Optimization Methods in Modern Transportation Systems

One of the greatest challenges in the public transportation network is the optimization of the passengers waiting time, where it is necessary to find a compromise between the satisfaction of the passengers and the requirements of the transport companies. This paper presents a detailed review of the available literature dealing with the problem of passenger transport in order to optimize the passenger waiting time at the station and to meet the requirements of companies (maximize profits or minimize cost). After a detailed discussion, the paper clarifies the most important objectives in solving a timetabling problem: the requirements and satisfaction of passengers, passenger waiting time and capacity of vehicles. At the end, the appropriate algorithms for solving the set of optimization models are presented

Optimising the process parameters of selective laser melting for the fabrication of Ti6Al4V alloy

This is the author accepted manuscript. The final version is available from Emerald via the DOI in this recordPurpose- Surface roughness is an important evaluation index for industrial components and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This paper aims to obtain an optimum SLM parameter set to improve the surface roughness of Ti6Al4V samples. Design/methodology/approach- A response surface methodology (RSM) based approach is proposed to improve the surface quality of selective laser molten Ti6Al4V parts and understand the relationship between the selective laser melting (SLM) process parameters and the surface roughness. The main SLM parameters (i.e. laser power, scan speed and hatch spacing) are optimised and Ti6Al4V parts are manufactured by the SLM technology with no post processes. Findings- Optimum process parameters were obtained using the RSM method to minimise the roughness of the top and vertical side surfaces. Obtained parameter sets were evaluated based on their productivity and surface quality performance. The validation tests have been performed and the results verified the effectivity of the proposed technique. It was also shown that the top and vertical sides must be handled together to obtain better top surface quality. Practical implications- The obtained optimum SLM parameter set can be used in the manufacturing of Ti6Al4V components with high surface roughness requirement. Originality/value- RSM is used to analyse and determine the optimal combination of SLM parameters with the aim of improving the surface roughness quality of Ti6Al4V components, for the first time in the literature. Also, this is the first study which aims to simultaneously optimise the surface quality of top and vertical sides of titanium alloys.This research was supported by the National High Technology Research and Development Program of China (863 Program: 2015AA042501)

SIMULACIÓN DE SISTEMAS PRODUCTIVOS NO BALANCEADOS: APLICACIÓN A LA PRODUCCIÓN DE MEZCAL (SIMULATION OF NONBALANCED PRODUCTION SYSTEMS: APPLICATION TO MEZCAL PRODUCTION)

ResumenLa simulación es aplicable a diferentes ramas técnicas del saber humano y por ende a sistemas administrativos y de negocios. El contexto de su tratamiento permite lograr importantes ahorros y es una herramienta poderosa de apoyo para la toma de decisiones bajo la representación de diferentes escenarios y lapsos de tiempo donde los sistemas se tornan complejos por la gran cantidad de variables que en estos interactúan.Este proyecto expone el método para la construcción de un modelo de simulación mediante el software ProModel para analizar sistemas de producción no balanceados en la industria de bebidas alcohólicas. El modelo asume que, los tiempos de proceso son deterministas. El estudio incluye una revisión de la literatura, conceptos de modelado y simulación, áreas de aplicación, análisis de datos, construcción de un modelo de simulación y análisis de resultados. Como conclusión, los datos indican que un pequeño aumento en la capacidad de algunos equipos, se traduciría en un mayor desempeño del sistema.Palabras Clave: Modelo, Simulación, ProModel, Sistemas de Producción No Balanceados. Abstract The simulation is applicable to different technical branches of human knowledge and therefore to administrative and business systems. The context of its treatment allows to achieve important savings and is a powerful support tool for decision making under the representation of different scenarios and time lapses where systems become complex due to the large number of variables that interact in them.This project exposes the method for the construction of a simulation model using ProModel software to analyze unbalanced production systems, applied in a Mezcal production plant. The model assumes that, the process times are deterministic. The study includes a review of the literature, concepts of modeling and simulation, areas of application, data analysis, construction of a simulation model and analysis of results. In conclusion, the data indicate that an increase in the capacity of some equipment, would result in a better performance of the system.Keywords: Mezcal, Model, Simulation, ProModel, Unbalanced Production Systems

