A Study of the Effects of Manufacturing Complexity on Product Quality in Mixed-Model Automotive Assembly

The objective of this research is to test the hypothesis that manufacturing complexity can reliably predict product quality in mixed-model automotive assembly. Originally, assembly lines were developed for cost efficient mass-production of standardized products. Today, in order to respond to diversified customer needs, companies have to allow for an individualization of their products, leading to the development of the Flexible Manufacturing Systems (FMS). Assembly line balancing problems (ALBP) consist of assigning the total workload for manufacturing a product to stations of an assembly line as typically applied in the automotive industry. Precedence relationships among tasks are required to conduct partly or fully automated Assembly Line Balancing. Efforts associated with manual precedence graph generation at a major automotive manufacturer have highlighted a potential relationship between manufacturing complexity (driven by product design, assembly process, and human factors) and product quality, a potential link that is usually ignored during Assembly Line Balancing and one that has received very little research focus so far. The methodology used in this research will potentially help develop a new set of constraints for an optimization model that can be used to minimize manufacturing complexity and maximize product quality, while satisfying the precedence constraints. This research aims to validate the hypothesis that the contribution of design variables, process variables, and human-factors can be represented by a complexity metric that can be used to predict their contribution on product quality. The research will also identify how classes of defect prevention methods can be incorporated in the predictive model to prevent defects in applications that exhibit high level of complexity. The manufacturing complexity model is applied to mechanical fastening processes which are accountable for the top 28% of defects found in automotive assembly, according to statistical analysis of historical data collected over the course of one year of vehicle production at a major automotive assembly plant. The predictive model is validated using mechanical fastening processes at an independent automotive assembly plant. This complexity-based predictive model will be the first of its kind that will take into account design, process, and human factors to define complexity and validate it using a real-world automotive manufacturing process. The model will have the potential to be utilized by design and process engineers to evaluate the effect of manufacturing complexity on product quality before implementing the process in a real-world assembly environment

