A methodology to analyze, design and implement very fast and robust controls of Buck-type converters

La electrónica digital moderna presenta un desafío a los diseñadores de sistemas de potencia. El creciente alto rendimiento de microprocesadores, FPGAs y ASICs necesitan sistemas de alimentación que cumplan con requirimientos dinámicos y estáticos muy estrictos. Específicamente, estas alimentaciones son convertidores DC-DC de baja tensión y alta corriente que necesitan ser diseñados para tener un pequeño rizado de tensión y una pequeña desviación de tensión de salida bajo transitorios de carga de una alta pendiente. Además, dependiendo de la aplicación, se necesita cumplir con otros requerimientos tal y como proveer a la carga con ”Escalado dinámico de tensión”, donde el convertidor necesitar cambiar su tensión de salida tan rápidamente posible sin sobreoscilaciones, o ”Posicionado Adaptativo de la Tensión” donde la tensión de salida se reduce ligeramente cuanto más grande sea la potencia de salida. Por supuesto, desde el punto de vista de la industria, las figuras de mérito de estos convertidores son el coste, la eficiencia y el tamaño/peso. Idealmente, la industria necesita un convertidor que es más barato, más eficiente, más pequeño y que aún así cumpla con los requerimienos dinámicos de la aplicación. En este contexto, varios enfoques para mejorar la figuras de mérito de estos convertidores se han seguido por la industria y la academia tales como mejorar la topología del convertidor, mejorar la tecnología de semiconducores y mejorar el control. En efecto, el control es una parte fundamental en estas aplicaciones ya que un control muy rápido hace que sea más fácil que una determinada topología cumpla con los estrictos requerimientos dinámicos y, consecuentemente, le da al diseñador un margen de libertar más amplio para mejorar el coste, la eficiencia y/o el tamaño del sistema de potencia. En esta tesis, se investiga cómo diseñar e implementar controles muy rápidos para el convertidor tipo Buck. En esta tesis se demuestra que medir la tensión de salida es todo lo que se necesita para lograr una respuesta casi óptima y se propone una guía de diseño unificada para controles que sólo miden la tensión de salida Luego, para asegurar robustez en controles muy rápidos, se proponen un modelado y un análisis de estabilidad muy precisos de convertidores DC-DC que tienen en cuenta circuitería para sensado y elementos parásitos críticos. También, usando este modelado, se propone una algoritmo de optimización que tiene en cuenta las tolerancias de los componentes y sensados distorsionados. Us ando este algoritmo, se comparan controles muy rápidos del estado del arte y su capacidad para lograr una rápida respuesta dinámica se posiciona según el condensador de salida utilizado. Además, se propone una técnica para mejorar la respuesta dinámica de los controladores. Todas las propuestas se han corroborado por extensas simulaciones y prototipos experimentales. Con todo, esta tesis sirve como una metodología para ingenieros para diseñar e implementar controles rápidos y robustos de convertidores tipo Buck. ABSTRACT Modern digital electronics present a challenge to designers of power systems. The increasingly high-performance of microprocessors, FPGAs (Field Programmable Gate Array) and ASICs (Application-Specific Integrated Circuit) require power supplies to comply with very demanding static and dynamic requirements. Specifically, these power supplies are low-voltage/high-current DC-DC converters that need to be designed to exhibit low voltage ripple and low voltage deviation under high slew-rate load transients. Additionally, depending on the application, other requirements need to be met such as to provide to the load ”Dynamic Voltage Scaling” (DVS), where the converter needs to change the output voltage as fast as possible without underdamping, or ”Adaptive Voltage Positioning” (AVP) where the output voltage is slightly reduced the greater the output power. Of course, from the point of view of the industry, the figures of merit of these converters are the cost, efficiency and size/weight. Ideally, the industry needs a converter that is cheaper, more efficient, smaller and that can still meet the dynamic requirements of the application. In this context, several approaches to improve the figures of merit of these power supplies are followed in the industry and academia such as improving the topology of the converter, improving the semiconductor technology and improving the control. Indeed, the control is a fundamental part in these applications as a very fast control makes it easier for the topology to comply with the strict dynamic requirements and, consequently, gives the designer a larger margin of freedom to improve the cost, efficiency and/or size of the power supply. In this thesis, how to design and implement very fast controls for the Buck converter is investigated. This thesis proves that sensing the output voltage is all that is needed to achieve an almost time-optimal response and a unified design guideline for controls that only sense the output voltage is proposed. Then, in order to assure robustness in very fast controls, a very accurate modeling and stability analysis of DC-DC converters is proposed that takes into account sensing networks and critical parasitic elements. Also, using this modeling approach, an optimization algorithm that takes into account tolerances of components and distorted measurements is proposed. With the use of the algorithm, very fast analog controls of the state-of-the-art are compared and their capabilities to achieve a fast dynamic response are positioned de pending on the output capacitor. Additionally, a technique to improve the dynamic response of controllers is also proposed. All the proposals are corroborated by extensive simulations and experimental prototypes. Overall, this thesis serves as a methodology for engineers to design and implement fast and robust controls for Buck-type converters.

