http://hdl.handle.net/2117/432 2013-05-24T14:45:10Z http://hdl.handle.net/2117/18539 Title: Principal component analysis vs. independent component analysis for damage detection Authors: Tibaduiza Burgos, Diego Alexander; Mujica Delgado, Luis Eduardo; Anaya, Maribel; Rodellar Benedé, José; Güemes, Alfredo Abstract: In previous works, the authors showed advantages and drawbacks of the use of PCA and ICA by separately. In this paper, a comparison of results in the application of these methodologies is presented. Both of them exploit the advantage of using a piezoelectric active system in different phases. An initial baseline model for the undamaged structure is built applying each technique to the data collected by several experiments. The current structure (damaged or not) is subjected to the same experiments and the collected data are projected into the models. In order to determine whether damage exists or not in the structure, the projections into the first and second components using PCA and ICA are depicted graphically. A comparison between these plots is performed analyzing differences and similarities, advantages and drawbacks. To validate the approach, the methodology is applied in two sections of an aircraft wing skeleton powered with several PZTs transducers. 2013-04-02T11:18:26Z http://hdl.handle.net/2117/18467 Title: Multivariable model predictive control of water levels on a laboratory canal Authors: Horvath, Klaudia; Van Overloop, P.J.; Galvis Restrepo, Eduard; Gómez Valentín, Manuel; Rodellar Benedé, José Abstract: Automatic control of irrigation canals can reduce the loss of water in considerable amounts, therefore it is generating ecologic and economic benefits. There have been many different types of automatic controllers developed, but only few of them had the opportunity of being tested on the field due to the long delay time and the inconveniences of interrupting the operation of the irrigation. Therefore, the automatic controllers developed for large irrigation canals should be tested before by means of numerical simulations and/or laboratory experiments. The Technical University of Catalonia possesses a laboratory irrigation canal with the length of 220m, with 3 motorized gates, and 11 level sensors that are connected to a SCADA system. This facility makes it possible to test controllers of any type, since all the instrumentation and real time operation runs within a flexible working environment running in Matlab-Simulink . The canal can be configured from one pool to three pools, which allows the development of multivariable control. A numerical model of the canal has been developed using the 1D hydrodynamic model SIC. With the help of this software it is possible to simulate the hydraulics of the canal and, due to the link between SIC and Matlab, also to test any controller developed previously in the Matlab environment. In this work a centralized multivariable model predictive controller for water levels is developed and validated by means of numerical simulation. 2013-03-22T09:16:04Z http://hdl.handle.net/2117/18449 Title: Simplified modeling of a laboratory irrigation canal for control purposes Authors: Galvis Restrepo, Eduard; Horvath, Klaudia; Gómez Valentín, Manuel; Rodellar Benedé, José Abstract: http://upcommons.upc.edu/e-prints/bitstream/2117/15391/1/SAICA2011_proceedings.pdf 2013-03-21T09:38:09Z http://hdl.handle.net/2117/17976 Title: Damage detection in piping systems using pattern recognition techniques Authors: Buethe, Inka; Torres-Arredondo, Miguel Angel; Mujica Delgado, Luis Eduardo; Rodellar Benedé, José; Fritzen, Claus-Peter Abstract: The interest in the propagation of ultrasound waves in pipe-like solid waveguides arises out of several areas of the structural health monitoring (SHM) community for the detection, localization and assessment of defects as well as the prediction of remaining life in civil, mechanical, aeronautic and aerospace structures. SHM premise offers a continuous observation of the structural integrity of operational systems. This is particularly convenient, therefore, for the reduction of time and cost for maintenance without decreasing the level of safety. Some practical applications are the monitoring of pipework in gas and oil industries, suspension bridge cables, nuclear fuel cladding tubes, etc. This paper describes an approach for SHM using guided waves in pipe-like structures in terms of a pattern recognition problem. The formalism is based on a distributed piezoelectric sensor network for the detection of structural dynamic responses. Several methods for signal filtration, feature selection and extraction, and data compression of the recorded time histories are discussed and evaluated. Principal Component Analysis (PCA), Non-Linear PCA (NLPCA) and Wavelet Transform are among them. Additionally, the different clusters, corresponding to each damage level are visualized with the help of Self Organizing Maps (SOM). Tests were performed on a piping system where the properties of the proposed methods are compared and appraised with experimental pitch-catch signals between the pristine and the damaged structure. 