Type-E Parallel Two-Sided Assembly Line Balancing Problem: Mathematical Model and Ant Colony Optimisation based Approach with Optimised Parameters

Copyright © 2015 Elsevier. This is a PDF file of an unedited manuscript that has been accepted for publication in Computers and Industrial Engineering (doi:10.1016/j.cie.2014.12.037). The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.There are many factors which affect the performance of a complex production system. Efficiency of an assembly line is one of the most important of these factors since assembly lines are generally constructed as the last stage of an entire production system. Parallel two-sided assembly line system is a new research domain in academia though these lines have been utilised to produce large sized products such as automobiles, trucks, and buses in industry for many years. Parallel two-sided assembly lines carry practical advantages of both parallel assembly lines and two-sided assembly lines. The main purpose of this paper is to introduce type-E parallel two-sided assembly line balancing problem for the first time in the literature and to propose a new ant colony optimisation based approach for solving the problem. Different from the existing studies on parallel assembly line balancing problems in the literature, this paper aims to minimise two conflicting objectives, namely cycle time and number of workstations at the same time and proposes a mathematical model for the formal description of the problem. To the best of our knowledge, this is the first study which addresses both conflicting objectives on a parallel two-sided assembly line configuration. The developed ant colony optimisation algorithm is illustrated with an example to explain its procedures. An experimental design is also conducted to calibrate the parameters of the proposed algorithm using response surface methodology. Results obtained from the performed computational study indicate that minimising cycle time as well as number of workstations help increase system efficiency. It is also observed that the proposed algorithm finds promising results for the studied cases of type-E parallel two-sided assembly line balancing problem when the results are compared with those obtained from other three well-known heuristics

Modelling and optimization of average travel time for a metro line by simulation and response surface methodology

This research presents a modelling and solution approach based on discrete-event simulation and response surface methodology for dealing with average passenger travel time optimization problem inherent to the metro planning process. The objective is to find the headways optimizing passenger average travel time with a satisfactory rate of carriage fullness. Due to some physical constraints, traffic safety and legal requirements, vehicle speeds cannot be raised any further to decrease travel time. But travel time can be optimized by arranging headways (i.e. the time period between the departure times of two consecutive transportation vehicles) in a timetable. In the presented approach, simulation metamodels that best fit the data collected from the simulated experiments are constructed to describe the relationship between the responses (average travel time and rate of carriage fullness) and input factors (headways). Then, the Derringer-Suich multi-response optimization procedure is used to determine the optimal settings of the input factors that produce the minimum value of the average travel time by providing a proper rate of carriage fullness. This methodology is applied for a real metro line, and good quality solutions are obtained with reduced number of experiments that needed to provide sufficient information for statistically acceptable results. (C) 2008 Elsevier B.V. All rights reserved

Modelling and optimization of average travel time for a metro line by simulation and response surface methodology

This research presents a modelling and solution approach based on discrete-event simulation and response surface methodology for dealing with average passenger travel time optimization problem inherent to the metro planning process. The objective is to find the headways optimizing passenger average travel time with a satisfactory rate of carriage fullness. Due to some physical constraints, traffic safety and legal requirements, vehicle speeds cannot be raised any further to decrease travel time. But travel time can be optimized by arranging headways (i.e. the time period between the departure times of two consecutive transportation vehicles) in a timetable. In the presented approach, simulation metamodels that best fit the data collected from the simulated experiments are constructed to describe the relationship between the responses (average travel time and rate of carriage fullness) and input factors (headways). Then, the Derringer-Suich multi-response optimization procedure is used to determine the optimal settings of the input factors that produce the minimum value of the average travel time by providing a proper rate of carriage fullness. This methodology is applied for a real metro line, and good quality solutions are obtained with reduced number of experiments that needed to provide sufficient information for statistically acceptable results.Average passenger travel time Optimization Simulation Metamodel Response surface methodology The Derringer-Suich optimization procedure

Utilização da Metodologia de Superfície de Resposta para otimização de Modelos de Simulação a Eventos Discretos.

