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Finite Element Analysis of the Electro-Mechanical Coupling in MEMS Rochus, Véronique ; Duysinx, Pierre ; Golinval, Jean-Claude Conference given outside the academic context (2002) This paper concerns the modelling of the strong electro-mechanical coupling appearing in micro-electro-mechanical systems (MEMS). These systems are very small devices (typical size of a few microns), in ... [more ▼] This paper concerns the modelling of the strong electro-mechanical coupling appearing in micro-electro-mechanical systems (MEMS). These systems are very small devices (typical size of a few microns), in which electric phenomena as well as mechanical and dynamical phenomena exist. The coupling between the electric and mechanical fields induce non-linear terms in the dynamic equilibrium equations of these microscopic structures so that instability may occur. In this paper, the finite element method (FEM) is used to perform modal analysis around non-linear equilibrium positions, taking into account large displacements. [less ▲] Detailed reference viewed: 52 (7 ULg)Integrated simulation of mechanical structures and their control system Bruls, Olivier ; ; Duysinx, Pierre et al in Proc. of the 2nd Int. Conf. on Advanced Computational Methods in Engineering (ACOMEN) (2002, May) This paper concerns the modeling and the integrated numerical simulation of flexible mechanisms subject to the action of a digital control system. A general method is proposed, based on the formalism of ... [more ▼] This paper concerns the modeling and the integrated numerical simulation of flexible mechanisms subject to the action of a digital control system. A general method is proposed, based on the formalism of flexible multibody systems (MBS) using the Finite Element Method (FEM). Nonlinear e ects in the mechanical structure or in the control system can be taken into account. The numerical simulation tool is applied to design an active control system in a hot-dip galvanizing line, which aims at reducing the vibrations of the steel strip. [less ▲] Detailed reference viewed: 16 (2 ULg)Active Control of the Steel Strip in a Hot-Dip Galvanizing Line Bruls, Olivier ; Golinval, Jean-Claude Conference (2002, March) This paper concerns the design of an active control system for a hot dip galvanizing line. The control system aims at reducing the vibrations of the steel strip in order to improve the quality of the ... [more ▼] This paper concerns the design of an active control system for a hot dip galvanizing line. The control system aims at reducing the vibrations of the steel strip in order to improve the quality of the product. The mechanical structure is quite flexible and many vibration modes need to be controlled. The actuators and the sensors are collocated and the control law is a direct velocity feedback, which doesn't require any model of the plant. This control law adds damping on all the vibration modes and it guarantees the stability of the system. The position of the actuators is chosen to maximize the controllability and the observability. The relevance of this strategy is discussed. The natural frequencies of the mechanical system are evaluated using the Finite Element Method. In this particular example, it was found that the frequencies of the flexion vibration modes almost match the frequencies of the torsion modes. The corresponding pole/zero pattern leads to very small root loci where the damping increment is strongly limited. A simulation of the closed loop system is required to evaluate the performance of the active control and to choose the feedback gain. The time-domain evolution of the mechanical structure is computed using the Finite Element Method and an implicit integration scheme. Assuming that the control system is digital and neglecting the dynamics of the actuators, the control system is introduced into the mechanical simulation as a users' routine called at each sampling time of the digital controller. This quite general approach allows to deal with nonlinear eff ects either in the mechanical structure or in the control system, what opens new perspectives in integrated simulation of controlled flexible mechanisms. The simulation shows that a single actuator is not able to control the whole steel strip. Even if the gain increases, the controlled point becomes quickly a fixed point, and the vibration of the rest of the structure is not significantly attenuated. At least three actuators are necessary to get the expected performance. [less ▲] Detailed reference viewed: 59 (0 ULg)Frequency domain approaches for the identification of an experimental beam with a local nonlinearity Kerschen, Gaëtan ; Golinval, Jean-Claude in 20th International Modal Analysis Conference, Los Angeles, 2002 (2002, February) Two approaches for