2013-02-26T12:22:01Z http://hdl.handle.net/2117/17972 Title: Damage assessment in a stiffened composite panel using non-linear data-driven modelling and ultrasonic guided waves Authors: Torres-Arredondo, Miguel Angel; Tibaduiza Burgos, Diego Alexander; Mujica Delgado, Luis Eduardo; Rodellar Benedé, José; Fritzen, Claus-Peter Abstract: Structural components made of composite materials are being used more often in aerospace and aeronautic structures due to their well-known properties such as high mass specific stiffness and strength. However, their application also increases the analysis complexity of such structures. Structural health monitoring (SHM) systems for these structures aim to determine the status of the system in real time such that a longer safe life and lower operational costs can be guaranteed. On that account, this paper is concerned with the experimental validation of a structural health monitoring methodology where a damage detection and classification scheme based on an acousto-ultrasonic (AU) approach is applied to a composite panel incorporating stiffening elements using a piezoelectric active sensor network in conjunction with time-frequency multiresolution analysis and non-linear feature extraction. Therefore, structural dynamic responses from the simplified aircraft composite skin panel are collected and signal features are then extracted with a signal processing and data fusion methodology in terms of the wavelet transform technique and hierarchical non-linear principal component analysis. A critical comparison with linear feature extraction methods indicates that the proposed method outperforms the traditional linear methods for the purpose of damage classification. Additionally, results show that all the damages were detectable and classifiable, and the selected features proved capable of separating all damage conditions from the undamaged state. 2013-02-26T11:52:08Z http://hdl.handle.net/2117/17971 Title: Un nuevo enfoque para detectar medidas de glucosa erróneas en los Sistemas de Monitorización Continuos de Glucosa Authors: Leal, Yenny; Gonzalez-Abril, Luis; Ruiz Ordóñez, Magda; Lorencio, Carol; Bondia, Jorge; Vehí, Josep Abstract: En este artículo se plantea un nuevo enfoque con el cual se pretende detectar mediciones correctas e incorrectas en los sistemas de monitorización continuos de glucosa (SMCG). Los datos recogidos de 23 pacientes en una Unidad de Cuidados Intensivos(UCI) se obtienen siguiendo los protocolos establecidos en el Hospital Universitario Josep Trueta de Girona. Las estimaciones de glucosa se clasifican usando una nueva máquina de soporte vectorial para distinguir entre mediciones correctas e incorrectas del SMCG, utilizando la información proporcionada por el propio monitor e incorporando variables acerca de la condición clínica del paciente. 2013-02-26T11:34:54Z http://hdl.handle.net/2117/17937 Title: A mathematical framework for structural control integration Authors: Rossell Garriga, Josep Maria; Rodellar Benedé, José; Palacios Quiñonero, Francisco; Rubió Massegú, Josep Abstract: In this paper, some control strategies to design decentralized controllers are developed and discussed. These strategies are based on the Inclusion Principle, a very useful mathematical framework to obtain decentralized controllers, mainly when the systems are composed by overlapped subsystems sharing common parts. A ve-story building model serves as example to show the advantages provided by this approach. Numerical simulations are conducted to assess the performance of the proposed control laws with positive results. 2013-02-22T12:29:46Z http://hdl.handle.net/2117/17821 Title: Damage detection using robust fuzzy principal component analysis Authors: Gharibnezhad, Fahit; Mujica Delgado, Luis Eduardo; Rodellar Benedé, José; Fritzen, Claus-Peter Abstract: In this work Robust Fuzzy Principal Component Analysis (RFPCA) is used and compared with comparing with classical Principal Component Analysis (PCA) to detect and classify damages. It has been proved that the RFPCA method achieves better result mainly because it is more compressible than classical PCA and also carries more information, hence not only it can distinguish the healthy structure from the damaged structure much sharper than the traditional counterparts but also in some cases traditional PCA is incapable of discerning the pristine from damaged structure. This work involves experimental results using pipe-like structure powered by a piezoelectric actuators and sensors. 2013-02-18T11:50:32Z http://hdl.handle.net/2117/17213 Title: Fuzzy control of dissolved oxygen and on-line OUR estimation in a SBR pilot plant Authors: Rubio, Monserrat; Ruiz Ordóñez, Magda; Teran, Fabiana; Arroyo, F.; Colomer, Joan; Colprim, Jesus 2013-01-08T13:30:11Z http://hdl.handle.net/2117/16562 Title: A unified approach for the identification of SISO/MIMO Wiener and Hammerstein systems Authors: Ikhouane, Fayçal; Giri, F. Abstract: Hammerstein and Wiener models are nonlinear representations of systems composed by the coupling of a static nonlinearity N and a linear system L in the form N-L and L-N respectively. These models can represent real processes which made them popular in the last decades. The problem of identifying the static nonlinearity and linear system is not a trivial task, and has attracted a lot of research interest. It has been studied in the available literature either for Hammerstein or Wiener systems, and either in a discrete-time or continuous-time setting. The objective of this paper is to present a uni ed framework for the identification of these systems that is valid for SISO and MIMO systems, discrete and continuous-time setting, and with the only a priori knowledge that the system is either Wiener or Hammerstein. 