published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

<p>U doktorskoj disertaciji su predstavljeni modeli za planiranje i upravljanje proizvodnim sistemom organizovanim putem virtuelnih proizvodnih ćelija. U modelima su razvijeni postupci određivanja dužine planskog perioda i broja faza obrade ili montaže. U modelima je razvijen postupak kreiranja virtuelnih proizvodnih ćelija imajući u vidu zahteve planskog i upravljačkog sistema. Modeli omogućuju rekonfiguraciju ćelija usled analize opterećenja tehnoloških sistema i mogućnosti realizacije terminskih planova proizvodnje. Modeli su ispitani na primerima dva proizvodna preduzeća sa teritorije Republike Srbije.</p> / <p>Doctoral dissertation presents models for production planning and control of<br />virtual manufacturing cells. Models present developed procedure for the<br />determination of the production planning period and the number of<br />processing or assembly stages. Models also present the process of creating<br />virtual manufacturing cells, bearing the requirements of the production<br />planning and control system.The models enable the reconfiguration of cells<br />due to the analysis of machines workload and due to the analysis of the<br />production schedule. The models were tested on the examples of two<br />production companies from the Republic of Serbia .</p>

The main question in this study was: do business units that exhibit a "linkage" or "fit" between their business strategy and manufacturing strategy variables, outperform competitors who lack such a fit? This exploratory research focused on two business strategies: cost leadership and differentiation. Based on existing literature, twenty-four hypotheses concerning the relationship between business strategy and selected manufacturing strategy variables were developed. The manufacturing executives of eighty-eight broadwoven cotton fabric mills (SIC 2211) were surveyed using a qualitative questionnaire. Two sets of comparisons were made between the manufacturing strategy variables of the sampled firms: first, high vs. low performers pursuing cost leadership strategy; and second, high vs. low performers focusing on differentiation strategy. Within each set of comparisons, high performers reported linkage between their business strategies and selected manufacturing strategy variables. This study re-affirms the importance of linking business strategy with manufacturing strategy variables as a forceful weapon for overcoming competition.

As empresas fornecedoras para o segmento automotivo estão inseridas em um mercado de constante variação e sujeitas às oscilações da economia. As montadoras, principais influenciadoras do restante da cadeia de suprimentos, aderiram às práticas do just in time, que objetiva a alta eficiência e estoques reduzidos. Este trabalho procura identificar como os fornecedores ao longo da cadeia automotiva se adequaram às novas práticas das montadoras no que se refere ao planejamento e controle da produção e estoques. É realizado um survey, em que se verifica que os profissionais de PCP dos fornecedores respondem satisfatoriamente à demanda, porém de maneira não uniforme, com baixa coordenação com o elo mais próximo, baixa acuracidade de estoque e nível de estoque de produto acabado e matéria-prima elevado. É realizada uma comparação entre o desempenho dos fornecedores mais próximos da montadora com os mais longes, verificando-se que não há diferenças significativas entre ambos / Automotive segment suppliers are part of a constant changing that is subject to oscillations in the economy. Automobile assemblers, the major influence over the rest of the supply chain, have adopted Japanese just in time practices,in order to achieve high levels of efficiency and low inventory. This paper seeks to identify how suppliers along the chain have adjusted to these new practices relating to production and inventory planning and control activities. A survey is conducted, showing that suppliers PPCs fulfill demand requests satisfactorily, although in a non-uniform way, with poor coordination between adjacent links in the chain, low inventory accuracy and high stock level of raw materials and finnished goods. It is concluded that there are no significant performance differences between the suppliers close to the assemblers and those further from them.

