43 research outputs found

    Bio-inspired multi-objective algorithms applied on production scheduling problems

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    Production scheduling is a crucial task in the manufacturing process. In this way, the managers must decide the job's production schedule. However, this task is not simple, often requiring complex software tools and specialized algorithms to find the optimal solution. In this work, a multi-objective optimization model was developed to explore production scheduling performance measures to help managers in decision-making related to job attribution under three simulations of parallel machine scenarios. Five important production scheduling performance measures were considered (makespan, tardiness and earliness times, number of tardy and early jobs), and combined into three objective functions. To solve the scheduling problem, three multi-objective evolutionary algorithms are considered (Multi-objective Particle Swarm Optimization, Multi-objective Grey Wolf Algorithm, and, Non-dominated Sorting Genetic Algorithm II), and the set of optimum solutions named Pareto Front, provided by each one is compared in terms of dominance, generating a new Pareto Front, denoted as Final Pareto Front. Furthermore, this Final Pareto Front is analysed through an automatic bio-inspired clustering algorithm based on the Genetic Algorithm. The results demonstrated that the proposed approach efficiently solves the scheduling problem considered. In addition, the proposed methodology provided more robust solutions by combining different bio-inspired multi-objective techniques. Furthermore, the cluster analysis proved fundamental for a better understanding of the results and support for choosing the final optimum solution.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020 and EXPL/EME-SIS/1224/2021. Beatriz Flamia Azevedo is supported by FCT Grant Reference SFRH/BD/07427/2021 The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CeDRI (UIDB/05757/2020 and UIDP/05757/2020) and SusTEC (LA/P/0007/2021).info:eu-repo/semantics/publishedVersio

    A methodology of improvement of manufacturing productivity through increasing operational efficiency of the production process

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    One of the most important aspects of manufacturing efficiency assessment is the determination of productivity. A study of the relevant literature and a review of business practices have led the authors to conclude that there is a niche for a comprehensive decision support methodology which would assist organizations in improving their manufacturing productivity. This paper presents a methodology of improvement of manufacturing productivity through increasing operational efficiency of the manufacturing process. The methodology was verified by a manufacturing company which is a supplier of goods for i.e. the automotive and medical industries. The effect of using methodology is reducing of cycle of lot, reducing number of changeovers and eliminating errors.This work has been supported by COMPETE: POCI01-0145-FEDER-007043 and FCT – Portuguese Foundation for Science and Technlology within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

    Simulation of cyber physical systems behaviour using timed plant models

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    When developing a reliable controller for cyber-physical systems, one of the main issues is to guarantee that all behaviour properties of such systems will be accomplished. For this purpose, it is very important to find and use formalisms and tools in order to model the controller and the respective plant. Moreover, it is very important to consider the same formalism for modelling both. The accurate model of a plant is usually difficult to obtain. To solve this problem, several techniques for modelling the plant have been developed in the recent past years. However, some of them have lacks that do not allow a fast, reliable and flexible way for plant modelling. In this paper a systematic approach for modelling cyber physical systems using timed automata is presented. The proposed approach allows defining a systematic way for creating global models for both the plant and the controller. These models, may be used to simulate and validate the cyber physical systems. For this purpose software tools, as UPPAAL, and other simulation configurations, as Model-in-the-loop and Hardware-in-the-loop, can be used. In order to present and explain the proposed methodology, a virtual platform and a physical workbench have been developed, from a transport objects station example, where Model-in-the-loop and Hardware-in-the-loop configurations are used in a subsequent manner in the context of the presented system modelling methodology.The authors are grateful to the Research Centres MEtRICs and Algoritmi for funding. Authors also want to thank OMRON Company for being partner in this project and supplying all controllers, networks and communication protocols that have been used on the context of the project.This work was funded by FEDER funds through the "Programa Operacional Factores de Competitividade - COMPETE" and by national funds by FCT- Fundacao para a Ciencia e a Tecnologia, project reference FCOMP-01-0124-FEDER-022674.info:eu-repo/semantics/publishedVersio

    The tool supporting decision making process in area of job-shop scheduling

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    Today most manufacturing companies from machine building industry are operating in single unit or short-run production which is very complex in terms of decision making processes in production planning area. The difficulty in decision making in the area of scheduling is caused by the necessity of analy sing multiple factors and evaluating various scheduling options due to numerous criteria. The article presents the author’s tool supporting decision making in the area of job-shop scheduling. The tool introduced in the article enables scheduling based on author’s priority rule allowing maximum usage of the most loaded resource (known as critical resource), which determines efficiency of the produc tion system. The tool has been designed and verified as a part of PhD dissertation research.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

    Cycle time reduction in deck roller assembly production unit with value stream mapping analysis

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    Cycle time reduction is of paramount importance in a manufacturing industry as the customer not only emphasizes on the quality of the product but also takes into consideration the timely delivery of the product. The proposed framework and the advanced methodology in this paper are capable of dealing with each stage of the considered manufacturing unit by maximizing the value of the product through reduction of cycle times and minimization of waste. The time required for all the processes in the manufacturing of the deck rollers is identified and are classified into value added (VA) and non-value added (NVA). Finally, the cycle times were reduced by applying the lean tools and principles on some managerial relevances. Also, Arena software was used to simulate the current and future value stream maps and the change in the cycle times, waiting times, machine utilization, etc. was determined.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

    A Cloud-Based Architecture with embedded Pragmatics Renderer for Ubiquitous and Cloud Manufacturing