2012-09-25T12:05:30Z http://hdl.handle.net/2117/16533 Title: A characterization of hysteresis systems Authors: Ikhouane, Fayçal Abstract: Hysteresis is a nonlinear phenomenon exhibited by systems stemming from various science and engineering areas. To detect experimentally the presence of hysteresis in a system, the graph output versus input of the system is plotted for different frequencies of the input. For hysteresis systems, these graphs converge to a quasi-static limit set when the frequency goes to zero. Moreover, the quasi-static graph approaches asymptotically a periodic orbit. Thus, hysteresis is nonlinear phenomenon that can be detected only in the quasi-static regime, that is when the frequency content of the input goes to zero. The relevance of hysteresis in applications and the fact that it is essentially a quasi-static phenomenon makes it important to characterize mathematically the quasi-static regime, which is the purpose of this paper. Although this work is motivated by hysteresis systems, the tools that are presented are not limited to this class of systems. For this reason, the systems that we consider are seen as operators that map an input signal and initial condition to an output signal, all of them belonging to some specified sets. The main result of this paper is a new criterion for the existence, uniqueness and mathematical characterization of the quasi-static regime. 2012-09-20T09:35:30Z http://hdl.handle.net/2117/16436 Title: Frequency identification of Wiener systems with Backlash operators using separable least squares estimators Authors: Giri, F.; Rochdi, Y.; Ikhouane, Fayçal; Brouri, A; Chaoui, F.Z Abstract: This paper deals with the identification of Wiener models that involve backlash operators bordered by possibly noninvertible parametric lines. The latter are also allowed to cross each other making possible to account for general-shape static nonlinearities. The linear dynamic subsystem is not-necessarily parametric but is BIBO stable. A frequency identification method is developed that provides estimates of the nonlinear operator parameters as well as estimates of the linear subsystem frequency gain. The method involves standard and separable least squares estimators that all are shown to be consistent. Backlash operators and memoryless nonlinearities are handled within a unified framework. 2012-09-05T11:43:48Z http://hdl.handle.net/2117/16230 Title: Hybrid RNC-isolation of structures under near-fault earthquakes Authors: Abdel Kareem Moustafa, Mohamed Ismail; Pozo Montero, Francesc; Rodellar Benedé, José Abstract: The problem of combining active damping with a purely passive isolation system, with hysteretic damping,to reduce possible pounding effects under near-fault ground motions is addressed. The used isolation system is a recentlyproposed one that is referred to as roll in cage (RNC) isolator. It has an integrated buffer mechanism to prevent excessive bearing displacements under strong seismic excitations. Therefore, possible pounding under such strong earthquakes will be within the bounds of RNC isolator to avoid adjacent structural pounding. Active control is invoked at a certain bearing displacement to reduce it before reaching its design limit, after which pounding takes place. It was found that increasing the RNC isolator’s inherent hysteretic damping reduces the bearing displacement and consequently alleviates or even eliminate pounding. Moreover, the integration of active control, at smaller bearing displacements, with the RNC isolator can reduce the bearing displacement but adds more rigidity to the isolation system, which leads to less efficient isolation. 2012-07-11T12:15:01Z http://hdl.handle.net/2117/16202 Title: Discrete-time static output-feedback semi-decentralized H-infinity controller design: an application to structural vibration control Authors: Palacios Quiñonero, Francisco; Rubió Massegú, Josep; Rossell Garriga, Josep Maria; Karimi, Hamid Reza 2012-07-09T09:29:28Z http://hdl.handle.net/2117/16139 Title: LMI control design on structural systems with experimental study Authors: Pujol Vázquez, Gisela; Acho Zuppa, Leonardo Abstract: A nonlinear robust control is developed for active mass damper system subject to external perturbation. This nonlinear controller is composed by the sum of a linear term plus a chattering component. The linear term is designed using linear matrix inequality (LMI) theory. Then, the chattering term is added to improve controller performance. Lyapunov theory is used to validate our control design. According with experiments, where a flexible two levels building with active mass damper and external perturbation is employed, they show that this chattering term improves controller performance. However, when a fault occurs, this chattering term is complaining. 2012-06-26T11:40:27Z