the identification of multi-degree-of-freedom non-linear systems in the frequency domain have recently been introduced, i.e., the conditioned reverse path (CRP) method and the non ... [more ▼] Two approaches for the identification of multi-degree-of-freedom non-linear systems in the frequency domain have recently been introduced, i.e., the conditioned reverse path (CRP) method and the non-linear identification through feedback of the outputs (NIFO) method. The key idea of these methods is to eliminate the distortions caused by the presence of non-linearities in frequency response functions. In this paper, the theoretical background of the CRP and NIFO methods is briefly recalled. Then, the ability of these techniques to identify the behaviour of an experimental cantilever beam with a local geometrical non-linearity is tested. The results obtained with both methods are compared and discussed. [less ▲] Detailed reference viewed: 34 (0 ULg)Physical interpretation of the proper orthogonal modes using the singular value decomposition Kerschen, Gaëtan ; Golinval, Jean-Claude in Journal of Sound & Vibration (2002), 249(5), 849-865 Proper orthogonal decomposition is a statistical pattern analysis technique for finding the dominant structures, called the proper orthogonal modes, in an ensemble of spatially distributed data. While the ... [more ▼] Proper orthogonal decomposition is a statistical pattern analysis technique for finding the dominant structures, called the proper orthogonal modes, in an ensemble of spatially distributed data. While the proper orthogonal modes are obtained through a statistical formulation, they can be physically interpreted in the field of structural dynamics. The purpose of this paper is thus to provide some insights into the physical interpretation of the proper orthogonal modes using the singular value decomposition. (C) 2002 Academic Press. [less ▲] Detailed reference viewed: 34 (6 ULg)COST Action F3 on Structural Dynamics: Benchmarks for Structural Health Monitoring ; ; et al Conference given outside the academic context (2002) This paper is concerned with the results from the COST Action F3 Working Group Two benchmarking exercise in Structural Health Monitoring. Data from two large-scale structures were modelled for the ... [more ▼] This paper is concerned with the results from the COST Action F3 Working Group Two benchmarking exercise in Structural Health Monitoring. Data from two large-scale structures were modelled for the purposes of damage detection, location and quantification. Several analysis papers have been submitted for a special issue of Mechanical Systems and Signal Processing and the conclusions of each are summarised here, together with more general conclusions arising from the concerted effort. [less ▲] Detailed reference viewed: 27 (0 ULg)Accelerated Fatigue Testing Methodology of Luminaires on Electro-Dynamic Shaker ; Golinval, Jean-Claude ; Conference given outside the academic context (2002) Detailed reference viewed: 42 (1 ULg)Finite Element Model Updating of Plate-like Structures Using Modal Holographic Measurement Field ; Golinval, Jean-Claude Conference given outside the academic context (2002) Optical measurement techniques are very promising for finite element (F.E.) model updating or error localisation of plate-like structures in the field of structural dynamics. The purpose of this work is ... [more ▼] Optical measurement techniques are very promising for finite element (F.E.) model updating or error localisation of plate-like structures in the field of structural dynamics. The purpose of this work is to investigate a way to better exploit the high spatial resolution inherent to these techniques in order to correct FE mesh discretisation errors and/or model parameter errors. An important assumption in F.E. model error detection is first to consider the initial mesh as sufficiently fine to well represent the measured (displacement or stress) field. In the case of model updating, the adjustment of the model is performed by minimising the difference between the outputs of the model and the exact solution with respect to design parameters. In the case of FE mesh adaptation, the exact solution has to be estimated whereas in the case of model parameter errors, the reference solution is assumed to be the measured one. The idea developed in this paper is to take advantage of the high spatial resolution offered by optical techniques to calculate successively two error estimators using only measurements. The experimental field is first used for the detection of singular regions corresponding to high gradients. This estimator indicates the regions where a mesh refinement is required. Thus a second estimator is calculated and used for parameter error detection. [less ▲] Detailed reference viewed: 26 (1 ULg)A