Nesta tese é realizado um estudo de caso em uma indústria química brasileira, no qual busca-se representar características da tomada de decisões para a programação da produção em plantas de bateladas. Para isso, foi proposto um modelo matemático do tipo MIP (Mixed Integer Programming) que considerou a disponibilidade de matérias-primas, múltiplas tarefas produtivas para um mesmo produto, tanques de armazenamento multiproduto, envase de produtos e demanda de produtos a granel e envasados. O objetivo principal desse estudo era permitir a obtenção de soluções compatíveis com a prática da empresa em tempo de processamento viável. A partir desse estudo de caso, foi efetuado um segundo estudo com objetivo de avaliar o desempenho de formulações matemáticas para a resolução de um problema de programação da produção. Foram considerados modelos clássicos das comunidades científicas de pesquisa operacional e de engenharia de sistemas de processo, além de um terceiro modelo desenvolvido a partir de conceitos dessas duas comunidades. Algumas características do estudo de caso não foram retratadas, como o consumo de matérias-primas e o envase dos produtos, porém, foram consideradas duas características comumente observadas em problemas da indústria de processos: bateladas com quantidade produzida flexível e tarefas que produzem mais de um produto. Por fim, um terceiro estudo foi realizado com base no estudo de caso da indústria química brasileira, porém, com um foco decisões mais próximas ao nível tático. Sendo assim, foi considerado apenas o dimensionamento de lotes, sem o sequenciamento da produção. Por outro lado, foram acrescentadas características pertinentes à aquisição de matérias-primas, como custos das matérias-primas e descontos por quantidade adquirida. O objetivo deste último trabalho era avaliar a influência da integração das decisões de dimensionamento de lotes e de aquisição das matérias-primas nos custos da cadeia produtiva durante todo o horizonte de planejamento. / In this thesis we developed a study case in a Brazilian chemical industry, in which the aim was to represent the characteristics of decision-making for production scheduling in batch plants. For this, a mixed integer programming model was proposed to consider the availability of raw materials, multiple productive tasks for the same product, multi-product storage tanks, product packaging and demand for products in bulk and packaged. The main objective of this study was develop a model that is able to obtain solutions that clould be used in practice for this chemical industry in viable processing time. From this study case, a second work was carried out to evaluate the performance of mathematical formulations to solve a problem of production scheduling. Classic models of operational research and process system engineering communities were considered, and a third model was developed from concepts of these two communities. Some features of the case study were not modelled, such as the consumption of raw materials and the product packaging, however, two characteristics usually present in process industries were considered: flexible batch production quantity and multi-product task production. Finally, a third study developed based on the study case of the Brazilian chemical industry, but with focus on decisions more familiar to the tactical level. Thus, only lot sizing was modelled, without production scheduling. On the other hand, features relevant raw material purchasing were included, such as raw material costs and discounts for quantity purchased. The objective of this last work was to evaluate the influence of integrating lot sizing decisions and raw material purchasing decisions in the overall costs of the production chain during the entire planning horizon.

Production planning problems are of paramount importance within supply chain planning, supporting decisions on the transformation of raw materials into finished products. Lot sizing in production planning refers to the tactical/operational decisions related to the size and timing of production orders to satisfy a demand. The objectives of lot-sizing problems are generally economical-related, such as saving costs or increasing profits, though other aspects may be taken into account such as quality of the customer service and reduction of inventory levels. Lot-sizing problems are very common in production activities and an efficient planning of such activities gives the company a clear advantage over concurrent organizations. To that end it is required the consideration of realistic features of the industrial environment and product characteristics. By means of mathematical modelling, such considerations are crucial, though their inclusion results in more complex formulations. Although lot-sizing problems are well-known and largely studied, there is a lack of research in some real-world aspects. This thesis addresses two main characteristics at the lot-sizing context: (a) setup crossover; and (b) perishable products. The former allows the setup state of production line to be carried over between consecutive periods, even if the line is not yet ready for processing production orders. The latter characteristic considers that some products have fixed shelf-life and may spoil within the planning horizon, which clearly affects the production planning. Furthermore, two types of perishable products are considered, according to the duration of their lifetime: medium-term and short-term shelf-lives. The latter case is tighter than the former, implying more constrained production plans, even