Object-oriented modelling and control

Simulation has proven to be a highly effective means of testing the operation of systems during development, and prior to in-service modification, but it is not as widely used in industry as might be expected. The prime reason for this is that model development for simulation often requires the combination of deep knowledge of the process and specialised modelling skills. One solution to this problem is the provision of a library of re-useable sub-models, which can facilitate development of hierarchically structured models. This paper illustrates the application of object-oriented methodology to achieving two major goals-the reduction of complexity by hierarchical decomposition, and maximisation of the re-use of developed models. Two applications are discussed-the generation of hierarchical models and the use of function blocks in control system design-with respect to the three dominant OO concepts of encapsulation, inheritance and polymorphism. It outlines requirements for a modelling and control tool and highlights how an OO methodology can help simplify the use of such a tool. OO implementations of modelling and control tools are described. The tools described were implemented using compiled OO languages (Pascal and C++), with the consequence that the user of she tool does not get all the advantages which would occur in an interpretive environment such as Smalltalk