Rafael de Carvalho Miranda

A New Approach to Reducing Search Space and Increasing Efficiency in Simulation Optimization Problems via the Fuzzy-DEA-BCC

The development of discrete-event simulation software was one of the most successful interfaces in operational research with computation. As a result, research has been focused on the development of new methods and algorithms with the purpose of increasing simulation optimization efficiency and reliability. This study aims to define optimum variation intervals for each decision variable through a proposed approach which combines the data envelopment analysis with the Fuzzy logic (Fuzzy-DEA-BCC), seeking to improve the decision-making units’ distinction in the face of uncertainty. In this study, Taguchi’s orthogonal arrays were used to generate the necessary quantity of DMUs, and the output variables were generated by the simulation. Two study objects were utilized as examples of mono- and multiobjective problems. Results confirmed the reliability and applicability of the proposed method, as it enabled a significant reduction in search space and computational demand when compared to conventional simulation optimization techniques.

Integrating soft systems methodology to aid simulation conceptual modeling

Discrete-event simulation is considered an increasingly common support tool for decision making, especially in manufacturing. Most simulation projects are divided into three distinct phases: conception, implementation, and analysis. Some authors believe the conception phase is the most important, as the simulation study objectives are defined and the projects foundation is laid at this point. Many researchers do not spend the necessary amount of time on this important initial phase. Thus, this article presents an integration method that makes use of soft systems methodology (SSM), a complex problem-solving approach, during the conceptual phase of simulation studies. SSM was used throughout the conceptual modeling phase for a real manufacturing simulation case study. Through the analysis of this study, it can be concluded that the use of SSM to develop the conceptual model enabled identification of the study objectives, thus avoiding errors and reworks. The studys results are presented and the methods application is justified by presenting a valid model capable of analyzing the systems key input variables.

Interactive learning of modeling and discrete-events simulation through Lego® parts

A discrete-events simulation course should develop in its students not only the abilities related to the programming language and statistical analysis, but also the ability to create an abstract of a real system into a model system. Thus, this paper has the objective to develop and evaluate an educational dynamic project for discrete event simulation courses, which are capable of developing the students ability to perform abstraction and representation of real systems in a conceptual and computational model. To meet this objective, Lego® was used in the educational dynamic. For the evaluation of the motivation presented by the students in the dynamic, the ARCS (Attention, Relevance, Confidence, Satisfaction) technique was used together with an Instructional Materials Motivational Survey (IMMS) questionnaire. An indicator was established to measure the students utilization and/or knowledge gained. The results demonstrate that the dynamic reached its objective, presenting a high utilization in the motivational criteria analyzed.

Sensitivity Analysis in Discrete Event Simulation Using Design of Experiments

However, one of simulation’s greatest disadvantages is that, on its own, it does not serve as an optimization technique [7]. This forces simulation practitioners to simulate multiple system configurations and choose the one which presents the best system performance. Computational development has helped alter this scenario due to the increasing availability of faster computers and ever improving search and heuristic optimization techniques.

Identification of the main methods used in simulation projects

Discrete event simulation is a tool to support decision-making that has been increasingly used to study complex systems. Several simulation research methods are found in the literature, each one has its own characteristics, to guide analysts during the development of simulation projects. In view of this, the current work identified the main research methods used in simulation projects. For this, a literature review was carried out on some of the major discrete event simulation books and papers from the proceedings of the Winter Simulation Conference, which is considered the main international conference on simulation. From the analysis performed in this study, it was possible to identify the most comprehensive methods, as well as the simplest ones. The common activities among them were presented and those that are important to conduct a simulation project were also discussed.

Increasing the efficiency in integer simulation optimization: Reducing the search space through data envelopment analysis and orthogonal arrays

The development of various heuristics has enabled optimization in simulation environments. Nevertheless, this research area remains underexplored, primarily with respect to the time required for convergence of these heuristics. In this sense, simulation optimization is influenced by the complexity of the simulation model, the number of variables, and by their ranges of variation. Within this context, this paper proposes a method capable of identifying the best ranges for each integer decision variable within the simulation optimization problem, thereby providing a reduction in computational cost without loss of the quality in the response. The proposed method combines experimental design techniques, Discrete Event Simulation, and Data Envelopment Analysis. The experimental designs called orthogonal arrays are used to generate the input scenarios to be simulated, and super-efficiency analysis is applied in a Data Envelopment Analysis model with variable returns to scale to rank the input scenarios. The use of the super-efficiency concept enables to distinguish the most efficient input scenarios, which allows for the ranking of all the orthogonal array scenarios used. The values of the variables of the two input scenarios that present the highest values of super-efficiency are adopted as the new range of the optimization problem. To illustrate this methods use and advantages, it was applied to real cases associated with integer simulation optimization problems. Based on the results, the effectiveness of this approach is verified because it delivered considerable reductions in the search space and in the computational time required to obtain a solution without affecting the quality.

