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Biblioteca Digital do IPB (53.442 recursos)

A Biblioteca Digital do IPB, tem por objectivo divulgar e permitir o livre acesso à produção científica produzida pela comunidade académica, promovendo a integração, partilha e a visibilidade da informação científica e garantindo a preservação da memória intelectual do Instituto Politécnico de Bragança.

DE - Artigos em Revistas

Mostrando recursos 1 - 20 de 27

  1. Past, present, and future of industrial agent applications

    Leitão, Paulo; Mařík, Vladimír A.; Vrba, Pavel
    Industrial agents technology leverages the benefits of multiagent systems, distributed computing, artificial intelligence techniques and semantics in the field of production, services and infrastructure sectors, providing a new way to design and engineer control solutions based on the decentralization of control over distributed structures. The key drivers for this application are the benefits of agent-based industrial systems, namely in terms of robustness, scalability, reconfigurability and productivity, all of which translate to a greater competitive advantage. This manuscript monitors the chronology of research and development of the industrial applications of multiagent and holonic systems. It provides the comprehensive overview of methodologies,...

  2. Adaptive image pre-processing for quality control in production lines

    Arroyo Esquivel, Esteban; Lima, José; Leitão, Paulo
    Flexible and self-adaptive behaviours in automated quality control systems are features that may significantly enhance the robustness, efficiency and flexibility of the industrial production processes. However, most current approaches on automated quality control are based on rigid inspection methods and are not capable of accommodating to disturbances affecting the image acquisition quality, fact that hast direct consequences on the system´s reliability and performance. In an effort to address the problem, this paper presents the development of a self-adaptive software system designed for the pre-processing (quality enhancement) of digital images captured in industrial production lines. The approach introduces the use of scene recognition as a key-feature to allow the execution of customized image pre-processing...

  3. Benchmarking flexible job-shop scheduling and control systems

    Trentesaux, Damien; Pach, Cyrille; Bekrar, Abdelghani; Sallez, Yves; Berger, Thierry; Thérèse, Bonte; Leitão, Paulo; Barbosa, José
    Benchmarking is comparing the output of different systems for a given set of input data in order to improve the system’s performance. Faced with the lack of realistic and operational benchmarks that can be used for testing optimization methods and control systems in flexible systems, this paper proposes a benchmark system based on a real production cell. A three-step method is presented: data preparation, experimentation, and reporting. This benchmark allows the evaluation of static optimization performances using traditional operation research tools and the evaluation of control system's robustness faced with unexpected events.

  4. Humanoid gait optimization resorting to an improved simulation model

    Lima, José; Gonçalves, José; Costa, Paulo; Moreira, António
    The simulation of a robot with a high number of joints can easily become unstable. Numerical errors on the first joint of the chain are propagated to the other joints. This is a very common problem in humanoid robots. A way to plan the gait for those robots is using simulation and optimization techniques. This paper addresses a new approach to optimize gait parameter sets using an Adaptive Simulated Annealing optimization algorithm combined with a new joint model that reduces its instability. The new model and the optimization are implemented in SimTwo (a developed physical robot simulator that is capable...

  5. Integration of virtual and real environments for engineering service-oriented manufacturing systems

    Leitão, Paulo; Mendes, João M.; Bepperling, Axel; Cachapa, Daniel; Colombo, Armando W.; Restivo, Francisco
    Engineering frameworks are currently required to support the easy, low-cost, modular and integrated development of manufacturing systems addressing the emergent requirements of re-configurability, responsiveness and robustness. This paper discusses the integration of 2D/3D digital software tools with Petri net based service-oriented frameworks to allow the design, configuration, analysis, validation, simulation, monitoring and control of manufacturing systems in a virtual environment and its posterior smooth migration into the real ”physical” environment. An experimental case study was implemented to validate the proposed concepts, using the Continuum platform to design, compose, analyze, validate and simulate the Petri nets based service-oriented manufacturing control system,...

  6. A holonic disturbance management architecture for flexible manufacturing systems

    Leitão, Paulo
    Manufacturing systems are dynamic, non-linear and often chaotic environments, subjected to the occurrence of unexpected disturbances that provokes deviations from the initial plans and degrades the system’s performance. Traditionally, disturbance management is performance in a centralized manner, using a fail-fix approach and considering only one type of disturbance, the machine failure. However, the new generation of intelligent manufacturing systems should be capable to treat emergency as earlier as possible and in an effective way, to minimize its negative impact in the production performance. This paper addresses this challenge by introducing a holonic disturbance management architecture based on the ADACOR foundations....

