Showing papers by "Jean-Claude Golinval published in 2004"

Structural damage diagnosis by Kalman model based on stochastic subspace identification

Abstract: This paper presents an application of statistical process control techniques for damage diagnosis using vibration measurements. A Kalman model is constructed by performing a stochastic subspace identification to fit the measured response histories of the undamaged (reference) structure. It will not be able to reproduce the newly measured responses when damage occurs. The residual error of the prediction by the identified model with respect to the actual measurement of signals is defined as a damage-sensitive feature. The outlier statistics provides a quantitative indicator of damage. The advantage of the method is that model extraction is performed by using only the reference data and that no further modal identification is needed. On-line health monitoring of structures is therefore easily realized. When the structure consists of the assembly of several sub-structures, for which the dynamic interaction is weak, the damage may be located as the errors attain the maximum at the sensors instrumented in the ...

Feature extraction using auto-associative neural networks

Abstract: Modal analysis is now mature and well accepted in the design of mechanical structures. It determines the vibration mode shapes and the corresponding natural frequencies. However, the validity of modal analysis is limited to structures showing a linear behaviour. In non-linear structural dynamics, it is well known that mode shapes are no longer useful for the characterization of the dynamic response. The purpose of the present paper is to define new features which efficiently capture the dynamics of a non-linear structure. The proposed methodology takes advantage of auto-associative neural networks to compute one-dimensional curves which allow for non-linear dependences between the coordinates. Synthetic data sampled from a non-linear normal mode motion are used to illustrate the method and to develop intuition about its implementation.

A model updating strategy of non‐linear vibrating structures

Abstract: SUMMARY The objective of this paper is to present a model updating strategy of non-linear vibrating structures. Because modal analysis is no longer helpful in non-linear structural dynamics, a special attention is devoted to the features extracted from the proper orthogonal decomposition and one of its non-linear generalizations based on auto-associative neural networks. The efficiency of the proposed procedure is illustrated using simulated data from a three-dimensional portal frame. Copyright 2004 John Wiley & Sons, Ltd.

Placement of Piezoelectric Laminate Actuator for Active Structural Acoustic Control

Abstract: The aim of this work is to investigate the problem of piezoelectric laminate placement. This problem is addressed in the case of modal identification and active control of plate like structures using piezoelectric laminates. The placement technique is based on the inspection of the controllability Grammian of the system expressed in a modal state-space coordinates. The controllability Grammian is able to quantify how structural modes are controllable with a set of predefined actuators. An initial finite element model or an experimental modal identification of the structure is required at the initial step. The procedure consists in making a selection of the smallest subset of actuators which gives a norm of the system transfer function as close as possible to the norm of the original full set. As the study context consists in noise reduction in buildings, the second part of this paper describes an application of this technique on a wooden shutter box in order to reduce the acoustic transmission towards the inner room.

Validation of two nonlinear system identification techniques using an experimental testbed

Abstract: The identification of a nonlinear system is performed using experimental data and two different techniques, i.e. a method based on the Wavelet transform and the Restoring Force Surface method. Both techniques exploit the system free response and result in the estimation of linear and nonlinear physical parameters.

Proper Orthogonal modes for the characterisation of nonlinear dynamic systems

Abstract: Modal analysis is extensively used for the analysis and design of structures. However, a major concern for structural dynamicists is that its validity is limited to systems showing a linear behaviour. New developments have thus been proposed in order to tackle nonlinear systems among which the theory based on the nonlinear normal modes is indubitably themost appealing. In this study, a different approach is adopted and the modes extracted from the proper orthogonal decomposition are considered for the characterization of nonlinear systems.

A systematic model reduction method for the control of flexible multibody systems

Abstract: Summary This paper presents a method to build closed-form dynamic equations for flexible multibody systems with a minimal kinematic description. Relying on the Finite Element formalism, the method is able to tackle complex topologies with closed-loops in a systematic way. Thus, it will be of great use in the framework of model based control of flexible mechanisms. The reduction procedure is based on an interpolation strategy: a Finite Element model is built and reduced for a number of selected points in the configuration space, and then, a piecewise polynomial model is adjusted to match the collected data. A few applications of the reduction method are considered: a serial pick-and-place machine, a flexible fou r bar mechanism, and a parallel kinematic manipulator.