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- Multi-agent platform and toolbox for fault tolerant networked control systemsPublication . Mendes, Mário J. G. C.; Santos, Bruno M. S.; Costa, José Sá daIndustrial distributed networked control systems use different communication networks to exchange different critical levels of information. Real-time control, fault diagnosis (FDI) and Fault Tolerant Networked Control (FTNC) systems demand one of the more stringent data exchange in the communication networks of these networked control systems (NCS). When dealing with large-scale complex NCS, designing FTNC systems is a very difficult task due to the large number of sensors and actuators spatially distributed and network connected. To solve this issue, a FTNC platform and toolbox are presented in this paper using simple and verifiable principles coming mainly from a decentralized design based on causal modelling partitioning of the NCS and distributed computing using multi-agent systems paradigm, allowing the use of agents with well established FTC methodologies or new ones developed taking into account the NCS specificities. The multi-agent platform and toolbox for FTNC systems have been built in Matlab/Simulink environment, which is in our days the scientific benchmark for this kind of research. Although the tests have been performed with a simple case, the results are promising and this approach is expected to succeed with more complex processes.
- Multi-agent platform for Fault Tolerant Control SystemsPublication . Mendes, Mário J. G. C.; Santos, Bruno M. S.; Costa, José Sá daThis paper proposes a new multi-agent platform for Fault Tolerant Control (FTC) Systems. Several multi-agent platforms exist to deal with different problems but none of them to deal with control systems tolerant to faults using the Matlab/Simulink environment, which is in our days the scientific bench to this kind of research. When dealing with large-scale complex networked control systems (NCS),designing FTC systems is a very difficult task due to the large number of sensors and actuators spatially distributed and network connected. To solve this issue, the FTC platform presented in this paper uses simple and verifiable principles coming mainly from a decentralized design based on causal modelling partitioning of the NCS and distributed computing using multiagent systems paradigm, allowing the use of agents with well established FTC methodologies or new ones developed taking into account the NCS specificities.
- 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.
- Control of the archimedes wave swing using neural networksPublication . Beirão, Pedro; Mendes, Mário J. G. C.; Valério, Duarte; Costa, José Sá daThis paper addresses the control of the Archimedes Wave Swing, a fully-submerged Wave Energy Converter (WEC), of which a prototype has already been built and tested. Simulation results are presented in which Internal Model Control (IMC) is used, both with linear models and with non-linear neural network (NN) models. To the best of our knowledge this is the first time NN-based control is being applied to design a controller for a WEC. NNs are a mathematical tool suitable to model the behaviour of dynamic systems, both linear and non-linear (as in our case). Significant absorbed wave energy increases were found, both using linear models and NNs. Results were better when IMC with NNs was employed (with a nearly sixfold increase against a fivefold increase), except for the May—September period, when IMC with linear models performs better.
- Comparison of control strategies performance for a Wave Energy ConverterPublication . Valério, Duarte; Beirão, Pedro; Mendes, Mário J. G. C.; Costa, José Sá daThe Archimedes Wave Swing (AWS) is a a fully submerged Wave Energy Converter (WEC), that is to say, a device that converts the kinetic energy of sea waves into electricity. A first prototype of the AWS has already been built and tested. This paper presents simulation results of the performance of several control strategies applied to this device, including PID control, reactive control, phase and amplitude control, latching control, feedback linearisation control, internal model control, switching control, and combinations thereof. Linear, white-box nonlinear, and neural network models were employed. Significant (above threefold) increases in yearly energy production were found to be possible with properly designed control strategies.
- Fault detection system for the Évora irrigation canalPublication . Louro, Diogo; Mendes, Mário J. G. C.; Valério, Duarte; Costa, José Sá daA model-based fault detection (FD) system was developed for a Simulink simulation of a four pool irrigation canal in ´Evora, Portugal. Incipient and abrupt faults in the gates, the water off-take valves and the water level sensors were considered. Neural Networks were used to model the canal and find the residue. The training algorithm employed for the NNs was found to be an important factor determining the success of the FD system.
- A matlab/simulink multi-agent toolkit for distributed networked fault tolerant control systemsPublication . Mendes, Mário J. G. C.; Santos, Bruno M. S.; Costa, José Sá daA general concern in industrial world is related to process maintenance, safety and availability problems in the presence of faults. Most industrial processes are very large or/and complex. Because of size and complexity, it is very difficult to make a diagnostic system for an entire process and to ensure the availability of it. Designing a Fault Tolerant Networked Control System (FTNCS) to deal with large-scale complex networked control systems is a very difficult task due to the large number of sensors and actuators spatially distributed and networked connected. This paper presents a toolkit to implement multiagent approaches on distributed FTNCS. The design methodology is made easier using the toolkit presented in this paper. The FTNCS design method 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 fault tolerant control methodologies, or new ones, developed taking into account the NCS specificities. A platform with a real process and four computers is used to test the toolkit and network infrastructure.
- Fault detection agents based on wavelet adaptive thresholdsPublication . Mendes, Mário J. G. C.; Costa, José Sá daDesigning a Fault Tolerant Networked Control System (FTNCS) to deal with large-scale complex networked control systems is a very difficult task due to the large number of sensors and actuators spatially distributed and networked connected. To deal with this problem, this paper presents a new agent based fault detection (FD) system for complex and dynamic processes, where the modularity and complexity of the processes are important aspects in the FD agent system constructed. The FD agents proposed here have hybrid architectures based in a horizontal layers, where the reactive layer is based on Wavelet Adaptive Thresholds. The results, using a distributed benchmark with a three tank process, show that the FD agents proposed are a good alternative to classic FD methods.
- Multi-agent toolbox for fault tolerant networked control systems designPublication . Costa, José Sá da; Santos, Bruno M. S.; Mendes, Mário J. G. C.The design of fault tolerant control (FTC) systems of 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 present the first version of a toolbox based on multi-agent systems (MAS) to design FTC systems for complex NCS. This toolbox is based on a decentralized FTC of NCS which relies on causal graph partitioning of the NCS digraph model and on intelligent distributed computing using MAS.
- A multi-agent approach to a networked fault detection systemPublication . Mendes, Mário J. G. C.; Costa, José Sá daNowadays, fault diagnosis systems design should have into account the distribution and complexity of the process and must be able to cooperate and communicate with other systems to achieve satisfactory performance. To this end a new agent based fault detection system for networked control process is proposed in this paper. A hybrid architecture based on horizontal layers as fault detection (FD) agents architecture is adopted. The reactive layer of the FD agents is based on neural networks models for residuals generation with adaptive threshold. The deliberative layers take into account the agent knowledge and goals, and also the process distribution and network. The new agent based FD system has been applied and tested with good results in a three tank process using a star Ethernet network topology.