  7. High-level petri nets for the process description and control in service-oriented manufacturing systems

    Leitão, Paulo; Mendes, João M.; Colombo, Armando W.; Restivo, Francisco
    The use of service-orientation principles in manufacturing systems is a promising solution to achieve modularity, flexibility, re-configurability and interoperability. Crucial issues in these service-oriented systems are the description and coordination of the execution of the services offered by the distributed entities. This paper introduces an integrated approach for the design, analysis, validation, simulation and process execution of service-oriented manufacturing systems, using the High-level Petri nets formalism as the formal language to describe the system behavior. The use of the proposed approach contributes to achieve an easier and faster development of these solutions and provides the basis to support modularity and...

  8. Nonlinear control of the doubly-fed induction generator in wind power systems

    Soares, Orlando; Gonçalves, Henrique; Martins, António A.; Carvalho, Adriano
    This paper describes the models of a wind power system, such as the turbine, generator, power electronics converters and controllers, with the aim to control the generation of wind power in order to maximize the generated power with the lowest possible impact in the grid voltage and frequency during normal operation and under the occurrence of faults. The presented work considers a wind power system equipped with the doubly-fed induction generator and a vector-controlled converter connected between the rotor and the grid. The paper presents comparative results between roportional-integral controllers and neural networks based controllers, showing that better dynamic characteristics can...

  9. A classification Fuzzy model for Minhota and Holstein Friesian cows milk based on functional fatty acids

    Ramalho, Heryka; Casal, Susana; Mendes, Eulália; Igrejas, Getúlio; Rodrigues, Pedro; Oliveira, M.B.P.P.
    Recent studies have focused on the healthy components of milk fats, including polyunsaturated fatty acids (PUFA) of the omega-3 group, and conjugated linoleic acid (CLA). Several cows from Holstein Friesian and Minhota (autochthonous from the north of Portugal) were evaluated for their milk fatty acid composition, with the latter presenting significantly higher CLA amounts (P<0.05), lower saturated fatty acids and a smaller n6:n3 ratio. Considering these potentially functional differences, a classification system for an effective and fast discrimination of milks from different cow breeds would be an interesting tool for the dairy industry. In this work a Fuzzy model system...

  10. Evaluation of a segmental durations model for TTS

    Teixeira, João Paulo; Freitas, D.
    In this paper we present a condensed description of a European Portuguese segmental duration’s model for TTS purposes and concentrate on its evaluation. This model is based on artificial neural networks. The evaluation of the model quality was made by comparison with read speech. The standard deviation reached in test set is 19.5 ms and the linear correlation coefficient is 0.84. The model is perceptually evaluated with 4.12 against 4.30 for natural human read speech in a scale of 5.

  11. Humanoid low-level controller development based on a realistic simulation

    Lima, José; Gonçalves, José; Costa, Paulo; Moreira, António
    This article describes a joint trajectory optimized controller developed in a humanoid robot simulator following the real robot characteristics. As simulation is a powerful tool for speeding up the control software development, the proposed accurate simulator allows to fulfill this goal. The simulator, based on the Open Dynamics Engine and GLScene graphics library, provides instant visual feedback. The proposed simulator, with realistic dynamics, allows to design and test behaviors and control strategies without access to the real hardware in order to carry out research on robot control without damaging the real robot. The low-level joints controller techniques, such as acceleration,...

  12. Real time cork classification method: a colour image processing approach

    Lima, José; Costa, Paulo
    This paper presents an automatic vision assortment method for cork classification. Cork is a natural material that is used to seal wine bottles due to its reliability and its chemical and mechanical properties. A colour image acquisition system is able to differentiate some cork defects. The developed and implemented system acquires images using a colour linear CCD camera, transmits that image through a fast acquisition card and processes that image to extract quantitative elements. This system can analyse and distinguish defects present on the surface of a cork stopper: the size, form and position of the defects are analysed.