The Distributed and Assembly Scheduling Problem

Tesis por compendio[EN] Nowadays, manufacturing systems meet different new global challenges and the existence of a collaborative manufacturing environment is essential to face with. Distributed manufacturing and assembly systems are two manufacturing systems which allow industries to deal with some of these challenges. This thesis studies a production problem in which both distributed manufacturing and assembly systems are considered. Although distributed manufacturing systems and assembly systems are well-known problems and have been extensively studied in the literature, to the best of our knowledge, considering these two systems together as in this thesis is the first effort in the literature. Due to the importance of scheduling optimization on production performance, some different ways to optimize the scheduling of the considered problem are discussed in this thesis. The studied scheduling setting consists of two stages: A production and an assembly stage. Various production centers make the first stage. Each of these centers consists of several machines which are dedicated to manufacture jobs. A single assembly machine is considered for the second stage. The produced jobs are assembled on the assembly machine to form final products through a defined assembly program. In this thesis, two different problems regarding two different production configurations for the production centers of the first stage are considered. The first configuration is a flowshop that results in what we refer to as the Distributed Assembly Permutation Flowshop Scheduling Problem (DAPFSP). The second problem is referred to as the Distributed Parallel Machine and Assembly Scheduling Problem (DPMASP), where unrelated parallel machines configure the production centers. Makespan minimization of the product on the assembly machine located in the assembly stage is considered as the objective function for all considered problems. In this thesis some extensions are considered for the studied problems so as to bring them as close as possible to the reality of production shops. In the DAPFSP, sequence dependent setup times are added for machines in both production and assembly stages. Similarly, in the DPMASP, due to technological constraints, some defined jobs can be processed only in certain factories. Mathematical models are presented as an exact solution for some of the presented problems and two state-of-art solvers, CPLEX and GUROBI are used to solve them. Since these solvers are not able to solve large sized problems, we design and develop heuristic methods to solve the problems. In addition to heuristics, some metaheuristics are also designed and proposed to improve the solutions obtained by heuristics. Finally, for each proposed problem, the performance of the proposed solution methods is compared through extensive computational and comprehensive ANOVA statistical analysis.[ES] Los sistemas de producción se enfrentan a retos globales en los que el concepto de fabricación colaborativa es crucial para poder tener éxito en el entorno cambiante y complejo en el que nos encontramos. Una característica de los sistemas productivos que puede ayudar a lograr este objetivo consiste en disponer de una red de fabricación distribuida en la que los productos se fabriquen en localizaciones diferentes y se vayan ensamblando para obtener el producto final. En estos casos, disponer de modelos y herramientas para mejorar el rendimiento de sistemas de producción distribuidos con ensamblajes es una manera de asegurar la eficiencia de los mismos. En esta tesis doctoral se estudian los sistemas de fabricación distribuidos con operaciones de ensamblaje. Los sistemas distribuidos y los sistemas con operaciones de ensamblaje han sido estudiados por separado en la literatura. De hecho, no se han encontrado estudios de sistemas con ambas características consideradas de forma conjunta. Dada la complejidad de considerar conjuntamente ambos tipos de sistemas a la hora de realizar la programación de la producción en los mismos, se ha abordado su estudio considerando un modelo bietápico en la que en la primera etapa se consideran las operaciones de producción y en la segunda se plantean las operaciones de ensamblaje. Dependiendo de la configuración de la primera etapa se han estudiado dos variantes. En la primera variante se asume que la etapa de producción está compuesta por sendos sistemas tipo flowshop en los que se fabrican los componentes que se ensamblan en la segunda etapa (Distributed Assembly Permutation Flowshop Scheduling Problem o DAPFSP). En la segunda variante se considera un sistema de máquinas en paralelo no relacionadas (Distributed Parallel Machine and Assembly Scheduling Problem o DPMASP). En ambas variantes se optimiza la fecha de finalización del último trabajo secuenciado (Cmax) y se contempla la posibilidad que existan tiempos de cambio (setup) dependientes de la secuencia de trabajos fabricada. También, en el caso DPMASP se estudia la posibilidad de prohibir o no el uso de determinadas máquinas de la etapa de producción. Se han desarrollado modelos matemáticos para resolver algunas de las variantes anteriores. Estos modelos se han resuelto mediante los programas CPLEX y GUROBI en aquellos casos que ha sido posible. Para las instancias en los que el modelo matemático no ofrecía una solución al problema se han desarrollado heurísticas y metaheurísticas para ello. Todos los procedimientos anteriores han sido estudiados para determinar el rendimiento de los diferentes algoritmos planteados. Para ello se ha realizado un exhaustivo estudio computacional en el que se han aplicado técnicas ANOVA. Los resultados obtenidos en la tesis permiten avanzar en la comprensión del comportamiento de los sistemas productivos distribuidos con ensamblajes, definiendo algoritmos que permiten obtener buenas soluciones a este tipo de problemas tan complejos que aparecen tantas veces en la realidad industrial.[CA] Els sistemes de producció s'enfronten a reptes globals en què el concepte de fabricació col.laborativa és crucial per a poder tindre èxit en l'entorn canviant i complex en què ens trobem. Una característica dels sistemes productius que pot ajudar a aconseguir este objectiu consistix a disposar d'una xarxa de fabricació distribuïda en la que els productes es fabriquen en localitzacions diferents i es vagen acoblant per a obtindre el producte final. En estos casos, disposar de models i ferramentes per a millorar el rendiment de sistemes de producció distribuïts amb acoblaments és una manera d'assegurar l'eficiència dels mateixos. En esta tesi doctoral s'estudien els sistemes de fabricació distribuïts amb operacions d'acoblament. Els sistemes distribuïts i els sistemes amb operacions d'acoblament han sigut estudiats per separat en la literatura però, en allò que es coneix, no s'han trobat estudis de sistemes amb ambdós característiques conjuntament. Donada la complexitat de considerar conjuntament ambdós tipus de sistemes a l'hora de realitzar la programació de la producció en els mateixos, s'ha abordat el seu estudi considerant un model bietàpic en la que en la primera etapa es consideren les operacions de producció i en la segona es plantegen les operacions d'acoblament. Depenent de la configuració de la primera etapa s'han estudiat dos variants. En la primera variant s'assumix que l'etapa de producció està composta per sengles sistemes tipus flowshop en els que es fabriquen els components que s'acoblen en la segona etapa (Distributed Assembly Permutation Flowshop Scheduling Problem o DAPFSP). En la segona variant es considera un sistema de màquines en paral.lel no relacionades (Distributed Parallel Machine and Assembly Scheduling Problem o DPMASP). En ambdós variants s'optimitza la data de finalització de l'últim treball seqüenciat (Cmax) i es contempla la possibilitat que existisquen temps de canvi (setup) dependents de la seqüència de treballs fabricada. També, en el cas DPMASP s'estudia la possibilitat de prohibir o no l'ús de determinades màquines de l'etapa de producció. S'han desenvolupat models matemàtics per a resoldre algunes de les variants anteriors. Estos models s'han resolt per mitjà dels programes CPLEX i GUROBI en aquells casos que ha sigut possible. Per a les instàncies en què el model matemàtic no oferia una solució al problema s'han desenrotllat heurístiques i metaheurísticas per a això. Tots els procediments anteriors han sigut estudiats per a determinar el rendiment dels diferents algoritmes plantejats. Per a això s'ha realitzat un exhaustiu estudi computacional en què s'han aplicat tècniques ANOVA. Els resultats obtinguts en la tesi permeten avançar en la comprensió del comportament dels sistemes productius distribuïts amb acoblaments, definint algoritmes que permeten obtindre bones solucions a este tipus de problemes tan complexos que apareixen tantes vegades en la realitat industrial.Hatami, S. (2016). The Distributed and Assembly Scheduling Problem [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64072TESISCompendi

