ISEP – DEI – Comunicações em eventos científicos
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- Abordagens ao Problema de Escalonamento em Ambientes Reais de ProduçãoPublication . Madureira, Ana Maria; Almeida, Ana[Resumo] Num sistema de fabrico do tipo Job-Shop podem ser identificados alguns factores que contribuem para a dificuldade do processo de escalonamento, nomeadamente, a complexidade, as restrições e a incerteza. Os ambientes industriais reais são sujeitos a várias fontes de mudança, as quais são tratadas como ocorrências aleatórias, tais como, lançamento de novas ordens de fabrico, avarias, alterações de prioridades, atrasos nas operações, etc. Por escalonamento dinâmico consideramos a situação na qual um plano flexível é executado, isto é, o plano inicial é dinamicamente ajustado (re-escalonado) sempre que eventos inesperados ocorrem no sistema. Esta comunicação tem por objectivo principal efectuar uma sistematização de conceitos e classificações de problemas e tipos de escalonamento, bem como das abordagens usadas na sua resolução. Inicialmente, é apresentado o problema de escalonamento, através da caracterização dos seus elementos e da referência a algumas definições encontradas na literatura, A seguir descrevem-se algumas classificações para os problemas de escalonamento e os tipos de abordagens de resolução a adoptar. Finalmente, são propostas duas arquitecturas para a resolução do problema de escalonamento em ambientes reais de produção caracterizados por um elevado grau de dinamismo. À primeira baseada em Sistemas de Apoio à Decisão e a segunda em Algoritmos Genéticos.
- CEPP: Conversion and execution of process plansPublication . Ramos, Carlos; Figueiredo, LinoThis paper deals with a method to produce a program in numerical control (NC) language from a part drawing in a CAD system. This method is applied to any piece with revolution axis that can be machined in a CNC lathe. The method was developed with the goal of being integrated in the control software of the flexible manufacturing system existent in the CIM center of ISEP. The proposed method involves three phases, which are presented and explained.
- CHARACTERIZATION OF MV CONSUMERS USING HIERARCHICAL CLUSTERINGPublication . Figueiredo, V.; Pinheiro, R.; Carvalho Ramos, Sérgio Filipe; Rodrigues, Maria de Fátima Coutinho; Vale, Zita; Ramos, Carlos; Vale, ZitaWith the electricity market liberalization, distribution and retail companies are looking for better market strategies based on adequate information upon the consumption patterns of its electricity customers. A fair insight on the customers’ behaviour will permit the definition of specific contract aspects based on the different, consumption patterns. In this paper, we propose a Knowledge Discovery in Databases project applied to electricity consumption data from a utility client’s database. To form the different customers’ classes, and find a set of representative consumption patterns, we have used the Two-Step algorithm which is a hierarchical clustering algorithm. Each consumer class will be represented by its load profile resulting from the clustering operation. Next, to characterize each consumer class a classification model will be constructed with the C5.0 classification algorithm.
- Constraint programming approach to solve facility layout design problemsPublication . Tavares, José António; Neves, José; Ramos, CarlosWe propose a methodology to solve the facility layout design problem by using constraint logic programming (CLP), which has proved to be a technology that gives good results when applied to a combinatorial problem optimisation. Methods to solve facility layout problems have to deal with a large set of factors, namely sales and production estimations, manufacturing process compatibilities, delivery dates, quality, spatial requirements, economics, management, human resources and environment. These factors make the facility layout design an extremely complex problem to solve. This complexity motivated the development of a methodology to solve the facility layout design problem using CLP.
- Cooperation in Learning Power Systems Restoration TechniquesPublication . Silva, António; Ramos, Carlos; Vale, Zita; Ramos, Carlos; Vale, ZitaAdequate training programs for power systems restoration tasks must take into account that this is a cooperative activity involving several entities. The proposed architecture of the Intelligent Tutoring System presented in this paper is based on a multi-agent system offering a simulated training environment.