The Balanced Cross-Layer Design Routing Algorithm in Wireless Sensor Networks Using Fuzzy Logic

Recently, the cross-layer design for the wireless sensor network communication protocol has become more and more important and popular. Considering the disadvantages of the traditional cross-layer routing algorithms, in this paper we propose a new fuzzy logic-based routing algorithm, named the Balanced Cross-layer Fuzzy Logic (BCFL) routing algorithm. In BCFL, we use the cross-layer parameters’ dispersion as the fuzzy logic inference system inputs. Moreover, we give each cross-layer parameter a dynamic weight according the value of the dispersion. For getting a balanced solution, the parameter whose dispersion is large will have small weight, and vice versa. In order to compare it with the traditional cross-layer routing algorithms, BCFL is evaluated through extensive simulations. The simulation results show that the new routing algorithm can handle the multiple constraints without increasing the complexity of the algorithm and can achieve the most balanced performance on selecting the next hop relay node. Moreover, the Balanced Cross-layer Fuzzy Logic routing algorithm can adapt to the dynamic changing of the network conditions and topology effectively.

Arquitectura industrial tabacalera en la España peninsular: secaderos y fábricas

La Arquitectura industrial del tabaco en España está representada por dos tipos de construcciones, que corresponden a las dos fases en las que se divide el proceso de producción del tabaco: los secaderos (arquitectura bioclimática donde se realiza el secado), y las fábricas (centros donde se elabora el tabaco procedente de los secaderos). Las fábricas se repartieron por todo el territorio español, ocupando preferiblemente los lugares costeros, aunque existen casos en los que su localización obedecía a razones políticas. Estos edificios, en su mayoría, incluidos en los centros históricos de las ciudades, han cambiando de uso, y las antiguas fábricas de tabaco se han transformado en su mayoría, en centros de cultura, o centros sociales y representativos. La tesis surge del análisis de las características constructivas de la arquitectura industrial del tabaco: de los secaderos y de las fábricas, por tratarse de una tipología con suficiente entidad y un ejemplo de arquitectura bioclimática de producción en el caso de los secaderos, y por conseguir haberse adaptado a otros usos en el caso de las fábricas. La arquitectura de producción emplea un lenguaje acorde con los avances de la industrialización, anticipando materiales y estructuras, y condensando en una tipología específica las complejas relaciones establecidas entre producto, hombres y espacio. Estos edificios tuvieron una extensa implantación en el territorio, y se caracterizan por una serie de valores tecnológicos, arquitectónicos, sociológicos y paisajísticos, que hacen de ellos un documento de primera magnitud para conocer: la evolución e implantación de las técnicas constructivas (materiales y estructuras), los procesos de innovación tipológica y la estructura económica y procedimientos técnicos utilizados. El territorio en el que se insertan constituye su contexto territorial, por lo que no sería adecuado considerar estos edificios como elementos aislados, sin analizar la relación con el entorno en el que se generaron. Por este motivo, se analizan las condiciones higrotérmicas ambientales de los secaderos para compararlas con las de confort humano y establecer relaciones y parámetros compatibles. Los ejemplos analizados de secaderos son todos de fábrica. El uso del ladrillo como módulo principal para la elaboración de un edificio, supone la consideración de un “grado cero” de todo el aparato constructivo y compositivo de la arquitectura. Dejar el ladrillo visto, supone hacer explícitos todos los procesos acumulativos. Este elemento mínimo, permite unas posibilidades enormemente abiertas, pero no absolutamente aleatorias, que definen su propia lógica combinatoria. La exigencia de sinceridad, característica de la arquitectura industrial, en la exposición de los materiales, exhibiéndolos en su propia naturaleza y en el modo real de ser utilizados, se hace patente en este tipo de construcción. Se realiza un estudio de permeabilidad en las fachadas de los secaderos, para determinar el grado de ventilación y su relación con la orientación, el patrón de celosía empleado y el volumen total. Este sistema de acondicionamiento climático específico, puede servir de recurso a otras construcciones, por lo que se podría trasladar el sistema constructivo y formal de los secaderos a otros usos, desde una doble vertiente: Arquitectura para la adaptación climática al entorno. Arquitectura como