On the Design of Functionally Integrated Aero-engine Structures: Modeling and Evaluation Methods for Architecture and Complexity

The drive for airplanes with radically reduced fuel consumption and emissions motivates engine manufacturers to explore innovative engine designs. The novelty of such engines results in changed operating conditions, such as newly introduced constraints, increased loads or rearranged interfaces. To be competitive, component developers and manufacturers must understand and predict the consequences of such changes on their sub-systems. Presently, such assessments are based on detailed geometrical models (CAD or finite element) and consume significant amounts of time. The preparation of such models is resource intensive unless parametrization is employed. Even with parametrization, alternative geometrical layouts for designs are difficult to achieve. In contrast to geometrical model-based estimations, a component architecture representation and evaluation scheme can quickly identify the functional implications for a system-level change and likely consequences on the component. The schemes can, in turn, point to the type and location of needed evaluations with detailed geometry. This will benefit the development of new engine designs and facilitate improvements upon existing designs. The availability of architecture representation schemes for functionally integrated (all functions being satisfied by one monolithic structure) aero-engine structural components is limited. The research in this thesis focuses on supporting the design of aero-engine structural components by representing their architecture as well as by developing means for the quantitative evaluation and comparison of different component designs. The research has been conducted in collaboration with GKN Aerospace Sweden AB, and the components are aero-engine structures developed and manufactured at GKN. Architectural information is generated and described based on concepts from set theory, graph theory and enhanced function–means trees. In addition, the complexities of the components are evaluated using a new complexity metric. Specifically, the developed modeling and evaluation methods facilitate the following activities: \ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 identification and representation of function–means information for the component\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 representation and evaluation of component architecture\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 product complexity evaluation\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 early selection of load path architecture\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 impact assessment for the component’s functioning in the systemBy means of the methods developed in this thesis, the design rationale for a component is made explicit, and the storing, communicating and retrieving of information about the component in the future is enabled. Through their application to real-life engine structures, the usability of the methods in identifying early load carrying configurations and selecting a manufacturing segmenting option is demonstrated. Together, the methods provide development engineers the ability to compare alternative architectures. Further research could focus on exploring the system (engine) effects of changes in component architecture and improvements to the complexity metric by incorporating manufacturing information