requiring an integration with other supply chain processes such as distribution planning. Research on stronger mathematical formulations and solution approaches for lot-sizing problems provides valuable tools for production planners. This thesis focuses on the development of mixed-integer linear programming (MILP) formulations for the lot-sizing problems considering the aforementioned features. Novel modelling techniques are introduced, such as the proposal of a disaggregated setup variable and the consideration of lot-sizing instead of batching decisions in the joint production and distribution planning problem. These formulations are subjected to computational experiments in state-of-the-art MILP-solvers. However, the inherent complexity of these problems may require problemdriven solution approaches. In this thesis, heuristic, metaheuristic and matheuristic (hybrid exact and heuristic) procedures are proposed. A lagrangean heuristic addresses the capacitated lot-sizing problem with setup carryover and perishable products. A novel dynamic programming procedure is used to achieve the optimal solution of the uncapacitated single-item lot-sizing problem with setup carryover and perishable item. A heuristic, a fix-and-optimize procedure and an adaptive large neighbourhood search approach are proposed for the operational integrated production and distribution planning. Computational results on generated set of instances based on the literature show that the proposed methods yields competitive performances against other literature approaches. / Problemas de planejamento da produção são de suma importância no planejamento da cadeia de suprimentos, dando suporte às decisões da transformação de matérias-primas em produtos acabados. O dimensionamento de lotes em planejamento de produção é definido pelas decisões tático-operacionais relacionadas com o tamanho das ordens de produção e quando fabricá-las para satisfazer a demanda. Os objetivos destes problemas são geralmente de cunho econômico, tais como a redução de custos ou o aumento de lucros, embora outros aspectos possam ser considerados, tais como a qualidade do serviço ao cliente e a redução dos níveis de estoque. Problemas de dimensionamento de lotes são muito comuns em atividades de produção e um planejamento eficaz de tais atividades, estabelece uma clara vantagem à empresa em relação à concorrência. Para este objetivo, é necessária a consideração de características realistas do ambiente industrial e do produto. Para a modelagem matemática do problema, estas considerações são cruciais, embora sua inclusão resulte em formulações mais complexas. Embora os problemas de dimensionamento de lotes sejam bem conhecidos e amplamente estudados, várias características reais importantes não foram estudadas. Esta tese aborda, no contexto de dimensionamento de lotes, duas características muito relevantes: (a) preservação da preparação total e parcial; e (b) produtos perecíveis. A primeira permite que o estado de preparação de uma linha de produção seja mantido entre dois períodos consecutivos, mesmo que a linha de produção ainda não esteja totalmente pronta para o processamento de ordens de produção. A ultima característica determina que alguns produtos tem prazo de validade fixo, menor ou igual do que o horizonte de planejamento, o que afeta o planejamento da produção. Além disso, de acordo com a duração de sua vida útil, foram considerados dois tipos de produtos perecíveis: produtos com tempo de vida de médio e curto prazo. O ultimo caso resulta em um problema mais apertado do que o anterior, o que implica em planos de produção mais restritos. Isto pode exigir uma integração com outros processos da cadeia de suprimentos, tais como o planejamento de distribuição dos produtos acabados. Pesquisas sobre formulações matemáticas mais fortes e abordagens de solução para problemas de dimensionamento de lotes fornecem ferramentas valiosas para os planejadores de produção. O foco da tese reside no desenvolvimento de formulações de programação linear inteiro-mistas (MILP) para os problemas de dimensionamento de lotes, considerando as características mencionadas anteriormente. Novas técnicas de modelagem foram introduzidas, como a proposta de variáveis de preparação desagregadas e a consideração de decisões de dimensionamento de lotes ao invés de decisões de agrupamento de ordens de produção no problema integrado de planejamento de produção e distribuição. Estas formulações foram submetidas a experimentos computacionais em MILP-solvers de ponta. No entanto, a complexidade inerente destes problemas pode exigir abordagens de solução orientadas ao problema. Nesta tese, abordagens heurísticas, metaheurísticas e matheurísticas (híbrido de métodos exatos e heurísticos) foram propostas para os problemas discutidos. Uma heurística lagrangeana aborda o problema de dimensionamento de lotes com restrições de capacidade, preservação da preparação total e produtos perecíveis. Um novo procedimento de programação dinâmica e utilizado para encontrar a solução ótima do problema de dimensionamento de lotes de um único produto perecível, sem restrições de capacidade e preservação da preparação total. Uma heurística, um procedimento x-and-optimize e uma abordagem por buscas adaptativas em grande vizinhanças são propostas para o problema integrado de planejamento de produção e distribuição. Resultados computacionais em conjuntos de instâncias geradas com base na literatura mostram que os métodos propostos obtiveram performances competitivas com relação a outras abordagens da literatura.

