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No description available.

Power electronic converters are being increasingly used on isolated marine power systems, to provide variable speed control of electric motors. As the rating of these drive converters increases, the converter load becomes a significant part of the total system load. Traditional methods for calculating the performance characristics, which assume the presence of an infinite busbar on the system, are not appropriate for such systems. The intercoupling which exists between system components such as synchronous generators, converters, and the drive motor must be included in the calculation. In this thesis, a commercially available software simulator Saber, is used to model a complete electrical cycloconverter propulsion drive, of the type which may be used for future Royal Navy frigates. This model includes the synchronous generators, cycloconverters, and induction motor drives. The simulation is performed in the time domain, which ensures that the intercoupling present between system components is preserved. The simulation is not restricted to one converter configuration, and has been used to investigate the relative merits of a number of possible converter connections. This method can be used to study drive performance under unbalanced conditions as well as for normal balanced operation. There is no perceived limit to the size, or complexity, of the converter systems which can be studied using this method. The only cost would be increased computer run times.

A significant portion of a modern digital system can be regarded as a network of many thousands of combinational logic functions. In a Very Large Scale Integration (VLSI) implementation each combinational logic function is realized as a logic gate on a silicon wafer. To synchronize the passage of a signal through a network of logic gates synchronizing elements are used. These inhibit or permit the flow of a signal through the network under the control of a global control signal. A portion of a digital system comprising a network of logic gates connected without feedback is referred to as a combinational logic network. A portion of a digital system containing both combinational logic functions and synchronizing elements is referred to as a synchronous logic network. This thesis is concerned with the development of techniques and theory for the computer aided design of combinational and synchronous logic networks including techniques for: organizing a combinational logic function for a dynamic logic macrocell style of VLSI implementation; rearranging synchronous logic networks with the goal of improving the performance of a VLSI realization and synthesizing logic expression representations of designs from recursive equations in a correctness preserving way. In particular, the following methods for assisting with the design of logic systems are presented: 1. A method for factoring logic equations which allows constraints specific to a dynamic logic macrocell implementation to guide the search for the factored form. 2. A method for retiming multiple phase synchronous logic networks. 3. A method for reorganizing the distribution of logic in a synchronous logic network so that the delay encountered by a signal rippling through the combinational logic between any pair of synchronizing elements is reduced. Particular results obtained from implementations of the methods proposed demonstrate their usefulness for the computer aided design of logic systems.

This thesis presents the design and development of the AHF, and the application of CAD in switching converters. The presentation begins by a review of previous work in AHF with special emphasis on its design principles. This is followed by a discussion and implementation of the CAD tools---CASA a control system software package and real time computer simulation. The former implements a novel approach toward the control loop stability analysis of switching converters. Essentially it employs the Block Diagram Technique to describe the circuit configuration allowing Active Compensation Technique (ACT) to be carried out. Real time simulation allows the investigation of the AHF transient behaviour in response to step changes in line voltage and load. A fast algorithm has been introduced that results in a tremendous reduction in simulation time. These CAD approaches were used to assist in the design and evaluation of the performance of AHF design. The final part of the thesis describes the development of a 400 and 600W prototypes which were designed with high specification. The process of the design is outlined in detail and the prototypes were implemented to a 400W output SMPS and a 288W UPS. The 400W SMPS was tested with and without the AHF. Comparison of these test results is included.

This work addresses the problem of difficulties in the implementation of Computer Aided Production Management systems, and presents a methodology for their implementation which significantly improves on current practice. The methodology provides a structured approach which leads the company through a series of strategic business decisions which establish the context within which the solution must operate. The work focusses attention upon the design of the whole system with respect to the relationship between computerised functions and the infrastructure of human elements which facilitate and govern the system's operation. A model of the tasks involved in production management is presented. The model is used to structure decisions relating to the design of the infrastructure. The research work described proceeded in two distinct stages. In the first stage the author participated with-other-researdhers Who jointly developed the framework of the process methodology for CAPM implementation. This stage provides the context for the development of the task model approach to the design of the system, which represents the author's individual contribution - (see section 1.8). The task model can be used as a-tool-to identify the options available for the way each task within production management may .be executed, giving the user a basis for the design,of.a.particular system while not advocating any particular solution. By the use of this approach the user is encouraged to consider the,options, pailatag, and to adopt an integrated approach which looks at all arPas of production management, not only those for which there is a pressing problem or a tempting solution. This work results in a contribution to the development of the process methodology, the development of a tool in the CAPM task model and a review of the factors involved in the design of a system including both human and computerised elements.