Planning and Scheduling Optimization

Although planning and scheduling optimization have been explored in the literature for many years now, it still remains a hot topic in the current scientific research. The changing market trends, globalization, technical and technological progress, and sustainability considerations make it necessary to deal with new optimization challenges in modern manufacturing, engineering, and healthcare systems. This book provides an overview of the recent advances in different areas connected with operations research models and other applications of intelligent computing techniques used for planning and scheduling optimization. The wide range of theoretical and practical research findings reported in this book confirms that the planning and scheduling problem is a complex issue that is present in different industrial sectors and organizations and opens promising and dynamic perspectives of research and development

모듈러 제품군 운영을 위한 다양성 관리 방법론

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 산업공학과, 2021. 2. 홍유석.글로벌 제조업체들은 다양한 제품을 출시하기 위해 모듈러 디자인 전략을 제품개발에 적용해왔다. 모듈러 디자인 전략은 제품을 모듈 단위로 구분한 후, 여러 종류의 모듈을 조합하여 새로운 제품을 만드는 전략이다. 모듈러 디자인은 제조업체가 제품다양성을 달성할 수 있도록 하였지만, 제공하는 제품의 수가 무수히 많아지면서 제품다양성으로 인한 안 좋은 영향들이 설계 영역뿐만 아니라, 시장, 생산 영역에서 지속적으로 발생하고 있는 실정이다. 따라서, 본 논문에서는 제품다양성의 안 좋은 영향을 줄일 수 있도록 이를 체계적으로 개발하고 운영하는 다양성 관리(variety management) 방법론을 제안한다. 다양성 관리를 성공적으로 수행하기 위해서는 교차영역 관점과 변종 수준 관점의 접근이 필요하다. 교차영역 관점은 제품다양성이 영향을 미치는 시장, 설계, 생산 영역의 요소들의 연결관계를 정립하는 메커니즘을 제공하며, 변종 수준 관점은 일반적인 요소(elements) 수준에서 한 단계 내려가 다양성 관리에 실제 문제가 되는 각 요소들의 변종들(variants)을 체계적으로 관리할 수 있도록 한다. 이 두 가지 관점에서, 본 논문은 다양성 관리에서 중요하게 다루어야 할 세 가지 과제–예상치 못한 변종의 발생 방지, 설계 복잡성 감축, 시장 점유율과 복잡성 비용 사이의 균형 잡기–를 해결하기 위한 방법론을 제안한다. 첫 번째 주제에서는, 아키텍처 기반의 접근법을 활용한 변종 관리 아키텍처(VA, variation architecture)를 도입하여 예상치 못한 변종의 발생을 방지하고자 한다. 개발 아키텍처는 모듈러 제품군을 개발할 때 사용하는 일종의 참조 아키텍처로, 시장 속성, 설계 모듈, 생산 설비의 연결관계를 정의하는 교차영역 연결 메커니즘을 제공한다. 변종 관리 아키텍처에서는 일반 수준의 계획과 변종 수준의 계획을 함께 세울 수 있다. 일반 수준에서는 요소 간 연결관계의 종류를 정의하여 제품군의 다양성 수준을 결정하고, 변종 수준에서는 변종들 간의 조합 규칙을 설정하여 불필요한 변종의 발생을 최소화한다. 또한, 본 연구에서는 제조업체가 변종 관리 아키텍처를 활용할 수 있도록 아키텍처 구축 프레임워크를 제안한다. 사례 연구에서는 자동차 프론트섀시 제품군을 통해 제품 및 변종의 수를 상당히 줄일 수 있음을 보여 줌으로써 프레임워크의 실용성을 검증한다. 다음으로, 인터페이스 표준화 개념을 적용하여 변종들 간의 복잡한 관계로부터 발생하는 설계 복잡성을 줄이는 연구를 수행한다. 본 연구에서 제안하는 인터페이스 설계 방법론은 하나가 아닌 다수의 표준 인터페이스를 사용하도록 허용한다. 모듈 변종들을 연결하기 위해 다수의 인터페이스를 도입하면, 인터페이스의 수와 적용범위에 따라 모듈러 제품군의 전체 구조가 달라지고 설계 복잡성 또한 다양한 양상으로 발생한다. 이를 측정하기 위해, 본 연구에서는 인터페이스의 선택에 영향을 받는 두 가지 복잡성 지표를–인터페이스 표준화 복잡성과 통합 복잡성을–정의한다. 인터페이스 표준화 복잡성은 표준 인터페이스를 설계할 때, 모듈 변종 설계자 간의 조율에 필요한 맨아워(person-hour)를 계산하고, 통합 복잡성은 각각의 모듈 변종과 인터페이스를 통합된 제품으로 설계하는데 필요로 하는 노력의 양으로, 위상적 복잡성(topological complexity) 지표를 기반으로 측정한다. 본 연구에서는 두 가지 복잡성을 최소화하는 인터페이스 설계 대안을 찾기 위한 프레임워크를 제공한다. 사례 연구에서 이의 적용성을 보여주기 위해 프론트섀시 제품군에 맞는 최적의 인터페이스 수와 제품군 구조를 도출한다. 마지막 주제에서는, 시장 점유율과 복잡성 비용의 균형을 맞추는 최적 제품 종수를 찾기 위한 최적화 모델을 개발한다. 최적화 모델은 제품을 구성하는 모듈 변종을 기반으로 모델링되고, 제품 및 모듈 종수가 증가함에 따라 시장 점유율의 증가분이 줄어들고, 반대로 복잡성 비용의 증가분은 늘어나는 특성을 반영한다. 시장 점유율을 구하기 위해 네스티드 로짓 모델(nested logit model)을 기반으로 하는 수요 모델을 개발한다. 네스티드 로짓 모델에서는 동일 제품군 내 제품들의 유사성을 고려하여 시장 점유율의 증가분이 줄어드는 특성을 반영한다. 다음으로, 제로베이스 원가계산 접근법(zero-based costing approach)을 활용한 복잡성 비용 모델을 도입한다. 이 접근법에서는 제품 혹은 모듈의 종수가 한 단위씩 늘어날 때 발생하는 비용을 단계적으로 계산하는 방법을 사용한다. 마지막으로, 수요 모델과 복잡성 비용 모델을 합친 최적화 모델(optimization model)을 모델링하여 최적 제품 종수와 제품의 모듈 구성을 도출하는 연구를 수행한다. 