Apesar do crescimento nas exportações de açúcar, a conjuntura atual do setor sucroalcooleiro e a instabilidade do mercado externo têm feito com que as usinas busquem mais competitividade. A Tecnologia da Informação (TI) tem participação nesta busca, visto que, hoje, é impossível uma empresa apresentar um gerenciamento integrado eficaz sem a utilização de sistemas informatizados. Alguns desses sistemas, os ERP, têm se desenvolvido muito nos últimos anos, chegando, por exemplo, a ponto de possuírem módulos específicos para determinados tipos de empresas. Um dos desenvolvedores desses sistemas criou módulos específicos para o Planejamento e Controle da Produção (PCP) em indústrias de processo contínuo. Os conceitos envolvidos em tais módulos são apresentados nesta dissertação e comparados com os módulos tradicionais de Planejamento e Controle de Produção. Depois do embasamento conceitual, e da apresentação dos processos industriais de uma determinada usina de açúcar e álcool, é desenvolvida a configuração de tais módulo, para análise da compatibilidade desses ao processo produtivo da usina. / In spite of the growth in the sugar exports, the current situation of the sector responsible for the production of sugar and alcohol, as well as the instability of the external market, responsible for the fact that sugar and alcohol mills are looking for an increase competitiveness. The Information Technology (IT) has a great degree of participation in this search for competitiveness, because it is impossible for a company to introduce an effective integrated management network without the utilization of computerized systems. Some of these systems, called Enterprise Resources Planning, have developed remarkably in the last years, reaching, for instance, the point of having their own specific modules for certain industry types. One of the developers of these systems developed specific modules for the production planning and control in industries of continuous process. The concepts involved in such modules are introduced in this dissertation, and compared with the traditional modules of production planning and control. Basic concepts are introduced at first, then the industrial processes of a plant are explained, and the modeling of such company is presented for the analysis of the compatibility of the modules to the productive process of the plant.

Este trabalho propõe a especificação e a criação de experimentos, modelos e interfaces padrões para o apoio ao processo de planejamento da produção de um sistema produtivo sucroalcooleiro, via simulação. Os modelos abrangem os setores agrícola e industrial das usinas sucroalcooleiras, da colheita da matéria-prima até a fabricação do açúcar e do álcool. A modelagem do sistema, utilizando softwares comerciais de simulação com flexibilidade de recursos para customização, visa a geração de um ambiente de simulação para análises de desempenho e sensibilidade. Os modelos padrões que compõem este ambiente de simulação permitem que sejam realizadas simulações em 3 diferentes escopos, desde a usina, passando pelos setores agrícola e industrial, e chegando ao nível dos processos de corte/carregamento, recepção de matéria-prima, extração, tratamento de caldo, fabricação de açúcar, fabricação de álcool e geração de vapor. A interação do usuário com o ambiente, por meio de interfaces amigáveis, tem como função fornecer ao planejador uma opção de ferramenta de trabalho simples e de fácil aplicação, que possibilita a obtenção de informações úteis sobre o comportamento e das inter-relações entre as principais variáveis que influenciam o desempenho do sistema, permitindo a escolha das opções mais adequadas na busca de melhorias. / This work proposes the specification and generation of standard experiments, models and interfaces for supporting to the process of production planning in the sugar cane industry, through simulation. Models embrace the agricultural and industrial sections of sugar cane plants, since the cane harvesting until the sugar and alcohol production. The system modelling, using commercial simulation softwares with flexibility of customization resources, seeks the generation of a simulation environment for performance and sensibility analyses. Standard models that compose this simulation environment allow simulations to be accomplished in 3 different scopes, from the plant, passing by the agricultural and industrial sections, and arriving at the level of the processes: cutting/loading, raw material reception, extraction, juice treatment, sugar production, alcohol production and stream generation. The user\'s interaction with the simulation environment through friendly interfaces, has the function of supplying the planner with an ease-to-use tool option, that makes possible the obtaining of useful information about the behavior and the interrelations among the principal variables that influence the system performance, allowing the choice of the most appropriate options in the search of improvements.

