Vibration-based damage assessment using local attractor variance

Recently proposed methodologies in the field of vibration-based structural health monitoring have focused on the incorporation of statistical-based analysis. The structure in question is dynamically excited, some feature is identified for extraction from a measured data set, and that feature is classified as coming from a damaged or undamaged structure by means of some statistical approach. Perhaps the most important aspect of this new paradigm is the selection of a "feature" which accurately details the appearance, and possibly the location and scope, of the damage. In this paper we propose a feature derived from the field of nonlinear time-series analysis. Specifically, system response is classified according to the geometry of its dynamical attractor. Emphasis is placed on the use of chaos for the purposes of system interrogation. The deterministic nature of chaos ensures that the dynamics are restricted to finite, often low-dimensional, attractors. By analyzing the ratio of local variance of the driving attractor to that of the response attractor, subtle geometric changes, and hence damage, are identified. Results are presented for a linear 8-D.O.F system subject to chaotic forcing. Comparisons are then drawn with some of the more familiar modal methods. The indication is that this particular statistic represents one of a potentially large class of features which may prove useful in the field of structural health monitoring. © 2001 SPIE - The International Society for Optical Engineering.