The research relates to the modelling and control of multi-stage production - inventory systems in high volume low-mix manufacturing industry. Examples of such class include typically the automotive and white goods industries. The research has included the investigation of available mathematical control techniques in the "optimal" control of manufacturing systems, a study of their applicability and the practical implications of their use in a manufacturing environment. Earlier work in the field of multivariable control theory has shown the potential of application in industrial management. In this thesis, previous work is extended whereby explicit consideration is given to some practical constraints existing in a typical manufacturing environment. It is considered that the research carried out has contributed to the development of multivariable control theory as applied to practical control problems with constraints. This has been achieved by the use of structured canonical forms and the exploitation of their particular ordered properties, resulting in the development of practical control models. The automotive industry has been used as a practical case study and modelled as a linear discrete-time control problem. The models have been developed in close liaison with a car manufacturing company in the U.K., and have been shown to produce practical control policies in the areas of both capacity requirements planning and inter-stage float levels. Particular attention is given to existing practical constraints of such systems. The approach is extended to deal effectively with a more general multi-product environment. It is noted that multi-product environment is of a more complex nature than single product since it involves the consideration of competition for the limited resources that have to be shared out "sub-optimally", in addition to providing smooth control of the responses. The development and application of multivariable control theory as described in this thesis is shown to provide an effective methodology for the solution of dynamic production control problems of multi-stage production-inventory systems in both single and multi-product environments.

This thesis is concerned with the engineering design requirement and the process by which it is elicited, evolved and recorded. The purpose of the research reported in the work is to achieve a more complete understanding of the engineering design requirement, and to apply that understanding to the better support of designers during the design requirement capture phases of the design process. Two perspectives dominate the approach to the research. The first concerns the relation between the design process and human cognition. The research subject is seen as being fundamentally a product of the human mind and that such things as knowledge, language and meaning – the things commonly associated with cognition – are crucial to its proper understanding. The second perspective is informed by the view that the development of the design requirement can be seen as a knowledge-intensive process of communication. Thus, understanding communication between humans and some aspects of communication failure can assist in understanding and remedying failure in design requirement capture.

This research work investigates the information requirements of the engineering designer during the early phases of the design process. In particular, it focuses on the use of standard components, and the information requirements associated with them. The research presents a system for the representation of information, both formal catalogue data, and also what the author has termed "Informal Information". Also presented is a system for the representation of catalogue information that will allow for standard component catalogue interfacing.

The development of a Semi-Open Refrigeration Cycle had been shown to be of economic value to the process of crystallisation. The experimentation took the form of several bench scale experiments to develop the designs of the individual vessels that were to constitute the final pilot plant. In view of the safety hazards involved with a plant contacting Sulphuric Acid and Liquid Butane, a substantial Hazop and HAZAN study has been carried out. From this data the pilot plant was constructed, with all necessary safety features. Computer monitoring and partial computer control was installed. The pilot plant was operated as a closed loop for extended periods, to enable the production of both Iron (2) and Copper (2) Sulphates to be produced on a continuous basis. The results showed that the crystals produced are of a small size, indicative of the instantaneous chilling of the mother liquor and are not contaminated to a significant degree with the refrigerant. The thermal efficiency of the cycle was lower than expected at 80%, but improvements in insulation coupled with the redesign of the condenser, eliminating the necessity for a separator vessel, should increase this to the expected 90%.

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The main objectives of this study are:- 1 - to construct a wiring connecting system between the pulsed and direct current units to produce a pulsed submerged arc weld. 2 - to determine the boundary conditions for the welding parameters used to control weld profile and metal transfer during pulsed current submerged arc welding. 3 - to establish a relationship between the pulsed current frequency and the geometry of the deposited weld metal, and to apply the results to narrow gap welding. 4 - to design and construct a microprocessor interface system capable of handling, presenting and storing the data. The thesis has been divided into three parts as follows:- Part I The feasibility of pulsed current submerged arc welding process. Part II The use of pulsed current to control the geometry and properties of welding metal. Part III Computer aided monitoring of the welding parameters. In the first part, a review of relevant information is presented together with a description of the experimental technique used in connecting the pulsed and background current units. In the second part attention is focus sed on the procedure for identifying the usable zones within which a successful weld can be obtained. Critical boundary conditions of welding parameters were established using the combination of pulsed and direct currents. Having established these boundaries, the effects of pulsed current frequency on the weld profile and weld metal properties were investigated and the results used to establish a practical guide line on narrow gap applications. In the third part the design and construction of a microprocessor- based system was designed to monitor the welding parameters using binary counter, an analogue switch and voltage to frequency converters which enables real time values of welding variables to be determined over a period of between 1 - 100 seconds, depending on the memory size of the microprocessor.

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No description available.