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Dynamic investigations of paddle MEMS cantilevers used in mass sensing applications Pustan, Marius ; ; Golinval, Jean-Claude in Arghir, Mariana (Ed.) Acta Technica Napocensis of The Technical University of Cluj-Napoca (2011) The dynamic behaviour of paddle MEMS cantilever oscillators under electrostatic actuation is investigated and presented in this paper. The scope is to estimate the influence of the geometrical dimensions ... [more ▼] The dynamic behaviour of paddle MEMS cantilever oscillators under electrostatic actuation is investigated and presented in this paper. The scope is to estimate the influence of the geometrical dimensions and operating conditions on the frequency response of mechanical paddle cantilevers fabricated from polysilicon. Theoretical approach and finite element analysis are developed considering the multiphysics coupling between the electrical field and the mechanical structure of oscillators. The;experimental tests are performed under ambient condition and in vacuum in order to characterize the effect of operating condition on the frequency response of paddle cantilevers. [less ▲] Detailed reference viewed: 65 (2 ULg)Industrial applications of extended output-only Blind Source Separation techniques Rutten, Christophe ; ; Golinval, Jean-Claude in Vibration Problems Icovp 2011: The 10th International Conference on Vibration Problems (2011) In the field of structural health monitoring or machine condition moni-toring, most vibration based methods reported in the literature require to measure responses at several locations on the structure ... [more ▼] In the field of structural health monitoring or machine condition moni-toring, most vibration based methods reported in the literature require to measure responses at several locations on the structure. In machine condition monitoring, the number of available vibration sensors is often small and it is not unusual that only one single sensor is used to monitor a machine. This paper presents industrial applications of two possible extensions of output-only Blind Source Separation (BSS) techniques, namely Principal Component Analysis (PCA) and Second Order Blind Identification (SOBI). Through the use of block Hankel matrices, these methods may be used when a reduced set of sensors or even one single sensor is available. The objective is to address the problem of fault detection in mechanical systems using subspace-based methods. The detection is achieved by comparing the subspace features between the reference and a current state using the concept of angular coherence between subspaces. [less ▲] Detailed reference viewed: 33 (6 ULg)Fault Diagnosis in Industrial Systems Based on Blind Source Separation Techniques Using One Single Vibration Sensor Nguyen, Viet Ha ; Rutten, Christophe ; Golinval, Jean-Claude in Maia NNM, Neves MM (Ed.) International Conference on Structural Engineering Dynamics (ICEDyn 2011) - Proceedings (2011) In the field of structural health monitoring or machine condition monitoring, most vibration based methods reported in the literature require to measure responses at several locations on the structure. In ... [more ▼] In the field of structural health monitoring or machine condition monitoring, most vibration based methods reported in the literature require to measure responses at several locations on the structure. In machine condition monitoring, the number of available vibration sensors is often small and it is not unusual that only one single sensor is used to monitor a machine. The aim of this paper is to propose an extension of fault detection techniques that may be used when a reduced set of sensors or even one single sensor is available. Fault detection techniques considered here are based on output-only methods coming from the Blind Source Separation (BSS) family, namely Principal Component Analysis (PCA) and Second Order Blind Identification (SOBI). The advantages of PCA or SOBI rely on their rapidity of use and their reliability. Based on these methods, subspace identification may be performed by using the concept of block Hankel matrices which make possible the use of only one single measurement signal. Thus, the problem of fault detection in mechanical systems can be solved by using subspaces built from active principal components or modal vectors. It consists in comparing subspace features between the reference (undamaged) state and a current state. The angular coherence between subspaces is a good indicator of a dynamic change in the system due to the occurrence of faults or damages. The robustness of the methods is illustrated on industrial examples. [less ▲] Detailed reference viewed: 77 (7 ULg)Design of Microswitch Systems Avoiding Stiction due to Surface Contact Wu, Ling ; Noels, Ludovic ; et al in Proulx, Tom (Ed.) MEMS and Nanotechnology, Volume 2 (2011) Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but ... [more ▼] Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but leads to an increase of the actuation voltage so that the switch’s efficiency is threatened. A statistical rough surfaces interaction model, based on Maugis’ and Kim’s formulations is applied to estimate the adhesive forces in MEMS switches. Based on the knowledge of these forces, the proper design range of the equivalent spring constant, which is the main factor of restoring force in MEMS switches, can be determined. The upper limit of equivalent spring constant depends mainly on the expected actuator voltage and on the geometric parameters, such as initial gap size and thickness of dielectric layer. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. It mainly depends on the adhesive work of contact surfaces and on the surfaces’ roughness. In order to study more complicated structures, this framework will be used in a multiscale model: resulting unloading micro adhesive contact-distance curves of two rough surfaces will be used as contact forces in a finite-element model. In this paper the extraction of these curves for the particular case of gold to gold micro-switches is pursued. [less ▲] Detailed reference viewed: 71 (24 ULg)Damage Detection Using Blind Source Separation Techniques Nguyen, Viet Ha ; Golinval, Jean-Claude in IMAC-XXIX: Conference & Exposition on Structural Dynamics - Advanced Aerospace Applications (2011) Blind source separation (BSS) techniques are applied in many domains since they allow separating a set of signals from their observed mixture without the knowledge (or with very little knowledge) of the ... [more ▼] Blind source separation (BSS) techniques are applied in many domains since they allow separating a set of signals from their observed mixture without the knowledge (or with very little knowledge) of the source signals or the mixing process. Two particular BSS techniques called Second-Order Blind Identification (SOBI) and Blind Modal Identification (BMID) are considered in this paper for the purpose of structural damage detection or fault diagnosis in mechanical systems. As shown on experimental examples, the BMID method reveals significant advantages. In addition, it is demonstrated that damage detection results may be improved significantly with the help of the block Hankel matrix. The main advantage in this case is that damage detection still remains possible when the number of available sensors is small or even reduced to one. Damage detection is achieved by comparing the subspaces between the reference (healthy) state and a current state through the concept of subspace angle. The efficiency of the methods is illustrated using experimental data. [less ▲] Detailed reference viewed: 191 (4 ULg)Modal testing of nonlinear vibrating structures based on nonlinear normal modes: Experimental demonstration Peeters, Maxime ; Kerschen, Gaëtan ; Golinval, Jean-Claude in Mechanical Systems & Signal Processing (2011), 25 Detailed reference viewed: 27 (1 ULg)Dynamic testing of nonlinear vibrating structures using nonlinear normal modes Peeters, Maxime ; Kerschen, Gaëtan ; Golinval, Jean-Claude in Journal of Sound & Vibration (2011), 330 Detailed reference viewed: 28 (1 ULg)Nonlinear Normal Modes of a Full-Scale Aircraft Peeters, Maxime ; Kerschen, Gaëtan ; Golinval, Jean-Claude et al in 29th International Modal Analysis Conference, Jacksonville, 2011 (2011) Detailed reference viewed: 37 (5 ULg)NANOTRIBOLOGICAL AND NANOMECHANICAL CHARACTERIZATIONS OF MEMS MATERIALS Pustan, Marius ; ; Golinval, Jean-Claude Poster (2010, December) Detailed reference viewed: 36 (5 ULg)Fault detection based on Kernel Principal Component Analysis Nguyen, Viet Ha ; Golinval, Jean-Claude in Engineering Structures (2010), 32 In the field of structural health monitoring or machine condition monitoring, the activation of nonlinear dynamic behavior may render the procedure of damage or fault detection more difficult. Principal ... [more ▼] In the field of structural health monitoring or machine condition monitoring, the activation of nonlinear dynamic behavior may render the procedure of damage or fault detection more difficult. Principal Component Analysis (PCA) is known as a popular method for diagnosis but as it is basically a linear method, it may pass over some useful nonlinear features of the system behavior. One possible extension of PCA is Kernel PCA (KPCA), owing to the use of nonlinear kernel functions that allow to introduce nonlinear dependences between variables. The objective of this paper is to address the problem of fault detection (in terms of nonlinear activation) in mechanical systems using a KPCA-based method. The detection is achieved by comparing the subspaces between the reference and a current state of the system through the concept of subspace angle. It is shown in this work that the exploitation of the measurements in the form of block Hankel matrices can improve effectively the detection results. The method is illustrated on an experimental example consisting of a beam with a geometric nonlinearity. [less ▲] Detailed reference viewed: 69 (5 ULg)Fault detection in mechanical systems based on subspace features Nguyen, Viet Ha ; Rutten, Christophe ; Golinval, Jean-Claude in International Conference on Noise and Vibration Engineering (2010, September) In the field of structural health monitoring or machine condition monitoring, the activation of nonlinear dynamic behavior complicates the procedure of damage or fault detection. Principal Component ... [more ▼] In the field of structural health monitoring or machine condition monitoring, the activation of nonlinear dynamic behavior complicates the procedure of damage or fault detection. Principal Component Analysis (PCA) is known as an efficient method for damage diagnosis. However, two drawbacks of PCA are the assumption of the linearity of the system and the need of many sensors. This