ESTiG - Publicações em Proceedings Indexadas à WoS/Scopus
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- Factory automation using OSI technologies: process automation in a transformers manufacturing plantPublication . Tovar, Eduardo; Oliveira, José Luís; Alves, Mário; Azevedo, Rui; Carvalho, Adriano; Sousa, Mário; Portugal, Paulo; Carvalho, José AugustoThis paper presents the work carried out in order to improve one of the areas of a factory plant, integrating it within the factory using different communication standards. The implementation described satisfies a set of data flow requirements and claims to be an example of different vendors and technologies integration. Distribution transformers have always been dried within ovens heated for the effect. This drying process has several drawbacks: a low efficiency dependence on the transformer volume and requiring a long time to complete. The new approach, presented in this paper, eliminates all those constraints.
- The vector control signal processing blockset for use with Matlab and SimulinkPublication . Araújo, Rui Esteves; Leite, V.; Freitas, Diamantino SilvaThis paper describes the newly developed Vector Control Signal Processing (VCSP) blockset for use with Matlab(R) and Simulink(R). The originality of this blockset consists of the extension of Simulink for design, simulation and prototyping of signal processing algorithms in motion control systems. This blockset is the first know collection of Simulink blocks to bridge the gap between digital algorithm development and subsequent implementation in motion control systems. The VCSP blockset together with Real-Time Workshop uses the inherent visual programming techniques of Simulink and a number of pre-built blocks to reach the above goals. Due to its open and flexible nature this approach is also very useful as a tool for teaching. This paper is focused on modelling and simulation of motion control systems, in particular employing rotating AC machines and vector control methods. The basic blockset functions and some examples of modelling techniques for simple drive and complex drive structures are presented. Simulations results are also presented and discussed
- A cell controller architecture solution: description and analysis of performance and costsPublication . Quintas, António; Leitão, PauloNowadays, with the globalization of the markets, the companies must to implement new manufacturing technologies and concepts for the improvement of manufacturing systems productivity. The integration is one of the keys to solve the problems in manufacturing systems. The arrangement of the resources in cells and the implementation of control systems allows the improvement of productivity, flexibility, quality and the reduction of production costs. This paper describes a Cell Controller architecture solution, implemented at the flexible manufacturing cell integrated into the demonstration pilot of an ESPRIT Program Project; special attention to the control structure and the system communication is taken. The last part of the paper focuses the costs involved in this solution and presents the alternative platforms and technologies to implement the Cell Controller.
- A new architecture for flexible shop control systemsPublication . Teunis, Gerrit; Leitão, Paulo; Madden, MichaelIn the last two decades, there has been a marked trend in manufacturing away from function-centered production organisations towards product-based manufacturing shops and smaller organisational units. These new organisational structures reduce management complexity and facilitate greater human involvement and empowerment. Modern manufacturing facilities must be flexible, to allow for rapid reconfiguring of resources as dictated by variable demands. Today's tools for production planning and scheduling are not flexible enough, most of them being based on a certain production structure. A newly developed kernel/shell technology aims at a software architecture for shop control not being based on any assumption of the production structure. It should be possible to support almost any structure, organisation and scheduling algorithm. A central kernel acts as a service provider for a broad array of shell modules for scheduling, interfacing with legacy systems, database I/O, user interaction, SCADA interfacing, etc. This technology for shop control provides a high degree of customisation, flexibility and extendibility.
- Performance analysis of a wireless MANPublication . Rufino, José; Lopes, Rui PedroA wireless network with metropolitan coverage was created to fulfill the data communication requirements for the Bragança Digital City program, part of the portuguese Digital Cities initiative. The wireless Metropolitan Area Network, based on IEEE 802.11b, still provides both a performant and an economical solution, tailored to the application scenario. Performance measurements have been done in order to apprehend the real network throughput under typical user applications and to have insight into other network characteristics. A comparison with a wired counterpart is also provided.
- Visualization/animation of programs based on abstract representations and formal mappingsPublication . Pereira, Maria João; Henriques, Pedro RangelIn the context of Alma (a system for program visualization and algorithm animation), we use an internal representation-based on the concept of an attributed abstract syntax tree decorated with attribute values, a DAST-to associate (static) figures to grammar rules (productions) and to step over program dynamics executing state changes in order to perform its animation. We do not rely upon any source program annotations (visual/animation statements, or parameters), neither on any special visual data types. On account of such principle, the approach becomes source language independent. It means that we can apply the same visualizer and animator, that is the Alma's back-end, to different programming languages; all that we need is different front-ends to parse each program into the DAST we use. In this paper we discuss Alma design goals and architecture, and we present the two mappings that associate to productions figures and rewriting rules to systematically draw a visual representation (exhibiting data and control flow) of a given source program and to animate its execution.
- A multi-agent based cell controllerPublication . Leitão, Paulo; Restivo, Francisco; Putnik, GoranThis paper discusses the opportunity to use multiagents technology in automation and distributed manufacturing systems and the expected improvements. To support the discussion, it is described a manufacturing cell control application developed using the multi-agent technology, and the results are compared with other control application developed in the past by some of the authors, using a traditional approach, for the same flexible manufacturing cell.
- Trends in agile and cooperative manufacturingPublication . Leitão, Paulo; Barata, José; Camarinha-Matos, Luís; Boissier, RaymondThis paper discusses the actual state of the manufacturing systems, focusing on the paradigms, requirements and problems for control and supervision. Based on the experience of the authors in those fields, a new approach to agile, distributed and cooperative manufacturing systems is presented and discussed. This new approach is based on a multi-agent platform that supports three main components: control and cooperation, communication, and re-engineering.
- Numerical and experimental evaluation of lateral torsional buckling of beams at elevated temperaturesPublication . Piloto, P.A.G.; Vila Real, Paulo M.M.; Franssen, J.-MarcWhen a beam is bent about its greatest flexural resistance axis it may twist and move laterally, before it reaches its strength limit. Although this problem of lateral torsional buckling of steel beams at room temperature is well known, the same problem at elevated temperature is not. This paper summarises the results obtained iii the scope of a research project entitled “Lateral buckling of steel I beams under fire conditions”, where a set of 120 experimental and numerical tests were performed on IPEIOO beams, submitted to temperature varying from 20 °C to 600 GC, to validate a new proposal for the buckling resistance moment of a laterally unrestrained beam under fire conditions. It will be shown that this new proposal is safer than the Eurocode 3 formulas.
- Distributed paged Hash tablesPublication . Rufino, José; Pina, António; Alves, Albano; Exposto, JoséIn this paper we present the design and implementation of DPH, a storage layer for cluster environments. DPH is a Distributed Data Structure (DDS) based on the distribution of a paged hash table. It combines main memory with file system resources across the cluster in order to implement a distributed dictionary that can be used for the storage of very large data sets with key based addressing techniques. The DPH storage layer is supported by a collection of cluster-aware utilities and services. Access to the DPH interface is provided by a user-level API. A preliminary performance evaluation shows promising results.