generadora de condiciones climáticas específicas, en el interior. La utilidad de los secaderos es fundamentalmente: proporcionar sombra, ventilación y un espacio cubierto, pero permeable en sus fachadas. La arquitectura industrial debe ser reconocida dentro del conjunto patrimonial, debido a sus características propias que permiten su diferenciación del resto de la arquitectura. Conocer la estructura productiva permite analizar correctamente estas construcciones, ya que el programa inicial es básico para entender la organización del espacio interior. Las fábricas no se situaron cerca de las zonas de producción del tabaco, excepto en dos casos: Cádiz y Palazuelo, en los que existen secaderos y campos de cultivo de hoja de tabaco en las áreas cercanas. La principal causa de esta separación es que el proceso de obtención de tabaco es un proceso dividido en dos fases principales: proceso primario y proceso secundario. En el proceso primario la hoja de tabaco se seca en los secaderos, en los que es determinante el clima, pero únicamente en el caso del secado del tabaco al aire. En el proceso secundario sin embargo, el tabaco llega previamente tratado a las fábricas, por lo que no influye el clima en esta parte del proceso. Esta razón determina que en las áreas climáticas donde se centra el estudio, haya zonas en las que existen fábrica y secaderos y otras en las que únicamente existe fábrica, o sólo secaderos. La localización de las fábricas atendía a razones de muy diferente índole, las más importantes fueron: geográficas, estratégicas, y políticas. En la mayoría de las fábricas la elección de la ciudad de emplazamiento estaba ligada a la recepción de la materia prima, que principalmente se hacía por vía marítima, o acuática (el caso de Sevilla), y por vía terrestre, utilizando como medio de transporte el ferrocarril. Sólo dos casos, de las antiguas fábricas, corresponden a razones políticas, son las dos únicas que no están en la costa: Madrid y Logroño. La de Madrid se construyó por centralidad política, y porque geográficamente ocupaba el punto central de todas las comunicaciones terrestres por carretera y ferrocarril. Muchas de las fábricas se situaron cercanas a las estaciones de ferrocarril. La de Logroño atendió, sin embargo, a razones políticas. Para finalizar, se realiza un estudio comparativo de las fábricas de Sevilla, Madrid y San Sebastián. Las razones que justifican esta elección son: - La de Sevilla fue históricamente la primera fábrica y la más importante. - La de Madrid fue la más importante a nivel administrativo, la sede de Tabacalera se instaló en la capital, y después de la de Sevilla, fue la que sirvió de modelo al resto de las fábricas. - La de San Sebastián era la más grande del Norte. Los análisis que se han realizado son de: volumen y superficies de patios, superficies de cubierta, permeabilidad o huecos en fachadas, orientación y soleamiento de patios, distribución espacial interior y organización, y evolución de usos. Podemos observar que en la mayoría de estas fábricas ha habido una transformación en el uso, pasando de ser edificios industriales a edificios culturales. Estas construcciones se pueden considerar como infraestructuras adaptables, por ser útiles, sostenibles y funcionales. ABSTRACT The Spanish industrial architecture of tobacco is represented by two construction types that correspond to the two phases of tobacco production: the drying sheds (bioclimatic constructions where the drying process takes place) and factories (centres where tobacco is processed after the drying process). The factories were distributed throughout the Spanish territory, preferably occupying coastal locations, although some of them were located elsewhere following political reasons. Most of the buildings inside city centres have suffered changes in their use, becoming cultural, social or representative centres. This thesis attempts the analysis of the constructive systems employed in tobacco industrial architecture, from drying sheds to factories. The drying sheds are an example of bioclimatic industrial architecture. The factories are a typology that have successfully adapted to new uses. Industrial architecture uses a language that follows the advances in industrialization, anticipating new materials and structures, and merging the complex relationships established among products, human beings, space and locations. These buildings were promoted extensively in the country. They are characterized by technological architectural sociological and landscaping innovations. They are considered as important examples of the evolution and the implementation of construction techniques (building materials and structures). They are also considered as examples of innovation