Robust FRF-based Technique for Model Updating ; ; Golinval, Jean-Claude et al Conference given outside the academic context (2002) Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models. Major reasons for this is that FRFs are very sensitive to damping properties at resonance peaks ... [more ▼] Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models. Major reasons for this is that FRFs are very sensitive to damping properties at resonance peaks, local modes influence is included and no modal analysis is required. Nevertheless, it is well known that due to their nature, the frequency responses may change its order of magnitude very rapidly for small parameter or frequency changes. This situation may cause serious discontinuities in the topology of the objective function, causing the updating strategy to diverge or to find a local non-physical minimum. A primary tool for the correlation of FRFs is the Frequency Domain Assurance Criterion. This technique introduces the concept of frequency shift between the frequency response shapes of a reference model (the experimental structure) and a perturbed model (an initial non-updated FE model). Such a concept opens the way for using residues at different frequencies. For instance, in reference the residue is composed by point FRFs at anti-resonances. This paper introduces a general FRF-based model-updating technique, which is focused in using stable residues during the interactive optimization procedure. A benchmark case from the Cost F3 action is used to assess the goodness of the method compared to other well known methods. [less ▲] Detailed reference viewed: 88 (2 ULg)Modeling of Electro-mechanical coupling in MEMS Rochus, Véronique ; Duysinx, Pierre ; Golinval, Jean-Claude Scientific conference (2002) Detailed reference viewed: 27 (7 ULg)Experimental identification of a non-linear beam, conditionned reverse path method Kerschen, Gaëtan ; ; Golinval, Jean-Claude in International Conference on Structural Systems Identification, Kassel, 2001 (2001, September) A new spectral approach for identification of multi-degree-of-freedom nonlinear systems, called the conditioned reverse path method, has recently been introduced. The key idea of this method is to ... [more ▼] A new spectral approach for identification of multi-degree-of-freedom nonlinear systems, called the conditioned reverse path method, has recently been introduced. The key idea of this method is to eliminate the distortions caused by the presence of non-linearities in frequency response functions. Conditioned frequency responses are then computed and yield the underlying linear properties without influence of non-linearities. The non-linear coefficient is estimated in a second step. The aim of the paper is twofold. Firstly, the conditioned reverse path method is described in details together with the spectral conditioning techniques. Secondly, the ability of this technique to identify the behaviour of an experimental cantilever beam with a geometrical non-linearity is tested. [less ▲] Detailed reference viewed: 30 (2 ULg)Application of ARMAV models to identification and damage detection of mechanical and civil engineering structures ; Golinval, Jean-Claude in Smart Materials & Structures (2001), 10(3), 479-489 In this paper, the application of auto-regressive moving average vector models to system identification and damage detection is investigated. These parametric models have already been applied for the ... [more ▼] In this paper, the application of auto-regressive moving average vector models to system identification and damage detection is investigated. These parametric models have already been applied for the analysis of multiple input-output systems under ambient excitation. Their main advantage consists in the capability of extracting modal parameters from the recorded time signals, without the requirement of excitation measurement. The excitation is supposed to be a stationary Gaussian white noise. The method also allows the estimation of modal parameter uncertainties. On the basis of these uncertainties, a statistically based damage detection scheme is performed and it becomes possible to assess whether changes of modal parameters are caused by, e.g. some damage or simply by estimation inaccuracies. The paper reports first an example of identification and damage detection applied to a simulated system under random excitation. The `Steel-Quake' benchmark proposed in the framework of COST Action F3 `Structural Dynamics' is also analysed. This structure was defined by the Joint Research Centre in Ispra (Italy) to test steel building performance during earthquakes. The proposed method gives an excellent identification of frequencies and mode shapes, while damping ratios are estimated with less accuracy. [less ▲] Detailed reference viewed: 