates on the methods and algorithms of model generation and qualitative simulation.

DOI:10.1049/ise.1993.0014

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Qualitative models of dynamical systems fall into non-causal or causal approaches. The non-causal approach is widely used in part because traditional physics describes phenomena by means of symmetric functional relations. It supports the idea that causality can be ignored or inferred from the model itself. Nevertheless, when people explain how things work, they use causal relations. Representing causality explicitly makes it possible to take advantage of exogenous knowledge necessary for understanding the phenomena and supporting self-explanatory simulation. The basic concepts used in both approaches, in addition to the representation formalisms and algorithms, are discussed in the light of recent works performed by teams affiliated to the MQ&D research group in France.

DOI:10.1049/ise.1993.0015

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A concept for distributed control systems is outlined. The concept is based on a plant database containing descriptions of the plant and the control system. The database is object based and supports multiple view of an objects. A demonstrator is presented where a DCS of this type is emulated. The demonstrator contains a number of control, monitoring and diagnosis applications that execute in real time against a simulation of a Steritherm sterilisation process.

DOI:10.1049/ise.1993.0016

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A good model is essential in simulating and analysing a system satisfactorily. This paper proposes a new computer-aided modelling methodology to construct parsimonious models for dynamic physical systems. A set of domain-independent modelling principles and domain-dependent modelling constraints has been formulated to guide parsimonious model construction. Models and the knowledge base for the enhancement of models have been described by bond graphs. After a parsimonious model is generated, two types of qualitative analysis are conducted; one is to derive unknown states from known states and the other is to predict the effects of parameter changes on the whole system. This methodology is only applicable when the structure of a dynamic system is known beforehand. A detailed case study is presented to demonstrate this approach.

DOI:10.1049/ise.1993.0017

出版商:IEE    

年代:1993

数据来源: IET