in the building typology, in their economic structure and in the technologies that they have applied. The settings in which the drying sheds are placed have an important influence in them. They cannot be considered as isolated elements. Instead, there is a close relationship between drying sheds and the surroundings in which they are located. Drying sheds’ hygrotermal and environmental conditions are analyzed in this thesis to compare them with the values of human comfort and find suitable relationships and parameters. All the drying sheds that have been analyzed are constructed with brick. This implies a consideration of “zero degree” for both the construction and the composition of the architectural process. The detailing - entails making all the accumulative processes explicit as the brick walls are left exposed. This minimal component allows a wide range of options that are never random but based on the logic of the way in which it is combined. The “sincerity” in the exposition of material, displaying them in their very nature and showing how they are really used, is a basic characteristic of industrial architecture, and it is even more expressive in these types of buildings. The walls of the drying sheds undergo a permeability assessment in order to determine the degree of ventilation and orientation, the lattice pattern used and the overall volume. This specific conditioning system can serve as a resource for other buildings, and consequently, it could be transferred to other uses within a two-pronged approach: -Climatically adapted architecture that takes into account the surroundings. -Architecture as a generator of specific climatic conditions indoors. Drying sheds’ main purposes / aims deal with how to provide shade, ventilation and a covered space as well as permeability. The industrial architecture must be recognized as historical valuable buildings due to its intrinsic and distinctive characteristics. Knowing the productive structure, allow us to make a proper analysis of these buildings, since the basic aim, is to understand the spatial organization indoors. Factories did not come close to the tobacco production, with the exception of Cádiz and Palazuelo, where there are sheds and tobacco croplands nearby. The main reason for this separation is that the process of obtaining tobacco has two processes: the primary process and the secondary process. In the primary process tobacco leaves are left to dry. In the secondary process, previously manufactured tobacco allocated in the factories where the weather conditions are not important. This fact determines that in the climate areas where this study tales place there are some cases in which we can find both factories and drying sheds, and others where there are either factories or drying sheds only. The location of these factories met various demands, being the most outstanding the ones related to geographic, strategic and political reasons. In most factories the choice of its location was often linked to the incoming of raw goods, mainly delivered through waterways –it is the case of Seville,) and by land, using railways. The location of the factories was linked to political reasons in only two cases Madrid and Logroño, which are the only ones that are not placed near the coast. The one in Madrid was built due to its political centrality and because geographically speaking, it was the reference landmark of means of land and rail transports. Many factories, in fact, were settled nearby rail stations. For the factory in Logroño, only political reasons were taken into consideration. I should like to close by undertaking a comparative study of factories in Seville, Madrid and San Sebastian. There are a number of reasons to substantiate this choice: -The factory in Seville was historically speaking the first that was built and the most important one. -The factory in Madrid was the most important one administratively. This factory was the headquarters as well as being, after Seville, the one which provided a model for other factories. -The factory in San Sebastian is the biggest in the North of Spain. The analysis carried out are related to the volume of the buildings and the surface areas of the courtyards, the surface of the roofs, the permeability of the walls and the openings of the façade, the orientation and the sun exposure, the indoor spatial distribution and organization and evolution of the uses (formerly and currently) I observe that in most of these factories there has been a change in the use of the buildings, from industrial cultural purposes. These buildings can be considered as adaptable infrastructures based on a combination of architectural practicability, sustainability and functionality.

