Sensor Placement for Damage Detection in Nonlinear Systems Using System Augmentations

Abstract

Currently, most sensor placement methodologies are focused on maximizing the controllability and observability of the monitored structure. Recently there have been several sensor placement techniques proposed for damage detection. The work herein provides an integrated sensor placement and reduced order health assessment approach that can be applied to both linear and nonlinear structures. The method uses the idea that often the damageable regions (hot spots) of the system are known in advance and therefore the modes that are sensitive to changes in these hot spots should be the ones exploited for damage detection. Generally,the sensors are placed near the hot spots. However if that is not possible, or if additional sensors are being used, then a generalized eectiv e independence distribution vector method is applied for the remaining sensors. The partial eigenvector information is expanded to the full space using the knowledge that damage is limited to the hot spots of the system. Modal based damage detection methods such as minimum rank perturbation theory (MRPT) can then be used to solve for the damage in a linear system. Also, an alternative damage identication by hot spot projection (DIHSP) method is a novel additional option for the damage detection presented herein. Nonlinear systems are handled by forming (higher dimensional) augmented linear systems that follow the same trajectory of the nonlinear system when projected onto the physical (lower dimensional) space. The sensor placement methodology for nonlinear systems is similar, but it requires that sensors be placed at the location of all nonlinearities as well as the hot spots. The damage can be detected using the multiple augmentations generalized MRPT approach previously developed by the authors or by DIHSP. Numerical simulations of the methodology are presented for linear and nonlinear 5-bay frame structures.