사례 연구에서는 민감도 분석을 수행하여 각 상황별 최적해가 어떻게 달라지는 지 보여주어 연구에서 제안하는 모델들의 효과를 검증한다.Global manufacturing companies have been achieving product variety by implementing a modular design strategy in which product variants are created by combining, adding, or substituting modules. Providing a high variety of products, however, causes negative effects not only on design but also on market and production. Variety management that defines the right range of variants is one of the most critical issues for most of the manufacturing companies. This thesis aims to propose methodologies that enable companies to systematically reduce negative effects of variety. In order to achieve successful variety management, this study approaches the issue from two viewpoints: cross-domain and variant-level viewpoints. A cross-domain viewpoint supports establishing relationships between elements in market, design, and production domain that are affected by product variety, and a variant-level viewpoint enables to explicitly manage variants of elements that are the main source of negative effects. In these viewpoints, this thesis focuses on dealing with three important challenges in variety management: to prevent unexpected variants, to reduce design complexity, and to balance market share and complexity cost. In the first theme, an architecture-based approach named variation architecture is introduced to prevent unexpected variants. Variation architecture (VA) is defined as a reference architecture for a modular product family providing the scheme by which variants in market, design, and production domain are arranged by cross-domain mapping mechanisms. The VA consists of generic-level and variant-level plans. At the generic-level, mapping types between domain elements are determined, and at the variant-level, combination rules between variants are set to reduce unexpected variants. Then, a framework is proposed to increase the practicality of the VA so that its compositions are well defined. In the case study, the framework is applied to an automobile front chassis family. The result shows that the number of module variants is significantly reduced compared to the current number of variants in operation. Secondly, the concept of interface standardization is introduced to manage design complexity caused by complicated combinations between module variants. This theme proposes an interface design methodology that addresses multiple standard interfaces in a modular product family. A product family structure is changed by implementing multiple standard interfaces, generating design complexity. This study defines two complexities resulting from the introduction of multiple standard interfaces: standardization effort and integration effort. Standardization effort is estimated as a required person-hours for coordinating module variants to design a standard interface, and integration effort is measured as an effort to integrate all design elements based on the concept of topological complexity. A framework is proposed to identify an optimal product family structure that minimizes the two complexities. In the case study, the proposed framework identifies an optimal structure and the number of standard interfaces for the front chassis family. Then, the study conducts a sensitivity analysis to demonstrate