Real time optimization in chemical process: evaluation of strategies, improvements and industrial application.

The increasing economic competition drives the industry to implement tools that improve their processes efficiencies. The process automation is one of these tools, and the Real Time Optimization (RTO) is an automation methodology that considers economic aspects to update the process control in accordance with market prices and disturbances. Basically, RTO uses a steady-state phenomenological model to predict the process behavior, and then, optimizes an economic objective function subject to this model. Although largely implemented in industry, there is not a general agreement about the benefits of implementing RTO due to some limitations discussed in the present work: structural plant/model mismatch, identifiability issues and low frequency of set points update. Some alternative RTO approaches have been proposed in literature to handle the problem of structural plant/model mismatch. However, there is not a sensible comparison evaluating the scope and limitations of these RTO approaches under different aspects. For this reason, the classical two-step method is compared to more recently derivative-based methods (Modifier Adaptation, Integrated System Optimization and Parameter estimation, and Sufficient Conditions of Feasibility and Optimality) using a Monte Carlo methodology. The results of this comparison show that the classical RTO method is consistent, providing a model flexible enough to represent the process topology, a parameter estimation method appropriate to handle measurement noise characteristics and a method to improve the sample information quality. At each iteration, the RTO methodology updates some key parameter of the model, where it is possible to observe identifiability issues caused by lack of measurements and measurement noise, resulting in bad prediction ability. Therefore, four different parameter estimation approaches (Rotational Discrimination, Automatic Selection and Parameter estimation, Reparametrization via Differential Geometry and classical nonlinear Least Square) are evaluated with respect to their prediction accuracy, robustness and speed. The results show that the Rotational Discrimination method is the most suitable to be implemented in a RTO framework, since it requires less a priori information, it is simple to be implemented and avoid the overfitting caused by the Least Square method. The third RTO drawback discussed in the present thesis is the low frequency of set points update, this problem increases the period in which the process operates at suboptimum conditions. An alternative to handle this problem is proposed in this thesis, by integrating the classic RTO and Self-Optimizing control (SOC) using a new Model Predictive Control strategy. The new approach demonstrates that it is possible to reduce the problem of low frequency of set points updates, improving the economic performance. Finally, the practical aspects of the RTO implementation are carried out in an industrial case study, a Vapor Recompression Distillation (VRD) process located in Paulínea refinery from Petrobras. The conclusions of this study suggest that the model parameters are successfully estimated by the Rotational Discrimination method; the RTO is able to improve the process profit in about 3%, equivalent to 2 million dollars per year; and the integration of SOC and RTO may be an interesting control alternative for the VRD process.

Logic-Based Outer-Approximation Algorithm for Solving Discrete-Continuous Dynamic Optimization Problems

We present an extension of the logic outer-approximation algorithm for dealing with disjunctive discrete-continuous optimal control problems whose dynamic behavior is modeled in terms of differential-algebraic equations. Although the proposed algorithm can be applied to a wide variety of discrete-continuous optimal control problems, we are mainly interested in problems where disjunctions are also present. Disjunctions are included to take into account only certain parts of the underlying model which become relevant under some processing conditions. By doing so the numerical robustness of the optimization algorithm improves since those parts of the model that are not active are discarded leading to a reduced size problem and avoiding potential model singularities. We test the proposed algorithm using three examples of different complex dynamic behavior. In all the case studies the number of iterations and the computational effort required to obtain the optimal solutions is modest and the solutions are relatively easy to find.