article presents industrial applications of two possible extensions of PCA: Null subspace analysis (NSA) and Kernel PCA (KPCA). The advantages of NSA rely on its rapidity of use and its reliability. The KPCA method, through the use of nonlinear kernel functions, allows to introduce nonlinear dependences between variables. The objective is to address the problem of fault detection in mechanical systems using subspace-based methods. The detection is achieved by comparing the subspace features between the reference and a current state through statistics. Industrial data are used as illustration of the methods. [less ▲] Detailed reference viewed: 76 (4 ULg)Localization and quantification of damage in beam-like structures using sensitivities of principal component analysis results Nguyen, Viet Ha ; Golinval, Jean-Claude in Mechanical Systems & Signal Processing (2010), 24(6), 1831-1843 Principal component analysis (PCA) is known as an efficient method for dynamic system identification and diagnosis. This paper addresses a damage diagnosis method based on sensitivities of PCA in the ... [more ▼] Principal component analysis (PCA) is known as an efficient method for dynamic system identification and diagnosis. This paper addresses a damage diagnosis method based on sensitivities of PCA in the frequency domain for linear-form structures. The aim is not only to detect the presence of damage, but also to localize and to evaluate it. The Frequency response functions measured at different locations on the beam are considered as data for the PCA process. Sensitivities of principal components obtained from PCA to beam parameters are computed and inspected according to the location of sensors; their variation from the healthy state to the damaged state indicates damage locations. The damage can be evaluated next providing that a structural model is available; this evaluation is based on a model updating procedure. It is worth noting that the diagnosis process does not require a modal identification achievement. Both numerical and experimental examples are used for better illustration. [less ▲] Detailed reference viewed: 69 (18 ULg)Detection of nonlinearity in a dynamic system using deformation modes obtained from the wavelet transform of measured responses Nguyen, Viet Ha ; Peeters, Maxime ; Golinval, Jean-Claude in Shock and Vibration (2010), 17(4-5), 491-506 An efficient approach to Structural Health Monitoring of dynamical systems based on the Wavelet Transform (WT) and the concept of subspace angle is presented. The objective is to propose a detection ... [more ▼] An efficient approach to Structural Health Monitoring of dynamical systems based on the Wavelet Transform (WT) and the concept of subspace angle is presented. The objective is to propose a detection method that is sensitive to the onset of nonlinear behaviour in a dynamic system. For this purpose, instantaneous frequencies are identified first from output-only vibration signals using the Wavelet Transform. Time varying deformation shapes are then extracted by analyzing the whole measurement data set on the structure. From this information, different dynamic states of the structure may be detected by inspecting time variations of 'modal' features. The experimental structure considered here as application example is a clamped beam with a geometric nonlinearity. Detection of nonlinearity is carried out by means of the concept of subspace angles between instantaneous deformation modes extracted from measurement data using the continuous Wavelet Transform. The method consists in controlling the angular coherence between active subspaces of the current and reference states respectively. The proposed technique, which shows a good sensitivity to small changes in the dynamic behaviour of the structure, may also be used for damage detection. [less ▲] Detailed reference viewed: 66 (17 ULg)Geometrical Effects on the Dynamical Behavior of MEMS structures Pustan, Marius ; Golinval, Jean-Claude ; Rochus, Véronique (2010, May 16) The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as ... [more ▼] The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as microbridges and microcantilevers are used to investigate the coupled electro-mechanic effect, frequency responses and the dynamic bending stress. The electrostatic principle is common in sensing and acting devices and there are many MEMS structures subjected to electrostatic forces. [less ▲] Detailed reference viewed: 28 (9 ULg)Modeling and Finite Element Analysis of Mechanical Behavior of Flexible MEMS Components Pustan, Marius ; ; Rochus, Véronique et al in Courtois, Bernard (Ed.) DTIP 2010 (2010, May 05) This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite ... [more ▼] This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite element analyses together with theoretical and experimental investigations are performed to estimate the mechanical behaviour of MEMS components as microcantilevers, microbridges and micromembranes. The finite element analysis of microcomponents deflections under different loading and the stress distribution in beams is determined and compared with the experimental measurements performed using atomic force microscope. The modeling of a micromembrane supported by four hinges that enable out-of-plane and in-plane motions is presented. Finite element analysis and experimental investigations are performed to estimate the deflection