ISEL - Eng. Mecan. - Artigos
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- Neuro-fuzzy structures in FDI systemsPublication . Mendes, Mário J. G. C.; Kowal, Marek; Korbicz, Józef; Costa, J. M. G. Sá daFault diagnosis systems have an important role in industrial plants because the early fault detection and isolation (FDI) can minimize damages in the plants. The main aim of this work is to propose a two-stage neuro-fuzzy approach as a fault diagnosis system in dynamic processes. The first stage of the system is responsible for fault detection and is implemented using a neuro-fuzzy (N-F) model. The second stage of the system is responsible for fault isolation and is built using an hierarchical structure of fuzzy neural networks. The FDI system is applied to fault diagnosis in the actuators of one sugar factory.
- Neuro and neuro-fuzzy hierarchical structures comparison in FDI: a case studyPublication . Calado, João Manuel Ferreira; Mendes, Mário J. G. C.; Costa, J. M. G. Sá da; Korbicz, JózefIn this paper a hierarchical structure of several artificial neural networks has been developed for fault isolation purposes. Two different approaches have been considered. The hierarchical structure is the same for both approaches, but one uses multi-layer feedforward artificial neural networks and the other uses fuzzy neural networks. A result comparison between the two architectures will be presented. It is aimed to isolate multiple simultaneous abrupt and incipient faults from only single abrupt fault symptoms. A continuous binary distillation column has been used as test bed of the current approaches.
- Fault detection using neuro-fuzzy networksPublication . Kowal, Marek; Korbicz, Józef; Mendes, Mário J. G. C.; Calado, João Manuel FerreiraGenerally three methodologies to develop and test fault detection (FD) algorithms can be distingguished: software benches, hardware benches and industrial data. The current approach uses a hardware bench that consists of process under supervision (two interconnected stations), supervision unit, fault diagnosis unit and fault simulation unit. All elements of the bench are connected to a PROFIBUS network that acts as the communication system exchaging information between automation system and distributed field devices. A realistic and fexible environment for developing and testing FD systems has been constructed using elements commonly used in industry. During the current studies actuator faults, sensor faults and leakages have been considered as incipiente and abrupt faults. The proposed FD algorithm bases on neuro-fuzzy models that are responsible for residual generation.
- Fault detection approach based on fuzzy qualitative reasoning applied to the DAMADICS benchmark problemPublication . Calado, João Manuel Ferreira; Carreira, F. P. N. F.; Mendes, Mário J. G. C.; Costa, J. M. G. Sá da; Bartys, M.A computer assisted fault detection methodology based on a fuzzy qualitative simulation algorithm is described. The adoption of fuzzy sets allows a more detailed description of physical variables, through an arbitrary, but finite, disaetisatioo of the quantity space. The fuzzy representation of qualitative values is more general than ordinary interval representation, since it can represent not only the information stated by a well defined real interval but also the knowledge embedded in the soft boundaries of the interval. Such a methodology was applied to a pneumatic servomotor actuated control valve that is the benchmark problem of the EC RTN DAMADlCS.
- Fault isolation based on HSFNN applied to DAMADICS benchmark problemPublication . Calado, João Manuel Ferreira; Louro, R.; Mendes, Mário J. G. C.; Costa, J. M. G. Sá da; Kowal, M.The present paper is concemed with the application of a hierarchical structure of fuzzy newal networks (HSFNN) to fault isolation on a pneumatic servo-motor actuated valve that is the benchmark considered for all the DAMADICS (Development and Application of Methods for Actuator Diagnosis in IndusIrial Control Systems) project partners. The adoption of a hierarchical structure of fuzzy newal netwoIks for fault isolation pwposes aims the development of an architecture that can localise abrupt and incipient single and multiple faults correctly or at least with a minimum misclassification rate and be easily trained, ftom only single abrupt fault symptoms.
- On the role of value systems and reciprocity in collaborative environmentsPublication . Abreu, António; Camarinha-Matos, Luis M.The establishment of a common value system is an important element for the sustainability of collaborative networks. This paper discusses the role of value systems in the VO breeding environment when the promotion of the cooperation is based on reciprocity mechanism. Some scenarios are included in the discussion and illustrations are given based on data from real networks.
- Fault diagnosis system based in agentsPublication . Mendes, Mário J. G. C.; Calado, João Manuel Ferreira; Costa, J. M. G Sá daIn this work is proposed a new agent based fault diagnosis system for complex and dynamic processes. The fault diagnosis systems of the future should have present the distribution and complexity of the processes and they must be able to cooperate and communicate with other systems to achieved a satisfactory performance. The fault detection and isolation (FDI) agents proposed here have hybrid architectures based in a horizontal layered architecture. The reactive layer of the FDI agents are based in decomposition wavelet methods for the fault detection and in neural networks for the fault isolation task. The new agent based FDI system is applied to fault diagnosis in a three tank process.
- Performance indicators for collaborative networks based on collaboration benefitsPublication . Camarinha-Matos, Luis M.; Abreu, AntónioCollaborative networks are typically assumed to bring clear benefits and competitive advantage to the participating members. However, the identification and characterisation of objective and measurable collaboration benefits is an important element for the wide adoption of this paradigm. Departing from a brief categorisation of the intuitive advantages of collaboration, this paper introduces an approach for the analysis of benefits in collaborative processes, introducing a number of performance indicators. The potential application of the indicators derived from this analysis is then discussed in the context of a virtual organisation’s breeding environment. Finally, experimental results based on data from two existing collaborative networks are presented and discussed.
- A design approach to FDI/FTC of complex networked control systemsPublication . Costa, José Sá da; Santos, Bruno M. S.; Mendes, Mário J. G. C.The design of fault tolerant control (FTC) systems for large-scale complex networked control systems (NCS) is a difficult task due to the large number of sensors and actuators spatially distributed and networked connected. Despite the research effort on developing FTC systems most of these developments are designed globally leading to centralized FTC solutions inadequate to NCS. In this paper we presente the first version of a toolbox based on multi-agent systems to design FTC systems for large-scale complex NCS. This toolbox is based on a decentralized FTC of NCS which relies on casual graph partitioning of the NCS digraph model and on inteligente distributed computing using multi-agents systems.
- Design of distributed fault tolerant control systemsPublication . Costa, José Sá da; Mendes, Mário J. G. C.When dealing with large-scale complex networked control systems, designing FDI/FTC systems is a very difficult task due to the large number of sensors and actuators spatially distributed and networked connected. Despite the research effort on developing FTC systems for NCS most of these developments still being designed globally leading to centralized FTC solutions inadequate to NCS or, assume the communication network and the process itself as two different entities loosing the potentiality of the integrated design. The FDI/FTC design method presented in this paper is able to use simple and verifiable principles coming mainly from a decentralized design, based on causal modelling partitioning of the NCS and distributed computing using multi-agents systems, allowing the use of well established FDI/FTC methodologies, or new ones, developed taking into account the NCS specificities. The design methodology is made easy using a FTCNS-MAS toolbox introduced in this paper.