Detección precoz de dificultades en el aprendizaje. Herramienta para la predicción del rendimiento de los estudiantes

Inspirados por las estrategias de detección precoz aplicadas en medicina, proponemos el diseño y construcción de un sistema de predicción que permita detectar los problemas de aprendizaje de los estudiantes de forma temprana. Partimos de un sistema gamificado para el aprendizaje de Lógica Computacional, del que se recolectan masivamente datos de uso y, sobre todo, resultados de aprendizaje de los estudiantes en la resolución de problemas. Todos estos datos se analizan utilizando técnicas de Machine Learning que ofrecen, como resultado, una predicción del rendimiento de cada alumno. La información se presenta semanalmente en forma de un gráfico de progresión, de fácil interpretación pero con información muy valiosa. El sistema resultante tiene un alto grado de automatización, es progresivo, ofrece resultados desde el principio del curso con predicciones cada vez más precisas, utiliza resultados de aprendizaje y no solo datos de uso, permite evaluar y hacer predicciones sobre las competencias y habilidades adquiridas y contribuye a una evaluación realmente formativa. En definitiva, permite a los profesores guiar a los estudiantes en una mejora de su rendimiento desde etapas muy tempranas, pudiendo reconducir a tiempo los posibles fracasos y motivando a los estudiantes.

A valorização da função do objecto de design em contexto museológico : lógicas expositivas - a museologia do design industrial

The design objects give us a testimony of those who imagined, designed, developed, manufactured and used them. Each object, intentionally or not, portrays its own story, all the visible details are part of a decision taken by someone at some time of its chronology. The act of collecting objects, as well as private collections are the basis for the creation of museums as we know them today. Musealization - taking objects into a museum - means that one is restoring, preserving, enhancing some objects compared to others. And when restoring these objects, one is restoring their symbolic capacity, i.e. the fact that they tell a story, means you are restoring its message. In a museum, although out of context and deprived of most of the functions to which they had been designed for, the objects acquire other function(s), preserving their importance. Design museums give us the possibility to have a closer view of the objects, rather than just look at them, along with the pedagogical function. Thus presents a proposal for museography regarding industrial design, which is based on the appreciation of the function of anonymous design objects, based on expository logic, that takes the visitor to see, instead of just looking at objects, offering the possibility of interaction with the same, increasing the relationship between human being - object - museum, including groups with special needs, which are often forgotten in these exhibitions. This dissertation is a reflection and a projectual intervention on the design object in a museum, clarifying the concepts of object and museum, covering issues regarding the relevance of design museums, and culminating in the presentation of a museography project, where the function of an object prevails

European Industrial Policy. Bruges European Economic Policy (BEEP) Briefing 15/2006

This survey of European industrial policy aims to set out and explain the great significance of European integration in determining (changes in) structure and performance of industry in the EU. This influence is explored from the policy side by analysing the transformation of the framework within which both EU and Member States' industrial policy can be pursued. Empirical economic analysis is not included because this BEEP Briefing was originally written for a handbook3 in which other authors were assigned a range of industrial economics subjects. In the last 25 years or so, the transformation is such that the nature and scope of industrial policy at both levels of government has profoundly changed as well. Indeed, the toolkit of measures has shrunk considerably, disciplines have been tightened and the economic policy views behind industrial policy have altered everywhere. The pro-competitive logic of deeper market integration itself is rarely questioned nowadays and industrial policy at the two levels takes on different forms. The survey discusses at some length the division of powers between, and the complementarity of, the Member States' and EU levels of government when it comes to industrial policy, based on a fairly detailed classification of industrial policy instruments. The three building blocks of the wide concept of industrial policy as defined in this BEEP Briefing consist of the EU framework of market integration, EU horizontal industrial policy and its EU sectoral or specific counterpart. Each one is surveyed at the EU level. Preceding these three sections is a discussion of three cross-cutting issues, namely, the indiscriminate use of the 'competitiveness' label in the EU circuit of business and policy makers, the relation between services and EU industrial policy and, finally, that of European infrastructure. One major conclusion is that, today, the incentive structure for industry and industrial markets is dominated by the stringency of the overall EU framework and to some moderate degree by the horizontal approach.

