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Casau P.,University of Lisbon | Rosa P.,Deimos Engineering | Silvestre C.,University of Macau
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2015

In this paper, we present the theoretical background for the implementation of FITBOX - a new, freely available fault isolation toolbox for MATLAB that makes use of novel set-membership methods for Fault Detection and Isolation (FDI). We apply the proposed methods to the FDI of a wind turbine and evaluate their performance in a simulation setting. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.


Casau P.,University of Lisbon | Rosa P.,Deimos Engineering | Tabatabaeipour S.M.,Technical University of Denmark | Silvestre C.,University of Lisbon | And 2 more authors.
IEEE Transactions on Control Systems Technology | Year: 2014

A complete methodology to design robust fault detection and isolation (FDI) filters and fault-tolerant control (FTC) schemes for linear parameter varying systems is proposed, with particular focus on its applicability to wind turbines. This paper takes advantage of the recent advances in model falsification using set-valued observers (SVOs) that led to the development of FDI methods for uncertain linear time-varying systems, with promising results in terms of the time required to diagnose faults. An integration of such SVO-based FDI methods with robust control synthesis is described, to deploy new FTC algorithms that are able to stabilize the plant under faulty environments. The FDI and FTC algorithms are assessed by resorting to a publicly available wind turbine benchmark model, using Monte Carlo simulation runs. © 2014 IEEE.


Camps A.,Polytechnic University of Catalonia | Gourrion J.,CSIC - Institute of Marine Sciences | Tarongi J.M.,Polytechnic University of Catalonia | Gutierrez A.,DEIMOS Engineering | And 2 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2010

SMOS im agery has been analyzed to stud y: 1) radio-frequency in terference (RFI) detection and mitigation algorithms, and 2) the statistical properties of RFI. Results show that with a high probability of detection (∼0.75), the probability of false alarm is very high as well (∼0.68), and most snap-shots seem to be contaminated, even though the estimated RFI value is so weak, and the impact in the SMOS im agery is not even noticeable. Results of the detection and mitigationalg orithm are presented, with the statistical analysis of more than 13000 L1b snap-shots. © 2010 IEEE.


Rosa P.,Deimos Engineering | Silvestre C.,University of Lisbon | Silvestre C.,Macau University of Science and Technology | Athans M.,M.I.T.
International Journal of Robust and Nonlinear Control | Year: 2014

This article introduces a new method for model falsification using set-valued observers, which can be applied to a class of discrete linear time-invariant dynamic systems with time-varying model uncertainties. In comparison with previous results, the main advantages of this approach are as follows: The computation of the convex hull of the set-valued estimates of the state can be avoided under certain circumstances; to guarantee convergence of the set-valued estimates of the state, the required number of previous steps is at most as large as the number of states of the nominal plant; and it provides a straightforward nonconservative method to falsify uncertain models of dynamic systems, including open-loop unstable plants. The results obtained are illustrated in simulation, emphasizing the advantages and shortcomings of the suggested method. Copyright © 2013 John Wiley & Sons, Ltd.


Bras S.,University of Lisbon | Rosa P.,Deimos Engineering | Silvestre C.,University of Lisbon | Silvestre C.,Macau University of Science and Technology | Oliveira P.,University of Lisbon
Systems and Control Letters | Year: 2013

The problem of attitude and rate gyro bias estimation is addressed by resorting to measurements acquired from rate gyros and vector observations. A Set-Valued Observer (SVO) is proposed that has no singularities and that, for any initial conditions, provides a bounding set with guarantees of containing the actual (unknown) rotation matrix. The sensor readings are assumed to be corrupted by bounded measurement noise and constant gyro bias. Conditions for the boundedness of the estimated sets are established and implementation details are discussed. The feasibility of the technique is demonstrated in simulation. © 2013 Elsevier B.V. All rights reserved.


Silvestre D.,University of Lisbon | Rosa P.,Deimos Engineering | Hespanha J.P.,University of California at Santa Barbara | Silvestre C.,University of Lisbon
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2015

This paper addresses the problem of fault detection in the context of a collection of agents performing a shared task and exchanging relative information over a communication network. A techniques in the literature is used to construct a meaningful observable system equivalent to the original unobservable system of systems. A solution involving Set-Valued Observers (SVOs) and a left-coprime factorization of the system is proposed to estimate the state in a distributed fashion and a proof of convergence of the estimates is given under mild assumptions. The performance of the detection algorithm against deterministic and stochastic faults; and when the system is subject to unmodeled disturbances is assessed through simulations. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.


