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The OSI-based data communication standards, and particularly the MAP-selected profile, have provided a genuine, vendor-independent communication environment, crucial to multiple computer-based control applications. One of the vital components in the Application Layer of these standards, aimed directly at supporting communications between programmable devices in manufacturing environments, is the 'Manufacturing Message Specification' (MMS). Although MMS has been acknowledged as vitally important in standardizing communications between shop-floor devices, and despite having been developed specifically for industrial environments, it does not have the capacity to support directly the time-critical services which are vital to real-time applications. Effort, therefore, needs to be expended in extending the current MMS concepts to fulfil real-time requirements. This thesis is dedicated to tackling this problem. It first analyzes the real-time requirements and the related OSI-based standards, especially MMS. Then it proposes services and functions which should be included within both the inherent OSI supporting structures and MMS itself, in order to fulfil these real-time requirements. The thesis also provides background comments on the support required from the associated computer architectures. Finally, it reviews a prototype implementation of the proposals and analyzes the results obtained. The original contribution of this work lies in the proposed extensions to the core MMS proposal - these being based on a fundamentally radical architecture, which it is suggested, is necessary to support a genuine real-time distributed computer control system.

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The demands from control engineers for more user-friendly, reliable and powerful design tools led to the necessity for a computer-aided control system design environment, which incorporates a general purpose graphical man-machine interface, a common database and a toolbox for modelling, analysis and simulation of control systems in pictorial representations as well as numerical ones. The work presented herein is mainly concerned with the development of such an environment, particularly the computer-aided design techniques used for modelling and manipulating pictorial representations of control systems. The infrastructure and major components of an environment have been studied. A general graphical man-machine interface and a set of graphical editors have been developed, allowing control engineers to interact graphically with the computer to construct pictorial representations of control systems such as block diagrams and signal flow graphs. In order to handle objects efficiently in the graphical editors, point inclusion algorithms, a classic problem in computer graphics and computational geometry, has been studied. Efficient and consistent point-in-polygon and point-in-polyhedron algorithms have been designed and developed. Artificial intelligence techniques have been applied to the problems in manipulating the pictorial representations of control systems, most of which would be found rather difficult to be solved using conventional programming techniques. The problems which have been studied include the methods for representing and manipulating diagraphs in an artificial intelligence oriented programming environment, structural controllability and observability, digraph numbering, algorithms for transformation between block diagrams and signal flow graphs, and automatic layout of block diagrams and signal flow graphs. This work is closely linked with the implementation of CES (ControlEngineering workStation) - a computer-aided control system design environment developed in the University College of Swansea.

The research presented in this Thesis aims to fill the gap between the principles used in the development of numerical software for computer-aided control system analysis and design and one of the novel software enginering principles; the object-oriented paradigm. The state-of-the-art in computer-aided control system analysis and design is based on FORTRAN code libraries that provide poor support for the actual data-types found in control systems design and are difficult to use safely. Although recent advances in Computer Science, such as object-oriented programming, already play an important role in the development of computer-aided control system design tools, their scope has been mainly limited to the user interface, database management and graphical data presentation. The object-oriented paradigm also has the potential to enable the writing of fast and efficient numerical software for control systems analysis and design which has not yet been sufficiently explored. In this Thesis it is shown how the object-oriented paradigm can be used to overcome some of the existing problems by providing a data-oriented rather than a functional view of a software library's contents. The rapidly developing theory of abstract data types is the foundation on which this work is laid. Abstract data types provide a language and implementation independent means of specifying data structures in terms of the functionality that they provide. The discussion also highlights some important questions that have to be asked when developing object-oriented software - such as how memory management and exceptions are to be handled - and offers some solutions. One of the main challenges in developing new software for control systems analysis and design is how to choose a strategy, tools and a software structure, that will preserve the investments made in the past in high quality software. The object-oriented paradigm offers a safe and efficient way of reusing existing software and also brings efficiency and convenience to both the developer and the end user of control engineering software.

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