Ngo-Tai Fong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 158-168). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Manufacturing Systems: An Overview --- p.1 / Chapter 1.2 --- Previous Research --- p.3 / Chapter 1.3 --- Motivation --- p.5 / Chapter 1.4 --- Outline of the Thesis --- p.8 / Chapter 2 --- Preliminaries --- p.11 / Chapter 2.1 --- Problem Formulation: Deterministic Production Planning --- p.11 / Chapter 2.2 --- Markov Chain --- p.15 / Chapter 2.3 --- Problem Formulation: Stochastic Production Planning --- p.18 / Chapter 2.4 --- Some Lemmas --- p.24 / Chapter 3 --- Open-Loop Production Planning in Stochastic Flowshops --- p.26 / Chapter 3.1 --- Introduction --- p.26 / Chapter 3.2 --- Limiting Problem --- p.29 / Chapter 3.3 --- Weak-Lipschitz Continuity --- p.34 / Chapter 3.4 --- Constraint Domain Approximation --- p.41 / Chapter 3.5 --- Asymptotic Analysis: Initial States in Sε --- p.47 / Chapter 3.6 --- Asymptotic Analysis: Initial States in S \ Sε --- p.61 / Chapter 3.7 --- Concluding Remarks --- p.70 / Chapter 4 --- Feedback Production Planning in Deterministic Flowshops --- p.72 / Chapter 4.1 --- Introduction --- p.72 / Chapter 4.2 --- Assumptions --- p.75 / Chapter 4.3 --- Optimal Feedback Controls --- p.76 / Chapter 4.3.1 --- The Case c1 < c2+ --- p.78 / Chapter 4.3.2 --- The Case c1 ≥ c2+ --- p.83 / Chapter 4.4 --- Concluding Remarks --- p.88 / Chapter 5 --- Feedback Production Planning in Stochastic Flowshops --- p.90 / Chapter 5.1 --- Introduction --- p.90 / Chapter 5.2 --- Original and Limiting Problems --- p.91 / Chapter 5.3 --- Asymptotic Optimal Feedback Controls for pε --- p.97 / Chapter 5.3.1 --- The Case c1 < c2+ --- p.97 / Chapter 5.3.2 --- The Case c1 ≥ c2+ --- p.118 / Chapter 5.4 --- Concluding Remarks --- p.124 / Chapter 6 --- Computational Evaluation of Hierarchical Controls --- p.126 / Chapter 6.1 --- Introduction --- p.126 / Chapter 6.2 --- The Problem and Control Policies under Consideration --- p.128 / Chapter 6.2.1 --- The Problem --- p.128 / Chapter 6.2.2 --- Hierarchical Control (HC) --- p.131 / Chapter 6.2.3 --- Kanban Control (KC) --- p.133 / Chapter 6.2.4 --- Two-Boundary Control (TBC) --- p.137 / Chapter 6.2.5 --- "Similarities and Differences between HC, KC, and TBC" --- p.141 / Chapter 6.3 --- Computational Results --- p.142 / Chapter 6.4 --- Comparison of HC with Other Polices --- p.145 / Chapter 6.5 --- Concluding Remarks --- p.151 / Chapter 7 --- Conclusions and Future Research --- p.153 / Bibliography --- p.158

by Chu Kwok-Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 91-93). / Abstracts in English and Chinese. / List of Figures --- p.vii / List of Tables --- p.viii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Literature Review --- p.4 / Chapter 1.2.1 --- Ordinary Dispatching Policies --- p.5 / Chapter 1.2.2 --- Setup-oriented Dispatching Policies --- p.7 / Chapter 1.3 --- Organization of Thesis --- p.10 / Chapter 2 --- Slack Based Policies --- p.11 / Chapter 2.1 --- Definition of Slack --- p.12 / Chapter 2.2 --- Least Slack Policy (LS) --- p.13 / Chapter 2.3 --- Least Weighted Slack Policy (LWS) --- p.15 / Chapter 2.3.1 --- Definition of Weighted