of the mobile plate of the micromembrane under an applied force and to visualize the distribution of the stress in hinges. In additional, this paper provides analytical relations for stiffness and stresses of the investigated flexible MEMS components. [less ▲] Detailed reference viewed: 38 (8 ULg)Theoretical and experimental modal analysis of nonlinear aerospace structures Peeters, Maxime ; Golinval, Jean-Claude ; Kerschen, Gaëtan in Proceedings of the AIAA Modeling and Simulation Technologies Conference (2010) Because nonlinearity is a frequent occurrence in aerospace applications, there is a need for e cient analysis procedures. In this context, nonlinear normal modes (NNMs) o er a solid mathematical tool for ... [more ▼] Because nonlinearity is a frequent occurrence in aerospace applications, there is a need for e cient analysis procedures. In this context, nonlinear normal modes (NNMs) o er a solid mathematical tool for interpreting a wide class of nonlinear dynamical phenomena. The objective of this study is to highlight the usefulness of NNMs for modeling and testing of nonlinear aerospace structures. Both theoretical and experimental modal analysis are described and are illustrated. [less ▲] Detailed reference viewed: 12 (0 ULg)Modal testing using nonlinear normal modes: experimental demonstration Peeters, Maxime ; Kerschen, Gaëtan ; Golinval, Jean-Claude in Proceedings of the International Conference on Noise and Vibration Engineering (2010) Modal testing and analysis is well-established for linear vibrating structures. While the common practice is to assume linear behavior, nonlinearity is a frequent occurrence in engineering applications ... [more ▼] Modal testing and analysis is well-established for linear vibrating structures. While the common practice is to assume linear behavior, nonlinearity is a frequent occurrence in engineering applications and can drastically alter the behavior of mechanical systems. In this paper, an attempt is made to extend experimental modal analysis methodology to a practical nonlinear analog. In this context, nonlinear normal modes (NNMs) offer a solid theoretical and mathematical tool for interpreting a wide class of nonlinear dynamical phenomena, yet they have a clear and simple conceptual relation to the classical linear normal modes. Based on a nonlinear extension of phase resonance testing (also called force appropriation), the proposed methodology excites the structure to isolate one single NNM during the experiments. Thanks to the invariance principle, the energy dependence of that nonlinear mode (i.e., the NNM modal curves and their frequencies of oscillation) can be extracted from the resulting free decay response using time-frequency analysis. The proposed method is demonstrated using an experimental cantilever beam with a geometrical nonlinearity. [less ▲] Detailed reference viewed: 25 (2 ULg)Nonlinear Normal Modes: Theoretical Curiosity or Practical Concept ?, KEYNOTE LECTURE, Peeters, Maxime ; Golinval, Jean-Claude ; Kerschen, Gaëtan in IMPACT 2010, Djerba, 2010 (2010) Detailed reference viewed: 50 (15 ULg)Prediction of Stiction in Microswitch Systems Wu, Ling ; Rochus, Véronique ; Noels, Ludovic et al in EUROSIME 2010 (2010) Stiction is a major failure mode of MEMS as microscopic structures tend to adhere to each other when their surfaces enter into contact. Although increasing the restoring forces of switch devices could ... [more ▼] Stiction is a major failure mode of MEMS as microscopic structures tend to adhere to each other when their surfaces enter into contact. Although increasing the restoring forces of switch devices could overcome the stiction effect, this is not practical, as in turn, it also increases the actuation voltage. Therefore stiction prediction is important to be considered when designing micro- and nano- devices. In this paper, the numerical prediction of stiction for capacitive MEMS switches is considered. Toward this end, a micro-adhesive-contact law is derived from previous work and combined with a finite-element model. [less ▲] Detailed reference viewed: 95 (32 ULg)Evaluation of Tribo-Mechanical Properties of Thin Films Using Atomic Force Microscope Pustan, Marius ; Rochus, Véronique ; Wu, Ling et al in First European Conference on Nanofilm ECNF2010 (2010) Experimental investigations of mechanical and tribological properties of thin films using an atomic force microscope and its combination with nanoidentation are presented in this paper. The normal mode of ... [more ▼] Experimental investigations of mechanical and tribological properties of thin films using an atomic force microscope and its combination with nanoidentation are presented in this paper. The normal mode of an atomic force microscope is used to measure the stiffness and hardness of thin films which are tribologically characterized by roughness, nano-scale adhesion forces and friction forces. The friction forces are measured using the lateral force mode of atomic force microscope. In order to measure the adhesion forces of thin films, spectroscopy in point with atomic force microscope was performed. Direct measurement of tribological and mechanical behaviour of thin films is important to increase the lifetime of microstructures which use thin films for friction and stiction reduction of microsystems. [less ▲] Detailed reference viewed: 89 (24 ULg) |
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