  13. On the use of prosodic labelling in corpus-based linguistic studies of spontaneous speech

    Braga, Daniela; Freitas, D.; Teixeira, João Paulo; Marques, Aldina
    This paper addresses the construction of a spontaneous speech cor-pus in European Portuguese (hereafter EP), the corpus is presented and a pro-sodic labeling scheme that is here proposed is explained. The objective of this work is to provide a tool for linguistic analysis suitable to several research top-ics, which have speech and dialogue as objects. The main features considered in the database will be described and justified. Methodological problems and some observed prosodic and pragmatic related phenomena deriving from the labeling of the speech signal are also presented. A discussion is done about some applications on pragmatic studies, speech synthesis...

  14. Tutorial introdutório para as competições de futebol robótico

    Gonçalves, José; Pinheiro, Pedro; Lima, José; Costa, Paulo
    Soccer was the original motivation for Robocup. Besides being a very popular sport worldwide, soccer brings up a set of challenges for researchers while attracting people to the event, promoting robotics among students, researchers and general public. RoboCup chose to use soccer game as a central topic of research, aiming at innovations to be applied for socially significant problems and industries. This paper describes the implementation of a system similar to the used by the teams participating in the Robocup small size league (SLL). The system, developed in Object Pascal, allows real time localization and control of an omnidirectional mobile robot....

  15. Learning mobile robotics using lego mindstorms

    Leitão, Paulo; Gonçalves, José; Barbosa, José
    The learning of some areas of knowledge requires the application of new learning methods in order to motivate and involve the students in the learning process. This paper describes an experience of the introduction of the flexible, modular and educational LEGO Mindstorms platform at high-degree studies to support the learning of mobile robotics topics.

  16. Controlo e estimação do posicionamento absoluto de um robot omnidireccional de três rodas

    Gonçalves, José; Costa, Paulo; Moreira, Paulo
    Este artigo aborda o tema Controlo de Robots Omnidireccionais. O robot usado como caso de estudo utiliza motores DC com encoders e possui 3 rodas especiais que permitem a sua omnidireccionalidade. O movimento destes robots não está sujeito às restrições dos robots mais usuais que utilizam apenas duas rodas normais, tendo como desvantagem o seu controlo ser mais complexo. O principal objectivo deste trabalho foi o de desenvolver um controlador que permita o seguimento de trajectórias pré-definidas com velocidade controlada, estimando-se o posicionamento absoluto do robot baseado na odometria. Os problemas de controlo em robótica incluem inevitáveis requisitos de tempo real muito...

  17. Agent-based distributed manufacturing control: a state-of-the-art survey

    Leitão, Paulo
    Manufacturing has faced significant changes during the last years, namely the move from a local economy towards a global and competitive economy, with markets demanding for highly customized products of high quality at lower costs, and with short life cycles. In this environment, manufacturing enterprises, to remain competitive, must respond closely to customer demands by improving their flexibility and agility, while maintaining their productivity and quality. Dynamic response to emergence is becoming a key issue in manufacturing field because traditional manufacturing control systems are built upon rigid control architectures, which cannot respond efficiently and effectively to dynamic change. In these...

  18. ADACOR: a holonic architecture for agile and adaptive manufacturing control

    Leitão, Paulo; Restivo, Francisco
    In the last decades significant changes in the manufacturing environment have been noticed: moving from a local economy towards a global economy, with markets asking for products with higher quality at lower costs, highly customised and with short life cycle. In these circumstances, the challenge is to develop manufacturing control systems with intelligence capabilities, fast adaptation to the environment changes and more robustness against the occurrence of disturbances. This paper presents an agile and adaptive manufacturing control architecture that addresses the need for the fast reaction to disturbances at the shop floor level, increasing the agility and flexibility of the...

  19. ADACOR, a collaborative production automation and control architecture

    Leitão, Paulo; Colombo, Armando W.; Restivo, Francisco
    An analysis of the ADACOR collaborative manufacturing control architecture from the point of view of the Collaborative Manufacturing Management paradigm shows how ADACOR supports integration and extension across the manufacturing value chain.

  20. A formal specification approach for holonic control systems: the ADACOR case

    Leitão, Paulo; Colombo, Armando W.; Restivo, Francisco
    Distributed manufacturing control systems, like holonic control systems, are difficult to apprehend and to design, due to the presence of many autonomous, concurrent and asynchronous activities. A formal specification methodology allowing to understand and to synthesize the system specifications and to validate the correctness of their models would play a key role in its design and later in its implementation. This paper presents an approach to the formal specification of holonic control systems based in Highlevel Petri nets. The proposed approach is tested in the specification of the ADACOR holonic control system.

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