57 (4 ULg)Proper orthogonal decomposition for model updating of non-linear mechanical systems ; Kerschen, Gaëtan ; Golinval, Jean-Claude in Mechanical Systems & Signal Processing (2001), 15(1) Proper orthogonal decomposition (POD), also known as Karhunen}Loeve (K}L) decomposition, is emerging as a useful experimental tool in dynamics and vibrations. The POD is a means of extracting spatial ... [more ▼] Proper orthogonal decomposition (POD), also known as Karhunen}Loeve (K}L) decomposition, is emerging as a useful experimental tool in dynamics and vibrations. The POD is a means of extracting spatial information from a set of time-series data available on a domain. The use of (K}L) transform is of great help in non-linear settings where traditional linear techniques such as modal-testing and power-spectrum analyses cannot be applied. These decomposition can be used as an orthogonal basis for e$cient representation of the ensemble. The POM have been interpreted mainly as empirical system modes and the application of POD to measured displacements of a discrete structure with a known mass matrix leads to an estimation of the normal modes. We investigate the use of the proper orthogonal modes of displacements for the identi"cation of parameters of non-linear dynamical structures with an optimisation procedure based on the di!erence between the experimental and simulated POM. A numerical example of a beam with a local non-linear component will illustrate the method. (C) 2001 Academic Press [less ▲] Detailed reference viewed: 45 (4 ULg)Theoretical and experimental identification of a non-linear beam Kerschen, Gaëtan ; Golinval, Jean-Claude ; in Journal of Sound & Vibration (2001), 244 The identi"cation of the dynamic characteristics of linear systems is now widely used and interest in non-linear systems has increased. The objective of this paper is to demonstrate the performance of the ... [more ▼] The identi"cation of the dynamic characteristics of linear systems is now widely used and interest in non-linear systems has increased. The objective of this paper is to demonstrate the performance of the restoring force surface method as far as the identi"cation of non-linear systems is concerned. The vibrations of a clamped beam are investigated for two di!erent kinds of non-linearity. Firstly, the beam shows a non-linear behaviour characterized by a piecewise linear sti!ness and secondly, the non-linearity comes from a bilinear sti!ness. Both numerical and experimental results are presented. (C) 2001 Academic Press [less ▲] Detailed reference viewed: 57 (3 ULg)Stabilisation vibratoire de la ligne de galvanisation Eurogal - Etude paramétrique Bruls, Olivier ; ; Golinval, Jean-Claude Report (2001) Detailed reference viewed: 133 (5 ULg)COST F3 Structural Dynamics 1997-2001, Presentation and Some Preliminary Results Golinval, Jean-Claude ; Conference given outside the academic context (2001) The COST Action F3 “Structural Dynamics” was initiated in 1997 by Professor Jean-Claude Golinval. The main objective of this COST Action is to increase the knowledge required for improving the structural ... [more ▼] The COST Action F3 “Structural Dynamics” was initiated in 1997 by Professor Jean-Claude Golinval. The main objective of this COST Action is to increase the knowledge required for improving the structural design, the mechanical reliability, and the safety of structures in linear and non-linear dynamics. This research Action is supported by the European Community and is divided into three working groups dealing with the following issues: WG1: “Finite Element Model Updating Methods”; WG2: “Health Monitoring and Damage Detection”; and WG3: “Identification of Non-linear Systems”. This paper presents the objectives of the COST Action F3, the organization of the Action, the members of the management committee, and the scientific program of each working group in more detail. Finally, preliminary results of the COST Action are presented. [less ▲] Detailed reference viewed: 23 (0 ULg)Damage Localisation Using Principal Component Analysis of Distributed Sensor Array ; Golinval, Jean-Claude Conference given outside the academic context (2001) The spatial information given by the distributed sensors (e.g., piezoelectric laminates) can be used to forecast structural damage on localised critical spot. It is well known that a localised structural ... [more ▼] The spatial information given by the distributed sensors (e.g., piezoelectric laminates) can be used to forecast structural damage on localised critical spot. It is well known that a localised structural damage with relative small amplitude does not affect significantly the modal response of the structure, at least at low frequencies. Nevertheless, a local de-lamination or electrode deterioration at the distributed sensor level