the methodologys applicability in interface management. In the last theme, an optimization model is developed to identify an optimal product variety to balance market share and complexity cost. The model focuses on module variants, not just product variants, because a modular product family creates product variants by combining module variants. The model reflects the trends of concave increase in market share and convex increase in complexity cost as the number of variety increases. A demand model is developed by the nested logit model that shows the concavity of market share based on the similarity of product variants in the same family, and a complexity cost model is constructed by the zero-based costing approach that an incremental cost is estimated as a variant is added. Combining the models, an optimization model is formulated to find an optimal variety and configurations of product variants. The case study demonstrates the models effectiveness by analyzing optimal solutions in various situations.Abstract i Contents iv List of Tables viii List of Figures ix Chapter 1 Introduction 1 1.1 Variety Management 1 1.2 Variety Management Challenges 5 1.3 Research Proposal: How to Deal with the Challenges? 7 1.4 Structure of Thesis 10 Chapter 2 Literature Review 11 2.1 Variety Management Methodologies 11 2.1.1 Modular product family design 11 2.1.2 Product family architecture 13 2.1.3 Classification of the contributions 15 2.2 Modular Design and Complexity 17 2.2.1 Modular design 17 2.2.2 Interface design 19 2.2.3 Design complexity 20 2.3 Product Family Design and Variety 22 2.3.1 Product family design 22 2.3.2 Variety optimization 25 Chapter 3 Variation Architecture for Reducing the Generation of Unexpected Variants 29 3.1 Introduction 29 3.1.1 Generation of unexpected variants 29 3.1.2 Needs for a systematic approach 31 3.2 Variation Architecture (VA) 33 3.2.1 Generic-level planning 34 3.2.2 Variant-level planning 41 3.3 Framework for Planning Product Variety 46 3.4 Application 47 3.4.1 Case description 47 3.4.2 Construction of variation architecture (VA) 49 3.4.3 Result and discussion 53 3.5 Summary 57 Chapter 4 Variant-level Interface Design for Reducing Design Complexity 59 4.1 Introduction 59 4.2 Variant-level Interface Design 61 4.3 Interface Design Complexity 64 4.3.1 Standardization effort 66 4.3.2 Integration effort 71 4.4 Framework for Variant-level Interface Design 76 4.5 Case Study 79 4.5.1 Application of the framework 79 4.5.2 Analysis and discussion 84 4.6 Summary 88 Chapter 5 Optimizing Product Variety for Balancing Market Share and Complexity Cost 91 5.1 Introduction 91 5.2 Evidence of the impact of variety on market share 94 5.3 Planning of Product Configurations 96 5.3.1 Product family architecture 96 5.3.2 Product configuration 98 5.4 Variety Optimization Model 100 5.4.1 Demand model 100 5.4.2 Complexity cost model 104 5.4.3 Optimization model 108 5.5 Case Study 110 5.5.1 Case description 110 5.5.2 Data source 112 5.5.3 Optimization setting 113 5.5.4 Result 115 5.5.5 Discussion 118 5.6 Summary 122 Chapter 6 Conclusion 125 6.1 Summary of Contributions 125 6.2 Limitations and Future Research Directions 127 Bibliography 129 Appendix A Variant-level Plan of a Front Chassis Family 147 Appendix B Adjacency and Combination Matrices of a Front Chassis Family 151 국문초록 155Docto