OTIMIZAÇÃO DOS PARÂMETROS DE SOLDAGEM A PONTO POR RESISTÊNCIA EM UMA INDÚSTRIA AUTOMOTIVA POR MEIO DA ANÁLISE DE EXPERIMENTOS E METODOLOGIA DE SUPERFÍCIE DE RESPOSTA

Uma das formas de se alcancar as caracteristicas de competitividade ou fatores criticos e, atender as necessidades e expectativas dos consumidores e por meio da aplicacao das tecnicas de projeto e analise de experimentos e metodologia de superficie de resposta, uma vez que o uso em conjunto destas tecnicas, possibilita a determinacao dos melhores ajustes para obtencao do resultado desejado. Nesse sentido, este trabalho tem por objetivo aplicar estas tecnicas, para otimizacao dos parâmetros envolvidos em um processo de soldagem a ponto por resistencia. Como parte deste objetivo, desenvolve-se uma aplicacao com a tecnica de planejamento fatorial completo, com intuito de descobrir quais parâmetros envolvidos no processo em questao (corrente, forca, tempo de solda e tempo de pre-solda), realmente promovem efeito significativo na resposta (resistencia a tracao). Com a realizacao dos experimentos e analise dos dados gerados pelo software MINITAB, verifica-se que sao significativos somente os parâmetros corrente e forca. A partir de entao, utiliza-se a tecnica do planejamento composto central, em seguida determina-se o ponto estacionario e, por fim, faz-se a analise dos autovalores da matriz Hessiana para determinacao dos valores de corrente e forca que promovem o melhor desempenho quanto a resistencia a tracao. Palavras-chave: projeto e analise de experimentos; metodologia de superficie de resposta; otimizacao; processo de soldagem a ponto por resistencia. ABSTRACT One way to achieve the competitive characteristics or critical factors and meet the needs and expectations of consumers is through the application of design techniques and analysis of experiments and response surface methodology, since the combined use of these techniques, enables the determination of optimal settings for obtaining the desired result. In this sense this paper aims to apply these techniques to optimization of the parameters involved in a resistance spot welding process. As part of this goal, an application is developed with the technique of full factorial design, in order to discover which parameters involved in the process in question (power, strength, weld time and pre weld time), actually promote significant effect on response (tensile strength). With the experiments and analyzing the data generated by the software MINITAB, it appears that only the current and strength parameters are significant. Thereafter, the technique of central composite design is used, the stationary point is determined and finally the analysis of eigenvalues of the Hessian matrix is conducted to determine the current and strength values that promote better performance in terms of tensile strength. Keywords: design and analysis of experiments, response surface methodology, optimization, resistance spot welding process.

Análise da aplicação da filosofia Kaizen para melhoria da capacidade de projetos de engenharia em uma empresa do setor energético

A participacao de todos nos processos de melhoria e de fundamental importância para o sucesso das organizacoes. E necessario que toda a equipe esteja motivada a alcancar as metas globais da empresa. Este artigo tem como objetivo principal a analise da metodologia de aplicacao da ferramenta Kaizen no departamento de Engenharia de uma empresa do setor energetico. Para isto sao apresentados, alem dos conceitos relacionados a filosofia Kaizen, os objetivos do departamento, as etapas e ferramentas utilizadas durante o evento Kaizen e os resultados obtidos pela equipe. Esta analise tambem busca ressaltar a importância da criacao de uma cultura organizacional que valorize o trabalho em grupo, onde todos colocam suas sugestoes para melhoria continua do processo. O principal resultado deste evento Kaizen foi o aumento da capacidade e da produtividade do departamento de Engenharia, por meio da melhoria do fluxo de informacoes, da identificacao das responsabilidades de cada setor e da padronizacao dos documentos.

UM MODELO FUZZY-DEA-GAME PARA ESTRATÉGIAS DE PRODUÇÃO SOB INCERTEZA

This study develops a new Fuzzy-DEA-Game (FDG) model to support the establishment of production strategies. This model combines Data Envelopment Analysis (DEA) with concepts of Fuzzy Set Theory and Nash Bargaining Game. The model permits an evaluation of the productive and economic efficiency of products, which may result in a portfolio of more profitable products with greater consumer market interest. The model was applied at an energy company. The results obtained applying the FDG model adhered to the reality of the studied company and provided goals for reducing resource levels (inputs) needed for manufacturing products and for increasing result levels (output) stemming from their commercialization. As an important additional outcome, the FDG model permitted the identification of portfolio products that are more sensitive to the occurrence of uncertainty.

Otimização dos parâmetros de pintura com múltiplas respostas: um estudo em problemas de pintura em anéis automotivos

The use of optimization assists in decision making in many industrial and business problems. The objective of this paper is to present a practical application of optimization with multiple responses to problems related to painting automotive rings, and evaluate the performance of these methods with the application of DOE (Design of Experiments). The spray painting system has showed significant advantages compared to other painting application methods. This is used as a reference for identifying the assembly of the piston rings. Considering this application system some variables were optimized: thickness of the paint, the paint strip width and the distance of the track. The parameters used included the distance of the application, the machine operating pressure and speed of application. The results showed the importance of choosing the correct method, aiming at obtaining results closer to the reality of the analyzed problem.