Slack --- p.15 / Chapter 2.3.2 --- Policy Mechanism and Discussion --- p.15 / Chapter 2.4 --- Least Mean Slack Policy (LMS) --- p.16 / Chapter 2.4.1 --- Batch Size and Its Lower Bound --- p.16 / Chapter 2.4.2 --- Policy Mechanism and Discussion --- p.17 / Chapter 2.5 --- Least Weighted Mean Slack Policy (LWMS) --- p.18 / Chapter 2.5.1 --- Definition of Weighted Mean Slack --- p.18 / Chapter 2.5.2 --- Policy Mechanism and Discussion --- p.18 / Chapter 2.6 --- Illustrative Example --- p.21 / Chapter 2.7 --- Due-date Window Expansion --- p.24 / Chapter 2.7.1 --- Due-date Window --- p.24 / Chapter 2.7.2 --- LWMS Policy: Due Date Window Expansion --- p.25 / Chapter 3 --- Simulation Study --- p.27 / Chapter 3.1 --- Models Description --- p.27 / Chapter 3.1.1 --- Two-Machines-Two-Products Model --- p.27 / Chapter 3.1.2 --- Assembly Lines Model --- p.29 / Chapter 3.1.3 --- Micro-Chips Testing Model --- p.31 / Chapter 3.2 --- Simulation Experiment Description --- p.32 / Chapter 4 --- Simulation Result and Analysis --- p.38 / Chapter 4.1 --- Simulation Result --- p.39 / Chapter 4.1.1 --- Two-Machines-Two-Products Model --- p.39 / Chapter 4.1.2 --- Assembly Lines Model --- p.39 / Chapter 4.1.3 --- Micro-Chips Testing Model --- p.43 / Chapter 4.2 --- Statistical Analysis --- p.44 / Chapter 4.2.1 --- Significance of Weighted Factor and Batch Size --- p.44 / Chapter 4.2.2 --- Comparison Among Different Policies --- p.46 / Chapter 4.3 --- Discussion of Results --- p.50 / Chapter 5 --- An Experimental Implementation and Conclusion Remarks --- p.51 / Chapter A --- Reducing MCT and SDCT by LS policy --- p.55 / Chapter A.1 --- Reducing Variance of Lateness --- p.55 / Chapter A.2 --- Reducing Variance of Cycle Time --- p.56 / Chapter A.3 --- Reducing Mean Cycle Time --- p.56 / Chapter B --- Complete Simulation Result --- p.58 / Chapter B.1 --- Two-Machines-Two-Products Model --- p.58 / Chapter B.1.1 --- "Wip, Batch Size and Throughput" --- p.58 / Chapter B.1.2 --- MCT and SDCT --- p.62 / Chapter B.1.3 --- Machine Utilization --- p.66 / Chapter B.2 --- Assembly Lines Model --- p.68 / Chapter B.2.1 --- "WIP, Batch Size and Throughput" --- p.68 / Chapter B.2.2 --- MCT and SDCT --- p.70 / Chapter B.2.3 --- Machine Utilization --- p.73 / Chapter B.3 --- Micro-Chips Testing Model --- p.82 / Chapter B.3.1 --- "WIP, Throughput, MCT and SDCT" --- p.82 / Chapter B.3.2 --- Machine Utilization --- p.84 / Chapter C --- MANOVA studies on Weighted Factor and Batch Size --- p.86 / Chapter C.1 --- Two-Machines-Two-Products Model --- p.86 / Chapter C.1.1 --- Least Weighted Slack Policy --- p.86 / Chapter C.1.2 --- Least Mean Slack Policy --- p.87 / Chapter C.1.3 --- Least Weighted Mean Slack Policy --- p.87 / Chapter C.2 --- Assembly Lines Model --- p.88 / Chapter C.2.1 --- Least Weighted Slack Policy --- p.88 / Chapter C.2.2 --- Least Mean Slack Policy --- p.88 / Chapter C.2.3 --- Least Weighted Mean Slack Policy --- p.89 / Chapter C.3 --- Micro-Chips Testing Model --- p.89 / Chapter C.3.1 --- Least Weighted Slack Policy --- p.89 / Chapter C.3.2 --- Least Mean Slack Policy --- p.90 / Chapter C.3.3 --- Least Weighted Mean Slack Policy --- p.90 / Bibliography --- p.91