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    The paper presents a Cloud-based architecture for Ubiquitous and Cloud Manufacturing as a multilayer communicational architecture designated as the Communicational Architecture. It is characterised as (a) rich client interfaces (Rich Internet Application) with sufficient interaction to allow user agility and competence, (b) multimodal, for multiple client device classes support and (c) communicational to allow pragmatics, where human-to-human real interaction is completely supported. The main innovative part of this architecture is sustained by a semiotic framework organised on three main logical levels: (a) device level, which allows the user `to use' pragmatics with the system, (b) application level which results for a set of tools which allows users pragmatics-based interaction and (c) application server level that implements the Pragmatics renderer,a pragmatics supporting engine that supports all pragmatics services. The Pragmatics renderer works as a communication enabler, and consists of a set of integrated collaboration technology that makes the bridge between the user/devices and the `system'. A federated or community cloud is developed using a particular cloud REST ful Application Programming Interface that supports (cloud) services registration, composition and governance (pragmatics services behaves as SaaS in the cloud).The work is supported by the Portuguese National Funding Agency for science, research and technology (FCT), (1) Grant No. UID/CEC/00319/2013, and (2) `Ph.D. Scholarship Grant' reference SFRH/BD/85672/2012.info:eu-repo/semantics/publishedVersio

    Telefacturing Based Distributed Manufacturing Environment for Optimal Manufacturing Service by Enhancing the Interoperability in the Hubs

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    Recent happenings are surrounding the manufacturing sector leading to intense progress towards the development of effective distributed collaborative manufacturing environments. This evolving collaborative manufacturing not only focuses on digitalisation of this environment but also necessitates service-dependent manufacturing system that offers an uninterrupted approach to a number of diverse, complicated, dynamic manufacturing operations management systems at a common work place (hub). This research presents a novel telefacturing based distributed manufacturing environment for recommending the manufacturing services based on the user preferences. The first step in this direction is to deploy the most advanced tools and techniques, that is, Ontology-based Protege 5.0 software for transforming the huge stored knowledge/information into XML schema of Ontology Language (OWL) documents and Integration of Process Planning and Scheduling (IPPS) for multijobs in a collaborative manufacturing system. Thereafter, we also investigate the possibilities of allocation of skilled workers to the best feasible operations sequence. In this context, a mathematical model is formulated for the considered objectives, that is, minimization of makespan and total training cost of the workers. With an evolutionary algorithm and developed heuristic algorithm, the performance of the proposed manufacturing system has been improved. Finally, to manifest the capability of the proposed approach, an illustrative example from the real-time manufacturing industry is validated for optimal service recommendation.This work has been supported by by COMPETE: POCI-01-0145-FEDER-007043 and FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

    Improving productivity and standard time updating in an industrial company - A case study

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    Today’s marketplace imposes ever-tightening product pricing and quality requirements, shorter delivery times, and increasingly customized products. With increasing competition in today’s global market, companies are increasingly pressured to improve the performance of their production systems in order to be more competitive and improve market share. In order to try to satisfy these requirements several companies seek for the application of methodologies that may enable them to respond to these challenges, such as the ones based on the Lean Manufacturing philosophy. In this work standard times of four extruders are determined and updated in the context of setup time’s analysis and minimization in a company, in Portugal. First, a diagnosis is made to the tire floor extrusion process in order to evaluate all of its inefficiencies with the greatest impact on the production process, after the standard time of each extruder is analysed and updated through an extended approach which does also consider setup times reduction, along with the production times, for reaching a higher process optimization rate and productivity in the underlying production system.This work has been supported by COMPETE: POCI01-0145-FEDER-007043 and FCT – Portuguese Foundation for Science and Technlology.info:eu-repo/semantics/publishedVersio

    Evaluation of the Simulated Annealing and the Discrete Artificial Bee Colony in the Weight Tardiness Problem with Taguchi Experiments Parameterization

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    Meta-Heuristics (MH) are the most used optimization techniques to approach Complex Combinatorial Problems (COPs). Their ability to move beyond the local optimums make them an especially attractive choice to solve complex computational problems, such as most scheduling problems. However, the knowledge of what Meta-Heuristics perform better in certain problems is based on experiments. Classic MH, as the Simulated Annealing (SA) has been deeply studied, but newer MH, as the Discrete Artificial Bee Colony (DABC) still need to be examined in more detail. In this paper DABC has been compared with SA in 30 academic benchmark instances of the weighted tardiness problem (1 parallel to Sigma w(j)T(j)). Both MH parameters were fine-tuned with Taguchi Experiments. In the computational study DABC performed better and the subsequent statistical study demonstrated that DABC is more prone to find near-optimum solutions. On the other hand SA appeared to be more efficient.This work is supported by FEDER Funds through the "Programa Operacional Factores de Competitividade - COMPETE" program and by National Funds through FCT "Fundacao para a Ciencia e a Tecnologia" under the project: PEst-OE/EEI/UI0760/2014, and PEst2015-2020.info:eu-repo/semantics/publishedVersio

    Production distribution planning in a multiechelon supply chain using carbon policies: A review and reflections

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    Sustainability of a supply chain has gained more attention from economists, environmentalists, consumers, manufacturers, government and the academia. In this paper, the literature survey has been performed on production allocation problem in a multi-echelon supply chain with carbon policies. With web-based search engines such as Scopus and Web of Science several resources such as journals, conference proceedings and books are selected and reviewed. It is observed from the literature that the mentioned problem traces the progression of carbon policies in a supply chain over the past 22 years to provide substantiation for Green Supply Chain. The research papers are then analyzed and categorized to construct the useful foundation of previous studies. Moreover, the importance of this problem in recent years needs has been highlighted by mentioning the gaps in the literature. Further, at the end of the paper, several future work directions in this area also suggested.(undefined)info:eu-repo/semantics/publishedVersio
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