In modern manufacturing technology with increasing automation of manufacturing processes and operations, the need for automated measurement has become much more apparent. Computer measuring machines are one of the essential instruments for quality control and measurement of complex products, performing measurements that were previously laborious and time consuming. Inspection of sculptured surfaces can be time consuming since, for exact specification, an almost infinite number of points would be required. Automated measurement with a significant reduction of inspected points can be attempted if prior knowledge of the part shape is available. The use of a vision system can help to identify product shape and features but, unfortunately, the accuracy required is often insufficient. In this work a vision system used with a Coordinate Measuring Machine (CMM), incorporating probing, has enabled fast and accurate measurements to be obtained. The part features have been enhanced by surface marking and a simple 2-D vision system has been utilised to identify part features. In order to accurately identify all parts of the product using the 2-D vision system, a multiple image superposition method has been developed which enables 100 per cent identification of surface features. A method has been developed to generate approximate 3-D surface position from prior knowledge of the product shape. A probing strategy has been developed which selects correct probe angle for optimum accuracy and access, together with methods and software for automated CMM code generation. This has enabled accurate measurement of product features with considerable reductions in inspection time. Several strategies for the determination and assessment of feature position errors have been investigated and a method using a 3-D least squares assessment has been found to be satisfactory. A graphical representation of the product model and errors has been developed using a 3-D solid modelling CAD system. The work has used golf balls and tooling as the product example.

In an environment of world competition in manufacturing, the application of information technology (IT) is seen an important component in the achievement of performance improvement. Computer Integrated Manufacturing (CIM) is interpreted as the realisation of an IT strategy for manufacturing to achieve competitive advantage. The thesis identifies the growing problems of change and uncertainty in manufacturing which make effective, centralised, monolithic control ever more difficult to achieve by automation. An alternative, more manageable approach is deonstrated in which artificial intelligence (AI) is distributed across an enterprise in order to carry out decision making at the locations where it would naturally take place. The concept of an intelligent nodal architecture has been defined, differentiating between the functions of decision making, recording business transactions and enabling communication. A detailed case study was undertaken of a manufacturer of printed circuit boards to investigate the criteria for effective application of the intelligent architecture to decision making procedures. In the process, the IDEF-O analytical methodology was critically appraised, and the conclusion reached that design based on top-down analysis is inferior to evolutionary design of manufacturing systems. A simulator to support the proposed intelligent architecture was developed using object-oriented, hypermedia software, and tested with a small scale factory model. The simulator, then applied to the case study, demonstrated the potential for improving performance using Kanban techniques implemented by means of distributed intelligent nodes. It was also observed that AI based simulation could provide better planning tools than centralised systems such as MRP (Manufacturing Resource Planning). In conclusion, evidence was provided to support the use of distributed intelligence in manufacturing automation and an intelligent architecture proposed and tested using simulation. The research shows potential for commercial development.

Thorough investigation and planning are essential steps in the deployment of Flexible Manufacturing Systems. At the present time, the most popular method of planning and analysis of these systems is computer-based modelling and simulation of which many varieties are commercially available. Ideally, during the modelling phase, the modeller should pay particular attention to such important details as reliability, damage propagation patterns, condition monitoring scenarios and the supervision aspects of these system as these factors are critical to the operation and performance of any envisaged configuration of FMS or its subsystems. In practice however, these are among the most neglected aspects of the models being constructed at the present time. This is in part because the present generation of commercially available simulation languages and environments are in many respects ill-equipped to deal with the challenges posed by the modelling of FMS. This thesis investigates the potential suitability of contemporary reliability and fault-mode description and analysis tools for inclusion within simulation models. Contemporary research work in analytical arid simulation-based reliability and fault-mode modelling and analysis of computer-integrated and flexible manufacturing systems have been investigated. A number of guidelines for the development of CIM and FMS simulation models have been developed. Four standard FMS models are developed and utilized as application examples in thesis. Analytical reliability techniques have been re-examined with special reference to the modelling of computer-integrated and flexible manufacturing systems. The potential sources of error and pitfalls of discrete-event simulation modelling have been outlined. The effect of the host languages, the different simulation time advancement modes, and the traditionally prescribed break-down modelling techniques have been investigated. Contemporary technology, programming and modelling concepts have been illustrated using PCModel and PROLOG. Fundamentals of "accurate" knowledge-based simulation modelling have been described and an alternative object-like structural implementation in a declarative environment has been proposed for the simulation models and tools. A detailed examination of the pre-requisites for the accurate simulation of reliability, fault-mode, and condition monitoring aspects of FMS has been performed. Some of the reliability and fault-mode modelling and analysis tools have been considered for their potential suitability as discrete-event simulation tools. Various possible resource-aging modes, health monitoring modules, and repairability /maintenance models have been developed. Micro-failure modelling and analysis has been proposed as an alternative to the traditional macro-failure modelling and analysis. Techniques for modelling of systems incorporating combinations of new and used equipment have been developed. A multi-phase development and demonstration of simulation models incorporating the tools and concepts proposed and cultivated during the course of the research has been undertaken. In each case, the model's evolution and the subsequent variations in its behaviour have been followed and examined from its bare-bone prototype to its fully developed stage. The research results in better understanding of reliability, condition monitoring and knowledge representation issues in simulation.