Localization And Recovery Of Damage In Smart Structures Through Sensitivity Enhancing Feedback Control

Structures such as planes, aircrafts, bridges and buildings may damage due to various loading applied and various accidents in their lives. The accumulated damage may give rise to the failure of structures and lead to the loss of property and life. To guarantee the safety of structures, it is desired to find an effective and efficient method to identify the occurrence, location of damage, and restore them.Non-destructive damage detection and isolation in structures using modal information is hindered by the sensitivity of modal frequencies to small changes in mass, stiffness, and damping parameters induced by damage. In this paper, the author adopts Genetic Algorithm to optimize the controlled model in order to obtain maximal modal frequency sensitivity. Combine Sensitivity Enhancing Control (SEC) and Coherence method to identify the occurrence and location of damage. The former uses pole placement, closed-loop modal frequencies are placed at locations where enhance sensitivity to particular types of damage. The later rely on a priori knowledge of how certain damage scenarios affect modal properties. Using this information, the correlation between measured frequency shifts and predicted modal frequency shifts for a given set of damage scenarios is used to find damage location. The methods are evaluated through finite-element simulation of controlled plate with stiffness and mass damage. Results show that the methods to measured closed-loop modal characteristics increases both the accuracy of locating damage and the ability to tolerate noise in measurement of modal properties used to locate damage.Negative mode displacement and velocity feedback were adopted and the control force applied to each piezoelectric element acting as actuator was calculated to restore the damaged smart structures. Simulation results show that the dynamical characteristic of damaged structures can be successfully restored by applying control force of the piezoelectric patches displaced in this way.This research is partially supported by the National Natural Science Foundation of China under Grant No.50478037 and No.10572058 and the Research Fund for the Doctoral Program of Higher Education under Grant No.20050287016.