Modelos de simulação são frequentemente aplicados à otimização de problemas complexos, que não podem ser resolvidos por métodos analíticos ou matemáticos. O presente trabalho busca analisar a aplicação da Metodologia de Superfície de Resposta (MSR) como uma forma organizada e eficiente de buscar a otimização na Simulação a Eventos Discretos (SED). Ele é categorizado como uma pesquisa quantitativa usando ferramentas estatísticas e o método de pesquisa de experimentação, seguindo um modelo empírico normativo. Os resultados encontrados são representados por meio dos valores de cada variável de entrada do Delineamento de Experimentos (DOE) obtido no ponto ótimo. Depois disso, é feita uma comparação com os resultados da otimização utilizada aqui com os de um software de mercado, em que foi constatado a eficácia do modelo de otimização adotado em quatro objetos de estudo. Sendo ainda que, o ponto ótimo foi atingido com uma redução de cerca de 80 % no número de experimentos, além das análises de sensibilidades geradas pela MSR

Development, implementation and performance evaluation of a self-tuning regulator adaptive controller applied to a FCC process

Orientador: Rubens Maciel FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Este trabalho teve como principal objetivo o desenvolvimento e implementação de um controlador adaptativo do tipo regulador auto-ajustável (STR - Self Tuning Regulator), com a subsequente comparação de seu desempenho com um controlador PID (proporcionalintegrativo-derivativo) e dois controladores preditivos: um preditivo baseado em redes neurais artificiais e um controlador DMC (Dynamic Matrix Control). Esses esquemas de controle foram todos implementados na ferramenta de simulação desenvolvida, o FCCGUI (Fluid Catalytic Cracking Graphical User Interface). Como modelo para estimativa dos parâmetros do controlador adaptativo foi treinada e validada uma rede neural. Esse modelo caixa-preta forneceu uma abordagem eficiente para identificação e controle não-linear do processo de craqueamento catalítico. Para implementação do controlador adaptativo foram estruturadas três novas malhas de controle PID a partir de estudos estatísticos desenvolvidos para a análise dos efeitos das variáveis de processo e suas interações. Dentre essas novas malhas de controle, optou-se pela implementação do controle adaptativo no par manipulada-controlada CTCV-SEVER (abertura de catalisador regenerado - severidade da reação). Após aperfeiçoamentos e reestruturações no simulador FCCGUI, foram realizadas várias simulações para avaliação gráfica e numérica do desempenho do controlador através do critério de desempenho dinâmico ITAE (Integral of Time and Absolute Error). O controlador adaptativo apresentou bons resultados, tanto para testes servo quanto para regulatórios em comparação com a estratégia PID sem adaptação, bem como para as demais estratégias disponíveis no simulador, MPC-RNA (Model Predictive Control baseado em uma Rede Neural Artificial) e DMC. A capacidade de ajuste dos parâmetros do controlador torna-o uma estratégia promissora para sistemas que sofrem com alterações contínuas em suas variáveis de processo ou mudanças de setpointAbstract: This work had as main objective the development and implementation of an selftuning regulator (STR) adaptive controller, with subsequent comparison of its performance with a PID (proportional-integral-derivative) controller and two predictive controllers, namely a predictive based on artificial neural networks (MPC-ANN) and a dynamic matrix controller (DMC). These control schemes were all implemented in the developed simulation tool, the FCCGUI - Fluid Catalytic Cracking Graphical User Interface. An artificial neural network, used as a model to estimate controller parameters, was trained and validated. This black box model provided an efficient approach for identification and nonlinear control of the catalytic cracking process. To implement the adaptive controller, three new PID control loops were structured based on statistical studies designed to analyze the effects of process variables and their interactions. The implementation of adaptive control was chosen to be in the manipulated-controlled pair CTCV-SEVER (regenerated catalyst valve opening - reaction severity). After restructuring and improvements in the simulator FCCGUI, several simulations were performed for graphical and numerical evaluation of controller performance through ITAE (Integral of Time and Absolute Error) dynamic performance criterion. The adaptive controller presented good results for both tests: servo and regulatory, in comparison with PID strategy without adaptation and other strategies available to the simulator, MPC-ANN and DMC. The ability to adjust the parameters of the controller makes it a promising strategy for systems that suffer from continuous changes in their process variables or setpointsDoutoradoDesenvolvimento de Processos QuímicosDoutor em Engenharia Químic