Interactive functional modelling of instruments
R. D. Liebner · City Research Online (City University London) · 1981
A Computer package has been developed which enables the interactive functional modelling of instrument systems to be undertaken. Instruments are multi-energy domain systems in general and this creates difficulties for interactive modelling using current established techniques. Consequently the first part of this thesis considers the main functional modelling representations, these being:- a) Signal Flow Graphs b) Linear Graphs c) Bond Graphs These are examined on a practical basis by the modelling, with results of five instrument systems. This led to a comprehensive review to be made of the benefits and drawbacks that each method allows in representing instrument systems. In general there are disadvantages to the current graphical representations as the evolved techniques do not take account of modern design concepts which allow computers to be used as design aids. By considering the process on a more global basis a new representation called ‘Structure Graphs' is formed. The language is described and formally defined, and shows with examples, the improvement of the following :- i) The ease of model construction ii) The ease of structural changes, thereby enhancing the man-machine dialogue essential for good interactive design (uni-directional flow being mainly described) . A package was then developed called MEDIEM (Multi Energy Domain Interactive Element Modelling) to implement this new approach and mounted on a PDP 11/10 computer. This is a small mini computer, but nevertheless the package will allow:- a) Linear and Nonlinear representations b) Modelling of five energy domains c) Multiport representations, The outputs obtained from the computer must enable the engineer to determine the performance characteristics of an instrument. There are three basic responses:- a) Time response b) Steady State response c) Frequency response. The developed package will give all these responses (b and c for linear systems only) and provides for four different ways of displaying the results. Although principally developed for modelling and designing instrument systems, the work should find important use in the more general modelling and design of multi-energy domain systems.