- Decision support system for dynamic production schedulingPublication . Marinho, José; Ramos, Carlos; Bragança, AlexandreThis paper presents a system to support decision-making of the production manager when scheduling the manufacturing orders. This system is mainly appropriate for small and medium size enterprises with productive systems like batch or job-shop. The manufacturing orders are dynamically scheduled considering namely deadlines and resource allocation. The system combines three modules: pre-scheduling, dynamic scheduling and re-scheduling. Each module applies heuristics to select the best solutions depending on the scheduling policies defined by the production manager.
- DEFINING A MODEL FOR AGENT-BASED PARTICIPANT SUPPORT IN GROUP DECISION MEETINGPublication . Marreiros, Goreti; Ramos, Carlos; Neves, José; Ramos, Carlos; Vale, ZitaThis paper aim to present a multi-agent model for a simulation system, whose goal is to help one specific participant of multi-criteria group decision making process. This model has five main intervenients types: the human participant, who is using the simulation and argumentation support system; the participant agents, one associated to the human participant and the others simulating the others members of the decision meeting group; the directory agent; the proposal agents, representing the different alternatives for a decision (the alternatives are evaluated based on criteria); and the voting agent responsible for all the voting mechanisms. At this stage it is proposed a two phase algorithm. In the first phase each participant agent makes his own evaluation of the proposals under discussion, and the voting agent proposes a simulation of a voting. In second phase, after the dissemination of the voting results, each one of the participant agents will argue to convince the others to choose one of the possible alternatives. The arguments used to convince a specific participant are dependent on agent knowledge about that participant. The two-phase algorithm is applied iteratively.
- DISTRIBUTED INTELLIGENT TUTORING SYSTEM FOR CONTROL CENTRE OPERATORS TRAININGPublication . Faria, Luiz; Ramos, Carlos; Vale, Zita; Ramos, Carlos; Vale, ZitaThe new requirements of power systems operation demand experienced and well trained operators. However, the training is not often considered a priority task, due mostly to its high costs and medium/long term results. Usually, the training programs available in industrial environment do not consider the particular training needs of each trainee. The application of the Intelligent Tutoring technology has proved to be a good alternative to the existing training approaches in the power systems area. This paper presents a Web-based Intelligent Tutoring System (ITS) to train Control Centre operators of the Portuguese electrical transmission network. One of the major advantages of the training based on the ITS technology is the ability to provide individualized training. To achieve this, our ITS maintains a trainee model, which models the trainee’s understanding of domain concepts. In this way, the paper describes a curriculum planning module used to choose the most appropriate problem to the trainee’s knowledge status. This module includes a neural network to perform a classification of each type of incident according to the trainee’s current knowledge. This paper also deals with a mechanism developed to obtain the trainee’s reasoning during problem solving.
- Distributed task schedulingPublication . Sousa, Paulo; Ramos, CarlosProposes an architecture for manufacturing enterprises based on the holonic concept. The main advantage of this approach is the decentralised, distributed nature of the system as well as its heterarchic organisation as opposed to the rigid hierarchic and centralised nature of computer integrated manufacturing (CIM). The system models products, resources and tasks and the planning, scheduling and order management functions of the enterprise. A negotiation protocol is defined for task assignment that is an extension of the contract net protocol. The protocol is based on the task-resource abstraction and is suited for negotiation in several situations not only for the dynamic scheduling of manufacturing orders. The negotiation protocol is able to handle exceptions such as machine breakdowns and rush orders.
- Dynamic scheduling of manufacturing orders: A decision support system approachPublication . Almeida, Ana; Ramos, Carlos; Silva, S. D. C.This paper presents a decision support system (DSS) based architecture and a new method for the dynamic scheduling of manufacturing systems. The proposed architecture is based on the DSS paradigm. The typical scheduling problems, namely the order allocation and order sequencing problems, are to be solved for a given production plan which defines a set of manufacturing orders to be processed. These specify product types to be manufactured, their quantities and due dates. The allocation problem deals with the assignment of n orders to m manufacturing processors, under the given production plan, and the solution to the sequencing problem identifies the input sequence and the instants of processing of the assigned orders on each manufacturing processor.
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