Automatic controllers for hydraulically powered deicing chemical spreaders. Final report.

Mode of access: Internet.

Magnetic control of industrial motors /

Part 1. Alternating-current control devices and assemblies.--Part 2. Alternating-current controllers.--Part 3. Direct-current controllers.

Robust multivariable control of complex biological processes

This paper addresses advanced control of a biological nutrient removal (BNR) activated sludge process. Based on a previously validated distributed parameter model of the BNR activated sludge process, we present robust multivariable controller designs for the process, involving loop shaping of plant model, robust stability and performance analyses. Results from three design case studies showed that a multivariable controller with stability margins of 0.163, 0.492 and 1.062 measured by the normalised coprime factor, multiplicative and additive uncertainties respectively give the best results for meeting performance robustness specifications. The controller robustly stabilises effluent nutrients in the presence of uncertainties with the behaviour of phosphorus accumulating organisms as well as to effectively attenuate major disturbances introduced as step changes. This study also shows that, performance of the multivariable robust controller is superior to multi-loops SISO PI controllers for regulating the BNR activated sludge process in terms of robust stability and performance and controlling the process using inlet feed flowrate is infeasible. (C) 2003 Elsevier Ltd. All rights reserved.

Pragmatic approach to the development of robust real-time protocols

This research is concerned with the development of distributed real-time systems, in which software is used for the control of concurrent physical processes. These distributed control systems are required to periodically coordinate the operation of several autonomous physical processes, with the property of an atomic action. The implementation of this coordination must be fault-tolerant if the integrity of the system is to be maintained in the presence of processor or communication failures. Commit protocols have been widely used to provide this type of atomicity and ensure consistency in distributed computer systems. The objective of this research is the development of a class of robust commit protocols, applicable to the coordination of distributed real-time control systems. Extended forms of the standard two phase commit protocol, that provides fault-tolerant and real-time behaviour, were developed. Petri nets are used for the design of the distributed controllers, and to embed the commit protocol models within these controller designs. This composition of controller and protocol model allows the analysis of the complete system in a unified manner. A common problem for Petri net based techniques is that of state space explosion, a modular approach to both the design and analysis would help cope with this problem. Although extensions to Petri nets that allow module construction exist, generally the modularisation is restricted to the specification, and analysis must be performed on the (flat) detailed net. The Petri net designs for the type of distributed systems considered in this research are both large and complex. The top down, bottom up and hybrid synthesis techniques that are used to model large systems in Petri nets are considered. A hybrid approach to Petri net design for a restricted class of communicating processes is developed. Designs produced using this hybrid approach are modular and allow re-use of verified modules. In order to use this form of modular analysis, it is necessary to project an equivalent but reduced behaviour on the modules used. These projections conceal events local to modules that are not essential for the purpose of analysis. To generate the external behaviour, each firing sequence of the subnet is replaced by an atomic transition internal to the module, and the firing of these transitions transforms the input and output markings of the module. Thus local events are concealed through the projection of the external behaviour of modules. This hybrid design approach preserves properties of interest, such as boundedness and liveness, while the systematic concealment of local events allows the management of state space. The approach presented in this research is particularly suited to distributed systems, as the underlying communication model is used as the basis for the interconnection of modules in the design procedure. This hybrid approach is applied to Petri net based design and analysis of distributed controllers for two industrial applications that incorporate the robust, real-time commit protocols developed. Temporal Petri nets, which combine Petri nets and temporal logic, are used to capture and verify causal and temporal aspects of the designs in a unified manner.