Lost in optimisation of water distribution systems? A literature review of system design

This is the final version of the article. Available from MDPI via the DOI in this record.Optimisation of water distribution system design is a well-established research field, which has been extremely productive since the end of the 1980s. Its primary focus is to minimise the cost of a proposed pipe network infrastructure. This paper reviews in a systematic manner articles published over the past three decades, which are relevant to the design of new water distribution systems, and the strengthening, expansion and rehabilitation of existing water distribution systems, inclusive of design timing, parameter uncertainty, water quality, and operational considerations. It identifies trends and limits in the field, and provides future research directions. Exclusively, this review paper also contains comprehensive information from over one hundred and twenty publications in a tabular form, including optimisation model formulations, solution methodologies used, and other important details

Listing Unique Fractional Factorial Designs

Fractional factorial designs are a popular choice in designing experiments for studying the effects of multiple factors simultaneously. The first step in planning an experiment is the selection of an appropriate fractional factorial design. An appro- priate design is one that has the statistical properties of interest of the experimenter and has a small number of runs. This requires that a catalog of candidate designs be available (or be possible to generate) for searching for the "good" design. In the attempt to generate the catalog of candidate designs, the problem of design isomor- phism must be addressed. Two designs are isomorphic to each other if one can be obtained from the other by some relabeling of factor labels, level labels of each factor and reordering of runs. Clearly, two isomorphic designs are statistically equivalent. Design catalogs should therefore contain only designs unique up to isomorphism. There are two computational challenges in generating such catalogs. Firstly, testing two designs for isomorphism is computationally hard due to the large number of possible relabelings, and, secondly, the number of designs increases very rapidly with the number of factors and run-size, making it impractical to compare all designs for isomorphism. In this dissertation we present a new approach for tackling both these challenging problems. We propose graph models for representing designs and use this relationship to develop efficient algorithms. We provide a new efficient iso- morphism check by modeling the fractional factorial design isomorphism problem as graph isomorphism problem. For generating the design catalogs efficiently we extend a result in graph isomorphism literature to improve the existing sequential design catalog generation algorithm. The potential of the proposed methods is reflected in the results. For 2-level regular fractional factorial designs, we could generate complete design catalogs of run sizes up to 4096 runs, while the largest designs generated in literature are 512 run designs. Moreover, compared to the next best algorithms, the computation times for our algorithm are 98% lesser in most cases. Further, the generic nature of the algorithms makes them widely applicable to a large class of designs. We give details of graph models and prove the results for two classes of designs, namely, 2-level regular fractional factorial designs and 2-level regular fractional factorial split-plot designs, and provide discussions for extensions, with graph models, for more general classes of designs

Assembly Line

An assembly line is a manufacturing process in which parts are added to a product in a sequential manner using optimally planned logistics to create a finished product in the fastest possible way. It is a flow-oriented production system where the productive units performing the operations, referred to as stations, are aligned in a serial manner. The present edited book is a collection of 12 chapters written by experts and well-known professionals of the field. The volume is organized in three parts according to the last research works in assembly line subject. The first part of the book is devoted to the assembly line balancing problem. It includes chapters dealing with different problems of ALBP. In the second part of the book some optimization problems in assembly line structure are considered. In many situations there are several contradictory goals that have to be satisfied simultaneously. The third part of the book deals with testing problems in assembly line. This section gives an overview on new trends, techniques and methodologies for testing the quality of a product at the end of the assembling line