Silvestre D.,University of Lisbon | Rosa P.,Deimos Engineering | Hespanha J.P.,University of Lisbon | Silvestre C.,University of California at Santa Barbara
Proceedings of the American Control Conference | Year: 2015

This paper addresses the problem of finite-time convergence in a social network for a political party or an association, modeled as a distributed iterative system with a graph dynamics chosen to mimic how people interact. It is firstly shown that, in this setting, finite-time convergence is achieved only when nodes form a complete network, and that contacting with agents with distinct opinions reduces to a half the required interconnections. Two novel strategies are presented that enable finite-time convergence, even for the case where each node only contacts the two closest neighbors. These strategies are of prime importance, for instance, in a company environment where agents can be motivated to reach faster conclusions. The performance of the proposed policies is assessed through simulation, illustrating, in particular the finite-time convergence property. © 2015 American Automatic Control Council.


Bras S.,University of Lisbon | Rosa P.,Deimos Engineering | Silvestre C.,University of Lisbon | Silvestre C.,Macau University of Science and Technology | Oliveira P.,University of Lisbon
IEEE Transactions on Automatic Control | Year: 2015

This work addresses the problem of Fault Detection and Isolation (FDI) for navigation systems equipped with sensors providing inertial measurements and vector observations. Assuming upper bounded sensor noise, two strategies are proposed: i) the first one takes advantage of existing hardware redundancy, requiring at least five sensor measurements to isolate faults; ii) the second approach exploits the analytical redundancy between the angular velocity measurements and the vector observations, by resorting to set-valued observers (SVOs). Necessary and sufficient conditions on the magnitude of the faults are provided, in order to guarantee successful detection and isolation, when hardware redundancy is available. Due to the set-based construction of the methods, none of the solutions generates false detections and no decision threshold is required. Using a simulation scenario, the proposed strategies are compared with two alternatives available in the literature. © 2015 IEEE.


Rosa P.,Deimos Engineering | Vasconcelos J.,Deimos Engineering | Kerr M.,Deimos Space
IFAC-PapersOnLine | Year: 2015

This paper addresses the problem of detecting and isolating faults in the angle -of-attack (AoA) measurements, when the faulty sensors outnumber the healthy ones. Such a scenario hinders the applicability of heuristic-based techniques, such as voting schemes. Rather than including additional sensors, which would increase payload and system complexity, the solution adopted herein takes advantage of the knowledge on the dynamics of the aircraft, modeled by a linear fractional transformation (LFT), to detect and isolate faults. This approach is used to minimize the impact of the faulty sensors on the control performance of the vehicle, by feeding the controller with the compensated measurement. An integrated design solution is adopted based on μ-synthesis, thus directly addressing the issue of model uncertainty. Simulation results are presented obtained from a very high-fidelity Airbus industrial simulator. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.


Castro R.,DEIMOS Engineering | Gutieerrez A.,DEIMOS Engineering | Barbosa J.,DEIMOS Engineering
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

The presence of radio frequency interferences (RFIs) in the data collected by the Soil Moisture and Ocean Salinity (SMOS) mission led by the European Space Agency is larger than what was anticipated, and it has a strong impact on the retrieval of these geophysical parameters. The first efforts to deal with this problem were proposed by DEIMOS Engenharia in the Level 1 Prototype Processor released in November 2010, and they are also a part of its latest versions. DEIMOS focused on three key aspects to detect the RFIs, to mitigate these sources, and to flag the data in SMOS products affected by RFIs. The detection algorithm is based on a statistic approach that computes the most probable position of the RFI source based on multiangular observations made by SMOS. The mitigation algorithm has been designed taking as reference the existing technique to remove the sun effect. The mechanism to flag the data has been developed in cooperation with the European Space Agency and consists in flagging geolocated pixels according to the strength of the RFI. In this paper, three algorithms will be presented, as well as their results. For completion, a high-level description of the data processing for SMOS is also a part of this text. © 2012 IEEE.

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