Computerised control of cellular manufacturing systems

This thesis reviews the existing manufacturing control techniques and identifies their practical drawbacks when applied in a high variety, low and medium volume environment. It advocates that the significant drawbacks inherent in such systems, could impair their applications under such manufacturing environment. The key weaknesses identified in the system were: capacity insensitive nature of Material Requirements Planning (MRP); the centralised approach to planning and control applied in Manufacturing Resources Planning (MRP IT); the fact that Kanban can only be used in repetitive environments; Optimised Productivity Techniques's (OPT) inability to deal with transient bottlenecks, etc. On the other hand, cellular systems offer advantages in simplifying the control problems of manufacturing and the thesis reviews systems designed for cellular manufacturing including Distributed Manufacturing Resources Planning (DMRP) and Flexible Manufacturing System (FMS) controllers. It advocates that a newly developed cellular manufacturing control methodology, which is fully automatic, capacity sensitive and responsive, has the potential to resolve the core manufacturing control problems discussed above. It's development is envisaged within the framework of a DMRP environment, in which each cell is provided with its own MRP II system and decision making capability. It is a cellular based closed loop control system, which revolves on single level Bill-Of-Materials (BOM) structure and hence provides better linkage between shop level scheduling activities and relevant entries in the MPS. This provides a better prospect of undertaking rapid response to changes in the status of manufacturing resources and incoming enquiries. Moreover, it also permits automatic evaluation of capacity and due date constraints and hence facilitates the automation of MPS within such system. A prototype cellular manufacturing control model, was developed to demonstrate the underlying principles and operational logic of the cellular manufacturing control methodology, based on the above concept. This was shown to offer significant advantages from the prospective of operational planning and control. Results of relevant tests proved that the model is capable of producing reasonable due date and undertake automation of MPS. The overall performance of the model proved satisfactory and acceptable.

The development and diffusion of industrial robots

This thesis describes the history of robots and explains the reasons for the international differences in robot diffusion, and the differences in the diffusion of various robot applications with reference to the UK. As opposed to most of the literature, diffusion is examined with an integrated and interdisciplinary perspective. Robot technology evolves from the interaction of development, supply and manufacture, adoption, and promotion. activities. Emphasis is given to the analysis of adoption, at present the most important limiting factor of robot advancement in the UK. Technical development is inferred from a comparison of surveys on equipment, and from the topics of ten years of symposia papers. This classification of papers is also used to highlight the international and institutional differences in robot development. Analysis of the growth in robot supply, manufacture, and use is made from statistics compiled. A series of interviews with users and potential users serves to illustrate the factors and implications of the adoption of different robot systems in the UK. Adoption pioneering takes place when several conditions exist: when the technology is compatible with the firm, when its advantages outweigh its disadvantages, and particularly when a climate exists which encourages the managerial involvement and the labour acceptance. The degree of compatibility (technical, methodological, organisational, and economic) and the consequences (profitability, labour impacts, and managerial effects) of different robot systems (transfer, manipulative, processing, and assembly) are determined by various aspects of manufacturing operations (complexity, automation, integration, labour tasks, and working conditions). The climate for adoption pioneering is basically determined by the performance of firms. The firms' policies on capital investment have as decisive a role in determining the profitability of robots as their total labour costs. The performance of the motor car industry and its machine builders explains, more than any other factor, the present state of robot advancement in the UK.

The control of technological change in the motor industry:a case study

This thesis is based upon a case study of the introduction of automated production technologies at the Longbridge plant of British Leyland in the period 1978 to 1980.The investment in automation was part of an overall programme of modernization to manufacture the new 'Mini Metro' model. In the first Section of the thesis, the different theoretical perspectives on technological change are discussed. Particular emphasis is placed upon the social role of management as the primary controllers of technological change. Their actions are seen to be oriented towards the overall strategy of the firm, integrating the firm's competitive strategy with production methods and techniques.This analysis is grounded in an examination of British Leyland's strategies during the 1970s.. The greater part of the thesis deals with the efforts made by management to secure their strategic objectives in the process of technological change against the conflicting claims of their work-force. Examination of these efforts is linked to the development of industrial relations conflict at Longbridge and in British Leyland as a whole.Emphasis is placed upon the struggle between management in pursuit of their version of efficiency and the trade unions in defence of job controls and demarcations. The thesis concludes that the process of technological change in the motor industry is controlled by social forces,with the introduction of new technologies being closely intertwined with management!s political relations with the trade unions.