will show significant changes on the response of the sensor by modifying its apparent electromechanical coupling. Assuming that the number of sensors is greater than the number of involved structural modes, a local structural damage, with relative small amplitude, will only affect a particular distributed sensor without affecting significantly the response of the others. By applying a principal component analysis (PCA) on the sensor time responses, it is possible to see that any change of one particular sensor electromechanical coupling factor will affect the subspace generated by the complete sensor response set. The subspace generated with the damaged structure can then be compared with the subspace of an initial state in order to diagnose damage or not. [less ▲] Detailed reference viewed: 38 (0 ULg)Modal Identification of the "Steel-Quake" Structure Using the Data-Driven Stochastic Subspace and ARMAV Methods ; Golinval, Jean-Claude Conference given outside the academic context (2001) In this paper, two techniques used for modal identification of output-only systems are presented and compared. The first technique is based on an ARMAV model. The method is known as the prediction error ... [more ▼] In this paper, two techniques used for modal identification of output-only systems are presented and compared. The first technique is based on an ARMAV model. The method is known as the prediction error method (PEM) and requires a non-linear iterative optimisation procedure. The second technique is a stochastic subspace method that estimates the system matrices of a stochastic state space model by a data-driven algorithm and by using numerical techniques such as singular value and QR decompositions. The comparison between both techniques is performed over the “Steel-Quake” benchmark proposed in the framework of COST Action F3 “Structural Dynamics”. The results show that the investigated techniques give good results in term of estimated modal parameters. Especially, it is found that the stochastic subspace technique is much faster than the PEM. [less ▲] Detailed reference viewed: 29 (1 ULg)Finite Element Model Updating of the Garteur SM-AG19 Structure ; Golinval, Jean-Claude Conference given outside the academic context (2001) This paper reports the procedure followed by the "LTAS-Vibrations et Identification des Structures" research group to generate a low order nite element (F.E.) model of the GARTEUR SM-AG19 structure ... [more ▼] This paper reports the procedure followed by the "LTAS-Vibrations et Identification des Structures" research group to generate a low order nite element (F.E.) model of the GARTEUR SM-AG19 structure proposed as benchmark in the framework of the European COST Action F3 in structural dynamics. The model is made of beam elements, local inertia and rigid body elements. First, the correlation of the experimental data with the results of the F.E. model shows different levels of discrepancies. To perform local error detection, the size of the measured mode shape vectors is first expanded to the size of the F.E. eigenvectors. Model error localisation is based on the computation of residual strain energy due to errors in the constitutive equations. Updating parameters are then selected using eigenvalue sensitivity and local error analyses. The error localisation procedure is followed by the updating process in order to improve the accuracy of the FE models. The quality of the results is assessed in terms of accuracy of the response prediction to structural modifications. [less ▲] Detailed reference viewed: 134 (3 ULg)Identification of wire rope isolators using the restoring force surface method Kerschen, Gaëtan ; ; Golinval, Jean-Claude in International Conference on Structural Systems Identification, Kassel, 2001 (2001) The restoring force surface method offers an efficient and reliable identification of non-linear single-degree-of-freedom systems. The method may be extended to multidegree-of-freedom systems but by ... [more ▼] The restoring force surface method offers an efficient and reliable identification of non-linear single-degree-of-freedom systems. The method may be extended to multidegree-of-freedom systems but by loosing the key advantage of the method which lies in the two-dimensional representation for single-degree-of-freedom systems. An experimental application of the restoring force surface method is considered in the present paper. The structure investigated consists of wire rope isolators mounted between a load mass and a base mass. These helical isolators were found to be characterised by a non-linear behaviour. The results obtained are discussed in details and the advantages and drawbacks of the method are underlined. [less ▲] Detailed reference viewed: 57 (1 ULg) |
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